Ghrelin and anterior pituitary function.
Ghrelin, a 28-amino-acid octanoylated peptide predominantly produced by the stomach, was discovered to be the natural ligand of the type 1a GH secretagogue receptor. Thus, it was considered as a natural GH secretagogue (GHS) additional to GHRH, although later on ghrelin has mostly been considered a major orexigenic factor. The GH-releasing action of ghrelin takes place both directly on pituitary cells and through modulation of GHRH from the hypothalamus; some functional anti-somatostatin action has also been shown. However, even at the neuroendocrine level, ghrelin is much more than a natural GHS. In fact, it significantly stimulates prolactin secretion in humans, independent of both gender and age and probably involving a direct action on somatomammotroph cells. Above all, ghrelin and synthetic GHS possess an acute stimulatory effect on the activity of the hypothalamus-pituitary-adrenal axis in humans, which is, at least, similar to that of the opioid antagonist naloxone, arginine vasopressin and even corticotropin-releasing hormone. Also, ghrelin plays a relevant role in the modulation of the hypothalamic-pituitary-gonadal function, with a predominantly CNS-mediated inhibitory effect upon the gonadotropin pulsatility both in animals and in humans.
Lanfranco
Fabio
F
Motta
Giovanna
G
Baldi
Matteo
M
Gasco
Valentina
V
Grottoli
Silvia
S
Benso
Andrea
A
Broglio
Fabio
F
Ghigo
Ezio
E
D000324:Adrenocorticotropic Hormone / Q000378:metabolism; D003346:Corticotropin-Releasing Hormone / Q000502:physiology; D054439:Ghrelin / Q000502:physiology*; D006062:Gonadotropins / Q000378:metabolism; D013007:Growth Hormone-Releasing Hormone / Q000502:physiology; D006801:Humans; D010903:Pituitary Gland, Anterior / Q000502:physiology*; D011388:Prolactin / Q000502:physiology
D054439:Ghrelin; D006062:Gonadotropins; D000324:Adrenocorticotropic Hormone; D011388:Prolactin; D003346:Corticotropin-Releasing Hormone; D013007:Growth Hormone-Releasing Hormone