Human chorionic gonadotropin (hCG) is a glycoprotein that consists of an alpha and beta subunit. The alpha subunit is structurally similar to the alpha subunits of FSH, LH and TSH. The beta subunit is distinct for hCG. The release of hCG into maternal circulation begins with embryo implantation 5 to 7 days after fertilization.. Human chorionic gonadotropin (hCG) conversion to mIU/mL, IU/L. Online conversion calculator for many types of measurement units in laboratory and medicine Human chorionic gonadotropin (hCG) ,. Human chorionic gonadotropin (hCG) is a hormone produced by the placenta after implantation. The presence of hCG is detected in some pregnancy tests (HCG pregnancy strip tests).Some cancerous tumors produce this hormone; therefore, elevated levels measured when the patient is not pregnant may lead to a cancer diagnosis and, if high enough, paraneoplastic syndromes, however, it is not known . HCG stimulates the corpus luteum which produces progesterone in the first week of pregnancy. Progesterone: Prevents menses. It supports pregnancy. The alpha subunit is the same for all the glycoprotein Like LH, FSH, and TSH while the beta unit is unique for HCG. Therefore the beta(β) subunit is specific for HCG.. . .