Inflammation and iron deficiency in the hypoferremia of obesity.

Abstract

Obesity is associated with hypoferremia, but it is unclear if this condition is caused by insufficient iron stores or diminished iron availability related to inflammation-induced iron sequestration. To examine the relationships between obesity, serum iron, measures of iron intake, iron stores and inflammation. We hypothesized that both inflammation-induced sequestration of iron and true iron deficiency were involved in the hypoferremia of obesity. Cross-sectional analysis of factors anticipated to affect serum iron. Outpatient clinic visits. Convenience sample of 234 obese and 172 non-obese adults. Relationships between serum iron, adiposity, and serum transferrin receptor, C-reactive protein, ferritin, and iron intake analyzed by analysis of covariance and multiple linear regression. Serum iron was lower (75.8+/-35.2 vs 86.5+/-34.2 g/dl, P=0.002), whereas transferrin receptor (22.6+/-7.1 vs 21.0+/-7.2 nmol/l, P=0.026), C-reactive protein (0.75+/-0.67 vs 0.34+/-0.67 mg/dl, P<0.0001) and ferritin (81.1+/-88.8 vs 57.6+/-88.7 microg/l, P=0.009) were higher in obese than non-obese subjects. Obese subjects had a higher prevalence of iron deficiency defined by serum iron (24.3%, confidence intervals (CI) 19.3-30.2 vs 15.7%, CI 11.0-21.9%, P=0.03) and transferrin receptor (26.9%, CI 21.6-33.0 vs 15.7%, CI 11.0-21.9%, P=0.0078) but not by ferritin (9.8%, CI 6.6-14.4 vs 9.3%, CI 5.7-14.7%, P=0.99). Transferrin receptor, ferritin and C-reactive protein contributed independently as predictors of serum iron. The hypoferremia of obesity appears to be explained both by true iron deficiency and by inflammatory-mediated functional iron deficiency.