Non-transferrin-bound iron is present in serum of hereditary haemochromatosis heterozygotes

BACKGROUND: Hereditary haemochromatosis (HH) is a common autosomal recessive disease. Recently, HH heterozygosity has been identified as an independent risk factor for myocardial infarction and cardiovascular mortality. Iron may play an important role in atherogenesis by catalyzing peroxidation of low-density-lipoprotein (LDL), an essential step in atherogenesis. In iron overload conditions, non-transferrin-bound iron (NTBI) is found in serum, which can catalyze lipid peroxidation. We investigated whether sera of HH heterozygotes contain more NTBI than sera of normal controls. METHODS: In 27 treated HH homozygotes, 22 HH heterozygotes and 17 healthy control subjects, conventional parameters of iron status (serum iron, transferrin saturation, serum ferritin) were measured. NTBI was detected using HPLC after addition of nitrilotriacetic acid and pretreatment with cobalt. RESULTS: The conventional parameters of iron status were similar in the HH heterozygous group and the control group. NTBI was significantly higher in homozygotes compared to heterozygotes (1.79 micromol L-1 vs. 0.51 micromol L-1, 95% CI of the difference = 0.6-1.95, P < 0.001), and controls (1.79 micromol L-1 vs. - 0.3 micromol L-1, 95% CI of the difference = 1.36-2.81, P < 0.001). The difference in NTBI between the heterozygous subjects and control subjects was also significant (0.51 micromol L-1 vs. - 0. 3 micromol L-1, 95% CI of the difference = 0.05-1.57, P < 0.05). CONCLUSION: Phlebotomy treated HH homozygotes maintain a high and potentially harmful serum NTBI. HH heterozygotes have a higher serum NTBI than normal controls. The reported increased risk of cardiovascular events in heterozygous haemochromatosis may be explained by NTBI-catalyzed LDL peroxidation.