Modulação da secreção do hormônio de crescimento pela (por la) ghrelina e secretagogos do hormônio de crescimento

Growth hormone-releasing hormone and somatostatin modulate growth hormone secretion. A third mechanism has been discovered in the last decade, involving the action of growth hormone secretagogues. Ghrelin is a new acylated peptide mainly produced by the stomach, but also synthesized in the hypothalamus. This compound increases both growth hormone release and food intake. The relative roles of hypothalamic and circulating ghrelin on growth hormone secretion are still unknown. Endogenous ghrelin might amplify the basic pattern of growth hormone secretion, optimizing somatotroph responsiveness to growth hormone-releasing hormone. This peptide activates multiple interdependent intracellular pathways at the somatotroph, involving protein kinase C, protein kinase A and extracellular calcium Systems. However, as ghrelin induces a greater release of growth hormone in vivo, its main site of action is the hypothalamus. In the current paper we review the available data on the discovery of this peptide, the mechanisms of action and possible physiological roles of growth hormone secretagogues and ghrelin on growth hormone secretion, and, finally, the regulation of growth hormone release in man after intravenous administration of these peptides.Univ Fed Sao Paulo, Disciplina Endocrinol, Escola Paulista Med, San Pabli, BrazilUniv Fed Sao Paulo, Sao Paulo, BrazilUniv Fed Sao Paulo, Disciplina Endocrinol, Escola Paulista Med, San Pabli, BrazilUniv Fed Sao Paulo, Sao Paulo, BrazilWeb of Scienc