IGFBP-7, an IGF binding protein involved in the regulation of the binding to the IGF-I receptor, was recently shown to be elevated in children with PWS and normalized on GH treatment indicating that IGFBP-7 may be a marker of GH sensitivity and that higher levels of IGF-I are acceptable in PWS (26). This evidence concerns the gene IGF1R and Prader-Willi syndrome.