Insulin-like growth factors (IGFs) play important roles in mammalian growth and development. They may also be involved in the development of cancers and atherosclerosis. IGF1 mediates many of the growth-promoting effects of growth hormone. IGF Binding Proteins Bind to IGF's. Raised circulating IGF binding protein-1 (IGF BP1) levels are found in subjects with severe preeclampsia. IGF BP3 can inhibit cell proliferation by binding to, and inactivating IGF-1 and IGF-2. Binding of IGF-1 to IGF-BP5 has a controling effect on the cellular action of IGF-1. It also prolongs the biological half-life of the IGF-1. IGF-1R strongly binds both IGF-1 and IGF-2.