Insulin, insulin-like growth factor-1 (IGF-1), and insulin-like growth factor-2 (IGF-2) are ligands for the transmembrane tyrosine kinase receptors, insulin receptor (IR), and IGF-1 receptor (IGF-1R), which have important roles in growth, development, cancer, and metabolic disease (120, 121). Here, IGF1 is linked to Other metabolic disease.