Failure to Thrive in Infants with Prader-Willi Syndrome and Long-Term Effects of GH Treatment on FTT

Failure to thrive (FTT) with feeding difficulties and hypotonia are well-known features in infants with Prader-Willi syndrome (PWS). Limited studies reported the percentage of infants with FTT and it is unknown whether growth hormone (GH) treatment affects body composition of infants with or without FTT differently. Aims of the study were to evaluate the percentage of infants with PWS with FTT from birth to age 6 months and to investigate the 5-year GH effects on body composition in infants with or without FTT at GH start.

We defined FTT as weight-for-length <-2 SDS and evaluated the percentage of infants with FTT in a group of 54 infants from birth to age 6 months. In addition, we investigated in 166 children the 5-year GH effects on body composition, comparing children with and without FTT at GH start. All infants were treated with 1.0 mg GH/m2/day (∼0.035 mg/kg/day). Body composition was determined by dual-energy X-ray absorptiometry.

From birth to age 6 months, 29% of infants had FTT at 1 month, 20% at 3 months, and 16% at 6 months. At GH start, at a median age of 1.03 (IQR 0.45, 1.89) years, 12% (20/166) had FTT (FTT_{GH start}). Infants with FTT_{GH start} had a lower lean body mass index (LBMI) compared to non-FTT_{GH start}, but a greater catch-up in LBMI in the first year of GH, resulting in a similar LBMI as the non-FTT_{GH start} after 5 years of GH treatment. Children with FTT_{GH start} had lower FM% after 5 years of GH treatment, but this difference disappeared after including covariates.

Twenty-nine percent of infants had FTT at 1 month, 20% at 3 months, and 16% at 6 months. Twelve percent had FTT at the start of GH treatment. Children with FTT at GH start showed greatest LBM improvement during GH treatment, resulting in a similar LBM after 5 years of GH treatment as those without FTT at GH start.