TSH - Thyroid‑stimulating hormone
Thyroid‑stimulating hormone (TSH, thyrotropin) is a glycoprotein having a molecular weight of approximately 30000 daltons and consisting of two subunits. The β‑subunit carries the TSH‑specific immunological and biological information, whereas the α‑chain carries species‑specific information and has an identical amino acid sequence to the α‑chains of LH, FSH and hCG.
TSH is formed in specific basophil cells of the anterior pituitary and is subject to a circadian secretion sequence. The hypophyseal release of TSH (thyrotropic hormone) is the central regulating mechanism for the biological action of thyroid hormones. TSH has a stimulating action in all stages of thyroid hormone formation and secretion; it also has a proliferative effect. The determination of TSH serves as the initial test in thyroid diagnostics. Even very slight changes in the concentrations of the free thyroid hormones bring about much greater opposite changes in the TSH level. Accordingly, TSH is a very sensitive and specific parameter for assessing thyroid function and is particularly suitable for early detection or exclusion of disorders in the central regulating circuit between the hypothalamus, pituitary and thyroid.
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