The kisspeptins are KiSS-1 gene-derived peptides that signal through the G protein-coupled receptor-54 (GPR54) and have recently been shown to be critical regulators of reproduction. Acute intracerebroventricular or peripheral administration of kisspeptin stimulates the hypothalamic-pituitary-gonadal (HPG) axis. This effect is thought to be mediated via the hypothalamic gonadotropin-releasing h...

Gonadotropin-inhibitory hormone (GnIH) is a hypothalamic neuropeptide that decreases gonadotropin synthesis and release by directly acting on the gonadotrope or by decreasing the activity of gonadotropin-releasing hormone (GnRH) neurons. GnIH is also called RFamide-related peptide in mammals or LPXRFamide peptide in fishes due to its characteristic C-terminal structure. The primary receptor for...

In many vertebrates, social interactions regulate reproductive capacity by altering the activity of the hypothalamic-pituitary-gonadal (HPG) axis. To better understand the mechanisms underlying social regulation of reproduction, we investigated the relationship between social status and one main component of the HPG axis: expression levels of gonadotropin-releasing hormone receptor (GnRH-R). So...

The distribution of orexin A-immunoreactive neurons and orexin type I receptors in the CNS suggests important roles in regulating the hypothalamo-pituitary gonadal (HPG) axis and sexual behaviors. We examined orexin A interactions in the HPG axis in vivo and in vitro. Orexin A stimulated LH-releasing hormone (LHRH) release in hypothalamic explants harvested from male rats (+133%) and from femal...

The current investigation examined stressors upon the coupling of the hypothalamic-pituitary-adrenal (HPA) and hypothalamic-pituitary-gonadal (HPG) axes. Emphasis is placed on the moderating role of context and time. One hundred and eighteen adolescent males and females provided up to 32 diurnal saliva samples across a visit to a research lab. This visit constituted a day-long stress through wh...

The amount of body fat and the energy balance are important factors that influence the timing of puberty and the normal reproductive function. Leptin is a key hormone that conveys to the central nervous system information about the individual energy reserve and modulates the hypothalamus-pituitary-gonad (HPG) axis. Recent findings suggest that the ventral premammillary nucleus (PMV) mediates th...

Oogenesis and folliculogenesis are key steps in reproduction leading to preservation of species. Oocytes are generated from primordial germ cells, mature in the ovaries, and full-grown oocytes are ovulated into oviducts. In vertebrates, follicle maturation is regulated by both the hypothalamus– pituitary–gonad (HPG) axis and the HPG axis-independent process. The former is initiated after pubert...

Copyright: © 2012 Asimakopoulos B. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. The structure and the function of the Hypothalamus-PituitaryGonadal (HPG) axis is an integral part of the knowledge on the phy...

Ultradian pulsatile hormone secretion underlies the activity of most neuroendocrine systems, including the hypothalamic-pituitary adrenal (HPA) and gonadal (HPG) axes, and this pulsatile mode of signalling permits the encoding of information through both amplitude and frequency modulation. In the HPA axis, glucocorticoid pulse amplitude increases in anticipation of waking, and, in the HPG axis,...

CONTEXT A trade-off between fertility and longevity possibly exists. The association of the male hypothalamic-pituitary-gonadal (HPG) axis with familial longevity has not yet been investigated. OBJECTIVE To study 24-h hormone concentration profiles of the HPG axis in men enriched for familial longevity and controls. DESIGN We frequently sampled blood over 24 h in 10 healthy middle-aged male...