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		produced by the anterior pituitary. The release of hormones from the pituitary is controlled by the hypothalamus. In this case, Gonadotropin Releasing Factor (GnRH) is produced by the hypothalamusand transported directly to the anterior pituitary through the connecting portal vein. GnRH also controls the release of Follicle-stimulating hormone (FSH). In males, FSH acts to increase sperm production. d. Negative feed back 46.14 The levels of GnRH, LH and FSH are controlled by negative feed back. Androgens inhibit the release of all three, and LH and FSH also inhibit the release of GnRH. 2. Human female a. Coordination of ovarian & menstral cycles46.15 GnRH, FSH and LH are also involved in reproduction in adult human females. Together with estrogens and progesterone secreted by the ovaries, they regulate and coordinate the ovarian cycle, that results in the release of the oocyte, and the menstrual cycle, that prepares the uterine lining to support a potential embryo. b. Fluctuations in LH and FSH, complex feedback circuits Unlike in males, the levels of LH and FSH vary tremendously. The fluctuations result from complex feed back circuits. i. Early Low levels of FSH stimulates growth of a follicle. The follicle cells secrete estrogens which tend to inhibit the secretion of LH and FSH. Estrogens also stimulate the proliferation of the uterine lining (the endometrium) ii. Mid The growing follicle produces large amounts of estrogen. Very high amounts of estrogen stimulate the release of GnRH. This results in a surge of LH and FSH. LH acts on the follicle to cause it to mature and induces ovulation. the high levels of estrogen also stimulate the proliferation of the endometrium. iii. Late LH causes the remaining follicular cells to form the corpus luteum which secretes estrogen and progesterone. These maintain the endometrium to support the potential embryo. The high levels opf estrogen and progesterone inhibit LH and FSH release. When the level of LH falls, the corpus luteum disintegrates. As a result the concentrations of estrogen and progesterone decline. When the levels of estrogen and progesterone fall, LH and FSH release resumes, and the cycle repeats.