Hepcidin and Erythroferrone Levels in p.C282Y Homozygotes and Control Subjects in the HEIRS Study

Most patients with hereditary hemochromatosis (HH) are homozygous for the p.C282Y mutation in the high-iron gene (HFE), leading to deficiency of hepcidin, the iron-regulatory hormone that normally controls dietary iron absorption. The hormone erythroferrone (Erfe), produced by marrow erythroblasts, also reduces hepcidin production and is a candidate modulator of HH severity. We analyzed 336 serum samples from the NIH BioLincc biorepository from Caucasian p.C282Y homozygotes (N=186) and control participants without HFE mutations (n=150) in the Hemochromatosis and Iron Overload Screening (HEIRS) Study. The relationships of hepcidin and Erfe concentrations with iron stores in this cohort were determined by linear regression analysis. In the entire cohort, our analysis revealed a strong positive relationship between serum hepcidin concentration and iron stores assessed as natural log of serum ferritin, Ln(SF) (p<0.0001). In contrast, there was a modest negative relationship between Erfe concentration and Ln(SF) (p=0.0479). Analyses of the relationships between hepcidin and Ln(SF) in p.C282Y homozygotes and controls revealed a marked difference such that, on average, the expected mean value of hepcidin in the homozygotes was 22.5 ng/ml lower than in controls (p=2.00×10^-14). After logarithmic transformation of hepcidin levels, this difference was even more significant (p=1.00×10^-26), illustrated by the parallel regression lines in Figure 1. The positive relationship between hepcidin and Ln(SF) in this cohort is consistent with the known increase of hepcidin levels with higher body iron stores. However, the fact that the expected mean value of hepcidin in p.C282Y homozygotes was significantly lower on average than in controls for any given value of Ln(SF) indicates a relative hepcidin deficiency in homozygotes regardless of iron stores, consistent with disordered hepcidin regulation. The modest inverse relationship between Erfe levels and Ln(SF) in the current cohort may reflect increased Erfe production in response to stimulation of red blood cell production by phlebotomy therapy to remove excess iron. Further research is needed to determine whether low hepcidin levels or elevated Erfe levels may predict the risk of severe iron overload in younger HH patients who have not yet accumulated increased iron stores.