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Insulin-like Growth Factor 2 (IGF-2) (Endocrine Sciences)
An adjunct to IGF-I in the clinical evaluation of growth hormone-related disorders
Plasma specimens produce falsely decreased results.
Radioimmunoassay (RIA) after acid:alcohol extraction
• Prepubertal: 258−882 ng/mL; mean: 570 ng/mL
• Pubertal: 273−892 ng/mL; mean: 583 ng/mL
• Adults: 333−967 ng/mL; mean: 650 ng/mL
Insulin-like growth factor II (IGF-II) is a 7.5 kilodalton, 67 amino acid peptide which 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 tissue and is postulated to have mitogenic and 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 >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 in acromegaly and during exogenous administration of IGF-I.
0.1 mL (Note: This volume does not allow for repeat testing.)
Transfer the serum into a LabCorp PP transpak frozen purple tube with screw cap (LabCorp N° 49482). Freeze immediately and maintain frozen until tested. To avoid delays in turnaround time when requesting multiple tests on frozen specimens, please submit frozen specimens for each test requested.
Causes for Rejection
Specimen not serum
|Order Code||Order Code Name||Order Loinc||Result Code||Result Code Name||UofM||Result LOINC|
|141770||IGF-2||141772||Insulin-Like Growth Factor II||ng/mL||2485-1|