The perturbed iron homeostasis of Tmprss6–/– mice is accompanied by elevated FGF23 levels in circulation but unchanged Fgf23 mRNA levels in the cortical bone. Shown for 8-week-old Tmprss6+/+, Tmprss6+/−, and Tmprss6–/– male littermates are (A) serum iron, (B) Hgb, (C) erythrocyte mean corpuscular volume (MCV), (D) erythrocyte mean corpuscular hemoglobin (MCH), (E) serum EPO, (F) liver nonheme iron concentration, (G) heart nonheme iron concentration, (H) kidney nonheme iron concentration, (I) spleen-to-body-weight ratio, (J) total spleen nonheme iron content, (K) plasma C-terminal FGF23 (cFGF23), (L) plasma iFGF23, (M) urine phosphate-to-creatinine ratio, (N) phosphate excretion index, (O) serum phosphate, and (P) Fgf23 mRNA expression relative to Actb in the bone cortex. The mean mRNA ratio of the Tmprss6+/+ mice was normalized to 1. n = 4 to 11 per group. For all graphs, data represent mean ± standard deviation. The total spleen nonheme iron content was calculated by multiplying the measured nonheme iron concentration by the total spleen weight. The phosphate excretion index was calculated as (urine phosphate ÷ serum phosphate) ÷ urine creatinine.82 ∗P < .05; ∗∗P < .01; ∗∗∗P < .001; and ∗∗∗∗P < .0001 using one-way analysis of variance (ANOVA) with Tukey post hoc test.
