Molecular integration of hypothalamo-pituitary-adrenal axis-related neurohormones on the GnRH neuron

Gonadotropin-releasing hormone (GnRH) secretion from the hypothalamus is pi votal to the regulation of reproductive physiology in vertebrates. GnRH and the reproductive axis, in general, can be inhibited during periods of stre ss or injury. Stress, in the form of mechanical, psychological or immunolog ical insult to an organism results in the activation of the hypothalamo-pit uitary-adrenal (HPA) axis initiated by the hypothalamic release of corticot ropin-releasing factor (CRF). Recent studies indicate that CRF may act eith er directly on the GnRH neuron to down-regulate GnRH synthesis, or indirect ly via a beta-endorphin-mediated pathway. Moreover, in vitro studies sugges t that CRF-related peptides can increase the sensitivity of the GnRH neuron to prolactin by increasing the synthesis of the prolactin receptor.