which body functions are affected by the thyroid​ hormones t3​(tri-iodothyronine) and t4​(thyroxine)
Thyroid hormones Thyroid hormones are two hormones produced and released by the thyroid gland, namely triiodothyronine (T3) and thyroxine (T4). They are tyrosine-based hormones that are primarily responsible for regulation of metabolism. T3 and T4 are partially composed of iodine. A deficiency of iodine leads to decreased production of T3 and T4, enlarges the thyroid tissue and will cause the disease known as simple goitre. The major form of thyroid hormone in the blood is thyroxine (T4), which has a longer half-life than T3.[1] In humans, the ratio of T4 to T3 released into the blood is sometimes claimed to be quite high, but thyroid removal patient data suggests it to vary between 4:1 to 2:1, the average being 100:36 (roughly 2.8:1). T4 is converted to the active T3 (three to four times more potent than T4) within cells by deiodinases (5'-iodinase). These are further processed by decarboxylation and deiodination to produce iodothyronamine (T1a) and thyronamine (T0a). All three isoforms of the deiodinases are selenium-containing enzymes, thus dietary selenium is essential for T3 production. Edward Calvin Kendall was responsible for the isolation of thyroxine in 1915.[2]
Thyroid The thyroid gland, or simply the thyroid, is an endocrine gland in the neck, consisting of two lobes connected by an isthmus. It is found at the front of the neck, below the Adam's apple. The thyroid gland secretes thyroid hormones, which primarily influence the metabolic rate and protein synthesis. The hormones also have many other effects including those on development. The thyroid hormones triiodothyronine (T3) and thyroxine (T4) are created from iodine and tyrosine. The thyroid also produces the hormone calcitonin, which plays a role in calcium homeostasis.[1]
Thyroid The thyroid gland, or simply the thyroid /ˈθaɪrɔɪd/, is an endocrine gland in the neck, consisting of two lobes connected by an isthmus. It is found at the front of the neck, below the Adam's apple. The thyroid gland secretes thyroid hormones, which primarily influence the metabolic rate and protein synthesis. The hormones also have many other effects including those on development. The thyroid hormones triiodothyronine (T3) and thyroxine (T4) are created from iodine and tyrosine. The thyroid also produces the hormone calcitonin, which plays a role in calcium homeostasis.[1]
Thyroid hormones Thyroglobulin (Tg) is a 660 kDa, dimeric protein produced by the follicular cells of the thyroid and used entirely within the thyroid gland.[citation needed] Thyroxine is produced by attaching iodine atoms to the ring structures of this protein's tyrosine residues; thyroxine (T4) contains four iodine atoms, while triiodothyronine (T3), otherwise identical to T4, has one less iodine atom per molecule. The thyroglobulin protein accounts for approximately half of the protein content of the thyroid gland.[citation needed] Each thyroglobulin molecule contains approximately 100-120 tyrosine residues, a small number of which (<20) are subject to iodination catalysed by thyroperoxidase.[26] The same enzyme then catalyses "coupling" of one modified tyrosine with another, via a free radical-mediated reaction, and when these iodinated bicyclic molecules are released by hydrolysis of the protein, T3 and T4 are the result.[citation needed] hence, each Tg protein molecule ultimately yields very small amounts of thyroid hormone (experimentally observed to be on the order of 5-6 molecules of either T4 or T3 per original molecule of Tg).[26]