Thyrotropin, also known as thyroid-stimulating hormone (TSH), is a peptide hormone synthesized and secreted by thyrotrope cells in the anterior pituitary gland at the base of the brain in response to signals from the hypothalamus. It regulates the endocrine function of the thyroid gland.
Thyrotropin stimulates the thyroid gland to secrete the hormones thyroxine (T4) and triiodothyronine (T3). Thyrotropin production is controlled by thyrotropin-releasing hormone (TRH), which is produced in the hypothalamus and transported to the anterior pituitary gland via the superior hypophyseal artery, where it increases thyrotropin production and release. Somatostatin is also produced by the hypothalamus, and has an opposite effect on the pituitary production of TSH, decreasing or inhibiting its release.
The thyrotropin receptor is found mainly on thyroid follicular cells. Stimulation of the receptor increases T3 and T4 production and secretion. Stimulating antibodies to this receptor mimic TSH and cause Graves' disease.