Bioscientifica Proceedings

In males, including the ram, testosterone, acting via its primary metabolites oestradiol and dihydrotestosterone (DHT), suppresses circulating LH concentrations. This effect is due primarily, although not totally, to decreased frequency of gonadotrophin-releasing hormone (GnRH) pulses. The arcuate–ventromedial region (ARC–VMR) of the mediobasal hypothalamus and possibly the medial preoptic area (mPOA) are sites at which oestradiol acts to suppress GnRH, but the site ...