The woman’s body produces little estrogen, this triggers her hypothalamus to produce “gonadotropin releasing hormone” (GnRH) which targets the pituitary gland. The pituitary gland then releases the “gonadotropin,” (FSH). While the endometrium is breaking down and the woman is menstruating (Days ___-___), FSH is targeting the in the ovary, stimulating the development of an . The follicle releases the hormone, , which targets the uterus and increases the thickness of the . As the follicle enlarges, the estrogen levels rise until, around Day ___, the pituitary releases a pulse of (LH) that triggers the release of the oocyte (a process called ) on Day 14. The follicle then turns into the , which releases the hormones estrogen and to further develop the endometrium. About two weeks after , the corpus luteum begins to break down and produces less and less and , causing the endometrium to break down (around Day ) and to begin. The low levels of estrogen also stimulate the hypthalamus to release GnRH, ( ), which targets the gland. If the egg is fertilized and implants in the endometrium,
it releases(HCG) which maintains the corpus luteum and sustains the levels of estrogen and progesterone to maintain the , where the embryo is receiving and from the mother’s blood stream.