The insulin-like growth factor (IGF-1) is a polypeptide with a high sequence similarity to insulin. It can trigger the same cellular responses like insulin, including mitogenesis in cell culture. There are two known insulin-like growth factor receptors, one of them closely resembling the insulin receptor.
IGF-1 is mainly secreted by the liver as a result of stimulation by human growth hormone (hGH). Almost every cell in the human body is affected by IGF-1, especially cells in muscle, cartilage, bone, liver, kidney, nerves, skin, and lungs. In addition to the insulin-like effects, IGF-1 can also regulate cell growth and development, especially in nerve cells, as well as cellular DNA synthesis.