The Insulin Growth Factors belong to the Insulin gene family, the prototypic members of which include insulin and relaxin. Also known as somatomedin C, IGF1 is known to stimulate the proliferation of a wide range of cells including muscle, bone, and those of the cartilage tissue. A dominant effector of the growth hormone, mature IGF1 is generated by proteolytic removal of the N- and C- terminal pro-peptide regions. Mature human IGF1 shares 94% and 96% amino acid sequence identity with mouse and rat IGF1, respectively, while exhibiting cross-species activity. Circulating IGF1 is produced by hepatocytes while local IGF1 is produced by various other tissues in which it exerts paracrine effects. Recombinant Human IGF1 is a globular, 7.7 kDa protein that contains 3 native intra-molecular disulfide bonds.