Insulin-like Growth Factor I (IGF-I), is the dominant effector of Growth Hormone (GH) and is structurally homologous to Proinsulin. The 7.6 kDa mature IGFI is identical between isoforms and is generated by proteolytic removal of the N- and C-terminal regions. Mature human IGF-I shares 94% and 96% amino acid (aa) sequence identity with the mouse and rat orthologs, respectively. The body growth of animals is regulated by growth hormone and IGF-I. The classical theory of this regulation is that most IGF-I in the blood originates in the liver and that body growth is controlled by the concentration of IGF-I in the blood. Meanwhile, IGF-I has been shown to enhance neuronal survival and inhibit apoptosis. IGF-1 promote the proliferation of multiple myeloma (MM) cells and protect them against dexamethasone (Dex)-induced apoptosis.