Cross‐sectional and longitudinal associations between insulin‐like growth factor I and metabolic syndrome: a general population study in German adults

Abstract Background A previous study showed an inverse association between the insulin‐like growth factor I (IGF‐I) and the risk of impaired glucose tolerance or diabetes mellitus. Moreover, myocardial infarction patients with high baseline IGF‐I levels had a lower risk of diabetes mellitus. These data suggested a protective effect of IGF‐I against the development of metabolic syndrome. However, there are no longitudinal data regarding IGF‐I and metabolic syndrome. The aim of the present study was to investigate the longitudinal association between IGF‐I and metabolic syndrome. Methods Data from the population‐based Study of Health in Pomerania, Germany, were used for cross‐sectional ( n = 3903) and longitudinal ( n = 2143) analyses (5‐year follow‐up). Metabolic syndrome was defined by three or more of the following five components: abdominal obesity, elevated triglycerides, reduced high‐density lipoprotein cholesterol, elevated blood pressure and elevated nonfasting glucose. Serum IGF‐I and IGF binding protein 3 (IGFBP‐3) were determined by chemiluminescence immunoassays. Logistic and Poisson regression analyses were performed to determine associations. Results In cross‐sectional analyses high IGFBP‐3 as well as high and low IGF‐I/IGFBP‐3 ratio levels were associated with prevalent metabolic syndrome. In longitudinal analyses, the direction of the relation changed: men but not women with high IGF‐I or IGF‐I/IGFBP‐3 ratio levels had an increased, whereas men with low levels had a decreased risk of incident metabolic syndrome. Conclusion In concordance with previous studies, our cross‐sectional analyses showed a relation between low IGF‐I/IGFBP‐3 ratio and the prevalence of metabolic syndrome. In contrast, the longitudinal analyses indicated that a high IGF‐I level was a risk marker for incident metabolic syndrome. Copyright © 2013 John Wiley & Sons, Ltd.