Physiology. The menstrual cycle has 2 parts: follicular and luteal. The follicular phase has FSH with stimulates ovarian follicle growth. The follicle secretes estrogen. Estrogen levels trigger lh to cause ovulation. After ovulation (luteal phase), the ovary secrete mostly Progesterone but also estrogen. The endometrium changes to receive the embryo. If pregnant then HCG cause the ovary to continue prog.