Relation of insulin-like growth factor-I and IGF binding protein 3 with markers of inflammation: results of a population-based study

Objective: Previous studies in acromegaly and growth hormone deficiency observed inverse associations between insulin-like growth factor-I (IGF-I) levels and inflammatory biomarkers including high-sensitive C-reactive protein (hsCRP), interleukin-6 or fibrinogen. We aimed to assess the relations between IGF-I or IGF binding protein 3 (IGFBP-3) levels and hsCRP, interleukin-6, fibrinogen and white blood cell count (WBC) in a population-based sample.

Design and patients: Data from 3480 subjects from the population-based Study of Health in Pomerania (SHIP) were used. IGF-I, IGFBP-3 and inflammatory biomarkers were measured. Analysis of variance (anova), quantile regression models and logistic regression models, adjusted for age, smoking, diabetes mellitus and waist circumference, were performed.

Measurements and results: anova and/or quantile regression showed inverse associations between IGF-I and hsCRP as well as positive associations between IGF-I and fibrinogen among both sexes. Furthermore, the odds of elevated fibrinogen levels increased with increasing IGF-I levels (per SD IGF-I increase: men: odds ratio (OR) 1·35 [95% confidence interval (CI) 1·04, 1·55]; women: OR 1·44 [95% CI 1·21, 1·71]) in both sexes, whereas the odds of increased hsCRP (women: OR 0·46 [95% CI 0·36, 0·58]) and interleukin-6 (men: odds ratio (OR) 0·77 [95% CI 0·61, 0·96]; women: OR 0·69 [95% CI 0·55, 0·86]) decreased.

Conclusion: Serum IGF-I levels are associated with inflammatory biomarkers including hsCRP, interleukin-6 and fibrinogen. Further experimental studies are needed to elucidate the mechanisms underlying the relation between the GH/IGF axis and the inflammatory system.