Associations of iron markers with type 2 diabetes mellitus and metabolic syndrome: Results from the prospective SHIP study.

Aims: To assess the role of serum ferritin and transferrin with prevalent and incident type 2 diabetes mellitus (T2DM) and metabolic syndrome (MetS) and whether these associations are independent of inflammatory markers and hepatic enzymes.

Methods: We analyzed data from 3,232 participants aged 20-81 years of the population-based Study of Health in Pomerania (SHIP) from Northeast Germany with a median follow-up time of 10.6 years. Logistic and Cox regression analyses were performed.

Results: Serum ferritin concentrations were associated with a higher prevalence of T2DM (total population OR: 1.16 [95% CI: 1.07, 1.26]; men OR: 1.18 [95% CI: 1.08, 1.30) and MetS (total population OR: 1.27 [95% CI: 1.16, 1.38]; men OR: 1.26 [95% CI: 1.15, 1.38]) in the total population and men independently of inflammatory markers and hepatic enzymes. In longitudinal analyses, baseline ferritin concentrations were associated with a higher risk of incident T2DM in women (HR: 1.38 [95% CI: 1.10, 1.71]), but not in men or in the total population and also with a higher risk of incident MetS (HR: 1.09 [95% CI: 1.01, 1.17]) in the total population. These longitudinal associations attenuated considerably after adjustment for hepatic enzymes but not inflammatory markers. Transferrin was not associated with any of the outcomes.

Conclusions: Our results suggest a link between ferritin and T2DM and MetS, which might be partially explained by hepatic dysfunction.