RESUMO
BACKGROUND: Individuals donating whole blood 13 times in a 2-year period without development of iron deficiency anemia (superdonors) are a self-selected population that is deferred for low hematocrit (Hct) level less frequently than other donors. STUDY DESIGN AND METHODS: Iron metabolism was assessed in 138 superdonors through a questionnaire and measurement of Hct, serum ferritin, serum hepcidin, and serum growth differentiation factor 15 (GDF15). Genetic testing for HFE and JAK-2 mutations was also performed. RESULTS AND CONCLUSIONS: Iron deficiency (ferritin level, <30 microg/L) is present in more than 60 percent of superdonors. Behaviors altering iron status included casual use of iron supplements in males, but not in females, and cigarette smoking that produced increased Hct associated with decreased ferritin. The striking biochemical characteristic of superdonors is greatly decreased serum hepcidin, consistent with their need to absorb maximal amounts of dietary iron to replace that lost from blood donation. GDF15 is normal in most superdonors, indicating that GDF15 overexpression arising from the expanded erythroid pool necessary to replace donated red cells is not the biochemical mechanism for the decreased serum hepcidin. Mutations in JAK-2 were not found, indicating that undiagnosed polycythemia vera is not a common cause for successful repeated blood donation by superdonors. Mutations in HFE associated with hemochromatosis were present in superdonors at the same frequency as the normal population. However, superdonors heterozygous for the H63D mutation in HFE had significantly decreased hepcidin : ferritin ratios demonstrating for the first time that the heterozygous state for HFE mutations is associated with alterations in hepcidin expression.