Ghrelin as a GH-releasing factor.

Growth hormone (GH) is secreted by the pituitary gland in a pulsatile manner. It is accepted that this pulsatility is primarily controlled by the hypothalamus, although this secretion can also be modulated by factors from GH-targeted organs, the pituitary and other regions of the central nervous systems, or by factors arriving from peripheral organs. In mammals, hypothalamic control of GH pulsatility is classically regulated by the interplay of two opposing hormones, stimulatory GHRH and inhibitory somatostatin (SS). Recognition of the gastric ghrelin peptide as the natural ligand for GH secretagogue receptor type 1a (GHS-R1a) added a new element to the complex physiological regulation of GH secretion and clarified some of its aspects that were previously not fully understood. In this review, we examine data that suggest that ghrelin may regulate GH secretion, as well as ghrelin's possible use as a therapeutic agent.