Discovery of the hypothalamic gonadotropin-releasing hormone pulse generator and of its physiologic significance

Abstract

Shortly after a specific radioimmune assay for monkey luteinizing hormone (LH) became available in the late 1960s, we began to investigate the dynamics of its secretion in a variety of physiologic and experimental circumstances. One such early study was designed to determine whether a circadian rhythm in the plasma levels of the peptide could be detected. To this end, hourly blood samples were obtained for 24 hours from chronically ovariectomized monkeys that were restrained in primate chairs. We were surprised to find frequent, apparently random, and often large LH peaks during this period that were unrelated to the time of day or to perturbations in the environment.