Kisspeptins in Reproductive Biology: Consensus Knowledge and Recent Developments1

Abstract

Kisspeptins, a family of neuropeptides encoded by the Kiss1 gene that are mainly expressed in discrete neuronal populations of the hypothalamus, have recently emerged as essential upstream regulatory elements of GnRH (gonadotropin-releasing hormone) neurons and, thereby, potent elicitors of gonadotropin secretion. Indeed, kisspeptins are now recognized as important regulators of key aspects of the maturation and function of the reproductive axis, including the sexual differentiation of the brain, the timing of puberty, the adult regulation of gonadotropin secretion by gonadal hormones, and the control of fertility by metabolic and environmental (e.g., photoperiod) cues. Appreciation of these fundamental biological features has led to the contention that kisspeptins are indispensable elements of the reproductive brain whose relevance goes beyond their crucial physiological roles and may pose potential pathophysiological and therapeutic interest. In spite of such a consensus, recent developments in the field have helped to expand, and somewhat challenged, our current understanding of the neuroendocrine and molecular mechanisms whereby some of the effects of kisspeptins are conducted. This review aims to provide a synoptic and balanced account of the consensus knowledge and recent findings in the field of kisspeptin physiology, which we predict will be crucial in shaping the progress of our understanding of the roles played by this family of neuropeptides in reproductive biology.