Utility of Free IGF-I Measurements

Frystyk, Jan

doi:10.1007/s11102-007-0025-y

Cited by 40 publications

(27 citation statements)

References 71 publications

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“…Furthermore, we relied on the IGF-1/IGFBP-3 molar ratio as a surrogate of bioactive IGF-1. Although this ratio is a reasonable approximation of free IGF-1 under normal physiological conditions (13), free IGF-1 is also influenced by levels of other IGFBPs (24). Finally, IGF-1 and IGFBP-3 levels are affected by multiple factors, including gender and race/ethnicity (25); therefore, these results may not be generalizable to men or to populations that are not predominantly Caucasian.…”

Section: Discussionmentioning

confidence: 99%

Effects of Dietary Weight Loss and Exercise on Insulin-Like Growth Factor-I and Insulin-Like Growth Factor-Binding Protein-3 in Postmenopausal Women: A Randomized Controlled Trial

Mason

Xiao

Duggan

et al. 2013

Cancer Epidemiology, Biomarkers &Amp; Prevention

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High levels of insulin-like growth factor (IGF)-1 may increase the risk of common cancers in humans. We hypothesized that weight loss induced by diet and/or exercise would reduce IGF-1 in postmenopausal women. Four hundred and thirty nine overweight or obese (BMI ≥25kg/m2) women (50–75 y) were randomly assigned to: i) exercise (N=117), ii) dietary weight-loss (N=118), iii) diet + exercise (N=117), or iv) control (n=87). The diet intervention was a group-based program with a 10% weight loss goal. The exercise intervention was 45 min/day, 5 days/week of moderate-to-vigorous intensity activity. Fasting serum insulin-like growth factor (IGF)-1 and insulin-like growth factor binding protein (IGFBP)-3 were measured at baseline and 12 months by radioimmunoassay. Higher baseline BMI was associated with lower IGF-1 and IGF-1/IGFBP-3 molar ratio. While no significant changes in either IGF-1 or IGFBP-3 were detected in any intervention arm compared to control, the IGF-1/IGFBP-3 ratio increased significantly in the diet (+5.0%, p<0.01) and diet + exercise (+5.4%, p<0.01) groups compared to control. Greater weight loss was positively associated with change in both IGF-1 (ptrend=0.017) and IGF-1/IGFBP-3 ratio (ptrend<0.001) in the diet group, but inversely with change in IGFBP-3 in the diet + exercise group (ptrend=0.01). No consistent interaction effects with baseline BMI were detected. Modified IGF-1 bioavailability is unlikely to be a mechanism through which caloric restriction reduces cancer risk in postmenopausal women.

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Section: Discussionmentioning

confidence: 99%

Effects of Dietary Weight Loss and Exercise on Insulin-Like Growth Factor-I and Insulin-Like Growth Factor-Binding Protein-3 in Postmenopausal Women: A Randomized Controlled Trial

Mason

Xiao

Duggan

et al. 2013

Cancer Epidemiology, Biomarkers &Amp; Prevention

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“…Only free IGF-I is believed to be the active form as it can readily cross the endothelium and interact with its own receptor. It has potentially greater physiological [43] and clinical relevance than total IGF-I. To date only three studies have addressed the relation of free IGF-1 and cardiovascular disease.…”

Section: Epidemiological Evidence Linking Igf-1 With Cardiovascular Dmentioning

confidence: 99%

Interaction between Insulin-Like Growth Factor-1 and Atherosclerosis and Vascular Aging

Higashi

Quevedo

Tiwari

et al. 2014

Frontiers of Hormone Research

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“…Thus, immunoreactive IGF-I equals the total peptide concentration within the circulation and accordingly, this measurement does not allow any discrimination between unbound IGF-I and IGF-I carried within ternary or binary complexes. More sophisticated assays for the measurement of complex-associated IGF-I, free IGF-I and bioactive IGF-I have been published within the last decade, but generally, although data for some of the newer assays are sparse [12][13][14][15], they do not appear to perform any better than the traditional IGF-I assays in the diagnosis and management of GH disorders [16]. Therefore, this review will focus on immunoreactive IGF-I assays.…”

Section: Technical Information Regarding Igf-i Immunoassaysmentioning

confidence: 99%

The current status of IGF-I assays – A 2009 update

Frystyk

Freda

Clemmons

2010

Growth Hormone & IGF Research

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178

129

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For almost three decades, the measurement of circulating IGF-I has constituted a highly important biochemical tool in the management of GH disorders. In fact, in acromegaly the importance of circulating IGF-I has increased following the introduction of the GH receptor antagonist pegvisomant, as the use of this drug makes it impossible to use circulating GH as a monitor of disease activity. In addition, determination of circulating IGF-I constitutes a valuable scientific tool in various research areas, from epidemiological investigations through clinical trials and experimental studies. The multiple facets of IGF-I physiology and patho-physiology may explain why numerous endocrine laboratories have invested in IGF-I assays, by means of either in-house assays or commercial kits. However, despite its widespread use, the measurement of IGF-I is by no means trivial. On the contrary, the pronounced binding of IGF-I to the high-affinity IGF-binding proteins (IGFBPs) constitutes a notorious source of error, which has necessitated the development of methods that more or less successfully circumvent interference from the IGFBPs. Furthermore, there are some unsolved issues with the international standardization of the different IGF-I assays and there is no consensus regarding the procedures used when collecting and storing samples for measurement of circulating IGF-I. The aim of this review is to discuss the current state of the art of IGF-I immunoassays and to present the current analytical problems with IGF-I measurements. Finally, we would like to suggest an agenda that may be used when trying to produce internationally accepted uniform requirements for future IGF-I assays.

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Utility of Free IGF-I Measurements

Cited by 40 publications

References 71 publications

Effects of Dietary Weight Loss and Exercise on Insulin-Like Growth Factor-I and Insulin-Like Growth Factor-Binding Protein-3 in Postmenopausal Women: A Randomized Controlled Trial

Effects of Dietary Weight Loss and Exercise on Insulin-Like Growth Factor-I and Insulin-Like Growth Factor-Binding Protein-3 in Postmenopausal Women: A Randomized Controlled Trial

Interaction between Insulin-Like Growth Factor-1 and Atherosclerosis and Vascular Aging

The current status of IGF-I assays – A 2009 update

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