Reproductive cycle

In normal ovulatory menstrual cycle, four hormones; follicular-stimulating hormone (FSH), luteinizing hormone (LH), estrogen, and progesterone-with central pulsatile release of GnRH regulate regular cyclical activities in human female reproductive system including continuous events of follicular growth, ovulation, endometrial readiness, or adaptability for blastocyst implantation. Actively high secretion of FSH through the luteal-follicular switch leads to staffing of a troop of follicles and appearance and progression of a dominant follicle called mature Graafian follicle. From the ovary, estradiol release and inhibin release are the main determinants of the ongoing excitatory release of FSH, while high estradiol with other prospective elements is significant for the LH surge, centrally regulated at the anterior pituitary gland in women. Corpus luteum releases progesterone and estradiol to prepare the uterine endometrium for implantation, and its reduced release leads to a high secretion of FSH at the start of the next cycle.