Effect of Hfe deficiency on hepatic iron concentrations and Bmp6, Id1, and Hamp gene expression in 3-week-old mice. Fold change in nonheme tissue iron content and expression ratio (and SE) of Bmp6, Id1, and Hamp transcripts normalized to the reference gene mRNA (Hprt) in 3-week-old Hfe-deficient mice relative to wild-type controls (8 mice per group). Statistical significance was determined using randomization tests. ***P < .001. At 3 weeks of age, wild-type mice have levels of Bmp6 and Id1 mRNAs similar to 7-week-old mice. Although they have slightly less Hamp gene expression than 7-week-old mice, the difference is not statistically significant (supplemental Figure 4).