Progesterone is a steroid hormone derived from pregnenolone (and cholesterol) in the corpus luteum during the post-ovulation phase of the menstrual cycle, and in the placenta up until delivery. Its secretion is stimulated by Luteinizing Hormone (LH). Since progesterone levels vary throughout the menstrual cycle, multiple (serial) measurements can be used to help recognize and manage some causes of infertility. Progesterone can be measured to determine whether or not a woman has ovulated, to determine when ovulation occurred, and to monitor the success of induced ovulation. It is also used to evaluate corpus luteum function. INCREASED progesterone levels are seen occasionally with some ovarian cysts, non-viable pregnancies known as molar pregnancies, a rare form of ovarian cancer, and overproduction of progesterone by the adrenal glands, or congenital adrenal hyperplasia (CAH). LOW levels of progesterone may be associated with toxemia late in pregnancy, decreased function of ovaries, and lack of menstruation (amenorrhea).