Glycoprotein hormones, alpha polypeptide is a protein that in humans is encoded by the CGA gene. The gonadotropin hormones, human chorionic gonadotropin, luteinizing hormone, follicle-stimulating hormone, and thyroid-stimulating hormone are heterodimers consisting of alpha and beta subunits that are associated non-covalently. The alpha subunits of these four human glycoprotein hormones are identical; however, their beta chains are unique and confer biological specificity. The protein encoded by this gene is the alpha subunit and belongs to the glycoprotein hormones alpha chain family.