In kidney patients on dialysis, giving recombinant erythropoietin (EPO) raised their blood hemoglobin and made them feel better, but the study didn't find any changes in several brain‑related peptides measured in the blood.

An improvement of quality of life and objective brain function has been reported in patients receiving regular hemodialysis treatment (RDT) during treatment with recombinant human erythropoietin (r-huEPO). The mechanisms explaining this improvement are unknown. In this study the plasma levels of peptides known to be involved in CNS functions, namely corticotropin-releasing hormone, delta sleep-inducing peptide, beta-endorphin, methionine-enkephalin, beta-lipotropin and alpha-melanocyte-stimulating hormone, were measured by radioimmunoassay in seven stable RDT patients before the start of r-huEPO therapy and during 28 weeks' treatment. All patients responded with significantly increased hemoglobin concentrations. An improvement of well-being, state of mood and physical fitness was reported by the patients. There were no significant changes during the study in the plasma concentrations of any of the peptides measured. However, as the plasma levels of neuropeptides will not necessarily reflect the local concentrations in the vicinity of the nerve terminals, changes in the intracerebral concentrations of these peptides might occur in response to r-huEPO.