GHRH
Growth hormone-releasing hormone (GHRH) is a hypothalamic neuropeptide, generated from a prohormone that yields the active 44-amino-acid amidated form, that stimulates growth hormone release from pituitary somatotrophs. Acting through the Gs-coupled GHRH receptor, it raises cAMP and intracellular calcium, promoting GH secretion, somatotroph proliferation and GH gene expression; somatostatin and IGF-1 feedback counterbalance its drive within the hypothalamic-pituitary axis. Ectopic GHRH secretion, rare and usually pancreatic or pulmonary, can cause acromegaly, while GHRH receptor mutations cause familial isolated GH deficiency, and GHRH analogs such as tesamorelin are approved for HIV-associated lipodystrophy. GHRH stimulation tests have also been used to probe somatotroph reserve.
