Ray Peat on Thyroid

Short answer: The thyroid is the center of Ray Peat's work. He wrote that low thyroid function is far more common than blood tests show, that it should be judged by temperature, pulse and symptoms, and that the active hormone T3 depends on sugar and on the liver.

What Ray Peat wrote about the thyroid

He gave the TSH test only moderate weight. Stress, illness and other factors can hold TSH down while the tissues are short of thyroid hormone. Source: TSH, temperature, pulse rate, and other indicators in hypothyroidism

He followed Broda Barnes, who used the waking body temperature as the main sign, but added the pulse. He wrote that the two together are much better than either alone. Source: TSH, temperature, pulse rate, and other indicators in hypothyroidism

He tied thyroid to sugar. The conversion of T4 to active T3 needs glucose, the liver's T3 output depends on available glucose, and T3 protects the heart by supporting glucose oxidation. Source: Glycemia, starch, and sugar in context, Glucose and sucrose for diabetes

By a thyroid supplement he meant one that contains some T3, not T4 alone. Source: Multiple Sclerosis and other hormone related brain syndromes

He linked low thyroid to high serotonin, high estrogen, high cholesterol and insomnia. Rising cholesterol with age is, in his view, partly a compensation for falling thyroid function. Source: Serotonin, depression, and aggression: The problem of brain energy, Cholesterol, longevity, intelligence, and health, Thyroid, insomnia, and the insanities: Commonalities in disease, Natural Estrogens

Thyroid hormone keeps carbon dioxide production up, which protects against water retention and the loss of sodium and magnesium. Source: Water: swelling, tension, pain, fatigue, aging

In animal experiments on learned helplessness, T3 falls during the helpless state, and giving thyroid beforehand prevents it. Source: The dark side of stress (learned helplessness)

What he suggested in practice

• Track temperature and pulse together, not TSH alone.
• Measure after breakfast as well as on waking.
• Enough sugar and protein, since both are needed to make and activate the hormone.
• Liver about once a week: he calls it a rich source of vitamins that can suppress the thyroid if eaten more often.

Where he wrote about it

This topic comes up in 85 of the articles on his site. These are the most relevant ones:

• TSH, temperature, pulse rate, and other indicators in hypothyroidism · original on raypeat.com ↗
• Thyroid: Therapies, Confusion, and Fraud · original on raypeat.com ↗
• Water: swelling, tension, pain, fatigue, aging · original on raypeat.com ↗
• Osteoporosis, aging, tissue renewal, and product science · original on raypeat.com ↗
• The dark side of stress (learned helplessness) · original on raypeat.com ↗
• Natural Estrogens · original on raypeat.com ↗
• Thyroid, insomnia, and the insanities: Commonalities in disease · original on raypeat.com ↗
• Osteoporosis, harmful calcification, and nerve/muscle malfunctions · original on raypeat.com ↗

My take

Most people are hypothyroid to some degree. Cold hands, a low pulse, constipation and brain fog go together. I check pulse and temperature, and I think anyone with those signs should talk to a doctor about their thyroid.

Quick answers

How did Ray Peat test thyroid function?

With body temperature and resting pulse together, plus symptoms. He wrote that the TSH test deserves only moderate weight.

What did Ray Peat say about TSH?

That it can look normal or low in a person who is functionally hypothyroid, because stress and other factors suppress it.

What did Ray Peat mean by a thyroid supplement?

One that contains some T3, the active hormone.