Erythropoietin, GDF15, IL6, hepcidin and testosterone levels in a large cohort of elderly individuals with anaemia of known and unknown cause

Epidemiologic studies have documented an increasing frequency of anaemia in individuals 65 yrs and older. Elderly individuals with anaemia have been categorised into the following: those with chronic disease, those with iron, B12 or folate deficiency and those with anaemia of unknown aetiology (AUE). There is considerable interest and debate as to whether AUE has an inflammatory component, is caused by cytokine dysregulation affecting production or response to erythropoietin (EPO) or iron availability or represents a novel pathologic process. Here, we compare a large cohort of AUE cases with a matched, non-anaemic control group and with individuals who have anaemia of defined cause. IL-6, hepcidin, GDF15, EPO and testosterone levels were compared. IL6 and hepcidin levels did not differ significantly between AUE and control groups, indicating that inflammation or iron restriction is not central feature of anaemia in this group. GDF15 levels were significantly elevated when comparing AUE with controls and were markedly elevated in patients with renal disease. Testosterone levels were lower in men from the AUE group compared with non-anaemic controls. EPO levels in the AUE group were increased relative to controls but were inappropriately low for the degree of anaemia. Our data indicate that an impaired EPO response, in the absence of evidence for iron restriction or inflammation, is characteristic of AUE.