IGF-1, or insulin-like growth factor, is a polypeptide protein hormone that is similar to insulin. IGF-1 is mainly produced in the liver. It is important to children for growth and throughout adulthood for anabolic processes. IGF-1 is made up of more than 70 amino acids. It can be found in just about every cell (especially cells in the muscles, cartilage, bone, liver, kidney, nerves, skin, and lungs) in the body and is involved in cell growth and development.