Decreased GH secretion and enhanced ACTH and cortisol release after ghrelin administration in Cushing's disease: comparison with GHRP-6

Abstract

GHRP-6-induced GH release is decreased in Cushing's disease (CD), and ACTH and cortisol responses are enhanced. Ghrelin stimulates GH, ACTH and cortisol release in men. We compared the GH, ACTH and cortisol responses to ghrelin and GHRP-6 in CD (n = 12) and controls (n = 9). In CD, peak GH levels (mu g/L; mean +/- SE) after ghrelin administration (7,7 +/- 2,6) were higher than those observed after GHRP-6 (2,7 +/- 1), but lower than in controls (58,4 +/- 10). Peak ACTH (pg/mL) and cortisol (mu g/dL) levels after ghrelin (187 +/- 35 +/- 4,5) were higher than in controls (93 +/- 32; 18,9 +/- 1,1), but similar to GHRP-6 (185 +/- 57; 33,3 +/- 4,7). The higher GH response to ghrelin compared to GHRP-6 in CD suggests activation of additional intracellular pathways by ghrelin. The same ACTH and cortisol releasing mechanisms are probably stimulated by both peptides.