Growth hormone therapy improves exercise capacity in adult patients with Prader-Willi syndrome

Background: Prader-Willi syndrome (PWS) is associated with an inappropriate proportion of fat mass (FM) to non-FM compared to simple obesity. Altered body composition in PWS resembles that seen in subjects with GH deficiency, in which a reduction of lean body mass (LBM) is observed. The low LBM may contribute to the reduced motor skills seen in PWS patients. Aim: The objective of the study was to investigate the effects of GH therapy on exercise capacity and body composition in a group of adult subjects with PWS. Subjects and methods: Twelve PWS adults (7 males and 5 females, aged 26.4 +/- 4.4 yr, body mass index 44.3 +/- 4.6 kg/m(2)) participated in the study. Body composition analysis and exercise stress test were carried out throughout the 12 months GH therapy. Body composition was measured by Dual Energy X-ray Absorptiometry. Physical performance was evaluated using treadmill exercise test. Exercise intensity was expressed as metabolic equivalents (MET, 1 MET = 3.5 ml O-2 kg(-1)min(-1)). Statistical analysis was performed by repeated-measures analysis of variance followed by post-hoc analysis with t test for paired data for comparisons among the different follow ups. Results: Compared to baseline GH therapy increased LBM at 6 (p<0.0001) and 12 months (p<0.005) (45.3 +/- 7.7 kg vs 48.6 +/- 6.7 kg vs 48.2 +/- 7.5 kg). FM% was significantly reduced both after 6 and 12 months (p<0.02) (56.1 +/- 4.8% vs 53.7 +/- 4.2% vs 53.3 +/- 4.8%). Attained MET were found to be improved by 16% after 6 months and by 19% after 12 months of GH (p<0.001), while the small further rise between 6 and 12 months was not significant. Conclusions: Our findings seem to support the view that GH therapy has beneficial effects on physical activity and agility as well as on body composition of adult patients with PWS.