TFRC and Iron deficiency anemia: In three out of the four iron deficiency definitions, women had a significantly higher IR compared to men: ferritin < 45 μg/L (IR 5.5 [95% CI 4.8–6.2] vs. 3.0 [95% CI 2.5–3.6], P < 0.0001), ferritin < 30 μg/L (IR 2.8 [95% CI 2.4–3.2] vs. 1.9 [95% CI 1.6–2.3], P = 0.002) and sTfR–ferritin index > 1.5 (IR 13.5 [95% CI 11.8–15.4] vs. 10.5 [95% CI 8.9–12.4], P = 0.02).