Thyroid-stimulating hormone (TSH) is a pituitary hormone that stimulates the thyroid gland to produce thyroxine (T4), and then triiodothyronine (T3) which stimulates the metabolism of almost every tissue in the body. It is a glycoprotein hormone produced by thyrotrope cells in the anterior pituitary gland, which regulates the endocrine function of the thyroid. TSH consists of two subunits, the alpha and the beta subunit. The α subunit is thought to be the effector region responsible for stimulation of adenylate cyclase (involved the generation of cAMP). The β (beta) subunit (TSHB) is unique to TSH, and therefore determines its receptor specificity. The TSH receptor is found mainly on thyroid follicular cells. Stimulation of the receptor increases T3 and T4 production and secretion.