IGF-II is a 7.5 kDa, 67-amino-acid peptide that is thought to mediate some of the actions of growth hormone (GH). IGF-II peptide is structurally homologous to IGF-I and proinsulin. IGF-II is secreted by the liver and other tissue and is postulated to have mitogenic and metabolic actions at or near the sites of synthesis. IGF-II also appears in the peripheral circulation, where it circulates primarily in a high molecular weight tertiary complex with IGF-binding protein-3 (IGFBP-3) and acid-labile subunit. The proportion of unbound IGF-II in the circulation has been estimated at >5%. Plasma levels of IGF-II are dependent on adequate levels of GH and other factors, including adequate nutrition. The actions of IGF-II are mediated by binding to specific cell surface receptors. Although its specific physiologic role has not been defined, it has been postulated that the interplay of IGF-I and IGF-II with the different cell surface receptors and circulating binding proteins modulates tissue growth.
Normal ranges:
Child, prepubertal: 334 " “642 ng/mL
Child, pubertal: 245 " “737 ng/mL
Adult: 288 " “736 ng/mL
GH deficiency: 51 " “299 ng/mL
Use
IGF-II is an adjunct to IGF-I in the clinical evaluation of GH-related disorders.
Interpretation
Increased In
Hypoglycemia associated with non " “islet cell tumors