The insulin-like growth factor 1 receptor (IGF-1R), located on the surface of human cells, is a transmembrane receptor activated by the hormone insulin-like growth factor 1 (IGF-1) and another related hormone, insulin-like growth factor 2 (IGF-2), and belongs to a large class of tyrosine kinase receptors.IGF-1R mediates the function of IGF-1, a polypeptide molecularly similar in structure to the insulin protein hormone that has an important role in growth and development and adult anabolism and can cause hyperproliferation of skeletal muscle or other target tissues. Mice deficient in IGF-1R die late in development, as evidenced by dramatic weight loss, demonstrating the strong growth-promoting effects of this receptor. Studies have linked IGF-1R to a number of cancers, including breast, prostate and lung cancer.