Related Experiment Videos
Cardiac effects of hexarelin in hypopituitary adults
1Division of Nuclear Medicine and Division of Endocrinology and Metabolism, Department of Internal Medicine, University of Turin, Ospedale Molinette, C.so Dogliotti 14, 10126 Turin, Italy. bisi@molinette.unito.it
Insights
Hexarelin, a growth hormone (GH)-releasing peptide, improved heart function in patients with GH deficiency (GHD). This positive inotropic effect in the heart was observed acutely and may be independent of GH release.
Area of Science:
- Cardiology
- Endocrinology
- Pharmacology
Background:
- Growth hormone (GH) secretagogues, like hexarelin, interact with specific receptors in the pituitary, hypothalamus, and heart.
- Patients with GH deficiency (GHD) often exhibit impaired cardiac function.
Purpose of the Study:
- To investigate the acute cardiac effects of hexarelin in adult male patients with GHD.
- To compare the cardiac response to hexarelin in GHD patients versus healthy controls.
Main Methods:
- Equilibrium radionuclide angiocardiography was used to assess left ventricular ejection fraction (LVEF).
- Seven adult male patients with GHD and nine adult male controls received intravenous hexarelin.
- Measurements included LVEF, catecholamine levels, mean blood pressure (MBP), and cardiac output.
Main Results:
- Patients with GHD showed significantly lower basal LVEF compared to controls (50% vs. 63%).
- Hexarelin administration led to a significant increase in LVEF in both GHD patients and controls (57% vs. 70%).
- The positive inotropic effect of hexarelin occurred without changes in catecholamine levels, MBP, or cardiac output.
Conclusions:
- Acute hexarelin administration exerts a transient positive inotropic effect on the human heart.
- This effect appears to be independent of GH release and may be mediated by myocardial receptors specific to GH secretagogues.
Abstract:
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 microg/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.