Nature's Sunshine Thyroid Support provides glandular extracts, amino acids, vitamins, minerals, enzymes and nutrients to support the thyroid. Thyroid hormones regulate metabolism in every cell in the body. Therefore, a deficiency of thyroid hormones can affect virtually all body functions, including body temperature, enzyme activity, growth, heart rate, oxygen consumption and respiratory rate. Nature's Sunshine Thyroid Support provides Vitamin B6, essential for growth and maintenance of almost every body function, and plays a role in amino acid and hormone metabolism and is important for production of thyroid hormones. Zinc plays an important role in thyroid hormone metabolism. It is a required co-factor for iodothyronine iodinase, the enzyme that converts T4 to T3. Copper is a trace mineral that is a required cofactor for iodothyronine iodinase, the enzyme that converts T4 to T3. Manganese is a trace mineral essential for the formation of T4.