Glucose homeostasis in adults with Prader-Willi syndrome during treatment with growth hormone: results from a 12-month prospective study.

OBJECTIVES: To investigate glucose homeostasis in relation to body mass index (BMI) in adults with PWS before and after GH therapy.

DESIGN: We prospectively investigated the effects of a 12-month GH treatment on body composition and glucose homeostasis in relation to BMI in 39 adults, mean (±SD) age=28.6 (6.5) years with genetically verified PWS. We compared the results for different BMI categories (<25 kg/m²; 25-30 kg/m²; >30 kg/m²) and performed a regression analysis to detect predictors for homeostasis model of assessment-insulin resistance (HOMA-IR).

RESULTS: The baseline HOMA-IR was higher, with BMI of >30 kg/m². Our main findings were as follows: i) GH treatment (mean final dose, 0.6 (0.25) mg) was associated with small increases in fasting p-glucose, 2-h p-glucose by oral glucose load tolerance test, HOMA-IR and lean mass, and a reduction in fat mass. ii) Whereas the baseline HOMA-IR was associated with increased BMI (>30 kg/m²), we found no differences in HOMA-IR among the BMI categories after 12 months of GH. iii) Stepwise linear regression identified the triglyceride level as the strongest predictor of HOMA-IR at baseline, whereas an increase in VAT was the strongest predictor of the increase in HOMA-IR after therapy.

CONCLUSIONS: GH treatment for 12 months in adults with PWS resulted in an increase in HOMA-IR, irrespective of BMI, confirming that control of HbA1c is essential during GH treatment in PWS.