Human Chorionic Gonadotropin, β Subunit

Chorionic gonadotropin (CG) is produced by the trophoblastic cells of the placenta and stimulates the ovaries to release steroids essential for maintaining pregnancy. The four human glycoprotein hormones (CG, luteinizing hormone, follicle stimulating hormone, and thyroid stimulating hormone) are dimers consisting of alpha and beta subunits. The alpha subunits of these hormones are identical, while they each have unique beta subunits that allow the hormones to bind specific receptors on target cells to activate distinct downstream signaling pathways. The beta subunit of CG is encoded by six highly homologous genes which are arranged in tandem and inverted pairs on chromosome 19. Abnormalities in the CG beta subunit can cause ectopic pregnancy.