Thyrotropin-releasing hormone (TRH; MIM 275120), a small neuropeptide, is widely distributed throughout the central and peripheral nervous system as well as in extraneural tissues. The peptide is synthesized in the hypothalamus and transported by the portal vascular system to the anterior pituitary where it acts on thyrotropic and lactotropic cells to promote secretion of TSH and prolactin, respectively. Thyrotropin-releasing hormone receptor is a G protein-coupled receptor that activates the inositol phospholipid-calcium-protein kinase C transduction pathway upon the binding of TRH. The TRHR gene is expressed in the thyrotrope cells of the anterior pituitary.