IGF-2   

Serum, frozen

0.5 mL

0.3 mL (Note: This volume does not allow for repeat testing.)

Gel-barrier tube, red-top tube or transfer tube

Transfer the serum into a Labcorp PP transpak frozen purple tube with screw cap (Labcorp No. 49482). Freeze immediately and maintain frozen until tested. To avoid delays in turnaround  time when requesting multiple test on frozen specimens, please submit separate frozen specimens for each test requested.

Freeze.

Specimen not serum

Insulin-like growth factor II (IGF-II) is crucial for fetal development and growth regulation, promoting cell proliferation and tissue growth in utero. Dysregulation of IGF-II expression is associated with certain cancers, as it can lead to uncontrolled cell growth and tumor development.

ELISA

An adjunct to IGF-I in the clinical evaluation of growth hormone-related disorders, insulin-like growth factor II (IGF-II) is a 7.5 kilodalton, 67 amino acid peptide that is thought to mediate some of the actions of growth hormone (GH). IGF-II peptide consists of the A, C and B chains and is structurally homologous to IGF-I and proinsulin. IGF-II is secreted by the liver and other tissues and is postulated to have mitogenic metabolic actions at or near the sites of synthesis; this has been termed the paracrine role of IGF-II. 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. A smaller proportion of IGF-II may circulate in association with other IGF-binding proteins. The proportion of unbound IGF-II in the circulation has been estimated at greater than 5%. 

Plasma levels of IGF-II are dependent upon adequate levels of GH and other factors, including adequate nutrition. The actions of IGF-II are mediated by binding to specific cell surface receptors. The function of the type II IGF receptor is not completely defined. IGF-II binds with lower affinity to the IGF-I type receptors and the insulin receptors. These latter receptors may mediate the mitogenic and metabolic actions of IGF-II. 

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 postnatal plasma IGF -II levels are assumed to be at maximum levels, since administration of GH does not result in increased IGF-II levels (unlike IGF-I levels, which increase). Postnatal plasma IGF-II levels show a moderate age-related increase throughout childhood and puberty, and there is no significant variability during the day. IGF-II levels decrease in GH deficiency and in malnutrition. IGF-II levels may also decrease exogenous administration of IGF-I. 

IGF-II overexpression is common in cancer and is a tumor marker for various tumor types, particularly those of mesenchymal and epithelial origin. Pre-clinical evidence demonstrates that not only is increased IGF-II symptomatic of cancer but also that IGF-II is tumorigenic and can promote tumor growth through autocrine or paracrine pathways. 

In addition to IGF-II levels having utility in detecting cancer, IGF-II also has prognostic value; elevated IGF-II correlates with poor prognosis and increased risk of anti-cancer drug resistance. IGF-II quantification can be particularly useful in diagnosing non-islet cell tumor hypoglycemia, which is characterized by a molar IGF-II:IGF-I ratio greater than 10.

Avnet S, Sciacca L, Salerno M, et al. Insulin receptor isoform A and insulin-like growth factor II as additional treatment targets in human osteosarcoma. Cancer Res. 2009 Mar 15;69:2443-2452. PubMed 19258511
 

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