Thyroid hormones
Thyroid hormones are two hormones produced and released by the thyroid gland, namely triiodothyronine (T) and thyroxine (T). They are tyrosine-based hormones that are primarily responsible for regulation of metabolism. T and T are partially composed of iodine. A deficiency of iodine leads to decreased production of T and T, enlarges the thyroid tissue and will cause the disease known as simple goitre. The major form of thyroid hormone in the blood is thyroxine (T), which has a longer half-life than T. In humans, the ratio of T to T released into the blood is approximately 14:1. T is converted to the active T (three to four times more potent than T) within cells by deiodinases (5'-iodinase). These are further processed by decarboxylation and deiodination to produce iodothyronamine (Ta) and thyronamine (Ta). All three isoforms of the deiodinases are selenium-containing enzymes, thus dietary selenium is essential for T production. Edward Calvin Kendall was responsible for the isolation of thyroxine in 1915.
Kenneth Sterling
Sterling was one of the first researchers to use radioactive iodine to treat thyroid diseases. He used radioisotopic labels to study the metabolism of human serum proteins and red blood cells. He discovered that the body converts the pro-hormone thyroxine into triiodothyronine, the primary active form of thyroid hormone. This breakthrough led to a new field of thyroid hormone research and led to the first early studies on the mechanism of action of thyroid hormones. Sterling developed the equilibrium dialysis method for measuring free thyroxine, which remains the gold standard for evaluating free hormone levels in blood today. Sterling was a pioneering investigator identifying mitochondrial thyroid hormone receptors, shortened isoforms of the full-length, nuclear receptors. He wrote a chapter on thyroid hormone receptors in the fifth edition of "Werner's The Thyroid: A Fundamental and Clinical Text", which is known as "the bible of modern thyroidology."