Measured resting energy expenditure by indirect calorimetry and energy intake in long-term growth hormone treated children with PWS.

Introduction: Severe obesity can develop in children with PWS when food intake is not controlled. Maintenance of body weight requires an energy balance, of which energy intake and energy expenditure are important components. Previous studies described a decreased resting energy expenditure (REE) in growth hormone (GH)-untreated children with PWS. In short-term studies, no difference in REE was found between GH-treated and untreated children with PWS. However, there are limited data on REE in children with PWS who were GH-treated for a long period.

Methods: This study describes measured REE (mREE), energy intake and body composition during long-term GH-treatment in children with PWS. Patients were treated with 1.0 mg GH/m2/day (~0.035mg/kg/day). REE was determined by indirect calorimetry; dietary energy intake was calculated using a 3-day dietary record. Body composition by Dual energy X-ray absorptiometry (DXA) scans.

Results: We included 52 GH-treated children with PWS with mean (SD) age of 8.53 (4.35) years and median (IQR) GH-treatment duration of 7 (4-11) years. mREE increased with age, but was not associated with GH-treatment duration. A higher LBM was associated with higher mREE. Mean energy intake was significantly lower compared to daily energy requirements (DER) for age- and sex-matched healthy children (p<0.001), ranging from 23-36% less intake in children aged 3.5-12 years to 49% less intake in children aged 12-18 years. Fifty percent of children had a normal REE, 17.3 % a decreased REE and 32.7% an elevated REE, according to predicted REE based on measured REE in a large group of healthy children.

Conclusion: In children with PWS, mREE increases with age. GH-treatment duration is not associated, whereas LBM is an important determinant of mREE. Children with PWS have a low to very low energy intake compared to DER for age- and sex-matched children, with a declining intake when becoming older.