Examination of the low hematocrit (HCT) deferral rates in whole blood donors based on gender/menstrual status and donation intensity unexpectedly revealed that low HCT deferral rates level off and even begin to decrease in frequent donors (>8 donations in 2 years) suggesting that frequent blood donors are a self-selected population possessing either behavioral or biochemical characteristics that allow greater iron absorption than the general population. To define these characteristics, 138 donors (101 male, 37 female, 136 Caucasian) that had donated 13 times in a 2-year period (“superdonors”) completed a questionnaire and had a blood sample analyzed for ferritin, hepcidin and HFE and JAK-2 genotypes. Ferritin was 31.0±20.3 ug/L for males and 25.2±14.8 ug/L for females. Two-thirds of both men and women had ferritin below 30 ug/L indicating that most have reduced iron stores. Average ferritin was ∼15 ug/L higher in donors taking multiple vitamins with iron or iron supplements than in those who did not take them. Hepcidin is an iron regulatory hormone that negatively regulates intestinal iron absorption. Serum hepcidin levels were determined using a liquid chromatography tandem mass spectrometry assay. The normal serum hepcidin concentration using this assay is 8–11 ng/ml [
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