In patients with homozygousTFR2 mutations, urinary hepcidin levels are inappropriately low relative to serum ferritin. Urinary hepcidin was normalized to urinary creatinine concentration (nanograms of hepcidin per milligram of creatinine). TFR2 m/m (○) indicates patients homozygous for the TFR2 mutations; TFR2 m/+ (▿), subjects heterozygous for TFR2 mutations. Healthy patients are indicated by □. (A) Relationship between normalized urinary hepcidin and serum ferritin. Linear regression in healthy subjects is represented by the dotted line and in TFR2 homozygous patients by the dashed line. (B) Ratio of normalized urinary hepcidin to serum ferritin levels.