HAMP and hemochromatosis type 1: Much information about the determinants controlling hepcidin expression was obtained from the genetics of hereditary hemochromatosis [12], which is characterized by insufficient hepcidin levels due to mutations in the transferrin receptor 2 (TfR2) gene, the hemochromatosis genes HFE and HFE2 (also designated hemojuvelin = HJV), or the hepcidin gene itself.