IGF1 and Prader-Willi syndrome: The median (IQR) free IGF-I was 1.20 (0.86 to 1.66) nmol/L in the GH-treated prepubertal children with PWS, which was significantly lower than the median free IGF-I of 1.90 (1.33 to 2.62) nmol/L in the GH-treated pubertal children with PWS (p < 0.001) (Table 2).