Purity >95% as determined by SDS-PAGE. Insulin-like growth factor I (IGF-I) is a growth factor that is produced by the liver. IGF-1 production is stimulated by growth hormone (GH). IGF-I binds the insulin-like growth factor 1 receptor (IGF1R) and the insulin receptor to stimulate systemic body growth. IGF-I is one of the most potent activators of the AKT signaling pathway, which stimulates cell proliferation and inhibits programmed cell death.