Pathogenesis insulinlike growth factor 1(IGF-1)is secreted and acts locally at the site of growing bone GF-1 binds to one of several IGF-binding proteins (IGFBPs)and circulates almost entirely (99%)in the bound state IGFBP-3 accounts for the majority of IGF-I binding and this binding proteins activity depends directly on GH• insulinlike growth factor 1 (IGF-1) is secreted and acts locally at the site of growing bone • IGF-1 binds to one of several IGF-binding proteins (IGFBPs) and circulates almost entirely (>99%) in the bound state • IGFBP-3 accounts for the majority of IGF-I binding and this binding protein’s activity depends directly on GH Pathogenesis