Cardiac effects of hexarelin in hypopituitary adults

Growth hormone (GH)-releasing peptides possess specific pituitary, hypothalamic, and myocardial receptors. Seven adult male patients with GH deficiency (GHD) (age, mean +/- S.E.M.: 42.0 +/- 4.0 year) were studied by equilibrium radionuclide angiocardiography after i.v. administration of hexarelin, a peptide GH secretagogue. Data for these patients were compared with those for nine adult male controls (37.0 +/- 2.7 year). The GH response to hexarelin was negligible in patients with GHD compared to control subjects (CS) (peak: 1.9 +/- 0.9 vs. 45.7 +/- 3.6 mu g/l, P < 0.001). Basal left ventricular ejection fraction (LVEF) in patients with GHD was lower than that in CS (50 +/- 1% vs. 63.2%, P < 0.001). Hexarelin administration increased LVEF both in patients with GHD and in CS (peak: 57 +/- 2 vs. 70 +/- 2, respectively, P < 0.05 vs. baseline) without changing catecholamine levels, mean blood pressure (MBP), or cardiac output in either group. In conclusion, the acute administration of hexarelin exerts a short-lasting positive inotropic effect in humans, probably GH-independent and mediated by specific myocardial receptors for GH secretagogues.