Growth metabolism

Insulin like Growth Factor - II

Serum, plasma, urine, saliva, CSF, cell culture media.

Samples have to be chilled as soon as possible after collection. Long-term storage should be carried out at –20°C or below. Avoid repeated freezing/thawing of specimens.

Age dependent. A detailed table for serum IGF-II reference values is included in the test procedure. IGF-II concentration in other body fluids or cell culture supernatants can deviate strongly from the serum values.

Human

The insulin-like growth factors (IGF)-I and-II play a pivotal role in the regulation of proliferation and differentiation of several tissue types. IGF-I also called Somatomedin C has a molecular weight of 7469 dalton. Its expression is mainly regulated by Growth Hormone and nutrition. But several hormones and peptide factors are known to influence IGF-II synthesis in different tissues. Bioavailability of the IGFs is regulated by specific binding proteins (IGFBP). Beside the high affinity Insulin-like Growth Factor Binding Proteins 1-6, IGFs are also bound by IGFBP-related Proteins. These binding proteins bind IGF-I and IGF-II with the same affinity or prefer IGF-II. Direct measurement of IGFs in serum samples without pretreatment results in false values. Because of the extremely slow dissociation of the IGF/IGFBP complexes during the assay incubation only a part of the IGF-II in the specimen can bind to the antibodies and be detected.

This assay is easy, fast and results do not depend on the binding protein concentration of the sample. Its based on the high specifity of the employed antibodies for IGF-II. There is virtually no cross-reactivity with IGF-I. This allows the separation of IGF-II from the binding proteins by acidification and blocking of the free binding proteins with IGF-I. Thus, the endogenous IGF-II is free in solution.
The assay is useful for scientific investigations in the field of neonatal hypertrophy (IGF-II is a foetal growth factor) and malignancies (IGF-II is an monogenic growth factor).
IGF-II is useful for the differential diagnostic of malignancies. Thus, it is possible to differentiate by IGF-II between adrenocortical carconimas and adenomas. Further tumor staging and differentiation between hyperplasia and carcinoma can be improved by IGF-II measurements in prostate tumors. The IGF-System seem to be of relevance in neurodegeneration as well, e.g. Alzheimer`s and Parkinson`s diseases.