In an IGF-I generation test study, 12 pre-pubertal NS children with mutations in PTPN11 did display a blunted increase in IGF-I compared with 12 children with idiopathic short stature; however, the majority of the NS children did not display classic biochemical GH insensitivity (41). Here, IGF1 is linked to short stature due to GHSR deficiency.