Thyroid Stimulating Hormone (TSH)

Thyroid Stimulating Hormone (TSH) is a pituitary hormone whose elevation Ray Peat considered not merely a marker of hypothyroidism but a direct cause of tissue damage and inflammation. 2 Peat argued that all of the known effects of TSH are harmful, recommending that blood levels be driven as close to zero as possible for optimal health. 2 He maintained that the conventional laboratory reference ranges for TSH are historically arbitrary, derived from a meaningless protein-bound iodine test that falsely established that only 5% of the population could be hypothyroid. 2 This statistical artifact was then applied to the more precise TSH immunoassay, leading doctors to ignore traditional diagnostic signs like low body temperature and metabolic rate. 2

Peat detailed several direct pathogenic mechanisms of TSH. He noted that TSH itself can produce lipolysis, raising circulating free fatty acids, which suggests that a high TSH could contribute to functional hypothyroidism through the antimetabolic effects of unsaturated fatty acids. 2 He further explained that TSH activates inflammatory systems, acting on the bone marrow, liver, and other tissues to increase inflammatory cytokines, making it a fundamental problem in hypothyroidism. 2 Peat specifically refuted the medical argument against suppressing TSH to protect bone density, explaining that TSH, like estrogen, increases osteoprotegerin, a protein that despite its name is associated with bone loss and the movement of calcium into soft tissues. 7

The elevation of TSH is often a response to dietary and hormonal interferences with thyroid function. Peat identified that chronic consumption of thyroid-blocking foods, such as raw cabbage-family vegetables or polyunsaturated fats, forces the pituitary to drive the thyroid gland harder to compensate, leading to nodule formation and enlargement. 2 He also noted that estrogen inhibits the liver's ability to convert thyroxine (T4) into the active T3 hormone, which explains why women have a much higher incidence of thyroid disease and why TSH can become elevated during times of estrogen imbalance like puberty or menopause. 2 Danny Roddy has synthesized this perspective, noting that TSH increases in stress and aging and that even a small increase can cause the formation of mucopolysaccharides, which are associated with the initial stages of pattern baldness. 8

Peat consistently cited epidemiological evidence to support a lower optimal range for TSH. He referenced a study finding that a population with a TSH of 0.4 and below had the lowest incidence of thyroid cancer, while another study associated a "normal" TSH of 1.5 to 3.5 with developing fatal coronary heart disease. 3 From his own clinical observation, Peat stated he never saw a comfortably healthy person whose TSH was over 2.0, and that everyone he saw with a level of 4.5 had intense symptoms. 2 He cautioned that TSH is not a reliable standalone diagnostic tool because stress hormones like adrenaline and cortisol can lower TSH, creating a misleading picture of thyroid status. 10 Roddy has noted that the accepted normal range has been repeatedly revised downward over the decades, and that thyroid specialists at the University of California Medical Center in San Francisco prefer a corrected level around 0.2. 8