chorionic gonadotropin

human chorionic gonadotropin (HCG) (hCG) a two-subunit glycopeptide hormone produced by syncytiotrophoblasts of the fetal placenta that maintains the function of the corpus luteum during the first few weeks of pregnancy, and is thought to promote steroidogenesis in the fetoplacental unit and to stimulate fetal testicular secretion of testosterone. The α subunit is identical to that of luteinizing hormone, follicle-stimulating hormone, and thyrotropin; the β subunit shares homology with luteinizing hormone but is antigenically unique, containing an additional glycopeptide sequence. Chorionic gonadotropin can be detected by immunoassay in the maternal urine within days after fertilization and thus provides the basis for the most commonly used pregnancy tests. [USP] the same principle obtained from the urine of pregnant women, used to treat certain cases of cryptorchidism and male hypogonadism, to induce ovulation and pregnancy in anovulatory women in whom the anovulation is secondary and not due to ovarian failure, and to increase the numbers of oocytes for patients attempting conception using assisted reproductive technologies such as gamete intrafallopian transfer (GIFT) or in vitro fertilization; administered intramuscularly. Called also choriogonadotropin. See also choriogonadotropin alfa.