Thyroid Medication (NDT)

Natural desiccated thyroid (NDT) is a glandular supplement derived from animal thyroid tissue, which Peat considered the most physiologically appropriate replacement for a missing or underactive gland because it provides the full spectrum of thyroid-related proteins and hormones. 2 The working human thyroid gland produces the equivalent of about 4 grains of desiccated thyroid per day, roughly 70% of which is the pro-hormone thyroxine (T4), allowing the liver to generate the active T3 hormone as needed when it is well-nourished and not inhibited by substances like polyunsaturated fats or estrogen. 1 Crucially, the glandular material itself does not contain free, active hormone; it is composed of thyroglobulin, a protein that releases T4 and T3 only upon digestion, which makes its absorption more gradual than that of pure synthetic hormones. 2

The pharmacokinetics of NDT differ sharply from isolated T3. Peat explained that taking even 10 micrograms of pure T3 at once signals the liver that it is being overdosed, triggering the production of enzymes that rapidly destroy the hormone. 2 Because NDT requires enzymatic breakdown, its hormonal release is inherently time-released, making it safer to take with meals and less likely to provoke this hepatic inactivation response. 2 Peat advised dividing the daily dose of desiccated thyroid, taking some with each meal and at bedtime, to prevent the blood level of active hormone from spiking too high at any single moment. 1 This contrasts with the common pharmaceutical advice to take thyroid on an empty stomach, a practice Peat noted had been promoted for over 50 years but was unnecessary for NDT. 4

Product quality and formulation are persistent concerns. Peat stated that most glandular products on the market are not what they claim to be, though he acknowledged that Armour thyroid, USP, currently seems acceptable. 6 He was highly critical of the industry, noting that thyroid supplements are often "compounded by crooks, morons, and pharmacists," and that the original Armour formula was altered after its acquisition by Revlon and subsequent companies, with the extraction of thyrocalcitonin for separate sale leaving little of the original substance intact. 7 Roddy and Littlewood have corroborated this variability, observing that brands like Nature-Throid and WP Thyroid experienced a noticeable drop in quality and effectiveness around 2019-2020, while the liquid NDT product Tyromax produced good responses for some users. 5 Dinkov has written that NDT occupies a legally murky status in the U.S., which has so far allowed vendors to operate, whereas isolated T3 is a controlled substance and clearly illegal to sell as a supplement. 9

For those unable to obtain reliable NDT, Peat recommended the Mexican pharmaceutical Cynoplus (also called Sinoplus), a synthetic tablet with a 4:1 ratio of T4 to T3, which he described as the closest imitation of traditional Armour thyroid. 2 A single Cynoplus tablet is slightly more potent than a 2-grain equivalent of desiccated thyroid, and Peat insisted that dosing begin with no more than one-eighth to one-fourth of a tablet, as starting with excessive amounts has created an epidemic of thyroid hormone intolerance syndrome. 2 He emphasized that a person's requirements are highly variable, increasing greatly during winter at high latitudes, and that the effects of any product must be monitored by watching pulse rate, temperature, and symptoms. 7 Roddy has extended this caution, noting that even a tiny dose of NDT can provoke anxiety and jitteriness if there is an underlying nutritional deficiency—particularly of protein, magnesium, calcium, or B vitamins—or if total cholesterol is dangerously low, as thyroid will further reduce this adaptive substance. 11