Factors accounting for high ferritin levels in obesity

Ferritin is a widely used marker of iron status. A relationship between iron stores, obesity and metabolic syndrome (METs) has been proposed.

To compare serum ferritin between obese women with and without METs, and to evaluate the main factors accounting for ferritin levels.

Prospective study.

A total of 239 consecutive postmenopausal women with body mass index (BMI) > or =30 kg/m(2) were included. Exclusion criteria were conditions that could influence body iron stores. In addition to ferritin, serum iron, transferrin, transferrin saturation index and the soluble transferrin receptor were measured. METs was defined according to the International Diabetes Federation guidelines. Multiple regression analyses were performed taking into account ferritin as the dependent variable.

Serum ferritin levels were significantly higher in obese women with METs (n=169) in comparison with obese women without METs (n=70): 81.00 (17-648) vs 48.50 (11-149) ng ml(-1), P<0.001. No differences in the other markers of iron status were observed. Diabetic patients (n=82) had higher ferritin levels than non-diabetic patients (P<0.001). Non-diabetic patients with METs (n=95) also showed higher ferritin levels than non-diabetic patients without METs (P=0.001). Among the components of METs only diabetes was independently associated with serum ferritin levels in both the whole group (P=0.02) and in patients with METs (P=0.005).

Metabolic syndrome and in particular type 2 diabetes is the main contributor to the high ferritin levels reported in obesity. Our findings suggest that ferritin should not be used as a reliable index of iron overload in obese patients with diabetes.