Ghrelin role in hypothalamus-pituitary-ovarian axis

Based on the available data, it was shown that ghrelin is involved in a series of physiological processes such as regulation of food intake, body weight, and cardiovascular or immune function. Recent studies have shown that ghrelin also plays an important role in the regulation of female reproduction. Information exists that its functional receptor, GHSR type 1a (GHS-R1a), is expressed in the hypothalamic-pituitary-ovarian axis. Ghrelin is synthesized locally in the hypothalamus, pituitary and ovaries of many species and has autocrine and/or paracrine effects. Most research indicates that ghrelin has inhibitory effect on gonadotropin secretion. Ghrelin also participates in the direct regulation of different ovarian functions such as steroid secretion, cell proliferation and apoptosis; these functions appear to be species-specific. Moreover, the importance of GHS-R1a or MAPK/IP3 pathway activation in ghrelin action in the ovary has been described. The article summarizes results of a series of recent studies on the effect of ghrelin on the hypothalamic-pituitary-ovarian axis, as well as on ovarian physiology with an indication that ghrelin via its biological functions such as energy metabolism and food intake could also be a key signal between animal energy status and control of ovarian function.