Withdrawal of which of the following hormones is the immediate cause of menstruation?
Menstruation is caused by the reduction of estrogen and progesterone (especially progesterone) at the end of monthly ovarian cycle. At ovulation, usually around day 12–14 of the menstrual cycle, increased estrogen levels trigger a sharp rise in Luteinizing Hormone (LH) from the pituitary gland, causing release of the egg from the follicle. The ruptured follicle (corpus luteum) now secretes progesterone and estrogen to continue to prepare the uterus for pregnancy. If the egg is not fertilized, estrogen and progesterone levels drop and, on day 28, the menses begins.