A time course of hepcidin response to iron challenge in patients with HFE and TFR2 hemochromatosis

Abstract

Background: Inadequate hepcidin production leads to iron overload in nearly all types of hemochromatosis. We explored the acute response of hepcidin to iron challenge in 25 patients with HFE-hemochromatosis, in two with TFR2-hemochromatosis and in 13 controls. Sixteen patients (10 C282Y/C282Y homozygotes, 6 C282Y/H63D compound heterozygotes) had increased iron stores, while nine (6 C282Y/C282Y homozygotes, 3 C282Y/H63D compound heterozygotes) were studied after phlebotomy-induced normalization of iron stores.

Design and methods: We analyzed serum iron, transferrin saturation, and serum hepcidin by both enzyme-linked immunosorbent assay and mass-spectrometry at baseline, and 4, 8, 12 and 24 hours after a single 65-mg dose of oral iron.

Results: Serum iron and transferrin saturation significantly increased at 4 hours and returned to baseline values at 8-12 hours in all groups, except in the iron-normalized patients who showed the highest and longest increase of both parameters. The level of hepcidin increased significantly at 4 hours and returned to baseline at 24 hours in controls and in the C282Y/H63D compound heterozygotes at diagnosis. The hepcidin response was smaller in C282Y-homozygotes than in controls, barely detectable in the patients with iron-depleted HFE-hemochromatosis and absent in those with TFR2-hemochromatosis. Conclusions Our results are consistent with a scenario in which TFR2 plays a prominent and HFE a contributory role in the hepcidin response to a dose of oral iron. In iron-normalized patients with HFE hemochromatosis, both the low baseline hepcidin level and the weak response to iron contribute to hyperabsorption of iron.

Figure 1.

Results of the oral iron test. Time course of serum iron (A), transferrin saturation (B) and serum hepcidin by mass spectrometry (C) and ELISA (D) methods in patients and controls (blue lines). Red and green lines represent C282Y homozygotes and C282Y/H63D compound heterozygotes studied at diagnosis (i.e. with increased iron stores), respectively. Purple lines represent HFE-hemochromatosis patients studied after iron depletion, including both genotypes. Orange lines represent the two TFR2-hemochromatosis patients, who were also studied after phlebotomy-induced normalization of iron stores. The asterisks indicate statistical significance: * P<0.05 **P<0.01 versus baseline values. For each parameter studied median levels are reported, while bars reflecting variations are not shown here because of partial overlapping. Details about variations (e.g. interquartile ranges) at each time point and statistics are given in Online Supplementary Table S1. “0” on the x-axis represents the baseline, before ingestion of the iron pill.

Figure 2.

Box plots of square root area under the curve (AUC) of serum hepcidin in the different groups. C282Y homozygotes and C282Y/H63D compound heterozygotes at iron depletion are grouped. (A) Serum hepcidin as measured by mass spectrometry (MS). *Significantly different versus controls (P=0.0053). Other significant differences: all patients at diagnosis versus all iron-depleted patients (P=0.0085); C282Y homozygotes at diagnosis versus C282Y homozygotes after iron depletion (P=0.0194). (B) Serum hepcidin as measured by ELISA. *Significantly different versus controls (P=0.023 for C282Y homozygotes, and P=0.0039 for iron-depleted patients). Other significant differences: all patients at diagnosis versus all iron-depleted patients (P=0.0294); C282Y homozygotes at diagnosis versus C282Y/H63D at diagnosis (P=0.0375).