The hormone of the CORPUS LUTEUM of the ovary (see OVARIES). After the escape of the OVUM from the ruptured follicle, the corpus luteum secretes progesterone, which stimulates the growth and secretion of the endometrial glands of the UTERUS during the 14 days before MENSTRUATION. In the event of pregnancy, the secretion of progesterone continues until the baby's birth. (See also NORETHISTERONE; PREGNANEDIOL; CONTRACEPTION.)