A classical question in reproductive neuroendocrinology is, “What is the mechanism of estrogen positive feedback that stimulates the luteinizing hormone (LH) surge?” This is a critical question in the field, since the LH surge triggers two central events in reproduction: ovulation and formation of the corpus luteum (which produces progesterone in the ovary). It is well-known that estrogen positive feedback is mediated by neural circuits that control the activity of gonadotropin releasing hormone (GnRH) neurons in the hypothalamus. Interestingly, in addition to estradiol, estrogen positive feedback requires progesterone – made by the brain.
