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Thyroid hormones act on nearly every cell in the body. They act to increase the basal metabolic rate, affect protein synthesis, help regulate long bone growth (synergy with growth hormone) and neural maturation, and increase the body's sensitivity to catecholamines (such as adrenaline) by permissiveness. [12]
The pituitary gland secretes thyrotropin (TSH; Thyroid Stimulating Hormone) that stimulates the thyroid to secrete thyroxine (T4) and, to a lesser degree, triiodothyronine (T3). The major portion of T3, however, is produced in peripheral organs, e.g. liver , adipose tissue , glia and skeletal muscle by deiodination from circulating T4.
Organification is a biochemical process that takes place in the thyroid gland. It is the incorporation of iodine into thyroglobulin for the production of thyroid hormone, a step done after the oxidation of iodide by the enzyme thyroid peroxidase (TPO) [1] Since iodine is an inorganic compound, and is being attached to thyroglobulin, a protein, the process is termed as "organification of iodine".
The active forms of thyroid hormone (T3 and T4), are then released into circulation where they are either unbound or attached to plasma proteins. [10] Iodine is recycled back into the follicular lumen where it can continue to serve as a substrate for thyroid hormone synthesis, while the non-modified residues of Tg reenter cellular metabolic ...
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.
Thyroid hormone synthesis. [2]Follicular cells take up iodide and amino acids from the blood circulation on the basolateral side, synthesize thyroglobulin and thyroperoxidase from amino acids and secrete these into the thyroid follicles together with iodide.
DIT is a modulator of the enzyme thyroid peroxidase (which is involved in the production of thyroid hormones). [1] Triiodothyronine is formed, when diiodotyrosine is combined with monoiodotyrosine (in the colloid of the thyroid follicle). Two molecules of DIT combine to make the thyroid hormone thyroxine ('T4' and 'T3').
Thyroid peroxidase, also called thyroperoxidase (TPO), thyroid specific peroxidase or iodide peroxidase, is an enzyme expressed mainly in the thyroid where it is secreted into colloid. Thyroid peroxidase oxidizes iodide ions to form iodine atoms for addition onto tyrosine residues on thyroglobulin for the production of thyroxine (T 4 ) or ...