Neuroendocrine regulation of growth hormone.

This short review is focused on the neuroendocrine regulation of growth hormone (GH) pulsatile secretory pattern and GH gene expression. The neuronal network involved in the central control of GH includes extrahypothalamic neurons such as the noradrenergic and cholinergic systems, which regulate the two antagonistic neurohormonal systems: somatostatin (SRIH) and GH-releasing hormone (GHRH). Intrahypothalamic Proopiomelanocortin- and Galanin-containing interneurons also participate in the regulation of SRIH and GHRH neuronal activity, which also is dependent on sex steroids and GH and/or insulin-like growth factor I (IGF-I) feedback. cAMP (controlled mainly by GHRH and SRIH), thyroid and glucocorticoid hormones. IGF-I and activin are among the factors that regulate GH gene expression at the transcriptional level and may play a role in somatotroph differentiation and proliferation during ontogeny as well as physiological and pathological states such as acromegaly.