Improving Male Sexual Health, Function & Fertility | Dr. Michael Eisenberg

1. 0:00 – 1:49

   Dr. Michael Eisenberg

   1. AHAndrew Huberman0:00

      Welcome to the Huberman Lab Podcast, where we discuss science and science-based tools for everyday life. I'm Andrew Huberman, and I'm a professor of neurobiology and ophthalmology at Stanford School of Medicine. My guest today is Dr. Michael Eisenberg. Dr. Michael Eisenberg is a medical doctor specializing in urology and an expert in male sexual function and fertility. He is both a clinician, who sees patients, as well as a research scientist, having published over 300 peer-reviewed articles on male sexual function, urology, and fertility, and he is considered one of the world's foremost experts in male sexual health. Today, we discuss a broad range of topics important to all men, including erectile dysfunction and function. We also discuss prostate health and urinary health. We discuss fertility and sperm count. We discuss even topics seemingly esoteric, such as why penile lengths are actually increasing over time while sperm counts seem to be decreasing. Today, you'll also learn some very interesting surprises, such as the fact that a very, very small percentage of erectile dysfunction actually stems from hormone dysfunction. Rather, the vast majority of erectile dysfunction stems from issues that are either vascular, that is, related to blood flow, or neural. And today, you'll learn about a large variety of treatments for erectile dysfunction. Dr. Eisenberg also dispels a lot of common myths that you hear out there, both on the internet and in popular culture, that relate to male sexual health and function. By the end of today's episode, I assure you that you will have a thorough understanding of what male sexual health is, how it relates to other aspects of health, and how to think about treating, maintaining, and improving all aspects of male sexual health, fertility, and function.

2. 1:49 – 4:20

   Sponsors: ROKA & Eight Sleep

   1. AHAndrew Huberman1:49

      Before we begin, I'd like to emphasize that this podcast is separate from my teaching and research roles at Stanford. It is, however, part of my desire and effort to bring zero-cost-to-consumer information about science and science-related tools to the general public. In keeping with that theme, I'd like to thank the sponsors of today's podcast. Our first sponsor is ROKA. ROKA makes eyeglasses and sunglasses that are of the absolute highest quality. The company was founded by two all-American swimmers from Stanford, and everything about ROKA eyeglasses and sunglasses were designed with performance in mind. Now, I've spent a lifetime working on the biology of the visual system, and I can tell you that your visual system has to contend with an enormous number of challenges in order for you to be able to see clearly. ROKA understands this and has designed eyeglasses both for sport and for wearing in casual settings or to work or to dinner that always allow you to see with crystal clarity. Their eyeglasses are extremely lightweight, and they won't slip off your face, even if you get sweaty. I wear ROKA sunglasses when I'm driving into direct sunlight or when it's particularly bright during the middle of the day. If you'd like to try ROKA eyeglasses or sunglasses, go to ROKA, that's R-O-K-A, dot-com and enter the code Huberman to save 20% off your first order. Again, that's ROKA, R-O-K-A, dot-com and enter the code Huberman at checkout. Today's episode is also brought to us by Eight Sleep. Eight Sleep makes smart mattress covers with cooling, heating, and sleep tracking capacity. I've spoken many times before on this podcast about the fact that getting a great night's sleep really is the foundation of mental health, physical health, and performance. One of the key things to getting a great night's sleep is to make sure that the temperature of your sleeping environment is correct, and that's because in order to fall and stay deeply asleep, your body temperature actually has to drop by about one to three degrees, and in order to wake up feeling refreshed and energized, your body temperature actually has to increase by about one to three degrees. With Eight Sleep, you can program the temperature of your sleeping environment in the beginning, middle, and end of your night. It has a number of other features, like tracking the amount of rapid eye movement and slow wave sleep that you get, things that are essential to really dialing in the perfect night's sleep for you. I've been sleeping on an Eight Sleep mattress cover for well over two years now, and it has greatly improved my sleep. I fall asleep far more quickly, I wake up far less often in the middle of the night, and I wake up feeling far more refreshed than I ever did prior to using an Eight Sleep mattress cover. If you'd like to try Eight Sleep, you can go to eight sleep dot com slash huberman to save $150 off their Pod 3 cover. Eight Sleep currently ships to the USA, Canada, UK, select countries in the EU, and Australia. Again, that's eight sleep dot com slash huberman. And now for my discussion with Dr. Michael Eisenberg.

3. 4:20 – 12:00

   Sperm Quality, Geographic & Environmental Factors

   1. AHAndrew Huberman4:20

      Dr. Eisenberg, welcome.

   2. MEMichael Eisenberg4:22

      Thank you. Good to be here.

   3. AHAndrew Huberman4:23

      I've been looking forward to talking to you for a long time, because these days, we hear a lot about the diminishing quality of sperm, which in some ways seems to be tacked to the conversation about diminishing quality of environment, people, intelligence, you know, there's a lot woven into this statement that sperm quality is declining.

   4. MEMichael Eisenberg4:47

      Mm-hmm.

   5. AHAndrew Huberman4:47

      And some of it, I think, people assume is related to environmental changes. Some of it, I think, people assume are related to changes in behaviors, so maybe less exercise, less sunlight, who knows?

   6. MEMichael Eisenberg5:03

      Mm-hmm.

   7. AHAndrew Huberman5:04

      Hopefully you'll tell us what's really going on, but the first question I have is, is sperm quality actually declining? And regardless, what is sperm quality?

   8. MEMichael Eisenberg5:15

      Yeah. Great question. So I think it's very controversial, I think as your question alludes to. So I think we'll start by just talking about what sperm quality is and why it's important. So, for reproduction, as you've covered on the podcast before, a man makes semen, uh, and that has sperm in it. And so, when we're talking clinically about a semen analysis, there's a few things we look at. We look at the amount of ejaculate and semen that comes out. We look at the sperm, how many there are. We look at their motility or movement. We look at their morphology or shape. There's some more advanced testing that's done in rare cases, looking at fragmentation of DNA, for example. There's some newer tests looking at epigenetic profiles of sperm. Uh, but essentially these are all markers of fertility. So, fertility in itself is a team sport, right? So it's hard to, you know, ma- label a man as fertile or not fertile without knowing about his partner.... um, but nevertheless, based on different, these different parameters, we try and quantify how likely a man is to be able to achieve a pregnancy. So the World Health Organization, every decade or so, looks over the existing literature and defines these different cut points of what's normal or what's subfertile, uh, for those levels. So that's sort of the backdrop of what semen is and how, you know, these, these tests are done, or, you know, what these tests represent. Now, the question of whether they've declined over time, um, has been, you know, a question for a number of years. There was a landmark paper in the early '90s by Carlsen and a group in Denmark that showed this temporal decline, you know, over the last 50 years from that time point. And so, what the investigators had done is looked over the literature for studies that reported semen quality around the world, and noted that, you know, the quality in the earliest studies, like in kind of the mid, uh, 20th century were here, and then over time they had sort of declined, the more recent studies. Um, now that study was very controversial. There was questions about weighting from different studies, putting... 'Cause there w- as you can imagine, these, there's not a lot of early studies, so putting a lot more importance on those rather than some of the later ones. Um, and so since then, there's been many other studies that have, that have come out in time. And even today, it remains very controversial. I think, you know, if I were to say that I believe there's a decline, some of my colleagues and friends would be very upset with me. If I say I don't believe it, some of my colleagues and friends would be very upset with me. So, I would say that, you know, my opinion really varies based on whose paper I've read. And I, there's some very convincing, you know, studies, uh, on each side of it. You know, there are... Most recently, just in the last year or so, there was a meta-analysis of, you know, tens of thousands of men where they looked at, again, a host of these studies over the last, uh, number of decades all around the globe. So prior studies were really just focused on the western hemisphere, western countries, 'cause there was more data from that. But more recently, we've gotten a lot of data from Africa, from Asian countries as well, uh, and those also support this decline. Um, so, you know, one of the counterarguments to why we're seeing that is just sort of an evolution of techniques over time. Um, so that's one of the, the, sort of the popular, um, questions about whether there's really a true decline. Um, you know, I think as you're alluding to, why there would be a decline is also, you know, unknown, and, but you've sort of labeled, you know, perfectly the kind of most common hypotheses, so whether it's an environmental exposures, right? A lot of things have changed over the last 50 years, and I think, you know, chemical exposure is certainly one of those. And there have been some fairly convincing, you know, pre-clinical studies, so, you know, mostly done in animals, uh, that show that, like, exposure to different chemicals, phthalates, um, uh, BPA, other things, may actually harm, you know, reproductive function for men and for women as well. Uh, and so it may be that, you know, these chemicals, you know, that are, that we're being exposed to as kids and adults or even probably, um, more sinisterly like when we're, um, you know, kind of developing in utero, that might be kind of the most harmful exposure. Um, but there's also been, you know, an obesity epidemic as well, and there's a strong link between a man's, man's reproductive function, um, and body weight. And so, uh, that's also, um, thought to play a role in some of this too. Um, so I think there are con- convincing studies. But the other, I guess, aspect to this is that there's variations in semen quality around the country and around the world. There's geographic variation. And so, that's also sort of an unknown, um, uh, explanation. Uh, you know, there could be different sort of genetic, you know, compositions of men, and so there's different reproductive potential in that source. There could be different environmental exposures, diet, exercise, lifestyle. And there was a famous study, um, done, uh, a number of years ago where they looked at semen quality among fathers. So these are men that had achieved a pregnancy, and at the first, you know, prenatal visit, they had, um, the fathers give a semen sample. And so this was done in four centers around the country. I think it, one in California. There was, um, I think one in the Midwest. Uh, there was one in New York. So they basically found that semen quality was real highest in the urban centers, and New York tended to be the highest numbers where it was, you know, lower in the Midwest. And so the hypothesis was potentially because it was a more rural setting, maybe there was pesticide exposure, and that had led to these lower numbers. But, you know, another equally plausible explanation may be that, you know, they're different, sort of a different population, and maybe, you know, that that could explain these differences. So I think it's, it's, you know, very important, um, and I think, you know, one of the sort of lacking things in this is there's not really longitudinal data. One of the greatest things would be if we just started tracking, um, semen quality around the country, just like we do obesity, like, you know, NHANES, uh, CDC's, uh, survey of health in, in the US. If we added semen quality onto that, that way you could really see, you know, how it varies around the country and, you know, sort of compare like to like to see over time if there's really this progression. You know, one of the only studies to do that in Denmark, um, they started around, you know, around 2000 and tracked semen quality among, um, you know, volunteers that came in when they were conscripted for military service in Denmark. They were offered the opportunity to participate in this study. Um, and so some men did, and what they found is actually that semen quality was fairly uniform over about 20 years where they had data. But sort of another very interesting part of that study is that only about a quarter of those men had normal semen quality. Um, so it was sort of very concerning. You know, it was, I guess, reassuring that it wasn't further declining, but very concerning that only a quarter of Danish men had, you know, normal semen quality. And they're one of the, I think, thought leaders in this field, um, just because sort of a reproductive crisis there.

4. 12:00 – 19:26

   Fertility & Sperm Quality; Testosterone, Cell Phones & Heat

   1. MEMichael Eisenberg12:00

   2. AHAndrew Huberman12:00

      You mentioned that some of this apparent decline in semen quality might be related to the fact that the tools to measure semen quality are getting better and better, and that would make sense if, for instance, one is just looking at total volume, uh...... morphology, which means shape, uh, I should've clarified that, um, how many forwardly motile sperm there are, and then also adding in, you know, a very sensitive measure such as, um, DNA fragmentation. You know, essentially, as the instruments get finer and finer, you discover more and more details, and if you are, um, rating quality a- along a number of different dimensions, then it would make sense that those would tier out into different levels. So if one were to simply ask, for couples who want to get pregnant, and assuming that egg quality is not the issue, what percentage of failures to achieve successful pregnancy are the consequence of deficient sperm, deficient in any way?

   3. MEMichael Eisenberg13:01

      Mm-hmm.

   4. AHAndrew Huberman13:02

      And is that number increasing over time?

   5. MEMichael Eisenberg13:06

      Yeah. So I think that's really key. I think when couples think about fertility, usually it's thought of as a female problem, um, and I think there's just historic reasons for that. You know, if you look at data in the US, when couples do seek care for fertility, the man is bypassed probably a third of the time, even though when you look at the reasons for infertility, the man contributes probably half of the time to infertility. So I think there's a-

   6. AHAndrew Huberman13:29

      Half?

   7. MEMichael Eisenberg13:29

      Half, yeah. So I think there's a huge need just to understand and evaluate the man. And, and one of the reasons for this, I think, is that, um, you know, one of the main treatments for infertility in the US is IVF, which is very powerful. I think one of the, you know, greatest marvels of medicine in probably the last, you know, quarter century is our ability to mix a sperm and egg in a dish and create a life. It's really remarkable. But because it now takes just a single sperm, you know, through something called intracytoplasmic sperm injection where you inject one egg, or one sperm into an egg, you know, the bar has gone down dramatically. You know, for couples just trying without, you know, any assistance, you probably need 20 to 40 million moving sperm. But now with, you know, these remarkable techniques, you just need one sperm. Um, and so because of that, you know, I think a lot of our innovation and research on male fertility has probably gone to the wayside just because clinically, you know, we just need, you know, a few dozen sperm for most couples.

   8. AHAndrew Huberman14:27

      What about testosterone levels? Are those also declining? We hear this, um, and when I look at the literature, I can find evidence for that, but the question is also whether or not the amount of decline in testosterone levels is significant in a way that impacts, let's say, fertility, but also, um, vitality in other ways, energy, mood, um, sexual health, et cetera. Um, what's the story with testosterone levels? Are they indeed declining on average across the male population in the US and elsewhere?

   9. MEMichael Eisenberg15:00

      I think there is pretty convincing evidence that that is happening, and I think the reason for that, again, is probably not certain, but, you know, there have been, you know, some pretty nicely designed cohort studies where they recruited, you know, men in the, the 2000s, the '90s, the '80s, and you can see that depending on when these men are recruited, just, you know, matching age for age, these testosterone levels tend to be lower. Um, and then NHANES, which is, again, this sort of longitudinal study run by the CDC, um, that has also shown, uh, looking at testosterone levels over, you know, decades, that testosterone levels have declined over time. Um, so there, you know, chemical exposure is one possible explanation, again, either in adult or adolescent life or in utero, um, but obesity I think is also sort of a convincing explanation as we're more sedentary, um, you know, we get bigger. That's one of the places that testosterone can decline. I think there's different sort of explanations for that. Um, you know, as testosterone's produced, it's aromatized in, uh, peripheral tissue. You know, in fatty tissue, fat has a lot of this aromatase, so that converts testosterone into estrogen. So, it necessarily, you know, lowers the testosterone level that's circulating in our body. Um, also just insulating the, the testicles. Our thighs get bigger. Insulating the testes can also sometimes lower the efficiency of production a little bit too.

   10. AHAndrew Huberman16:16

       Because of heat effects?

   11. MEMichael Eisenberg16:17

       Because of heat effects.

   12. AHAndrew Huberman16:18

       Mm-hmm. Uh, I was going to ask about this later, but I'll ask about it now since we're talking about heat effects and, um, sperm and testosterone, um, the heat, of course, being, uh, not good for-

   13. MEMichael Eisenberg16:29

       Right.

   14. AHAndrew Huberman16:29

       ... um, sperm health and testosterone, which is, I've read a meta-analysis, I don't know, um, how high quality it is, but, um, that explained that there is some evidence for, um, either heat effects or possibly non-heat related effects of cellphone, you know, smartphone in the pocket-

   15. MEMichael Eisenberg16:52

       Mm-hmm.

   16. AHAndrew Huberman16:53

       ... i- impairing sperm health, maybe even testosterone levels. Now, you hear this more often in kind of biohacky, um, I don't know, uh, circles, um, which, you know, uh, I'm not a fan of the word biohacking. Um, it do- it's not clear what it means, but it, it, it sounds like it means something about taking a shortcut using one thing for a purpose it wasn't intended.

   17. MEMichael Eisenberg17:15

       Mm-hmm.

   18. AHAndrew Huberman17:15

       But, you know, it also makes sense to me that, uh, a smartphone could generate some heat, um, some radiation that might impair, um, testicular function and therefore impair sperm quality and/or testosterone levels. But is there any real solid data that carrying your cellphone in your pocket, let's assume on, that the cellphone is on-

   19. MEMichael Eisenberg17:39

       Right.

   20. AHAndrew Huberman17:39

       ... is bad for sperm health or testosterone levels?

   21. MEMichael Eisenberg17:42

       Yeah. So, um, I think there's not convincing evidence that it's gonna help s- um, testosterone levels. I think that, you know-

   22. AHAndrew Huberman17:49

       It's gonna hurt testosterone?

   23. MEMichael Eisenberg17:50

       It's not gonna hurt, yeah.

   24. AHAndrew Huberman17:51

       Yeah.

   25. MEMichael Eisenberg17:51

       So I should m- you know, make clear that I think that in terms of production and heat effects, you know, sperm production is much more sensitive than testosterone production. Uh, but there have been some studies looking at cellphone exposure because, again, you're getting this, whether it's heat, whether it's sort of the, you know, radio frequency, you know, waves coming in, I think you could posit sort of different explanations of why that may be harmful. So there have been some studies that, you know, looked early on, you know, men that use cellphones more or less....they had lower semen quality if they used it more. But you can also imagine there's huge differences in men that do and do not use cell phones. So, you know, it's, it's, it's a hard experiment to design. But there have been some studies, uh, doing this in vitro, so in the laboratories. So taking, you know, sperm in a cup basically and putting a cell phone next to it, or not next to it, to try and see if that played a role. There've been studies done where they, um, sort of normalized the, the heat. You know, they kind of put it on, um, sort of a special stage so that it's not heat necessarily, but maybe it's RF exposure. So those studies, I think, don't show sort of a mea- a clinically meaningful change. But there have been some studies that say that maybe DNA fragmentation of sperm can go up a little bit if there's close proximity, uh, to a cell phone. Um, so I think, you know, I, when patients ask me that, which is a common question I get in the clinic, obviously patients are coming in, they want to do, you know, whatever they can, um, to try and improve their chances. Um, so I think generally I think the data is not convincing. Um, but, you know, if it's easy enough certainly to be aware of it. You know, I think putting a laptop on a desk rather than in your lap I think for heat exposure is probably the biggest thing that we want to minimize.

5. 19:26 – 26:49

   Testosterone, Age, Obesity

   1. MEMichael Eisenberg19:26

   2. AHAndrew Huberman19:26

      About a year and a half ago, I did an episode about testosterone and estrogen, where it's manufactured in the male and female body, et cetera, and found a very interesting graph in a, uh, textbook on, uh, behavioral endocrinology by a guy named Randy Nelson who I happen to know through the field of behavioral endocrinology as it's typically studied in animals. So most of that book centers on animal studies, but there's a, a fraction of the studies that center on human, uh, data. And there was a very interesting graph that showed testosterone levels as a function of age in males. Um, and as one might expect, testosterone levels were on average much higher in late teens, early 20s, 30s, and there was a progressive decline.

   3. MEMichael Eisenberg20:09

      Mm-hmm.

   4. AHAndrew Huberman20:09

      But what was remarkable to me about that graph is that even when exploring the, um, the scatter plots, 'cause he, they showed individual points, they didn't just show the averages, of testosterone levels in men in their 50s, 60s, 70s, 80s, even 90s, there were these outliers, these guys who had testosterone levels that were on par with, uh, testosterone levels of men in their 30s, but these guys were in their 50s, 60s, 70s, 80s, even 90s. So do you observe this clinically? Do you observe that, um, men are coming in, you know, aft- who are older than 40 and have testosterone levels and presumably free testosterone levels as well, um, that are still very high? You know, I, and the reason I ask this is I think we've all been told and we presume that testosterone levels decline with age, and one would expect some outliers. And of course we don't know whether or not those guys in their 90s who have the testosterone levels of, uh, that match the averages of men in their 30s didn't have even greater testosterone levels in their 30s. But given that they were ceilinged out around 900 nanograms per deciliter, (laughs) you know, toward the high end normal depending on the scale, um, in, already at age 90, it's kind of hard to imagine that earlier they were walking around with, you know, 2,000 nanogram per deciliter testosterone. So do you see this? Are there some, is there just a lot of natural variation in testosterone levels of men who walk into the clinic at any age? And of course, what is special about these individuals that are, you know, maintaining high normal testosterone levels into their, uh, later years?

   5. MEMichael Eisenberg21:42

      Yeah, that's a great question. I think this is such a common question. Any time we talk about testosterone, I think, or any time we talk about most sort of, uh, clinical tests that we do, you know, what is average? What is normal? Um, so we do see great variation. I mean, I think just like you're saying, I usually let everybody know that, you know, usually testosterone peaks, you know, kind of early 20s, and then it tends to go down probably one percent a year forever. Uh, but there are people that have very, you know, very, very high levels. I, you know, just mirroring, you know, that graph that you describe, I certainly have patients, you know, we screen for testosterone levels, you know, when patients come in with complaints where we're worried about that low energy level, you know, low libido, some of the symptoms of low testosterone, sexual dysfunction. And, you know, to my surprise, sometimes these men, you know, I've seen 80 year olds that certainly have the highest testosterone level I'll see, you know, for six months. Um, you know, why that is I think is not certain. Maybe it has to do with, you know, I would think, with everything there's probably sort of a bell-shaped curve and everybody's a little bit different. Um, but androgen sensitivity, you know, sensitivity of the receptor, you know, they make it more efficiently. But I have not really noticed, again 'cause at least in clinical practice, you know, when patients come in, they come in with a complaint. And so even men, you know, with very high levels, they may have some of the same dysfunction in men with low levels. So I think with low levels, you can try and treat that and that may be the solution. Um, let me frame the question I was going to ask a little bit differently. When someone comes into your clinic and you measure their testosterone levels, as you mentioned, they're likely coming in because they have some issue. Prostate issue, sexual function issue, et cetera. But you do get a read on their, you know, sort of crude morphology of their body, right? So you could visibly determine whether or not they're likely to be obese or not. Um, regardless of age. So earlier you mentioned obesity is a risk factor for lowering testosterone and sperm quality. You mentioned that fat aromatizes testosterone into estrogen, so that's at least one mechanism by which that could happen. But if you were to just step back and say, "Okay, if somebody who walks into my clinic tends to be, um, let's say healthier looking, you know, not obese." Let's just put the cutoff at w- what you would presume is obese. Um, is there a higher probability that their testosterone levels are going to be within normal range? Conversely, when somebody walks in and they're obese, uh, do you fully expect their testosterone levels to be subnormal? Um, or are you sometimes seeing obese people walking in with, you know, high testosterone? Um, and the reason I'm asking this is not to create confusion. It's that I think that...

   6. AHAndrew Huberman24:24

      ... everybody out there who's thinking about sperm quality and testosterone levels and this, uh, apparent decline, trying to figure out, you know, okay, what can we do in order to maintain the health metrics that are going to, of course, increase fertility, but for those that don't want to have kids or already have kids are going to at least maintain or improve vitality? Is obesity really the thing to avoid? So is there a, not one for one, but is there a tight correlation between obesity and testosterone levels?

   7. MEMichael Eisenberg24:54

      I would say that you cannot predict. I think that sort of would be the take home. And so I think that, you know, more information is always better. You know, when I see patients in clinic, um, you know, some patients are walking around, you know, with, yeah, everything is totally normal and they're very healthy. All the numbers come in at the normal range. But sometimes when men, you know, look totally normal, they talked about taking care of their life, they exercise, you know, five, seven days a week, their testosterone levels can be very low. So e- even despite, you know, having what we would consider should really give them, you know, symptoms, um, they're able to compensate. You know, maybe they've lived their whole life and that they don't know what normal is. Now when we get them, you know, to sort of normal levels, a lot of times they feel better, again because they have no idea how they should feel. Um, but I think that that's just sort of important that everybody, you know, should be screened. I think that, you know, testosterone, semen quality, they have been shown to even be barometers of health. Um, so you know, men with lower testosterone levels have higher risk of, you know, heart disease, diabetes, mortality. The same studies exist for semen quality as well. Um, and you know, again, they may have sort of a similar relationship and explanation why that may be, but I think it's hard to just predict, you know, based on appearance what, you know, testosterone will be, what semen quality will be, what testicular function will be without actually getting some objective data. And actually if you look at the trend of tes- of semen quality decline over time, kind of getting back to some of those earlier points you were making, if you were to overlay that on the known association between obesity, um, its effects on semen quality, that actually doesn't explain the whole decline 'cause the, you know, the purported decline in semen quality is about 50%. But if you just l- if you were to say, "Well, what would we expect if, you know, we look at..." You know, 'cause we were able to track exactly how much fatter we are now than we used to be. That actually only explains about a 10% decline. So I think there is, you know, to your point, something more. Um, and it is not something that you can just identify by eye.

6. 26:49 – 35:26

   Tool: Optimize Sperm Quality, Exogenous Testosterone, hCG

   1. MEMichael Eisenberg26:49

   2. AHAndrew Huberman26:49

      What are the dos and don'ts as it relates to, I don't want to use the word optimizing. It's gotten me into trouble before because (laughs) the word optimize or optimal suggests that there's a perfect number that one should all attain, if possible. But in reality, um, optimal is a day to day thing, um, at least. But what should people avoid in order to get their sperm quality as high as possible, their testosterone level... Again, here I will have to be careful. I don't want to say as high as possible because some people might not want excessive androgen. Um, but at the high end of normal perhaps would be the ideal for many people. What should people do? What should they avoid? And here I'm setting aside any prescription clinical treatments that, such as testosterone injections or things like, uh, chorionic gonadotrope, human chorionic gonadotropin, things that we can talk about a little bit later. But what should every male be doing in order to optimize these health parameters?

   3. MEMichael Eisenberg27:51

      Yeah, so I think that there are some risk factors that we do, like we'll start with semen quality. So we talked about heat. I think that's a big one. So like hot tubs, saunas, trying to avoid those. Some, you know, light data on seat warmers. Anytime, you know, we kind of get this external heat source to the scrotum, you know, the testicles are outside the body 'cause they need to be a little cooler. So anything that warms them up can certainly be a problem.

   4. AHAndrew Huberman28:11

      Could I just, uh, briefly interrupt there, um, to ask, uh, we've done episodes on sauna and some of the health benefits of sauna. Um, is it sufficient for somebody to bring in a cold pack to the sauna and put that up in their groin? I actually have suggested that. That's actually what I do when I go into the sauna. Um, and I have suggested this on podcasts, um, not just for people who are trying to conceive because it seems like heat, as you mentioned, is bad for sperm, not quite as bad for testosterone levels. But is it also true that heating the testicle too much is generally bad for endocrine function in males and therefore would, if one is going to go into a hot sauna for 20 minutes or more to essentially cool the, the scrotal area?

   5. MEMichael Eisenberg28:57

      Yeah, I mean, I think the spermatogenesis or sperm production is certainly a lot more sensitive. You know, whether you can sort of thwart the effects of external heat with a cooling pack, I think it makes sense. There are studies that have looked at different ways to cool the scrotum and have compared s- you know, semen quality before and after. And there's some data that may help. Um, it just depends how long you're going to spend in the sauna and how cold, you know, that pack is going to remain.

   6. AHAndrew Huberman29:19

      So ice pack and in the sauna for 20 to 45 minutes.

   7. MEMichael Eisenberg29:23

      Yeah. And is the ice pack still cold afterwards?

   8. AHAndrew Huberman29:25

      Yeah. Yeah, they actually sell, and by the way, I have no relationship to any of these companies, but they actually sell cold packs that are designed to be worn in your shorts so if you go to a, you know, a, I'll go to a Russian banya every once in a while. Now I guess I'm outing myself.

   9. MEMichael Eisenberg29:38

      (laughs)

   10. AHAndrew Huberman29:38

       Yes, I have a, yes, I have a cold pack in my shorts when I go to the Russian banya.

   11. MEMichael Eisenberg29:42

       (laughs) .

   12. AHAndrew Huberman29:42

       Um, but, um, but they have a, a sort of an insulation so that you're, the cold, the very cold surface is cold enough but it's not right up in contact with the scrotal skin because that could get, um... I don't want to make a bad joke and say it could get sticky, uh, that situation. You don't want it getting so cold that it actually would stick to the skin and then it could potentially damage the skin when you're trying to remove the cold pack. So it has a thin insulating layer. Um, and, uh, yeah, that's essentially what it is.

   13. MEMichael Eisenberg30:12

       Yeah, I mean, frostbite to the scrotum is not theoretical. It could certainly happen. So you do want to be careful.

   14. AHAndrew Huberman30:16

       Yeah.

   15. MEMichael Eisenberg30:16

       So I mean, in theory that should be, that should be adequate to sort of, you know, to decrease the risk of that particular effect. Um, you know, I keep coming back to health, how important that is to maintain, um-... you know, adequate sperm production because I think these two are very linked. You know, there have been studies that show that men with more comorbid conditions, so obesity, hypertension, hyperlipidemias, these sort of stack up. We see a decline in testicular function, so lower testosterone levels and lower sperm quality. So I think, you know, taking ownership of your, your health, I think, is important as well. Um, you know, a lot of times, um, fertility tends to be one of the first touchpoints that some men have with healthcare, you know, because generally what brings men to the doctor? It's usually pain or, you know, kind of a problem. Um, so, you know, if men are in their 20s and 30s getting ready to start a family, or 40s in some cases, sometimes they haven't, you know, seen a primary care doctor. So some of these things and some of this relationship has not been established yet. So I think, you know, thinking about ways to start that I think would be important too. Um, and then I know you don't want to talk about testosterone, but testosterone is actually a fairly common problem that we see in fertility clinics. Um, I would say that, you know, estimates say maybe about one in 20 infertile men are that way because of testosterone. So I think when... You know, people get testosterone from different places and hopefully, you know, whatever provider you're getting it from tells you that one of the side effects of this, um, is lower sperm production. It's actually been tested as a contraceptive and, you know, with some other agents, it can actually be fairly effective. So we just want to make sure that, you know, if men are starting testosterone, they're doing it for the right reasons and they're doing it safely, I think.

   16. AHAndrew Huberman31:49

       You're talking about testosterone replacement therapy. Although, as we were talking about before we started recording, I, I am really on a push now to rename what people call TRT, testosterone replacement therapy, because indeed some people have low testosterone and need it replaced-

   17. MEMichael Eisenberg32:05

       Right.

   18. AHAndrew Huberman32:05

       ... the R in TRT. But I think what you're referring to, if I'm not mistaken, is that there are probably millions-

   19. MEMichael Eisenberg32:13

       Yeah.

   20. AHAndrew Huberman32:13

       ... of young men and older men taking exogenous testosterone injections, creams, pills, pellets, you know, any number, nasal sprays now, you know, any number-

   21. MEMichael Eisenberg32:24

       Mm-hmm.

   22. AHAndrew Huberman32:24

       ... of different, uh, routes of delivery of exogenous, um, testosterone and that, um, dramatically reduces one's endogenous testosterone production and dramatically reduces one's sperm count and maybe even quality. We'll maybe talk about this a little bit later, but maybe even can... There, there's... I've been told that it can perhaps introduce a DNA fragmentation, uh, within the remaining viable sperm as well. So do I have that correct? You're saying that, that you see 1 in 20 men have issues with fertility because they are taking testosterone.

   23. MEMichael Eisenberg32:56

       Right.

   24. AHAndrew Huberman32:57

       So their testosterone levels presumably are gonna be high and normal or more, but they are doing presumably not testosterone replacement therapy, but they are doing what I call testosterone augmentation therapy, meaning they were somewhere in the 300 to 900 nanograms per deciliter range, but decided to start taking testosterone anyway, and then their t- their sperm count essentially diminishes to nil or close to it?

   25. MEMichael Eisenberg33:23

       In some cases, yeah. So, I mean, I think there's various reasons you would take testosterone. I think, you know, s- some people have been treated, you know, years ago, and so they do need to replace testosterone, you know. Um, but some people do it for augmentation. I just usually say testosterone therapy just so it's Mm-hmm. ... correct, covers all.

   26. AHAndrew Huberman33:38

       Oh, you kill the R. I like that. That's better than the TAT, which doesn't help very good. Okay. Just testosterone therapy.

   27. MEMichael Eisenberg33:44

       Yeah.

   28. AHAndrew Huberman33:44

       Okay.

   29. MEMichael Eisenberg33:45

       But if you had... You know, for example, we take 100 of my infertile patients that come in to see me in clinic. At least five of those men will be infertile because they're on testosterone therapy. And some of them do h- you know, have that suspicion. They say, "You know, I'm gonna level with you. This is why my levels are probably low." But a lot of men were not told that, you know, when they started therapy. So I think certainly for reproductive age men, that's then a very important conversation to have, um, because there can be some other, you know, ways that we kind of maintain sperm production. I think sperm cryopreservation is a good option for these men as well. Um, or there may be other therapies they can think about just because of reproductive toxicity.

   30. AHAndrew Huberman34:21

       What about, um, hCG, human chorionic gonadotropin? I hear about a lot of people who go on testosterone therapy who take hCG every other day or so.
7. 35:26 – 36:57

   Sponsor: AG1

   1. MEMichael Eisenberg35:26

   2. AHAndrew Huberman35:26

      As we all know, quality nutrition influences, of course, our physical health, but also our mental health and our cognitive functioning, our memory, our ability to learn new things and to focus. And we know that one of the most important features of high-quality nutrition is making sure that we get enough vitamins and minerals from high-quality, unprocessed or minimally processed sources, as well as enough probiotics and prebiotics and fiber to support basically all the cellular functions in our body, including the gut microbiome. Now, I, like most everybody, try to get optimal nutrition from whole foods, ideally mostly from minimally processed or non-processed foods. However, one of the challenges that I and so many other people face is getting enough servings of high-quality fruits and vegetables per day, as well as fiber and probiotics that often accompany those fruits and vegetables. That's why way back in 2012, long before I ever had a podcast...... I started drinking AG1, and so I'm delighted that AG1 is sponsoring the Huberman Lab Podcast. The reason I started taking AG1 and the reason I still drink AG1 once or twice a day is that it provides all of my foundational nutritional needs. That is, it provides insurance that I get the proper amounts of those vitamins, minerals, probiotics, and fiber to ensure optimal mental health, physical health, and performance. If you'd like to try AG1, you can go to drinkag1.com/huberman to claim a special offer. They're giving away five free travel packs plus a year's supply of vitamin D3 K2. Again, that's drinkag1.com/huberman to claim that special offer.

8. 36:57 – 43:27

   Tool: Lifestyle Factors & Sperm Quality, Alcohol

   1. AHAndrew Huberman36:58

      So if somebody is not taking testosterone exogenously, they gotten their, um, body fat level down to a point where they're not considered obese, so they're hopefully doing some cardiovascular exercise each week, maybe doing some sport or some resistance training too, um, uh, with the intention of maintaining all-around good health, stave off, you know, cerebrovascular, cardiovascular issues, what are some of the other don'ts? Um, I'm going to assume that smoking cigarettes or vaping cigarettes is bad. Uh, are there any studies that look specifically at vaping and sperm quality or testosterone levels? Um, and is there any evidence that, uh, smoking cigarettes is good for testosterone levels or sperm production? 'Cause I'm guessing the answer is no. I feel like nowadays we just say, "Don't smoke," um, but the data are the data. Who knows? Maybe nicotine can help sperm. I have no idea.

   2. MEMichael Eisenberg37:47

      Right. Uh, it's possible. I don't think we have the data on that yet. But yeah, I mean, I think, like, to your point, I think lifestyle factors are certainly a big one and, you know, some of these, you know, potentially, um, you know, kind of unhealthy habits. So smoking is certainly something you should not do. There have been, you know, lots of studies that do link that to, you know, lower quality, again, all the different measures that we look at. Um, also looking at fertility, these men tend to have a longer time to get pregnant. Um, alcohol, I think, is another very common question we get asked as well.

   3. AHAndrew Huberman38:15

      Mm-hmm.

   4. MEMichael Eisenberg38:15

      And I think for that, there's, you know, I think less of a strong association that we've seen. So there, um, you know, there have been some studies that show that very high levels of alcohol, and I guess that's sort of subjective what some would consider higher or not, but, you know, when you get above maybe 20 drinks a week, there have been some effects. But usually-

   5. AHAndrew Huberman38:34

      That's a lot of drinking.

   6. MEMichael Eisenberg38:35

      It's... I would think that's a lot, yeah. But some people don't, but yeah.

   7. AHAndrew Huberman38:38

      Whew.

   8. MEMichael Eisenberg38:38

      Um-

   9. AHAndrew Huberman38:38

      I did an episode on alcohol. I think anything more than two dr- I know people are going to, um, you know, balk at this, but, you know, I think any more than two drinks per week is where you start to see some negative effects on some health parameters, but, you know, I'm, I'm not a teetotaler, so you know.

   10. MEMichael Eisenberg38:53

       Yeah. (laughs) Um, but when you get to this 20 drink, that's when we started to see some effects on semen quality. But the ot- you know, the thing about that is that usually if these men are drinking 20, they're doing other things too, smoking, there can be other drug use as well. So it's hard to tease that out, but in general, that's, you know, I think certainly anything in moderation is probably o- you know, is probably better, and so that's how I counsel patients. I think, again, it's very rare that I see men that are at that level, but I certainly let them know when I do. Um, there's some new data coming out of... that, that we've started to work on looking at if there are different sensitivities to alcohol. So, you know, some East Asians have a mutation that leads to flushing, um, and so that may put those men at higher risk. When they mix alcohol, we may see some, you know, slightly lower, uh, sperm parameters.

   11. AHAndrew Huberman39:39

       You mean skin flushing because they don't make alcohol dehydrogenase? Is that the idea?

   12. MEMichael Eisenberg39:43

       Exactly. Yeah.

   13. AHAndrew Huberman39:43

       Yeah. Um, and is it... I've, I've heard about that in Asian cultures. Is there, um, in Asian populations, excuse me, but is there any evidence that other populations might have slight variance on alcohol dehydrogenase that perhaps maybe they don't lack it altogether, but they have, I don't know, um, they're hypomorphs for whatever gene makes alcohol dehydrogenase and therefore they don't metabolize it as well and therefore, the toxic form of alcohol is active in their system longer? Is there any evidence for that?

   14. MEMichael Eisenberg40:14

       No, I think, yeah, you're exactly right. I mean, I think the one that we think about is East Asian cultures where it can be, you know, depending on, you know, the region, like, um, Chinese, Taiwanese, probably about 40 to 50% of the population has, you know, mutation in the ALDH2 gene. But other populations, um, in people with African ancestry, there's a, a rate of mutation, I think. I'm not going to remember the exact percentage, but I think a few percentage points is some, um, individual with Hispanic ancestry, Ashkenazi Jewish ancestry. So in this particular gene, there's a mutation, not the same one that East Asians have, but, you know, again, I think it gets to why a mutation, you know, where we see sort of negative effects would persist and the hypothesis that, you know, millennia ago poten- potentially, you know, gave some sort of benefit for maybe an infectious disease or something similar to cystic fibrosis, why, you know, again, this mutation would persist in our population if there's not, you know, re- you know, some sort of advantage, uh, to those carrying it. Uh, but we do see it in other, you know, other men as well. So I think if, you know, it's a simple question, do you flush? If you flush, then maybe alcohol may have, you know, more of a, a harm than, than someone else. And then, you know, get- sort of getting along the lines, I think drug use is also something that we should try and, you know, we, we do counsel patients about 'cause that can also negatively affect semen quality.

   15. AHAndrew Huberman41:32

       Do you think it's fair to say that, okay, moderation is best, but if somebody had the option to either not drink or drink in moderation, that they should not drink, would that be even better? Is there any evidence for that? I mean, it seems like nowadays we take the stance that, um, not smoking at all is better than smoking a little bit. Actually, when I was a postdoc at Stanford from 2005? Yes, 2005 to, uh, end of 2010, um, you could still smoke on the Stanford campus.

   16. MEMichael Eisenberg42:01

       Oh.

   17. AHAndrew Huberman42:01

       I'm not a smoker, but there was this collection of... I have to be careful what I say here. There was a particular group on campus of postdocs and graduate students that would, um, you know, that would colonize this little area outside the hospital and smoke because that's where you could smoke. That was eventually, um, eliminated as a possibility. You can't smoke on Stanford campus-

   18. MEMichael Eisenberg42:19

       Right.

   19. AHAndrew Huberman42:19

       ... as far as I know. But they would smoke right outside the hospital. Actually, a lot of the hospital workers would, you know, take a cigarette on their break. This is very common.

   20. MEMichael Eisenberg42:25

       The irony. Yeah, exactly.

   21. AHAndrew Huberman42:26

       Yeah, and, and this was common all over the country, right? This isn't unique to Stanford, but nowadays, you just don't see that-

   22. MEMichael Eisenberg42:31

       Mm-hmm.

   23. AHAndrew Huberman42:31

       ... um, because it's not allowed. Um-... and we hear, "Don't smoke, it's terrible for X, Y, Z," and everything, every other letter of the alphabet. With alcohol, um, we tend to hear that if you're going to drink, drink in moderation. Um, it's not clear exactly what number that is, but is it possible that zero alcohol is better for sperm and endocrine health than any alcohol? Or is that not- not a fair assumption?

   24. MEMichael Eisenberg42:59

       I mean, I think it's a good question. I think, you know, the- your point about tobacco is an excellent one, 'cause I think any smoking is bad. Um, but alcohol, I think we don't have that data for yet, and so I think it's- it's harder to de- it's harder for me to make that recommendation to patients, especially because, you know, people do it for different reasons, um, and if it's not necessarily going to help them, you know, it'll harm them in social situations or other things. Um, yeah. I usually just- I usually give the- the moderation one, unless, again, for the- the very high drinkers, I definitely talk about that.

9. 43:27 – 46:56

   Sperm Quality, Recreational & Over-the-Counter Drugs, Cannabis

   1. MEMichael Eisenberg43:27

   2. AHAndrew Huberman43:27

      Um, you mentioned other drug use. Um, I'm going to assume that, uh, unless prescribed for sort of post-surgical pain or something like that, that benzodiazepines, heroin, opiates of any kind, um, are just bad for sperm and testosterone. I think that we could probably make that a short discussion, right?

   3. MEMichael Eisenberg43:47

      Yeah.

   4. AHAndrew Huberman43:48

      You know, I can't imagine any of that would be good, um, for reproductive health.

   5. MEMichael Eisenberg43:53

      (laughs) Yeah, that's true. I mean, there's again, you'd imagine, or- or may- maybe not, but there's not a lot of data on it. Um, it'd be h- difficult to enroll or maybe easy to enroll, but a lot of those studies have not been done. Um, but there's limited ones of, you know, people in rehab, uh, where they have shown, you know, these associations with, you know, addicts or users and lower quality. So, um, yeah, that's how we talk to patients.

   6. AHAndrew Huberman44:15

      What about cannabis? I did an episode of this podcast about cannabis, and I did highlight some of the medical applications of cannabis. Uh, I also highlighted that very high THC cannabis, um, may predispose especially young males to later psychotic episodes. There are more and more data coming out about that all the time. I, um, got a lot of flak for- for saying that, but that's my take on the data, um, and, um, I know a lot of people use cannabis, uh, recreationally, um, and in a kind of pseudo-therapeutic way. I say pseudo-therapeutic because I think a lot of people use cannabis to manage their anxiety and as an alternative to alcohol, um, for a number of reasons. What is the relationship between cannabis use and testosterone and sperm production? Or I should say sperm quality, excuse me.

   7. MEMichael Eisenberg45:05

      Yeah, so this is also a very common question, um, again, with this wave of legalization across the country, I think more and more men and women are exposed to it. Um, so again, there's data that the more men are exposed to it, it can lead to some harm in terms of sperm morphology and sperm numbers as well, um, you know, one of the sort of landmark studies was about 1,200 men and it found that men that used cannabis daily had significantly lower concentration, motility, morphology compared to those that didn't use it. Um, so I think that's generally how men are counseled, but there's also, you know, other data that shows really a null effect and I think that it's- it goes into probably the composition, how men are taking it, the frequency, because a lot of that data is not well teased out in a lot of these studies. Um, so, you know, I think I- I sometimes struggle with this with patients because some of 'em are taking it for, you know- you know, s- some what they consider legitimate reasons, anxiety, sleep, pain, um, and if there's not sort of very convincing evidence that it's going to help, and they're taking it maybe lower than the threshold where I know that there's good data that it'll cause harm, you know, I- I guess I'm- I try and be sort of honest about where we are, but I think with a lot of things related to sperm, I think our- our level of evidence is not great.

   8. AHAndrew Huberman46:23

      Are there any common over-the-counter medications that can negatively impact sperm quality and/or testosterone? Things like, um, non-steroid anti-inflammatory drugs, Tylenol, Advil type stuff, um, you know, ibuprofen, acetaminophen, um, things of that sort that I and others might not be aware of? I'm not- I'm not probing for anything in particular here, I just- I- I know that, um, you know, a lot of over-the-counter drugs have effects that we're just simply not aware of.

   9. MEMichael Eisenberg46:52

      Yeah, I mean, I think we probably need more data, but I think currently, we think all those

10. 46:56 – 49:55

    High-Impact Sports, Traumatic Brain Injury (TBI), Pituitary & Testosterone

    1. MEMichael Eisenberg46:56

       are safe.

    2. AHAndrew Huberman46:57

       I'm curious about the pituitary. Pituitary gland, as many of the listeners of this podcast al- already know, is a gland that receives signals from the brain, um, the gland sits near the roof of the mouth.

    3. MEMichael Eisenberg47:09

       (laughs)

    4. AHAndrew Huberman47:09

       (laughs) Um, I think that's fair. Um, and releases critical hormones into the bloodstream that control the output of testosterone from the testes as well as output of hormones from other glands. Um, I know a number of people who end up playing sports like football or rugby or even lacrosse or even soccer, I've read, there are data on this, you know, they're heading the soccer ball quite a lot, or martial arts, or they get a head injury at some point, and, um, I certainly hear a lot from people who played these high contact sports and then to their surprise, later, they have diminished testosterone levels. I also work with a number of military groups that talk about this, you know, that they leave and maybe it's from combat-related stress, et cetera, but, um, they wonder whether or not there's any traumatic head injury or maybe pituitary injury related, um, impairment to the reproductive axis that includes brain, pituitary, and the testes. Do you see that? Um, and if somebody played a contact sport, in particular, a contact sport where the head was hit or they were hitting things with their head often, um, or if they have a TBI or had a TBI, that, um, their reproductive health can be, uh- uh, impaired?

    5. MEMichael Eisenberg48:29

       That's fa- that's fascinating. Um, I have- I have not. I mean, I think, you know, it's interesting, I guess, you know, what the pituitary does, you've obviously covered this before, but it does go to a lot of our therapies. I mean, so, you know-...for your listeners, you know that pituitary produces two hormones, LH, luteinizing hormone, and FSH, follicle stimulating hormone, which then stimulates the testicle. So the luteinizing hormonone- hormone stimulates the Leydig cells to make testosterone, and then the follicle stimulating hormone, or FSH, stimulates sperm production. Uh, so both of those are very key, you know, in terms of production, and interestingly wh- when exogenous testosterone is used, you know, it shuts down that access, as you know. So we get less of these gonadotropins, this LH, FSH, um, to stimulate the testicle. Um, and the other sort of reason that sperm production is lost with exogenous testosterone use is it... is actually the intratesticular testosterone is much higher than serum levels. So, you know, our serum levels are, you know, between 300 and 900, uh, nanograms per deciliter on average. But in the testicle, they're probably tenfold higher, at least. So when men are given exogenous testosterone, they're not producing their own, the levels of testosterone in the testicle, which are necessary for sperm production, are much, much lower. Um, but it, it's interesting 'cause I think, um... I, I'm not aware of sort of how tram- traumatic injuries would, would do that.

    6. AHAndrew Huberman49:52

       Okay. Um, that's good to know.

11. 49:55 – 55:39

    Bicycling, Numbness & Sexual Dysfunction; Walking & Testosterone

    1. AHAndrew Huberman49:55

       I'm curious about the non-endocrine, non-chemical, so... effects on sperm quality and testosterone levels. So here I'm thinking about, uh, a bunch of news stories we heard a few years ago about how bicycle seat pressure on the prostate, or maybe it was other, other portions of the, um... it was the, uh, nerves running to the penis itself, um, or surrounding areas, maybe it was pelvic floor related and s- somehow, you'll tell us I'm sure, uh, was impairing sexual function. Was it impairing sexual function in any way by impairing testosterone levels, cutting off blood flow to the testes? Um, and here, perhaps the most important thing to ask straight off, is, um, is riding a bicycle bad for, uh, male reproductive health and sexual health?

    2. MEMichael Eisenberg50:46

       Yeah. These are great questions. These, again, living in the Bay Area, working in the Bay Area, uh, cycling is very, very popular so these are questions that I get a lot. So I think, you know, I... In general, like we talked about before, anything that's good for your heart, it's gonna be good for fertility. So good diet and exercise, maintaining a good body weight. And so I always try and encourage physical fitness. I think that's important. But, you know, it may be possible that some particular, um, activities may put men at more risk. So I think cycling could be one of them if... But it would sort of depend on exactly why we think that may be a problem. So I guess the theory is heat. If you're in the saddle for a long time, you know, for these prolonged, you know, rides that men take, you know, on weekends, you know, hours, um, that maybe if there's too much heat exposure, that may be the mechanism where sperm production would decline. So there have been some studies that say maybe five hours a week would be... you know, that may be too much. So if you're above that level, the sperm count's shown to be lower. If you're less than that, that may be okay. So when I talk to patients about it, I try and just encourage them to, you know, stand up in the saddle, to try and, again, sort of air things out, to try and dissipate heat if, if that's the mechanism we're gonna think. Regarding sexual dysfunction, um, that is thought to be pressure, as you're alluding to. So, you know, the way that the saddle is configured, ideally all the pressure is put on our ischial tuberosities or our sit bones. That's what I'm sitting on now. But on the saddle, you know, there's obviously kind of the rigid nose and if there's too much pressure on that, that actually squeezes between the ischial tuberosities where, you know, the main blood flow to the penis goes and the main nerve supply is too. And so if there's compression on this, you get this sort of lack of blood flow or ischemia and you can get a nerve palsy as well if you crush these nerves. And so that, over time, can lead to problems. So, you know, some patients will say that, "You know, after I cycle, you know, things are numb down there for 30 minutes, um, or a day," or, "I don't get erections for that sort of, uh, same amount of time." Or sometimes, you know, men just sort of, you know, ride through it, um, and, you know, hopefully things come back in a day or two. So that's... that could be the mechanism. There are some saddles that, you know, hopefully it'll be a little safer and, you know, I think that this sort of first was noted probably around 2000 or so and there was a big redesign in terms of saddles to try and make them a little bit more, you know, anatomically correct to try and minimize some of this. And there's, you know, cycle fit that can be done, or saddle fit rather, that can be done at some of the cycling shops to try and, you know, look at your body position, look at your size, and try and find a saddle that's safer. Um, you know, not... This doesn't happen to everybody. I would say maybe if you, if you were to, um, survey cyclists, maybe 20 to 30% of men and women tend to be susceptible to this. So I think if you are having discomfort in... when you cycle, whether it be pain, numbness, or you notice dysfunction, I think certainly you should, you know, think about changing saddles or think about changing riding style. Um, you know, there's other strategies that are sometimes used but, you know, it's absolutely something that, that everybody should be aware of.

    3. AHAndrew Huberman53:52

       I meant to ask this earlier, but I seem to recall a study that drew a, a correlation between, um, amount of walking and maybe it was sperm quality, but I think it was testosterone levels. You know, maybe some other metrics of, um, male sexual health. Uh, forgive me, I'm not recalling the details now. Um, is there any evidence that walking more, standing more, maybe even using a standing desk, uh, is beneficial for, um, you know, pelvic floor health, blood flow, um, prostate health, i-... who knows, could be any and all of those things, in some way that is beneficial for sperm quality, testosterone level, and/or overall male sexual health?

    4. MEMichael Eisenberg54:34

       Yeah. I think, you know, one of the ways that we can characterize activity is step count, right? I think... I know I have a, a watch that tells me that. It's something that I look at every day and kind of strive for. And, and it turns out that the more active you are, uh, it's been shown, sort of looking at, you know, large national data pools across different age ranges, that it is associated with testosterone levels. So being more active, I think, is very important and that's another thing that, you know...... everybody can do to try and improve sort of testicular function broadly, but testosterone specifically.

    5. AHAndrew Huberman55:02

       And d-do you know whether or not that can be separated out from the relationship between being more active and less obese? I mean, is this something that's independent of, of obesity? In other words, can we incentivize people to walk more, um, simply on the, on the promise of, um, improved sexual health?

    6. MEMichael Eisenberg55:21

       Well, I don't know. You know, sexual health will be a different one. But we can, I think, there is association between testosterone levels and step count, uh, across different BMI straight up. So I think, you know, whether you're, have the ideal body weight, whether you have a few pounds to lose perhaps, if you walk more, you will see higher levels of testosterone.

    7. AHAndrew Huberman55:38

       Okay.

12. 55:39 – 58:39

    Exogenous Testosterone Therapy & Cancer

    1. AHAndrew Huberman55:39

       And another question I meant to ask earlier and then we can, um, close the hatch on, on exogenous testosterone therapy, at least for the time being, maybe we'll come back to it, is, um, assuming that somebody can maintain adequate sperm production through the use of HCG or some other, uh, therapy, or perhaps they don't care if they're still making sperm because they've already had children or they don't care to have children, maybe they've banked sperm, in any event, assuming that somebody takes t- testosterone therapy because they were prescribed that, um, let's say in your clinic.

    2. MEMichael Eisenberg56:10

       Mm-hmm. Okay.

    3. AHAndrew Huberman56:10

       Let's just use, uh, you and your clinic as an example. And they are happy with the psychological and physical consequences of that, and they are comfortable with the trade-offs, is there any increased risk of, say, prostate cancer or other forms of cancer? And here, I'm going to assume that this person is keeping their, um, their lipid levels in check, right? Because we, you hear about some hyperlipidemia with testosterone therapies. Let's assume that they're either taking a statin or they're not taking a statin, they're getting enough cardiovascular exercise, that things are in check in terms of LDL, HDL, ApoB and all of that.

    4. MEMichael Eisenberg56:45

       Mm-hmm.

    5. AHAndrew Huberman56:46

       And their testosterone levels are now high normal and they're feeling better, um, and they don't have to worry about sperm production because it, they're either maintaining it or it's been banked or they don't care about that, um, is there an increased risk of prostate cancer? My understanding is the answer is no. But what's the real deal? Does taking testosterone therapy, assuming all other things are being held in a, in check, in a healthy check, does it increase the risk of any kind of cancer?

    6. MEMichael Eisenberg57:14

       Yeah, I mean, this is a, another great question, because I think there's a lot of myths around testosterone, and that's one of them. You know, there's, the origin is that prostate cancer is thought to be, or is, sort of androgen mediated. You know, one of the Nobel Prizes, um, you know, again, decades ago, was awarded because it was found that when we lowered a man's testosterone, the prostate cancer would regress dramatically. So that put that association between testosterone and prostate cancer. So then the concern became if we were to, you know, either replace testosterone or augment testosterone, give a man testosterone, is that going to alter his risk or increase his risk? Um, so I think we have pretty convincing data that that's not the case. You know, there's lots of longitudinal data spanning decades where if a man is given testosterone, um, it doesn't change his risk. The reason for that, and it's sort of seeming contradis-, you know, this contradiction between, you know, prostate cancer, a therapy where we lower testosterone, where if you give a man testosterone, it doesn't change his prostate cancer risk, uh, is not certain, but there's this popular model called the saturation model. So that once there's enough testosterone in the body, and it's, that tends to be a fairly low level, um, that all the sort of, the prostate testosterone receptors, you know, you can kind of think of as, have been filled. So if you were to give a man more testosterone, it doesn't change anything regarding the prostate cancer, prostate growth, any of that. So it is, it is safer when we're looking at prostate cancer as a, as an outcome.

13. 58:39 – 59:57

    Sponsor: LMNT

    1. MEMichael Eisenberg58:39

    2. AHAndrew Huberman58:39

       I'd like to just take a brief break and thank one of our sponsors, which is LMNT. LMNT is an electrolyte drink that has everything you need and nothing you don't. That means plenty of salt, sodium, magnesium, and potassium, the so-called electrolytes, and no sugar. Now, salt, magnesium, and potassium are critical to the function of all the cells in your body, in particular to the function of your nerve cells, also called neurons. Now people, of course, have varying levels of requirements for sodium. So people with hypertension or pre-hypertension probably shouldn't increase their sodium. However, many people are surprised to find that by increasing their sodium intake, they are able to function better cognitively and physically. And that's because a lot of people, especially people who are following low carbohydrate or even moderate carbohydrate and really clean diets, oftentimes they're excreting a lot of water and electrolytes along with it, and simply by increasing their electrolyte intake using LMNT, they just feel better and function better. I typically drink LMNT first thing in the morning when I wake up in order to hydrate my body and make sure I have enough electrolytes, and while I do any kind of physical training, and certainly I drink LMNT in my water when I'm in the sauna and after going in the sauna because that causes quite a lot of sweating. If you'd like to try LMNT, you can go to DrinkLMNT, that's L-M-N-T .com/huberman, to claim a free LMNT sample pack with your purchase. Again, that's Drink LMNT, L-M-N-T .com/huberman.

14. 59:57 – 1:03:12

    Sexual & Urinary Health, Nighttime Urination

    1. AHAndrew Huberman59:57

       Getting back to prostate health and, um, neural innervation of the penis and, uh, and blood flow to the penis, you mentioned the bike seat-related issues. Are there other things that men should do in order to maintain prostate health, stave off prostate diseases, and to maintain healthy blood flow and neural innervation of the penis for obvious reasons? And we'll get, um, into the specifics of those reasons in, in our later discussion.

    2. MEMichael Eisenberg1:00:27

       Yeah, I mean, I think that, you know, I, I always kind of think of the penis as a use-it-or-lose-it organ. So that doesn't mean necessarily that you have to have sex. But, you know, normally we get erections every night, so that should be maintained. And if there's any reason to sort of suspect that that may not be going on, um, usually i- in my practice, that would be from, you know, some s- pelvic surgical intervention or something like that.

    3. AHAndrew Huberman1:00:47

       Mm-hmm.

    4. MEMichael Eisenberg1:00:47

       Sometimes we can intervene to try and maintain that. ...

    5. AHAndrew Huberman1:00:49

       You're talking about spontaneous erections during sleep.

    6. MEMichael Eisenberg1:00:52

       Right.

    7. AHAndrew Huberman1:00:52

       So, um, and...... uh, short of assigning, uh, one's partner to, uh, to check, um, frequency and tumescence, what is the, uh, way that men would know that that's happening? Are you talking about waking up with an erection? Is that, uh, requisite for knowing that nocturnal erections are occurring?

    8. MEMichael Eisenberg1:01:11

       Well, I... Yeah. I think you've... Yeah, you've kind of caught me. I think that's a good question. So, I think a lot of times you won't know, but I think if you have sort of normal response, you know, when... Either by yourself, with a partner, I think that generally means, um, that you are gonna get normal erections. So, I think w-... I guess when I say use it or lose it, it doesn't mean necessarily that the man has to stimulate himself or kind of, um, make sure that he does have, you know, adequate function. Because usually most of that normal function just occurs, you know, with this nocturnal penile tumescence, which we all get. You know, I think sometimes men do notice when they wake up at night. Sometimes in the morning, you wake up with an erection. Men notice that. But the absence of that doesn't mean it's not happening. It likely is, just, you know, most people sleep through it, which is normal. Otherwise, men would never get any sleep because it (laughs) happens many, many times a night. Um, so I think, you know, again, if you're not having normal function, I think that's something you should probably see, you know, a physician about. And then same for, like, urinary function. I think if it bothers you, if there's, you know... If you're waking up at night, if you have to go to the bathroom often, if your stream is getting weaker, those are all sort of complaints that we hear about.

    9. AHAndrew Huberman1:02:16

       What is often... Um, uh, my understanding is that it's, uh, normal to wake up perhaps once during the night to urinate. Um, and this is, of course, assuming... And, again, forgive me for all the caveats, but I've done this long enough that, you know, if I don't get really granular about some of this, then people say, "Well, what if I drank, you know, 32 ounces of fluid right before sleep and I'm urinating three times per night?" Well, w- we're assuming that people are tapering their liquid intake as they approach bedtime. Um, and that waking up once, maybe twice, but once in the middle of the night to urinate is normal for somebody, let's say, age, I don't know, 18 to 40, and maybe from 40 to, uh, 100, um, that number might be in the, uh, one to two times per night. Is that about right?

    10. MEMichael Eisenberg1:03:01

        Yeah. I mean, I think once a night, yeah, is normal for most men.

    11. AHAndrew Huberman1:03:04

        Mm-hmm.

    12. MEMichael Eisenberg1:03:04

        And then I think, you know, if things start to bother you, I think you could certainly see somebody. But it's hard to get better than once or twice a night, yeah, for most men.

15. 1:03:12 – 1:09:19

    Sleep & Semen Quality; Overall Health

    1. AHAndrew Huberman1:03:12

       Um, my understanding is that there's a pretty good relationship between the, um, nocturnal erection and the amount of REM sleep, rapid eye movement sleep, that one is getting, that this tends to be more frequent toward morning as the, uh, proportionate of rapid eye movement sleep increases. I don't know if that's true or not, but I found a couple of studies that at least point in that direction.

    2. MEMichael Eisenberg1:03:32

       Mm-hmm.

    3. AHAndrew Huberman1:03:32

       No pun intended.

    4. MEMichael Eisenberg1:03:33

       (laughs)

    5. AHAndrew Huberman1:03:34

       Uh, so that raises a, a bigger issue that we haven't talked about yet, which is getting adequate amounts of quality sleep each night. And, um, I think for most people, that's seven to nine hours ideally, um, which means getting sufficient slow wave, deep sleep, as well as rapid eye movement sleep. But nowadays, a lot of people, including young people who are not working excessive hours, are, um, getting, you know, four, five, six hours of sleep per night. Is there a direct relationship between getting less than sufficient amounts of sleep and sperm quality, testosterone levels and, um, sexual health?

    6. MEMichael Eisenberg1:04:09

       Yeah. I mean, I think certainly there's reasonable data for semen quality. And there tends to be, um, you know, we call, like, in science, sort of a U-shaped relationship, so that it's not sort of linear, so as you get more sleep, things are better. It... There's sort of... There's this concept of too much sleep and not enough sleep.

    7. AHAndrew Huberman1:04:26

       Mm.

    8. MEMichael Eisenberg1:04:26

       So, the idea, I think, as you pointed out, is seven to nine hours. And for men that are not getting that, semen quality tends to be lower. And then for men getting too much, um, we also see a decline. And, you know, why that is is, again, not certain. These... Again, if you're able to get that much sleep, maybe there's other things as well that we should look at. But, um... So, I think kind of getting in that ideal sleep amount is best for semen quality and probably for broad testicular function as well.

    9. AHAndrew Huberman1:04:54

       You keep bringing up semen quality, um, in a way that makes me wonder whether or not s-... Is semen quality a proxy for overall vitality and health? Or is testosterone level a proxy for overall vitality and health? Um, it sounds like semen quality is the, the metric that you keep coming back to in a way that, um, I have to assume reflects your, you know, your clinical experience and the, the, the many, um, papers that you've authored in this area. Um, I think for people that hear "semen quality" and who are not interested in conceiving children now or who are r-... W- which of course could include people who've already had children or who don't want children, um, semen quality sounds like something that relates to fertility. But is semen quality something that is a good goal for those who are interested in overall male vitality and health? Is it... Is it one of the better metrics of overall male vitality and health?

    10. MEMichael Eisenberg1:05:53

        Well, I think, you know, it's... I think it's an excellent marker for overall health. I think there are studies that support it can be a measure of how healthy you are. You know, if you look at e- men with more health problems, they can have lower semen quality. But also, if you look at semen quality just by itself and then you look into the future how these men tend to do, if they have higher semen quality, um, they tend to live longer, need to go to the doctor less, lower rates of cancer. So, I think there's a lot of different ways that semen quality may be a good barometer of health. Um, you know, it's... You know, why that link exists, I think, is not, is not known, but there's lots of theories. So, one is that, you know, probably about 10% of the male genome is devoted to reproduction. Um, and so it makes sense given that we only have about, you know, 24,000 genes in the body, that there's a lot of, um, you know, overlap. So, one gene that plays a role in reproduction may play a role in, you know, the cardiovascular system or, uh, the neurological system. And so, if we get the first, you know, sort of sign that reproduction is not perfect, there may be some other health consequences down the line.Um, another sort of hypothesis is that, again, sort of going along this line that reproduction is one of the first things that we see, is that, um, you know, gestation is sort of very critical to our, you know, existence, right? You know, perturbations to that system have prolonged, um, you know, effects, sort of the so-called sort of developmental origin of adult disease, or the Barker hypothesis. Um, and so we know that, you know, premature children have higher risk of cardiovascular disease. There have been studies to show that. But we also know that, you know, these gestational effects can also, uh, play out on reproductive function too. So that also may be kind of a link, you know, sort of early seeding of reproductive function, and then that's maybe the first marker that we're going to have for other health effects later on. Um, there are also just sort of, sort of inherent, um, sort of similarities between, um, reproduction and some other sort of social effects. So you know, kind of one sort of confounding factor when we're looking at some of these studies, I talked about looking at mortality, for example, and semen quality, is that, you know, there's sort of factors that necessarily involve reproduction, so your children and having a partner. And having a partner prolongs life. Um, having kids prolong life. Even though it feels like kids are killing you, if you look at studies, men with kids tend to live longer. Um, so you know, that's another possible explanation. But I think, you know, really sort of this health, um, you know, link between fertility, I think, is sort of a powerful one. So I do think it should be a barometer. I think that, you know, it should be a, sort of, when I've given lectures on this, I call it the sixth vital sign. I think it's something that we should probably check, because if there is, you know, sort of lower levels, that may tell us about something else going on. You know, when, when men come in for infertility evaluations, a lot of time we do diagnose, you know, these new medical problems. Sometimes we diagnose cancer, you know, sort of alluding to some of the questions that you've asked, diabetes and some other, you know, very significant genetic conditions as well. And you know, the first way that we would identify it is reproductive failure because their sperm counts are low, um, and, and other things. So it is something, I think, that it, it's sort of, it's very important, I think, for people to realize, um, and it would be great, I think, you know, another, um, I think, advantage to, like, the Centers for Disease Control, for example, to, to start tracking it.

16. 1:09:19 – 1:13:21

    Tool: Sperm Analysis & Overall Health; Sperm Banking

    1. MEMichael Eisenberg1:09:19

    2. AHAndrew Huberman1:09:19

       Would it be a good idea for, um, males in their 20s and 30s to get a sperm analysis just to have a baseline? I confess, I'm 47 now. Um, one thing I wish I had done in my 20s was to get my, uh, blood hormone profiles and lipid profiles done when I was in my teens and 20s, because I'd have something to compare to. Um, I started doing that in my mid-30s, and I'm so glad I did because I can now compare to my mid-30s levels. I started including, um, sperm analysis about eight years ago, um, with the intention of freezing sperm, and I did that, um, because I was also reading at that time about the increased risk of autism, um, in offspring of males older than 40, something that I really would like your take on. But, um, it seems like it's inexpensive enough to do a sperm analysis. Um, I think now they, people can get it done at home. They have mail, mail kits. Although I don't understand how the motility could be maintained if you're mailing your sperm back, um, at room temperature or, you know, it's heading through the post office. Now everyone's imagining all these sperm traveling through the, the postal service.

    3. MEMichael Eisenberg1:10:23

       (laughs)

    4. AHAndrew Huberman1:10:23

       It's out, they're out there folks. Um, yeah. What, what are your thoughts? Should, um, should people invest the, I think it was a couple hundred dollars to get a, a sperm analysis, more, um, costly to get the DNA fragmentation, then you get up into the low thousands. Um, but if people have the disposable income, is it a good idea for them to do?

    5. MEMichael Eisenberg1:10:44

       I mean, I think it's a worthwhile test. I think more information is always good. Um, you know, I think sort of one of the same reasons that, um, you know, you're talking about checking, like, lipid levels or we tell, you know, men and women to get blood pressure checked. I think, you know, getting that sort of early health indicator I think can be important. I think, you know, going back to not knowing exactly why semen quality is telling us about health, what the exact link may be, you know, means that if somebody is coming in with a low sperm count or completely absent sperm count, it's hard to know exactly how to counsel that, that person other than there may be re- reproductive difficulties. Um, but I think just as sort of a marker for reproductive potential, I think it's useful. And like you said, I think it's become a lot easier. One of the sort of innovations in the space, um, and you know, as somebody that, you know, is in the reproductive world, I think it's just really great to see sort of this influx in capital and new companies coming in that try to just decrease the barrier to, you know, getting a semen test. It used to be you have to go to a lab, schedule an appointment. Sometimes they would send you to a bathroom, which can be uncomfortable, you know, 'cause people are doing, you know, you know what people do in a bathroom just next to you while you're trying to collect a sample.

    6. AHAndrew Huberman1:11:50

       Oh, they would send them into a, in a common space bathroom.

    7. MEMichael Eisenberg1:11:52

       A common space bathroom, yeah.

    8. AHAndrew Huberman1:11:53

       They wouldn't even give them the quiet room with the, with the red light, which is, uh ...

    9. MEMichael Eisenberg1:11:57

       Right. Well-

    10. AHAndrew Huberman1:11:57

        What I hear they do now. Yeah.

    11. MEMichael Eisenberg1:11:59

        Some of them do have video, so there are some higher level

    12. AHAndrew Huberman1:12:01

        ... Oh, I didn't even mean videos.

    13. MEMichael Eisenberg1:12:03

        ... more comfortable ones.

    14. AHAndrew Huberman1:12:03

        I just, I, I think that, um ... Okay, yes, I've done this. I'll just say, I mean, I'm trying to normalize things related to a- all aspects of mental health, physical health.

    15. MEMichael Eisenberg1:12:11

        Mm-hmm.

    16. AHAndrew Huberman1:12:12

        Um, so, um, yeah. I, I decided to freeze sperm, and basically they sent me to a room. I went to a university-based clinic.

    17. MEMichael Eisenberg1:12:19

        Mm-hmm.

    18. AHAndrew Huberman1:12:19

        It actually wasn't Stanford, but a different university. And, um, uh, yeah, they put the cup through the window. They give you the cup. They, um, they close the door and they tell you that as long as that red light is on over the door, no one's going to walk in.

    19. MEMichael Eisenberg1:12:32

        Mm-hmm.

    20. AHAndrew Huberman1:12:32

        And then they leave. And I think the, the assumption now is that, uh, you figure it out one way or another, um, how to provide the sample, and then you put the sample back through the, the thing. And then one thing these clinics really need to work out is that any time you're walking out, you, you see the people processing your sample as you walk out. So there's all this, um-... this, uh, feigning of, of, uh, you know, anonymity. But really, it isn't there, you know.

    21. MEMichael Eisenberg1:12:56

        Right.

    22. AHAndrew Huberman1:12:56

        'Cause they're like, "See you later."

    23. MEMichael Eisenberg1:12:57

        (laughs)

    24. AHAndrew Huberman1:12:57

        And you're like, "Great." You know? Did you ... You know, they, they rarely ask you questions on the way out. But it's a pretty simple process overall. And, um, and I must say that the, the data, uh, are informative.

    25. MEMichael Eisenberg1:13:07

        Mm-hmm.

    26. AHAndrew Huberman1:13:08

        You get the, you know, you get the volume, number, motile, forwardly motile. I did opt for the DNA fragmentation, um, data, um, and I, I just love data, so I think it's really interesting. But again, um,

17. 1:13:21 – 1:26:42

    Paternal Age & Puberty Trends; Older Fathers & Child Health Risk

    1. AHAndrew Huberman1:13:21

       and maybe this is a good time to flag this, what, this set of findings, I believe that there seems to be a small but statistically significant increase in the number of autistic births due to, uh, pregnancies where the male was over 40 at the time of, um, of, uh, conception. Um, so I figured, you know, why not freeze some sperm and it's relatively inexpensive. Yeah.

    2. MEMichael Eisenberg1:13:44

       Yeah. So I think paternal age is also, you know, something that's increasing in this country. So over the last 40 years or so, we've seen that the average paternal age has increased from about 27 and a half to about 31. Um, and I should say that this is all fathers. So, um, birth certificate data or birth data is collected at a maternal level. So, you know, when a child is born, somebody comes in to collect data on the birth. So they ask, you know, all the characteristics of the mother, and they also ask characteristics of the father, you know, age, education, obviously region of the country the child was born. Um, so we don't know, you know, what number child that was for the father. We know it for the mother, they do ask, you know, "Is this your first, second, third," et cetera, "child?" Um, so the father, unfortunately, we just have data that's sort of all lumped together. Um, but over the last, again, 40 years, we've seen that increase. Interesting, over the last 40 years, the youngest father was 11 and the oldest was 88.

    3. AHAndrew Huberman1:14:38

       11?

    4. MEMichael Eisenberg1:14:38

       Quite a span, yeah.

    5. AHAndrew Huberman1:14:39

       88?

    6. MEMichael Eisenberg1:14:40

       Mm-hmm.

    7. AHAndrew Huberman1:14:41

       Goodness. Unrelated?

    8. MEMichael Eisenberg1:14:43

       I, I don't know.

    9. AHAndrew Huberman1:14:44

       (laughs)

    10. MEMichael Eisenberg1:14:44

        I assume. I assume.

    11. AHAndrew Huberman1:14:45

        (laughs) Goodness.

    12. MEMichael Eisenberg1:14:45

        It's anonymized data, but I assume.

    13. AHAndrew Huberman1:14:47

        11. Uh, I have to ask this. Sorry to, uh, take us, uh, on a slight tangent, but what is the average age of puberty in males in the United States, um, now?

    14. MEMichael Eisenberg1:14:59

        Yeah, so you're asking about I guess sort of super marquee, when like sperm production begins.

    15. AHAndrew Huberman1:15:03

        Mm-hmm.

    16. MEMichael Eisenberg1:15:04

        So, um-

    17. AHAndrew Huberman1:15:04

        Yeah, there are a lot of markers of, of puberty.

    18. MEMichael Eisenberg1:15:07

        Yeah.

    19. AHAndrew Huberman1:15:07

        Secondary sexual characteristics, beard growth, deepening of voice, et cetera.

    20. MEMichael Eisenberg1:15:09

        Mm-hmm.

    21. AHAndrew Huberman1:15:09

        They happen at different rates in different people. But yeah, thank you. Um, at what point, um, are, um, yeah, males undergoing puberty-

    22. MEMichael Eisenberg1:15:17

        Yeah.

    23. AHAndrew Huberman1:15:17

        ... uh, at the, at the level of, of, that we're talking about here?

    24. MEMichael Eisenberg1:15:21

        Yeah, so it's, yeah, there has been data that we're going through puberty a little bit earlier now than we used to. Um, but it really varies. So you don't, I think it's not, um, you know, just like testosterone ranges between like 300 and 900, that's a wide range for anybody. I think for most individuals, you know, puberty is, you know, probably 12 to kind of 15, 16 in general. So I just give sort of a very wide range when we're going to say that's okay. And, you know, some of the data I'm basing it on is, um, when sperm production begins in boys. And it's actually, you know, not that simple to be able to figure that out because, you know, we don't generally talk to, you know, young boys about how to masturbate, how to collect and then check on that. But there's something called first morning voided urine where we can actually look at that, and there have been some studies done, and they see if there were sort of, you know, nocturnal emissions, whether there's sperm in there. And so generally, it probably starts around, um, the earliest would be kind of 11, 12, 13, but usually most is probably a little later. So maybe I'll refine that puberty and move it a little bit later, probably 14 to 16, um, is when probably about 70, 80% of boys are going to have produced, started producing sperm.

Episode duration: 2:37:13