Thyroid hormones regulate the metabolism of proteins, fats, and carbohydrates, thus affecting how these macro-nutrients produce energy. A deficiency or excess of thyroid hormones can have far-reaching effects. For example, a high cortisol level can interfere with thyroid function, resulting in low thyroxine (T4) or poor conversion of T4 to the active form, triiodothyronine (T3). Each thyroid hormone has multiple important functions in the body; for example, T4 supports cardiac output, heart rate, respiratory rate, and basal metabolic rate ?? a low basal metabolic rate can cause a person to be fatigued, chilly, and have trouble losing weight. Thyrocsin provides nutritional and botanical support for healthy thyroid function, for the conversion of T4 to T3, and for normal cortisol levels. This non-glandular thyroid-support formula is available only from Thorne. Thorne’s Thyrocsin formula contains key ingredients for thyroid support, including iodine, which is necessary for formation of T4, and L-tyrosine, which is a necessary component of both T4 and T3 formation. Animal studies have indicated that the Ayurvedic botanical, ashwagandha, can increase T4 concentrations. Thyrocsin also includes several nutrient cofactors necessary for converting T4 to T3, including the minerals selenium, zinc, and copper. Thyrocsin includes vitamin B12 because a deficiency of this vitamin appears to interfere with the activity of thyroid hormones. Conversion of T4 to T3 can be inhibited by heavy metal toxicity and lipid peroxidation; hence, the inclusion of antioxidant vitamins C and E to counterbalance this inhibition.