Concordant and discordant adrenocorticotropin (ACTH) responses induced by growth hormone-releasing peptide-2 (GHRP-2), corticotropin-releasing hormone (CRH) and insulin-induced hypoglycemia in patients with hypothalamopituitary disorders: evidence for direct ACTH releasing activity of GHRP-2

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The insulin-induced hypoglycemia test (insulin tolerance test: ITT) and corticotropin-releasing hormone (CRH) test are used to examine the activities of the hypothalamo-pituitary-adrenal (HPA) axis. Growth hormone-releasing peptide-2 (GHRP-2), a potent GH secretagogue, also stimulates adrenocorticotropin (ACTH) secretion. To evaluate the role of GHRP-2 in assessing the HPA axis, we examined 6 patients with various hypothalamo-pituitary disorders, and measured ACTH and cortisol responses during provocative tests (ITT, CRH, and GHRP-2 test). None of the 6 patients showed any significant ACTH or cortisol responses to ITT, but significant ACTH release was observed during CRH and GHRP-2 tests. These findings suggest GHRP-2 may directly stimulate ACTH secretion in patients with hypothalamopituitary disorders.