Lengyel Ana Maria J
Division of Endocrinology, Federal University of São Paulo (UNIFESP/EPM), São Paulo, Brazil.
Arq Bras Endocrinol Metabol. 2006 Feb;50(1):17-24. doi: 10.1590/s0004-27302006000100004. Epub 2006 Apr 17.
Growth hormone (GH)-releasing hormone and somatostatin modulate GH secretion. A third mechanism has been discovered in the last decade, involving the action of GH secretagogues. Ghrelin is a new acylated peptide produced mainly by the stomach, but also synthesized in the hypothalamus. This compound increases both GH release and food intake. The relative roles of hypothalamic and circulating ghrelin on GH secretion are still unknown. Endogenous ghrelin might amplify the basic pattern of GH secretion, optimizing somatotroph responsiveness to GH-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 GH in vivo, its main site of action is the hypothalamus. In this paper we review the available data on the discovery of ghrelin, the mechanisms of action and possible physiological roles of GH secretagogues and ghrelin on GH secretion, and, finally, the regulation of GH release in man after intravenous administration of these peptides.
生长激素释放激素和生长抑素调节生长激素的分泌。在过去十年中发现了第三种机制，涉及生长激素促分泌素的作用。胃饥饿素是一种主要由胃产生，但也在下丘脑合成的新的酰化肽。这种化合物既能增加生长激素的释放，又能增加食物摄入量。下丘脑和循环中的胃饥饿素对生长激素分泌的相对作用仍不清楚。内源性胃饥饿素可能会放大生长激素分泌的基本模式，优化生长激素细胞对生长激素释放激素的反应性。这种肽在生长激素细胞中激活多个相互依赖的细胞内途径，涉及蛋白激酶C、蛋白激酶A和细胞外钙系统。然而，由于胃饥饿素在体内诱导生长激素的释放更多，其主要作用部位是下丘脑。在本文中，我们综述了有关胃饥饿素的发现、生长激素促分泌素和胃饥饿素对生长激素分泌的作用机制及可能的生理作用的现有数据，最后还综述了静脉注射这些肽后人体生长激素释放的调节情况。
