Background GH-deficient (GHD) adults have reduced anaerobic exercise capacity(1), a performance measure dependent on energy derived from anaerobic glycolysis and on muscle strength. Short-term GH therapy improves anaerobic exercise capacity in recreational athletes without a change in muscle strength(2), an effect on energy metabolism rather than on muscle anabolism.
Aim To investigate whether short-term GH improves anaerobic capacity and physical function in GHD adults.
Method 17 hypopituitary adults, aged 47±2.4 years on conventional replacement therapy were randomized into a 2-month double-blind placebo-controlled GH replacement (0.5mg/day) study with a crossover at 1-month. Anaerobic capacity (watts) was assessed by the Wingate test and aerobic capacity by the VO2max (L/min) test. Physical function was assessed by the stair-climb test, chair-stand test and 7-day pedometry. Lean body mass (LBM) was quantified by DEXA. Data were analyzed by repeated-measures ANOVA and tested for carry-over effects. Results are expressed as mean±SE.
Results
There were no statistically significant changes in body composition, anaerobic capacity, aerobic capacity and functional measures between placebo and GH treatments.
|
Baseline |
Placebo |
GH |
|
|
LBM (kg) |
43.9±1.6 |
43.0±1.7 |
44.3±1.5 |
|
Anaerobic power (W/kg.LBM) VO2max (mL/kg.LBM/min) |
5.9±0.3 36.8±5.4 |
6.0±0.3 38.7±6.9 |
5.7±0.3 37.6±5.5 |
|
Stair climb test (secs) Chair stand test (number/30 sec) Pedometry (Steps/day) |
19.5±0.7 19.1±1.0 7029±567 |
19.1±0.7 21.7±1.1 6652±455 |
19.1±0.8 21.4±0.9 6594±566 |
Summary One month of GH replacement did not increase LBM, anaerobic power, VO2max or measures of physical function.
Conclusion
Short-term GH replacement does not stimulate the anaerobic energy system. Longer term studies are required to ascertain whether GH improves anaerobic capacity in GHD adults.