The IGF-I, t-IGFBP-3 concentrations, and the IGF-I/t-IGFBP-3 molar ratio in patients with PWS were higher by 2-fold (p < 0.001), 20% (p = 0.016), and 50% (p < 0.001) than in controls, respectively. This evidence concerns the gene IGF1 and Prader-Willi syndrome.