Question

When declining levels of estrogens and progesterone stimulate secretion of GnRH, is this a positive or negative feedback effect and why?

Answer 1

At the end of the menstrual cycle if the egg is not implanted in the uterus, the corpus luteum degenerates and the levels of estrogen and progesterone decline. The decreasing levels stimulate the GnRH to be released from the hypothalamus. This, in turn, stimulates the anterior pituitary to release LH and FSH and begin the next cycle. So, the declining levels stimulate the release of GnRH and therefore has a positive feedback effect.