Neuroanatomy of the human hypothalamic kisspeptin system.

Hypothalamic kisspeptin (KP) neurons are key players in the neuronal network that regulates the onset of puberty and the pulsatile secretion of gonadotropin-releasing hormone (GnRH). In various mammalian species, the majority of KP-synthesizing neurons are concentrated in two distinct cell populations in the preoptic region and the arcuate nucleus (ARC). While studies of female rodents have provided evidence that preoptic KP neurons play a critical sex-specific role in positive estrogen feedback, KP neurons of the ARC have been implicated in negative sex steroid feedback and they have also been hypothesized to contribute to the pulse generator network which regulates episodic GnRH secretion in both females and males. Except for relatively few morphological studies available in monkeys and humans, our neuroanatomical knowledge of the hypothalamic KP systems is predominantly based on observations of laboratory species which are phylogenetically distant from the human. This review article discusses the currently available literature on the topographic distribution, network connectivity, neurochemistry, sexual dimorphism, and aging-dependent morphological plasticity of the human hypothalamic KP neuronal system.