(c) : Menstrual cycle is controlled by several endocrinal parameters. In beginning of the cycle FSH (follicle stimulating hormone) of pituitary initiates development of an ovarian follicle. A growing ovarian follicle gradually secretes increasing amount of estrogen. This in turn leads to sudden surge of LH secretion by the pituitary. As the LH (leutinising hormone) level in blood suddenly increases there is ovulation. Thus only FSH or LH cannot control all the events of menstrual cycle. Progesteron is released by a corpus luteum after ovulation which actually prepares the uterus for a possible pregnancy. If there is no fertilisation progesteron level falls and there is beginning of a new cycle.