PathwayStep2556 PathwayStep2555 PathwayStep2554 PathwayStep2553 PathwayStep2559 PathwayStep2550 PathwayStep2551 PathwayStep2552 PathwayStep2549 Regulation of thyroid hormone activity Thyroxine biosynthesis Authored: Jassal, B, 2008-10-01 13:18:42 Edited: Jassal, B, 2008-05-28 09:06:10 GENE ONTOLOGYGO:0006590 Pubmed3297964 Reactome Database ID Release 43209968 Reactome, http://www.reactome.org ReactomeREACT_15292 Reviewed: D'Eustachio, P, 2008-05-28 08:30:54 Thyroxine (3,5,3',5'-tetraiodothyronine, T4) promotes normal growth and development. It also regulates heat and energy production. T4 is released from the thyroid gland, the largest endocrine organ in the human body. The primary hormone released is T4 although T3 (3,5,3'-triiodothyronine) is also released in small quantities. Tyrosine residues in thyroglobulin (a glycoprotein scaffold containing many tyrosine residues) are iodinated to form mono- or diiodo-tyrosine which can then couple to form either T3 or T4. Iodide is taken up by thyroid epithelial cells Iodide is organified Tyrosine is monoiodinated Monoiodinated tyrosine can be deiodinated Tyrosine is diiodinated Diiodinated tyrosine can be deiodinated Two DITs combine to form thyroxine DIT and MIT combine to form triiodothyronine