Iron metabolism in chronic kidney disease

Abstract While whole-body (‘absolute’) iron deficiency is common and probably increased in frequency in chronic kidney disease (CKD), functional iron deficiency is a particular problem in CKD. Absolute iron deficiency is likely to be present in advanced CKD when the ferritin falls below 100 ng/mL and the TSAT falls below 20%. Functional iron deficiency is characterized by the presence of adequate iron stores (as defined by conventional criteria), but with an inability to mobilize this iron rapidly enough to adequately support erythropoiesis with the administration of erythropoietin. Among such patients, the serum ferritin level is either normal or elevated (usually between 100 and 800 ng/mL), with a TSAT typically ≤20%. Hepcidin, a novel peptide discovered at the turn of the twenty-first century, is an iron gatekeeper that plays a key role in functional iron deficiency, and the ‘anaemia of chronic disease’. The main function of hepcidin is homeostatic regulation of iron metabolism and mediation of host defence and inflammation. Hepcidin is the predominant negative regulator of iron absorption in the small intestine, iron transport across the placenta, and iron release from the macrophages. Novel strategies that modulate hepcidin and its target ferroportin for the treatment of anaemia of chronic diseases are currently undergoing extensive research.