Despite variability in the triggers, timing, and pace of sexual maturity between species, all species utilize the final pathway of hypothalamic secretion of GnRH to initiate and maintain the reproductive axis. Thus, GnRH is required for reproductive competence in the human. The classic studies of Knobil and his colleagues in the 1970s clearly demonstrated that pulsatile release of GnRH from the hypothalamus is a prerequisite for physiologic gonadotrope function, with continuous stimulation resulting in a paradoxical decrease in gonadotrope responsiveness.