Overview
T3 (triiodothyronine) is the active thyroid hormone, the molecule that actually drives oxidative metabolism in every cell. The thyroid gland itself secretes a roughly three-to-one ratio of T4 to T3, but about two-thirds of the T3 circulating in the body is produced in the liver from T4, and that conversion requires glucose and selenium. Stress, estrogen, polyunsaturated fats, fasting, and aerobic exercise all interfere with that conversion and can divert T4 into reverse T3, which blocks the active hormone (T3) at the receptor. The original 1940s thyroid studies were done on healthy male medical students whose livers converted T4 perfectly, which is why doctors still default to T4-only prescriptions like Synthroid; in women, with their higher estrogen and more strained livers, this can produce or worsen hypothyroidism rather than treat it. T3 in physiological amounts (one to four micrograms per hour, taken with food in small doses through the day) is the most direct way to restore metabolism, and it can resolve very serious symptoms like myxedema coma, arrhythmias, insomnia, breast pain, or arthritic pain within minutes.
Key Points
-
T3 is the active thyroid hormone, and the liver makes most of it. The thyroid gland secretes about three parts T4 to one part T3. Roughly two-thirds of the active T3 in circulation is produced by the liver converting T4. Selenium is the essential mineral cofactor for this conversion and glucose is the essential fuel. Without enough sugar in the liver, the conversion fails and T3 production crashes within hours.
-
T4-only prescriptions can fail or worsen hypothyroidism, especially in women. Women have five to ten times the incidence of thyroid problems because estrogen interferes with both the thyroid gland's secretion and the liver's T4 to T3 conversion. Ray observed a hypothyroid woman whose dose was raised from 100 to 500 micrograms of T4 only over months, growing progressively worse until she went into a myxedema coma; she came out of the coma immediately when given intravenous T3.
-
Stress turns T4 into reverse T3, which blocks the active hormone at the receptor. Cortisol, adrenaline, estrogen, hypoxia, lactic acid, and inflammation all shift T4 metabolism toward reverse T3 instead of T3. Reverse T3 occupies the same receptor site as T3 and competes against it, and even excess T4 can outcompete T3 if there is too much of it. A stressed person can have a normal T4 level on a blood test while being functionally hypothyroid because most of that T4 is being routed into the inactive blocking form.
-
T3 should be taken in small doses spread throughout the day, not in one morning dose. A normal body produces roughly four to five micrograms of T3 per hour, or about 50 micrograms total per day. Taking 25 micrograms on an empty stomach in the morning gives a dose roughly 25 times higher than physiological at that moment, which the body perceives as toxic and the liver responds by upregulating excretory enzymes. After a couple of weeks of this pattern, the liver begins clearing T3 so fast that by 12 to 15 hours later the person is experiencing extreme hypothyroidism, sometimes with heart arrhythmias. Eight to ten micrograms with each meal plus five to ten at bedtime works much better, and food slows absorption to about two or three micrograms per hour.
-
T3 produces dramatic, near-instantaneous effects when needed. Insomnia can disappear five minutes after chewing a 10 microgram tablet. Arthritic pain or breast pain can stop within fifteen minutes. An interrupted heart rhythm can be restored to perfect rhythm in 15 seconds by chewing a tablet and absorbing it through the mouth. Cholesterol of 400 to 500 mg/dL can be brought down to the normal range of around 200 in a week using frequent small doses of about five micrograms per hour.
-
Every tissue can produce T3 locally, and fructose specifically activates this. Muscles, skin, kidneys, and brain all have the deiodinase enzymes to make T3 from T4 locally to supplement what arrives from the bloodstream. Glucose supports this, but fructose has a special ability to activate local tissue T3 production, which is one of the reasons orange juice and other fruit throughout the day support metabolism.
-
Polyunsaturated fats block thyroid hormone at every step. PUFAs inhibit the proteolytic enzyme that releases hormone from the thyroid gland, inhibit transport on blood proteins, and inhibit the cellular response to T3 inside the cell. The blockade is proportional to the number of double bonds: linoleic acid with two double bonds inhibits transport about 30%, three double bonds about 50%, and fish oils with five and six double bonds are nearly total inhibitors. After the age of 45, the body is "really soaked" in PUFA and tissues become resistant to thyroid, even with adequate hormone levels.
-
Temperature and pulse are more reliable than blood tests for assessing thyroid function. A working metabolism produces a temperature of around 37°C (98.6°F) and a pulse of roughly 80 to 85 by the middle of the day. Temperature and pulse rising after a good meal indicate functional T3 production; temperature falling after breakfast indicates the metabolism was being held up by stress hormones. TSH should be kept below 1, and George Crile at the Cleveland Clinic in the 1970s found that a TSH near zero kept down almost all recurrences of thyroid cancer.
-
The historical natural desiccated thyroid standard is up to three grains daily, divided across the day. One grain contains about 38 to 40 micrograms of T4 and 8 to 10 micrograms of T3. Dr Broda Barnes and other clinicians who studied this established that up to three grains was, for the most part, the upper end of what produces a healthy effect. Anything beyond that points to a problem preventing T3 from working: liver disease, diabetes, cancer, or another condition that is increasing T3 deactivation.
-
Carbohydrates and protein are required for proper T3 conversion. Adequate protein is needed for liver function, and without proper liver function T4 cannot be converted into T3. Sugar is needed for the synthesis of thyroid hormone itself. Saturated fat, particularly medium chain triglycerides like coconut oil, helps T3 actually get into cells.
Notable Quotes
"T3 is the essential active thyroid hormone. And under stress, T4 is converted to reverse T3, which interferes. So you can't at all interpret thyroid function with T4 and TSH."
[Ray Peat — Ask Your Herb Doctor (KMUD): The Metabolism of Cancer]
"I experimented on myself taking 25 micrograms at a time, and after two or three weeks of doing that, 12 hours later, if I didn't take another dose, I would go into a very intense hypothyroid state with my heart stopping every six seconds or so. And, 30 seconds after I took more T3, that would get regular again."
[Ray Peat — Ask Your Herb Doctor (KMUD): Q and A 1]
"Avoiding polyunsaturated fat is very important because it blocks the activation of thyroid into T3."
[Ray Peat — Ask Your Herb Doctor (KMUD): Particles]
"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]
Important Things To Consider
A single 25 microgram dose on an empty stomach is dangerous after a couple of weeks. Ray developed an extremely erratic heart rhythm taking his T3 only in the morning, with his heart pausing every 10 seconds at sunset and once long enough to start blacking out with a shrinking visual field. The fix is to spread doses through the day with food. Cynomel and Cynoplus tablets contain about 25 to 30 micrograms of T3 per tablet, which is too much to take at one time on an empty stomach.
T3 should be approached gradually over two to three months, not by jumping straight to a target dose. Increase steadily while watching temperature and pulse, and adjust according to how you feel. People who jump to what they think is going to be their final dose are most likely to build up too much T4 (when using a combination product) and to experience swings.
Generic T3 tablets are unreliable for potency. Cynomel and Cynoplus tablets can be counted on for the labeled amount per tablet, but no generic Ray has tried has been reliably to the labeled potency. Even within a single tablet, the T3 may not be evenly distributed, so accuracy from splitting tiny fragments is more illusion than reality.
Fluoridated water can knock out an oral T3 dose. Ray developed a migraine within days while supplementing T3 in fluoridated San Francisco. If T3 is in the stomach at the same time as fluoridated water, the fluoride will bind and inactivate it. This effect continues to some extent as long as ionic fluoride is circulating in the body.
People with severely high adrenaline and cortisol can react badly when first taking thyroid. Long-standing hypothyroidism can produce extremely high adrenaline and cortisol; introducing thyroid into that state can transiently exaggerate the stress symptoms (pounding heart, weak muscles, high pulse) for upto a couple of weeks. Magnesium, pregnenolone, calcium, sugar, and protein support the transition. In extreme cases, people use sub-microgram doses for one to two weeks before increasing.
Heart attack patients should not take more than about one microgram of T3 at a time. People with cardiovascular fragility need a slow gradual increase in metabolism rather than the surge that comes with a normal dose, so individual doses are kept very low.
Aerobic exercise crashes T3 quickly. In one experiment, a moderate fast walk that kept the pulse around 119 to 120, barely borderline aerobic, dropped T3 close to zero after one hour. T3 recovered after rest in healthy people but the pattern means even moderate aerobic work routinely dismantles the active thyroid hormone.
T3 with natural desiccated thyroid behaves more gently than pure synthetic T3. When glandular (T4 and T3) thyroid is taken with food, some of it is not digested for hours and travels further down the intestine, so the absorption profile is gentler than a pure chemical bolus. This is why pure T3 demands more attention to timing than a balanced T3/T4 product like natural desiccated thyroid or Cynoplus.
Pulse and temperature can mislead when serotonin or adrenaline is high. Serotonin can inappropriately raise body temperature, particularly in carcinoid syndrome and clinical depression. Adrenaline can be elevated in hypothyroidism, producing high pulse and high temperature without genuine thyroid sufficiency. Cross-check with capnometry (exhaled CO2), bicarbonate testing, urination patterns (less urination is better) and the Achilles tendon reflex.
No one should supplement thyroid before reading at least one of Broda Barnes' books. Self-supplementing without understanding the basics produces predictable problems.
Where To Buy
Coming Soon.