How to Control Your Metabolism by Thyroid & Growth Hormone

High-Level Overview

In this Essentials episode, Andrew Huberman focuses on the two hormone systems he considers most important for setting overall metabolism: thyroid hormone and growth hormone. He defines metabolism broadly, not as eating, but as the use of energy in the body's cells for growing tissue, repairing it and maintaining daily function, including brain function across the lifespan. A healthy, reasonably high metabolism, he argues, means more lean tissue, bone and muscle and less fat, and as he puts it, "metabolism isn't just about losing weight."

The tone is clear and teacherly, with Huberman repeatedly simplifying the hormone cascades into easy rules and giving specific numbers and precautions. The conversation moves from how the brain controls hormone release, to nutrients the thyroid needs, then to growth hormone and the behavioral and supplement tools that raise it, from sleep and meditation to exercise, arginine and sauna, and ends with a cautious look at peptides like sermorelin.

The Discussion Explores:

• The brain-to-pituitary-to-gland logic of releasing hormones and stimulating hormones
• What thyroid hormone (T3) does for fat burning, glucose use, bone and tissue repair
• Iodine, L-tyrosine and selenium as the building blocks of thyroid hormone, with food sources
• Growth hormone's role in repair and body composition, its decline with age, and the risks of injecting it
• Deep slow-wave sleep, low bedtime blood sugar and meditation as triggers for growth hormone
• Exercise, warm-up, cool-down and arginine protocols that raise growth hormone 300 to 500 percent
• Sauna protocols that increased growth hormone up to 16-fold, and the safety caveats
• Peptides such as sermorelin and why they carry real risks

Deep Dive into Main Ideas

The Brain Controls the Hormone Cascade

Huberman starts with a simple rule for reading hormone names. Neurons in the hypothalamus, at the base of the brain roughly above the roof of the mouth, release releasing hormones. These act on the pituitary, which releases stimulating hormones into the bloodstream, which then prompt a target gland to act. For the thyroid, thyroid-releasing hormone from the brain tells the pituitary to release thyroid-stimulating hormone, which tells the thyroid, a small butterfly-shaped gland around the Adam's apple, to release T4 and T3. He tells listeners they can largely forget about T4; T3 is the active form.

Growth hormone follows exactly the same logic: growth hormone-releasing hormone from the brain tells the pituitary to release growth hormone, which acts on muscle, ligaments, bone, fat and other tissues. The two systems overlap so much that Huberman groups them together in one episode.

What Thyroid Hormone Does

T3 promotes metabolism in the full sense of using energy, including building tissues. It acts on muscle, liver, cartilage and bone; it helps break fats into fatty acids and turn them into ATP, the cell's energy currency; it helps turn sugars into energy; and it liberates fat from white fat cells to be burned. That is why higher thyroid levels are associated with leaner bodies and lower levels with less lean ones.

Thyroid also increases glucose uptake into tissues, especially muscle and bone, and can increase bone mineral density, which matters more from about age 30 onward. Because it directs energy toward bone, muscle and cartilage repair, a healthy thyroid helps people recover faster from injuries, and it supports the brain's ability to use glucose or ketones. For people concerned about thyroid levels that are too high or too low, Huberman urges looking up the symptoms and seeing a physician, noting that prescription thyroid hormone, drugs that block receptors or pathways, and even removal of the gland are the big-gun treatments. His focus, though, is keeping healthy levels through diet and supplementation.

Iodine, L-Tyrosine and Selenium

The thyroid needs three raw ingredients. Iodine, found in sea salt, kelp, seaweed and almost all table salt, combines with the amino acid L-tyrosine, found in meat, nuts and some plant sources, to make T3 and T4. The third ingredient, selenium, is needed for iodine and L-tyrosine to interact properly, and Huberman believes most people don't get enough because they don't eat selenium-rich foods.

Recommended selenium intake varies by country, from 100 to 200 micrograms, averaging about 155 micrograms in the countries he looked at, and far lower for children 14 and under, around 30 to 40 micrograms. "Brazil nuts are the heavyweight champion of foods to get selenium from": six or eight contain about 550 micrograms. Ham and pork are also rich sources, while beef, turkey, chicken, cottage cheese, eggs and brown rice contain around 30 to 50 micrograms per serving. People eating little animal food and no Brazil nuts may be falling short, and those taking a multivitamin should make sure they aren't overdoing it. He notes that highly processed diets may leave many people short on these nutrients.

Growth Hormone, Aging and the Risks of Injecting It

During puberty the pituitary churns out growth hormone, driving growth including height. As we age we make less, which helps explain slower injury recovery, fat gain and a slowing metabolism. Huberman notes that between ages 30 and 40, nightly growth hormone release drops two- to three-fold. This has made growth hormone replacement therapy very popular over the last 20 years.

But he warns of its main problem: too much growth hormone causes growth of all tissues, not just muscle, including the heart, lungs, liver and spleen. That is the concern with abuse. The good news is that there are actionable tools that can raise growth hormone three, four or five hundred percent or more for short periods, with powerful effects on metabolism and tissue repair. He advises talking to a doctor before starting or stopping anything.

Sleep, Bedtime Eating and Meditation

Growth hormone is released every night early in sleep, during deep slow-wave sleep. Two conditions must be met: you need to reach slow-wave sleep, and blood insulin and glucose need to be relatively low, so eating within two hours of bed suppresses growth hormone release. What actually triggers the pituitary is delta wave activity, the big sweeping brain waves characteristic of slow-wave sleep.

That insight opens a waking option. Huberman points to the book Altered Traits by Goleman and Davidson, which describes how meditation changes both passing states and, over time, lasting traits. Certain types of meditation can bring the brain into states that closely mimic slow-wave sleep, with delta-type activity, which may be beneficial for people wanting more growth hormone because those brain waves, not just the time of day, gate its release.

Exercise and Arginine

Across hundreds if not thousands of studies, exercise reliably increases growth hormone both during or after exercise and the following night, but only with the right duration and intensity. Huberman's distilled protocol: weight training or endurance training limited to about 60 minutes; a roughly 10-minute warm-up that actually warms the body, since body temperature seems to be a prerequisite; and, for weights, getting close to the final reps you can't complete without pushing through to failure. That produced 300 to 500 percent increases in growth hormone, plus similar increases the following night. Low blood glucose matters: a sugary sports drink flatlined growth hormone. And cooling the body back to normal fairly quickly afterward was linked to the second spike; exercising too long or staying hot too long lost the nighttime increase.

The amino acid arginine can raise growth hormone by 400 to 600 percent above baseline, whether taken by mouth or intravenously, typically at 3 to 10 grams before bed or exercise, again with low blood glucose. But "this is definitely a case of more is not better": above 9 grams the effect is blunted, and large doses can cause stomach upset and nausea. Importantly, arginine and exercise don't stack; combining them still caps out around 300 to 500 percent. Huberman finds it encouraging that behaviors alone, exercise, not eating close to bed and good sleep, can potentially offset the two- to three-fold age-related decline.

Sauna: Up to a 16-Fold Increase

The hypothalamus regulates temperature as well as growth hormone, and the growth hormone-releasing neurons may sit close to or intermixed with temperature-regulating neurons. Warming the body raises growth hormone, and the effects of deliberate heat are dramatic. Short sessions of 20 to 30 minutes at 80 to 100 degrees Celsius have been reported to raise growth hormone 16-fold. In a study of 17 people doing repeated sauna, a pattern of 20 minutes in the sauna, 30 minutes of cooling, and 20 minutes in again produced a five-fold increase, and repeating it on three consecutive days led to increases of up to 16-fold. Other hormones such as prolactin and cortisol changed too.

Huberman is emphatic about the risk: it takes only a small rise in brain temperature to damage neurons permanently, and people can die from hyperthermia. Not everyone should do this, and he says to "proceed with extreme caution."

Peptides and Sermorelin

Finally, Huberman addresses peptides, not to encourage them but because they are increasingly used. Peptides are short strings of amino acids, and some resemble a hormone closely enough to mimic its effects. Sermorelin, a prescription drug, is a partial sequence of growth hormone-releasing hormone that acts as a secretagogue, prompting the pituitary to release growth hormone rather than supplying it directly.

Do they work? Yes. But they can shut down the body's own production of growth hormone-releasing hormone, and unlike short, transient spikes from exercise, arginine or sauna, repeated injections that keep levels constant can trigger long-lived gene expression changes. Tumors, too, grow when exposed to growth hormone. His goal is simply that listeners understand the biology well enough to think rationally about whether such compounds are right for them.

Conclusion

Huberman's takeaway is that thyroid hormone and growth hormone are the master dials of metabolism, deciding how the body uses nutrients, draws on fat, repairs muscle, bone and cartilage, and supports the brain. Both follow the same brain-to-pituitary-to-tissue logic, and both can be supported with straightforward habits. For thyroid, that means getting enough iodine, L-tyrosine and especially selenium, for example from Brazil nuts or animal foods. For growth hormone, it means protecting deep early-night sleep and not eating within two hours of bed, exercising for up to about an hour with a real warm-up and a prompt cool-down, and possibly using arginine or carefully managed sauna sessions. These behaviors may even offset the steep decline in growth hormone that begins in our 30s, while injected hormones and peptides come with risks worth understanding before anyone considers them.

This is a summary of "How to Control Your Metabolism by Thyroid & Growth Hormone" from Huberman Lab, giving you the GIST so you can decide if you want the REST. Listen to the full episode.