Menstrual cycle is regulated by hypothalamus through the pituitary gland. At the end of menstrual phase, the pituitary FSH gradually increases resulting in follicular development within the ovaries. As the follicles mature, Estrogen secretion increases resulting in a surge in (FS, He and LH).The surge of LH responsible for ovulation. LH also induces luteinisation. This leading to the formation of corpus luteum. Corpus luteum secretes progesterone and some estrogen which help in maintaining the uterine endometrium for implantation.