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 micrograms/kg BW was self-administered daily sc.
Oxygen consumption (VO2), CO2 production, and ventilatory volumes
were measured during exercise on a bicycle spiroergometer. M-Mode
echocardiography was performed using standard techniques. The VO2
max data, expressed per kg BW (mL/min.kg BW) showed a significant
increase from 23.2 +/- 2.4 to 30.0 +/- 2.3 (P < 0.01) in the
hGH-treated group, whereas the VO2 max data, expressed per lean
body mass (milliliters per min/kg lean body mass) did not change
significantly in either group. Maximal O2 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 power 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 constant in the placebo group. Cardiac
structure (left ventricular posterior wall, interventricular septum
thickness, left ventricular mass, left ventricular end-systolic
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 group. 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 contribute to the improvement in exercise
performance during hGH treatment. According to our data, hGH
replacement therapy leads to an improvement of exercise capacity
and maximal oxygen uptake, but has no significant effect on cardiac
structure.