ESPE Abstracts

Context: In the newborn period, failure to thrive (FTT) with feeding difficulties and severe hypotonia are prominent in Prader-Willi syndrome (PWS). Despite the low weight, abnormal body composition is already present at birth in both children with FTT and those without. Limited studies reported the prevalence of FTT in infants with PWS and it has not yet been described whether GH-treatment has different effects in infants with FTT compared to those without.

Objective: Evaluate the prevalence of FTT in a large group of infants with PWS and the effects of 5 years of GH-treatment on body composition in infants with FTT compared to those without.

Methods: An open-label, prospective study in 164 infants with PWS. FTT was defined as weight-for-length (W/L) <-2 SDS. All children were treated with 1.0 mg GH/m2/day (~0.035 mg/kg/day). Body composition was determined by Dual energy X-ray absorptiometry (DXA) scans.

Results: Twenty-four of the 164 (14.6%) infants had FTT at start of GH-treatment. Infants with FTT had a median (IQ) age of 0.74 (0.36 to 1.31) years at start of GH-treatment and infants without FTT an age of 0.70 (0.53 to 1.41) years (P = 0.37). Infants with FTT had a median (IQR) birthweight SDS of -1.03 (-1.83 to -0.36), compared to -0.95 (-1.59 to -0.32) in infants without FTT (P = 0.56). Both groups had the same length SDS of -1.45 (-2.31 to -0.51) and -1.54 (-2.48 to 0.71) (P = 0.62), resp. The increase in estimated mean weight-for-length (W/L) SDS during the first 2 years of GH-treatment was greater in infants with FTT at start of GH compared to infants without (P = 0.001), but the W/L SDS trajectory during 5 years of GH remained lower in infants who had FTT. At GH-start, there was a significant positive correlation between fat mass % (FM%), Lean Body Mass Index (LBMI) and W/L SDS. After 5 years, children who had FTT at GH-start, still had a lower FM% compared to those without FTT. At GH-start, infants with FTT had a lower LBMI compared to those without, but after 5 years of GH, LBMI was not different between the groups.

Conclusion: Infants with FTT show greater catch-up in weight-for-length in the first two years of GH-treatment compared to those without FTT of similar age, mainly due to catch-up in LBMI, resulting in a similar LBMI after 5 years of GH.