(chorionic gonadotropin for injection, USP)
Human chorionic gonadotropin (HCG), a polypeptide hormone produced by the human placenta, is composed of an alpha and a beta subunit. The alpha subunit is essentially identical to the alpha subunits of the human pituitary gonadotropins, luteinizing hormone (LH) and follicle-stimulating hormone(FSH), as well as to the alpha subunit of human thyroid-stimulating hormone (TSH). The beta subunits of these hormones differ in amino acid sequence.
PREGNYL (chorionic gonadotropin for injection, USP) is a highly purified pyrogen-free preparation obtained from the urine of pregnant females.
It is standardized by a biological assay procedure.
The action of HCG is virtually identical to that of pituitary LH, although HCG appears to have a small degree of FSH activity as well.
It stimulates the production of gonadal steroid hormones by stimulating the interstitial cells (Leydig cells) of the testis to cycle, LH participates with FSH in the development and maturation of the normal ovarian follicle, and the mid-cycle LH surge triggers ovulation.
HCG can substitute for LH in this function. During a normal pregnancy, HCG secreted by the placenta maintains the corpus luteum after LH secretion decreases, supporting continued secretion of estrogen and progesterone and preventing menstruation.