T3 is synthesized in the thyroid gland, which is located in the neck. The production process involves the iodination of the amino acid tyrosine, forming monoiodotyrosine (MIT) and diiodotyrosine (DIT). The coupling of one MIT and one DIT molecule yields T3. Although the thyroid gland secretes some T3 directly, the majority of T3 in the bloodstream is derived from the peripheral conversion of T4 by deiodinase enzymes in tissues such as the liver and kidneys.
