How to Control Your Metabolism by Thyroid & Growth Hormone | Huberman Lab Essentials

Thyroid hormone (T3) requires iodine and the amino acid L‑tyrosine, with selenium enabling their proper interaction in the thyroid gland. Most table salt is iodized, but selenium intake is often low, especially in people who avoid animal products and Brazil nuts. Reviewing your diet—sea salt/seaweed for iodine, some animal or plant protein for L‑tyrosine, and selenium-rich foods (Brazil nuts, fish, pork, beef, eggs, brown rice)—or a well-formulated multivitamin can help ensure adequate precursors for healthy thyroid function.

T3 increases glucose uptake in muscle and bone, promotes ATP production, and mobilizes fat from adipose tissue. This supports faster repair of muscle, cartilage, and bone and can increase bone mineral density from about age 30 onward. Ensuring healthy thyroid levels (via diet, sleep, and medical evaluation when needed) can therefore improve injury recovery and cognitive performance, not merely lean out body fat.

Growth hormone is naturally released in the early part of the night during slow-wave (delta) sleep, but elevated blood glucose and insulin blunt this release. Not eating—or at least avoiding significant caloric intake—within about two hours before bedtime helps keep insulin and glucose low, allowing a robust nocturnal spike in growth hormone that supports fat loss and tissue repair.

Both resistance and endurance training can raise growth hormone if structured properly: include ~10 minutes of true warm-up that raises core temperature, keep the hard work phase to about 60 minutes or less, and work near, but not beyond, muscular failure. Train with relatively low blood glucose (no sugary pre-workout or sports drinks), and allow body temperature to return to baseline afterward. This approach can increase growth hormone 3–5x both acutely and during the following night’s sleep.

Oral arginine (about 3–9 g taken with low blood glucose) can raise growth hormone levels by 400–600%, though higher doses often cause GI distress and can blunt the effect if exceeded. However, combining arginine with exercise does not create an additive effect; total growth hormone increase still clamps around 300–500%. Anyone considering high-dose arginine should account for total amino intake, potential side effects, and underlying health conditions.