Insulin-like Growth Factors, IGFs

The insulin-like growth factors (IGFs) are proteins with high sequence similarity to insulin. IGFs are part of a complex system that cells use to communicate with their physiologic environment. This complex system (often referred to as the IGF "axis") consists of two cell-surface receptors (IGF1R and IGF2R), two ligands (IGF-1 and IGF-2), a family of seven high-affinity IGF-binding proteins (IGFBP1 to IGFBP7), as well as associated IGFBP degrading enzymes, referred to collectively as proteases. The IGF "axis" is also commonly referred to as the Growth Hormone/IGF-1 Axis. Insulin-like growth factor 1 (IGF-1) is mainly secreted by the liver as a result of stimulation by growth hormone (GH). IGF-1 is important for both the regulation of normal physiology, as well as a number of pathological states, including cancer. The IGF axis has been shown to play roles in the promotion of cell proliferation and the inhibition of cell death.