Peat Archive

Thyroid function is arguably the most central concept in Ray Peat's framework. He viewed the thyroid as the master regulator of metabolic rate and cellular energy production. Peat argued that hypothyroidism is vastly underdiagnosed because standard TSH testing misses many cases of inadequate thyroid function at the cellular level. He emphasized that the active hormone T3 (triiodothyronine), not just T4 (thyroxine), is critical for health, and that many factors in modern life — polyunsaturated fats, estrogen, endotoxin, and stress — suppress thyroid function.

Peat advocated for the use of desiccated thyroid (Armour) or combinations of T4 and T3, rather than T4-only medications like Synthroid. He noted that adequate thyroid function is evident in warm hands and feet, a body temperature near 98.6°F (37°C), a pulse rate of 75-85, and overall vitality. He considered low body temperature, cold extremities, and morning fatigue as signs of functional hypothyroidism regardless of lab values.