Background: Because growth hormone (GH) exerted beneficial effects in various experimental models of heart failure, we investigated the effects of GH on physical exercise capacity and cardiopulmonary performance in patients with dilated cardiomyopathy and chronic heart failure (CHF).

Metthods: Twenty-two patients with CHF (NYHA functional class II-III) underwent spirometry and a symptom-limited, cardiopulmonary exercise testing before and after three months of GH (n=11; 7 males; 7 ID; 57±11 y; 4 IU subcutaneously every other day) or placebo (n=11; 8 males; 6 ID; 54±10 y) administration, in a randomised, double-blind trial. Background CHF therapy remained unchanged.

Results: GH, but not placebo, increased IGF-I serum concentration (from 144±35 to 293±58 ng/ml; p<0.005) and improved NYHA functional class (from 2.4±0.5 to 1.8±0.4; p<0.005), exercise duration (from 831±273 to 925±266 sec; p<0.005), peak power output (from 245±127 to 280±132 watt; p<0.05), peak VE (from 52.5±16.1 to 61.3±17.3 L/min; p<0.05), peak VO₂ (from 19.8±5.6 to 25.1±5.6 ml/kg/min; p<0.005), and anaerobic threshold (from 14.9±4.8 to 20.0±4.5 ml/kg/min; p<0.005), without affecting lung function parameters. Furthermore, the slope of the relationship between VE and VCO₂ (ventilatory efficiency) decreased from 34.7±5.1 to 31.7±5.3 (p<0.005), whereas the slope of the relation between percent predicted heart rate reserve used and percent observed metabolic reserve used (chronotropic index) rose from 0.57±0.20 to 0.69±0.18 (p<0.005).

Conclusion: Given the predictive value of physical exercise capacity and cardiopulmonary performance in CHF progression, these data provide additional insights into the mechanisms by which GH may potentially benefit CHF patients.