IGF1 and cancer: Other mechanisms that may explain the increased cancer risk include the mitogenic effect of insulin through either insulin-like growth factor-1 (IGF1) receptors or through hybrid IGF1-insulin receptors as well as the increased concentrations of free IGF1, as a consequence of the lower concentrations of IGF binding proteins 1 and 2 (IGFBP1 and IGFBP2) in obese individuals [51].