Tmprss6^−/−Hjv^−/− and Tmprss6^+/+Hjv^−/− mice show similar hepcidin mRNA levels and tissue iron concentrations. (A) Effect of Hjv genotype on iron deficiency–related hair loss in 19-day-old Tmprss6-deficient littermates. Tmprss6^−/−Hjv^+/+ pups (top) develop overt alopecia before weaning age. Tmprss6^−/−Hjv^+/− mice (middle) exhibit normal hair growth on the head but less dense hair on the body; red arrow indicates hair growth transition zone. Tmprss6^−/−Hjv^−/− mice (bottom) show normal body hair. (B-F) Phenotypic analysis of 8-week-old female mice of all Tmprss6-Hjv genotype combinations. Graphed are mean values obtained from analyses of hepcidin (Hamp) mRNA expression relative to β-actin (Actb) mRNA expression (B), serum transferrin saturation (C), and nonheme iron concentrations of liver (D), heart (E), pancreas (F), quadriceps muscle (G), and spleen (H). For each parameter, 6 to 8 female mice per genotype were analyzed. For panel B, mRNA expression ratios are normalized to a Tmprss6^+/+Hjv^+/+ mean value of 1. Error bars represent SEM. §P < .001 compared with Tmprss6^+/+Hjv^+/+; #P < .005 compared with Tmprss6^+/+Hjv^+/+; ‡P < .05 compared with Tmprss6^+/+Hjv^+/+; †P value not significant compared with Tmprss6^−/−Hjv^+/+; *P value not significant compared with Tmprss6^+/+Hjv^−/−; and ¶P < .001 compared with Tmprss6^+/−Hjv^+/+ mice.