Rapid secretion of LH leading to its maximum level during the mid-cycle called LH surge induces rupture of the Graafian follicle and thereby the release of the ovum. The ovulation is followed by the luteal phase during which the remaining parts of the Graafian follicle transform as the corpus leteum. The corpus luteum secretes large amounts of progesterone, which is essential for the maintenance of the endometrium. Endometrium is necessary for implantation of the fertilized ovum and other events of pregnancy.
LH level falls, which causes regression of corpus luteum and hence stoppage of progesterone production.