Thyroid — Ray Peat & Georgi Dinkov Summary

Overview

The thyroid is the master gland of metabolism. Its function is to energize every cell in the body to consume oxygen and produce carbon dioxide efficiently, which is what distinguishes complex animal life from a fungus or a plant. Almost every degenerative condition (heart disease, cancer, osteoporosis, depression, infertility, dementia, diabetes, autoimmune disease) traces back to insufficient active thyroid hormone, and almost any of them can be improved or reversed by restoring proper metabolic function. The medical industry has systematically falsified what we know about thyroid for nearly a century: replacing functional diagnostic methods with meaningless lab tests, pushing T4-only synthetic prescriptions that fail in women, removing thyroid from the food supply by law in 1940, and calling people "gluttons" whhen they were actually hypothyroid. Temperature, pulse, cholesterol, the speed of the Achilles reflex relaxation and the calories required to maintain weight are far more reliable indicators than TSH or T4 blood tests. The modern population is dramatically more hypothyroid than the medical system admits, largely because of polyunsaturated fats, estrogen exposure, and the destruction of dietary thyroid sources.

Key Points

Thyroid is the master regulator of energy production in every cell of the body. Plants, fungi, and amoebas don't need thyroid, but anything with organized animal life uses it. The basic function is to give cells enough energy and oxygen consumption to differentiate and perform their function rather than just eat and grow. If you remove the pituitary (the so-called "master gland") and give thyroid hormone, animals can live ten times longer than normal, showing thyroid is more fundamental than the pituitary.
The thyroid gland secretes about three parts T4 to one part T3, but the liver produces about two-thirds of the active hormone. When the liver senses enough fuel (especially glucose), it converts T4 (inactive form of thyroid) to T3 (active form of thyroid). Selenium is the critical mineral. Without enough sugar in the liver, T3 production crashes by 60 to 70% within hours. This is why fasting, low-carb diets and stress all suppress thyroid function within a single day, and why eating sugar throughout the day is more effective than supplementation alone.
TSH is a meaningless and even harmful diagnostic standard. TSH itself is an inflammation-promoting hormone, directly causing hypertension and tissue damage in blood vessels and bone marrow. Healthy populations without heart disease or cancer have a TSH below 0.4. Doctors have been instructed not to look at the physiological signs that traditionally identified hypothyroidism. The "normal" TSH range of 3 to 5 captures people who are clinically hypothyroid by every functional measure. Stress lowers TSH, so a stressed person with high cortisol can have near-zero TSH while their thyroid produces almost nothing.
Temperature, pulse, and the Achilles reflex are the reliable functional measures. A healthy waking temperature is around 97.8°F, rising to 98.6°F or higher after breakfast and staying there until sunset. A healthy resting pulse is 80 to 85 (one experiment of high schoolers found the highest grades averaged 85 bpm at rest). The Achilles reflex test: when you thump the achilles tendon with the person kneeling, the foot should flop back instantly like jelly. In hypothyroidism, the foot returns slowly like a door with a pneumatic closer, and the same delayed relaxation appears in the T-wave on an EKG.
T4-only prescriptions like Synthroid frequently fail in women. When synthetic T4 was tested in the 1940s, the trial subjects were two dozen male medical students aged 20 to 22, who had perfect liver function. Women have five to ten times the rate of thyroid problems because estrogen interferes at every step: blocking the proteolytic enzyme that releases hormone from the gland, blocking the liver's T4-to-T3 conversion, and driving up TSH which pushes the gland to enlarge and become "Hashimoto's." Pure T4 in these women can suppress the small amount of T3 their gland is making while not adding usable hormone, making them progressively more hypothyroid as the dose is raised.
Polyunsaturated fats block thyroid at every level. PUFAs inhibit the proteolytic enzyme that releases hormone from the gland, block transport on blood proteins, and block the cellular response to T3 inside cells. The blockade is proportional to the number of double bonds: linoleic acid blocks transport about 30%, longer chain PUFAs can block up to nearly 100%. This makes PUFA the single most important environmental cause of hypothyroidism over the last 50 years. Coconut oil acts as an antidote because the short and medium chain saturated fats compete against PUFA in the mitochondria and produce energy quickly.
Hypothyroidism produces lactic acid even at rest, which causes systemic inflammation. A hypothyroid person sitting still produces lactic acid as if they were exercising hard, because they cannot oxidize sugar all the way to CO2. The lactic acid then triggers histamine, serotonin, fibrosis, calcification of soft tissues, hardening of arteries, arthritis, and heart failure. The thyroid produces a high CO2-to-O2 ratio that suppresses lactic acid; when thyroid is low, the cell stays in an inflammatory excited state because there is not enough CO2 to carry calcium out of cells.
Estrogen, polyunsaturated fats, and a sluggish liver create a vicious circle that reinforces hypothyroidism. Estrogen blocks the gland's secretion, blocks T4 to T3 conversion, and drives TSH up. The hypothyroid liver fails to detoxify estrogen, which then accumulates further and slows the liver more. The liver also fails to detoxify endotoxin from the intestine, which itself activates serotonin, which raises TSH and prolactin, and lowers thyroid further. Breaking the circle anywhere (raw carrot daily, antibiotics in extreme cases, thyroid supplementation, eliminating PUFA) tends to unwind the others.
Most cases benefit from a combined T3/T4 supplement, not pure T3 or pure T4. Pure T3 alone produces extreme swings: TSH crashes overnight and rebounds with inflammatory effects. Pure T4 alone may not be converted to T3 in stressed or estrogen-loaded people. The natural ratio coming out of the gland is about three or four to one T4 to T3; products like Cynoplus, Thyrolar, or Armour replicate this. Broda Barnes typically used about two grains of Armour, starting at half a grain (30 milligrams) and watching temperature over weeks before increasing.
Endocrine disruptors like BPA and phthalates are direct thyroid receptor antagonists while simultaneously acting as estrogen agonists. BPA is more estrogenic than estradiol itself. These compounds block thyroid function while activating the stress and growth pathways, which is the worst possible combination. They are also carcinogenic and pro-inflammatory. Vitamin E and progesterone displace BPA from cell receptors and partly mitigate the damage.

Notable Quotes

"The basic function of thyroid is to energize cells and to give them enough energy and efficiency to allow them to differentiate so that they don't just concentrate on eating and growing the way plants and amoebas and fungi and such do."

[Ray Peat — Ask Your Herb Doctor (KMUD): The Thyroid]

"When you have enough actual thyroid hormone to completely shut down your pituitary, you turn off practically all of these toxic inflammatory processes."

[Ray Peat — Ask Your Herb Doctor (KMUD): The Thyroid]

"If you have, say, a 500 milligram cholesterol blood level, that's considered very high. You can bring it down in a week to 200 or 180 by giving frequent small doses of a quick-acting thyroid (T3)."

[Ray Peat — Cholesterol and Saturated Fats]

"About 10 years ago, I started hearing people telling me that their doctors had diagnosed them as being both hyperthyroid and hypothyroid at the very same moment (used as an example to show doctors' confusion around thyroid)."

[Ray Peat — Ask Your Herb Doctor (KMUD): The Thyroid]

"Up to about 50 years ago, obesity used to be treated by giving people thyroid hormone. It wasn't treated by making people run on a treadmill."

[Georgi Dinkov — Interview on metabolism and weight]

"If your TSH is above two, you are not healthy. It does not matter that your TSH is in range."

[Georgi Dinkov — Interview on thyroid and metabolism]

"What really keeps us humans and in the shape of a human is thyroid hormone."

[Georgi Dinkov — Interview on cancer and metabolism]

Important Things To Consider

Thyroid was legally removed from the American food supply in 1940. Slaughterhouses are required to take out thyroid glands, while most cultures historically got a small amount of supplemental animal thyroid through soup, sausage, blood, or organ meat. This was never standard supplementation, just a normal part of a diet that included whole animals. Cow's milk still contains a moderate helpful amount of thyroid hormone, which is one of several reasons milk is a valuable part of the diet.

The 1940s synthetic-thyroid marketing campaign convinced doctors that 95% of the population is not hypothyroid. Before that, using oxygen consumption and temperature as standards, about 40% of Americans would have qualified as hypothyroid. The first lab test sold to support this new prescribing was protein-bound iodine, which was eventually shown to have nothing to do with thyroid function. By then doctors had been trained for 15 years to use it. TSH replaced it but kept the same arbitrary cutoff that very few people are hypothyroid.

Doctors sometimes diagnose people as both hyperthyroid and hypothyroid simultaneously, which is incoherent. This typically happens because estrogen and a stressed liver are blocking T4-to-T3 conversion, so a woman taking T4 has high T4 in the blood (suppressing TSH and looking "hyperthyroid") while functionally having very low active hormone (looking "hypothyroid" by symptoms). The fix is T3 in physiological doses, not removing or destroying the gland.

Doctors will frequently destroy a normally adapting thyroid gland. When the gland is enlarged and storing colloid because of estrogen blockade, the natural recovery process (when estrogen drops and the stored hormone is released over a few weeks) produces a temporary state with pulse around 125, warm pink hands, and a feeling of well-being. People have told Ray they never felt better in their life during this phase. Doctors interpret it as hyperthyroidism and either remove the gland surgically or destroy it with radioactive iodine.

Don't start a thyroid supplement at full force if cholesterol is already low. Thyroid converts cholesterol into bile acids, pregnenolone, progesterone, and DHEA, so very low cholesterol must be corrected first with sugar (especially fruit) before significant thyroid is added. Below about 160 mg/dL is the danger zone; very low cholesterol is associated with increased mortality from cancer, accidents, suicide, and homicide.

Pulse and temperature can be misleadingly high due to stress hormones. Serotonin can inappropriately raise temperature, especially in carcinoid syndrome and clinical depression. Adrenaline can keep pulse elevated even when thyroid is low. So pulse and temperature alone are not enough; the pattern matters. A high waking pulse that drops after eating is a sign of running on stress hormones, not thyroid. A healthy pattern is a moderate waking pulse that rises after a meal as the body shifts from cortisol to thyroid as the dominant signal.

Women with an enlarged thyroid should not take progesterone until the enlargement has resolved. Progesterone activates the proteins that allow the thyroid to secrete its stored colloid, which can produce a temporary hyperthyroid state for a few weeks. It's better to address the root cause first.

A daily raw carrot supports the thyroid by clearing intestinal endotoxin and reabsorbed estrogen. Shred it lengthwise (not in a blender), with a few drops of vinegar, a teaspoon of olive or coconut oil, and a pinch of salt. Within three to four days, blood tests can show drops in estrogen and cortisol, and rises in progesterone. The carrot's antifungal and antibacterial fibers act like a mild antibiotic on the intestine. Use raw carrots specifically; cooked carrot loses its antiseptic effect and the absorbed carotene can itself be antithyroid.

Hyperthyroid symptoms (sometimes a normal phase of recovery) can be slowed with cabbage juice if needed to keep doctors at bay. This is mostly to manage the doctor relationship rather than for the person's own health, since the supposedly hyperthyroid state often feels excellent and represents the gland releasing stored hormone.

Thyroid supplementation is not pure speed or stimulation; it should produce calmness and deep sleep. People with low thyroid usually have insomnia or shallow sleep, often with adrenaline up to 40 times the normal level. Taking the right amount of thyroid can bring on deep sleep, sometimes within minutes. If thyroid feels stimulating like adrenaline or speed, the dose is wrong, the protocol is wrong, or stress hormones are too high to begin with (they often reduce after 2 weeks of thyroid).

The "grain" measurement is messy and product-dependent. A grain is technically 62.5 milligrams. Cynoplus and Cynomel from the same Mexican manufacturer have been reliable for at least 30 years. Many generic versions of T3 have not been reliable to their labeled potency.

At high altitude, thyroid function tends to recover spontaneously. Around 8,000 to 10,000 feet near the equator, people lose unnecessary fat, the thyroid starts working properly and heart disease and dementia rates drop. Mountain climbers consistently report euphoria and well-being at altitude. Living at high altitude with a good diet can often be more effective than thyroid supplementation alone.

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