Growth hormone deficiency in Prader-Willi syndrome

To search for arguments supporting the presence of a growth hormone deficie ncy (GHD) in Prader-Willi syndrome (PWS), the clinical and biochemical aspe cts of PWS are compared with nonsyndromal obesity and to GHD without PWS. R eviewing recently published studies and our own results, it is shown that t he following observations support the presence of a hypothalamic GHD in PWS : short adult stature and decreasing growth velocity despite onset of obesi ty; reduced lean body mass despite increased body fat; relatively low insul in-like growth factor-I (IGF-I) and low insulin levels; as well as the dram atic effect of growth hormone (GH) treatment on growth. Gn therapy changes the phenotype of PWS in childhood; height and weight become normal, and, in combination with increased physical activity and control of energy intake, there is a sustained impact on the net loss of body fat. The existence of true GHD in PWS might be difficult to prove because of the obesity-induced counter-regulation, but the GH/IGF axis clearly differs from that in simple obesity.