, Volume 10, Issue 2, pp 181–187 | Cite as

Utility of Free IGF-I Measurements

  • Jan Frystyk
Original Paper


For nearly 30 years, the endogenous bioactivity of insulin-like growth factor I (IGF-I) has been estimated by its circulating concentrations of immunoreactive IGF-I, obtained after either removal or inactivation of the IGF-binding proteins (IGFBPs), and today serum/plasma total IGF-I serves as a useful parameter in the diagnosis and clinical control of growth hormone (GH) disorders. Different assays for the measurement of free, unbound IGF-I were introduced more than a decade ago. Nevertheless, this measurement remains controversial, and in daily clinical practice serum total IGF-I has retained its position as the most widely used IGF-related measurement in GH disorders. This review will provide a survey of data on free versus total IGF-I, with particular reference to GH disorders. As it will be clear, there is reasonable clinical evidence to conclude that both in the diagnosis of as well as during treatment of patients with GH disorders, serum/plasma total IGF-I should remain the primary IGF-related measurement. However, in certain patients the inclusion of free IGF-I may be useful and therefore, some guidelines for the inclusion of free IGF-I measurements will be given.


Free IGF-I Total IGF-I IGF-I bioactivity GH disorders Obesity Chronic renal failure 



JF is supported by a grant from the Danish Medical Research Council.


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Copyright information

© Springer Science+Business Media, LLC 2007

Authors and Affiliations

  1. 1.Medical Research Laboratories, Clinical Institute and Medical Department M (Diabetes and Endocrinology)Aarhus University HospitalAarhus CDenmark

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