Endocrine Abstracts

The GH response to standard provocative tests is significantly lower in adult patients with Prader–Willi syndrome (PWS) than obese controls with similar body mass index (BMI). Nevertheless, BMI is an inadequate measure of body composition in PWS, because PWS harbour a higher fat mass than simple obesity, under the same degree of weight excess. This study evaluated either the GH response to combined GHRH+arginine administration and the fat body mass, by dual energy X-ray absorptiometry, in a group of 11 PWS adults (8 females, aged 20.1–41.1 years), in comparison to those obtained in a group of 10 patients with essential obesity (8 females, aged 23.5–45.8 years), matched for BMI and percentage of total body fat (FM%). The study protocol was approved by the local Ethical Committee. Statistical analysis was performed by t-test for unpaired data, and using analysis of variance for parametric and nonparametric (Mann–Whitney test) data, where appropriate. Mean (+S.E.M.) FM% was similar in PWS and obese subjects (53.0+1.5 vs 51.5+1.0, respectively). The GH response to GHRH+arginine was significantly lower in PWS patients (GH peak 5.4+1.3 μg/l; area under the curve (AUC) 311.2+72.5 μg/l per h) than obese subjects (GH peak 21.0+4.1 μg/l, P<0.005; AUC 1241.1+272.8 μg/l per h; P<0.01). In PWS group, the GHRH+arginine induced GH rise in patients with del15q11–q13 was significantly higher than those observed in subjects with UPD15 (GH peak 7.7+1.7 μg/l vs 2.7+1.0 μg/l, P<0.05; AUC 458.5+91.0 μg/l per h vs 134.4+46.0 μg/l per h, P<0.02). These findings suggested that GH secretory pattern is different in PWS adults when compared to patients with simple obesity and that reduced GH secretion is not exclusively related to adiposity in PWS subjects. In addition, our data seem to indicate that GH secretory pattern is significantly different in PWS individuals having separate genetic subtypes.