GH1 and neoplasm: In addition to the GH-IGF-I axis being able to favor tumor development, it increases the risk of mutations, stimulates cell proliferation and angiogenesis (IGF-I is expressed in endothelial cells during angiogenesis and increases vascular endothelial growth factor, the main proangiogenic factor responsible for neovascularization), invasion, and metastasis; other components of the somatotropic system, such as IGF-II and IGF binding proteins (IGFBPs), exert an antitumoral effect by stimulating apoptosis and inhibiting mitogenesis, although the strength of these actions are weaker (27, 32–35).