IGF1 and Laron syndrome: Homozygous or compound heterozygous mutations in GHR gene cause complete GH insensitivity (GHI), known as Laron syndrome, characterized by extreme short stature, high or normal GH concentrations, very low IGF-1 and IGFBP-3 levels, and no increase in IGF-1 concentration after exogenous GH stimulation (39).