Synonyms: TSH, hTSH, TSH 1, Thyreotropin, thyroid stimulating hormone, thyrotropic hormone
German: Thyrotropin
The thyroid stimulating hormone is a peptide hormone that is produced and secreted by the anterior lobe of the pituitary gland. It induces an increased synthesis of thyroid hormones by the thyroid gland. Reciprocally, the secretion of thyroid-stimulating hormones is inhibited by thyroid hormones (thyrotropic feedback control).
The hormone TSH is a glycoprotein consisting of two subunits. It has a shared alpha-subunit with HCG, FSH and LH. The beta subunit conveys the hormone specific signal. Thyrostimulin (TSH 2, A2B5), a related glycoprotein that also has a thyroid stimulating effect, has and additional second alpha-subunit and a fifth beta-subunit.
The following factors influence secretion of TSH:
TSH binds to heptahelical receptors located on the surface of thyroid cells. This leads to an increase in the intracellular concentration of cAMP via stimulation through [G protein|[G proteins]]. The result is a significant increase of synthesis and secretion of T4. To a lesser extent, an increased cAMP concentration within thyrocytes also stimulates the intrathyroidal deiodation. This has the effect that in case of hypothyroidism the sum activity of peripheral deiodinases is increased and results in a redundant compensatory regulation in the early stages of thyroid deficiency.[1]
This page was last edited on 24 September 2017, at 19:36.
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