Question

· What major hormonal change must occur before the next menstrual cycle begins?

Answer 1

The gonadotropin releasing hormone or GnRH stimulates the production of FSH i.e. follicle stimulating hormone from the pituitary gland. FSH starts the development of egg and also rises the level of estrogen. There is another pituitary hormone which also helps in the reproductive cycle – leutenizing hormone or LH. LH stimulates the release of egg from the ovary.

At the first day of menses, estrogen is low. in response to low estrogen, FSH and LH are secreted before the onset of the menstrual cycle. Both the pituitary hormones also stimulate the growth of ovarian follicles containing eggs. Estrogen levels begin to rise as the follicle grows and it inhibits the further secretion of FSH. A sudden release of LH triggered by the rise in the levels of estrogen around the thirteenth day of the menstrual cycle results in the maturation of egg and its extrusion.

Left over ovarian follicles become the corpus luteum and produce large amounts of progesterone for implantation. If implantation of the embryo does not occurs then the circulating levels of hormones decreases and endometrium lining breaks that results in the menstrual flow.