Background: Insulin-like growth factor I (IGF-I) immunoassays are primarily used to estimate IGF-I status. Recently an IGF-I-specific kinase receptor activatio assay (KIRA) was developed as an alternative method for measuring IGF-I bioactivity. When compared with IGF-I immunoassays, the IGF-I KIRA has the theoretical advantage of measuring the net effects of IGF-binding proteins on IGF-I receptor activation. The IGF-I KIRA is sensitive and specific and has, for a bioassay, a very low intra-and inter-assay coefficient of variation (<7 and <15%, respectively). Several studies have shown that the IGF-I KIRA is more sensitive than IGF-I immunoassays for detecting differences in clinical state. In addition, the IGF-I KIRA seems superior to IGF-I immunoassays for monitoring acute effects of therapeutic interventions. Conclusions: It is not known if IGF-I KIRA is superior to IGF-I immunoassays for evaluating the efficacy of growth hormone (GH) treatment for GH deficiency and of GH receptor antagonist treatment for acromegaly. However, IGF-I KIRA undoubtedly will provide new insights into the factors that regulate IGF-I bioactivity in the circulation in both healthy and diseased states.

Additional Metadata
Keywords Insulin-like growth factor I, Kinase receptor activation assay
Persistent URL dx.doi.org/10.1159/000329191, hdl.handle.net/1765/34549
Citation
Janssen, J.A.M.J.L.. (2011). Insulin-like growth factor I: Pros and cons of a bioassay. Hormone Research in Paediatrics, 76(SUPPL. 1), 106–110. doi:10.1159/000329191