Insulin-like growth factor I (also known as somatomedin C and somatomedin A) and insulin-like growth factor II (multiplication stimulating activity or MSA) belong to the family of insulin-like growth factors that are structurally homologous to proinsulin. Mature IGF-I and IGF-II share approximately 70% sequence identity. Both IGF-I and IGF-II are expressed in many tissues and cell types and may have autocrine, paracrine and endocrine functions. Mature IGF-I and IGF-II are highly conserved (100% identity between human, bovine and porcine proteins) and exhibit cross-species activity. IGF-II is a potent mitogenic growth factor.
IGF-II binding is significantly increased in the diabetic kidney and could play a role in diabetic neuropathy. It also appears to be involved significantly in the progression of many tumors