Body composition in Prader-Willi syndrome: assessment and effects of growth hormone administration

Children and adults with Prader-Willi syndrome are usually overweight, if not obese. Nevertheless, it is now thought that the body composition exhibited by such individuals is markedly dissimilar to that found in simple obesity. In fact, the body composition typical of Prader-Willi syndrome is actually more characteristic of that found in individuals with growth hormone (GH) deficiency, namely an increased level of adiposity in the limbs in comparison with the trunk and an overall reduction in fat-free mass. This variation in body composition may impact upon the assumptions inherent in many techniques used to measure body size and body composition, such as the use of body mass index and skinfolds. Therefore, it is important that the potential error in body composition assessment is understood by professionals evaluating patients with Prader-Willi syndrome. Accurate assessment of body composition is critical in Prader-Willi syndrome, as a number of recent studies have revealed extremely similar findings relating to the effect of exogenous GH on the body composition of patients with this syndrome. Other notable findings of these studies include significant increases in muscle strength and exercise capacity, which probably result from the changes in body composition. The routine use of exogenous GH to treat this extremely debilitating syndrome should now be considered.