Iron absorption in erythropoietin-treated haemodialysis patients: effects of iron availability, inflammation and aluminium.

BACKGROUND: The response to recombinant human erythropoietin (rHuEpo) is determined primarily by the availability of iron. In contrast to i.v., iron, oral iron supplementation is often insufficient for an optimal response.
METHOD: We studied iron absorption and the effects of iron status, aluminium status and inflammation in 19 chronic haemodialysis patients on maintenance rHuEpo therapy. Iron mucosal uptake after 24 h, iron retention after 2 weeks and mucosal transfer of iron were determined with a whole-body counter using an oral dose 59Fe. Iron absorption was measured once without, and once after the ingestion of 2 g aluminium hydroxide.
RESULTS: On the basis of transferrin saturation, two groups of dialysis patients were distinguished: a group with a functional iron deficiency (n = 9), and an iron-replete group (n = 10). In the iron-deficient dialysis patients group, mucosal uptake, mucosal transfer, and iron retention were 49.9% +/- 29.4, 0.73 +/- 0.29, and 41.6% +/- 32.2, being significantly lower than in a non-uraemic iron deficient population (P < 0.01, P < 0.05, P < 0.01 respectively). In the iron-replete dialysis patients group, mucosal uptake, mucosal transfer, and iron retention were 20.0 +/- 12.3, 0.59 +/- 0.18, and 11.1 +/- 6.7, mucosal uptake and iron retention being lower than in a normal iron-replete population (P < 0.0005 and P < 0.003 respectively). Dialysis patients with high C-reactive protein (CRP) values showed lower iron absorption. Iron absorption data correlated significantly with transferrin saturation and CRP in the iron-deficient group, and with serum ferritin in the iron-replete group. Iron absorption decreased after an aluminium hydroxide challenge in the iron-deficient patients to the lower levels of the iron-replete subjects. Body aluminium stores, estimated by the desferrioxamine test, did not correlate with parameters of iron absorption.
CONCLUSION: The absorption of iron in dialysis patients is decreased in haemodialysis patients, which may, at least in part, be due to inflammation. Aluminium ingestion further reduces absorption in functional iron-deficient patients.