EFFECT OF GROWTH-HORMONE (HGH) REPLACEMENT THERAPY ON PHYSICAL WORK CAPACITY AND CARDIAC AND PULMONARY-FUNCTION IN PATIENTS WITH HGH DEFICIENCY ACQUIRED IN ADULTHOOD

The effects of 6 months of replacement therapy with recombinant human GH (hGH) on physical work capacity and cardiac structure and function were investigated in 20 patients with hGH deficiency of adult onset in a double blind, placebo-controlled trial. The GH dose of 12.5 mu g/kg BW was self-administered daily sc. Oxygen consumption (VO2), CO2 prod uction, and ventilatory volumes were measured during exercise on a bic ycle spiroergometer. M-Mode echocardiography was performed using stand ard techniques. The VO, max data, expressed per kg BW (mL/min.kg BW) s howed a significant increase from 23.2 +/- 2.4 to 30.0 +/- 2.3 (P < 0. 01) in the hGH-treated group, whereas the VO, max data, expressed per lean body mass (milliliters per min/kg lean body mass) did not change significantly in either group. Maximal O-2 pulse (milliliters per beat ) increased significantly from 15.2 +/- 5.6 to 19.6 +/- 3.3 ml/beat (P < 0.01), but remained constant in the placebo group. The maximal powe r output (watts +/- SE) increased significantly(P < 0.01) from 192.5 /- 13.5 to 227.5 +/- 11.5 in the hGH-treated group, but remained const ant in the placebo group. Cardiac structure (left ventricular posterio r wall, interventricular septum thickness, left ventricular mass, left ventricular endsystolic dimension, and left ventricular end-diastolic dimension) as well as echocardiographically assessed cardiac function did not change significantly after 6 months of treatment in either gr oup. We conclude that hGH replacement in hGH-deficient adults improves oxygen uptake and exercise capacity. These improvements in pulmonary parameters might be due to an increase in respiratory muscle strength and partly to the changes in muscle volume per se observed during hGH replacement therapy. Furthermore, an increased cardiac output might co ntribute to the improvement in exercise performance during hGH treatme nt. According to our data, hGH replacement therapy leads to an improve ment of exercise capacity and maximal oxygen uptake, but has no signif icant effect on cardiac structure.