Purity >95% by non-reducing SDS-PAGE and HPLC, MW: 7.7 kDa (SDS-PAGE). Insulin-like growth factor I (IGF-I) also known as Somatamedin C is a hormone similar in molecular structure to insulin. Human IGF-I has two isoforms (IGF-IA and IGF-IB) which is differentially expressed by various tissues. Mature human IGF-I respectively shares 94% and 96% aa sequence identity with mouse and rat IGF-I. Both IGF-I and IGF-II (another ligand of IGF) can signal through the IGF-I receptor (IGFIR), but IGF-II can alone bind the IGF-II receptor (IGFIIR/ Mannose-6-phosphate receptor). IGF-I plays an important role in childhood growth and continues to have anabolic effects in adults. Recombinant human Insulin-like growth factor I (rhIGF-I) produced in E. coli is a single non-glycosylated polypeptide chain containing 70 amino acids. A fully biologically active molecule, rhIGF-I has a molecular mass of 7.7 kDa analyzed by reducing SDS-PAGE and is obtained by chromatographic techniques.