Glycoprotein Hormone Family

Abstract The classic glycoprotein hormone (GPH) family consists of four members: FSH, LH, and TSH secreted from the pituitary, and CG secreted from the placenta. They are heterodimers consisting of a common α-subunit and a hormone-specific β-subunit. The α- and β-subunits contain a cysteine-knot motif and several N -linked glycosylation sites, which are important for biological activity of the hormone. FSH, LH, and CG have gonadotropic activity, and TSH has thyrotropic activity. Another heterodimeric GPH, thyrostimulin, which consists of glycoprotein α-subunit 2 (GPA2) and glycoprotein β-subunit 5 (GPB5), has been identified in both vertebrates and invertebrates. Thyrostimulin has thyrotropic activity in human. The synthesis and release of FSH and LH are regulated by hypothalamic neurohormones such as GnRH and GnIH, and the feedback effects of gonadal steroids. The synthesis and release of TSH are regulated by TRH and the feedback effects of thyroid hormones.