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Biosynthesis and Degradation of Thyroid Hormones

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Iodide, which is ingested in food and water, is actively concentrated by the thyroid gland, converted to organic iodine by TPO (Thyroid Peroxidase also known as Iodide Peroxidase), and incorporated into tyrosine in intrafollicular thyroglobulin within the colloid at the basal cell surface of the thyroid follicular cell. The tyrosines are iodinated at one (Monoiodotyrosine) or two (Diiodotyrosine) sites and then coupled to form two active hormones, Thyroxine (T4, a Tetra-Iodinated Tyrosine derivative) and Triiodothyronine (T3). Unlike the other endocrine hormones, these are not peptides. They are derived from the amino acid tyrosine. T4 is the major active hormone. In tissues outside the thyroid, particularly in the liver and kidney, T4 is converted to T3, an active metabolite, by monodeiodination [...]


1.Cloning and characterization of the thyroid iodide transporter.
Dai G, Levy O, Carrasco N.
Nature. 1996 Feb 1; 379(6564):458-60.
2.Thyroid hormone synthesis and storage in the thyroid gland of human neonates.
Savin S, Cvejic D, Nedic O, Radosavljevic R.
J Pediatr Endocrinol Metab. 2003 Apr-May; 16(4):521-8.
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