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Inactivation of thyroid hormones occurs by removal of an iodine atom on the inner ring, which converts thyroxine to the inactive reverse triiodothyronine (rT 3), or which converts the active triiodothyronine to diiodothyronine (T 2). The major part of thyroxine deiodination occurs within the cells. Deiodinase 2 activity can be regulated by ...
Iodotyrosine deiodinase contributes to breakdown of thyroid hormones. It releases iodine , for renewed use, from iodinated tyrosines resulting from catabolism of iodothyronines. Iodotyrosine deiodinase employs a flavin mononucleotide cofactor and belongs to the NADH oxidase/flavin reductase superfamily.
Iodotyrosine deiodinase facilitates iodide salvage in the thyroid by catalyzing deiodination of mono- and diiodotyrosine, the halogenated byproducts of thyroid hormone production. [13] Iodide is also an important micronutrient in the biosynthesis of thyroid hormone, creating a cycle of iodide use in the thyroid. [14]
It catalyzes the inactivation of thyroid hormone by inner ring deiodination of the prohormone thyroxine (T 4) and the bioactive hormone 3,3',5-triiodothyronine (T 3) to inactive metabolites, 3,3',5'-triiodothyronine (RT 3) and 3,3'-diiodothyronine (T 2), respectively. This enzyme is highly expressed in the pregnant uterus, placenta, fetal and ...
The sum activity of peripheral deiodinases (G D, also referred to as deiodination capacity, total deiodinase activity or, if calculated from levels of thyroid hormones, as SPINA-GD [a]) is the maximum amount of triiodothyronine produced per time-unit under conditions of substrate saturation. [1]
Reverse T 3 is the third-most common iodothyronine the thyroid gland releases into the bloodstream, at 0.9%; tetraiodothyronine (levothyroxine, T 4) constitutes 90% and T 3 is 9%. However, 95% of rT 3 in human blood is made elsewhere in the body, as enzymes remove a particular iodine atom from T 4. [1]
At the cellular level, T 3 is the body's more active and potent thyroid hormone. [2] T 3 helps deliver oxygen and energy to all of the body's cells, its effects on target tissues being roughly four times more potent than those of T 4. [2] Of the thyroid hormone that is produced, just about 20% is T 3, whereas 80% is produced as T 4.
The thyroid system of the thyroid hormones T 3 and T 4 [1] Thyroid hormones are two hormones produced and released by the thyroid gland, triiodothyronine (T 3) and thyroxine (T 4). They are tyrosine-based hormones that are primarily responsible for regulation of metabolism. T 3 and T 4 are partially composed of iodine, derived from food. [2]