thyroid-stimulating hormone receptor (or thyrotropin receptor), member of the class A family of seven-transmembrane G protein-coupled receptors
The glycoprotein hormone receptors are seven transmembrane domain receptors with a very large extracellular N-terminal domain containing many leucine-rich repeats responsible for hormone recognition and binding. The glycoprotein hormone family includes the three gonadotropins: luteinizing hormone (LH), follicle-stimulating hormone (FSH), chorionic gonadotropin (CG), and a pituitary thyroid-stimulating hormone (TSH). The glycoprotein hormones exert their biological functions by interacting with their cognate GPCRs. Both LH and CG bind to the same receptor, the luteinizing hormone-choriogonadotropin receptor (LHCGR); FSH binds to FSH-R and TSH to TSH-R. TSH-R plays an important role thyroid physiology, and its activation stimulates the production of thyroxine (T4) and triiodothyronine (T3). Defects in TSH-R are a cause of several types of hyperthyroidism. The receptor is predominantly found on the surface of the thyroid epithelial cells and couples to the G(s)-protein and activates adenylate cyclase, thereby promoting cAMP production. TSH and cAMP stimulate thyroid cell proliferation, differentiation, and function.