This iron sensing machinery appears to be altered by the TMPRSS6 gene mutations in humans (3, 4, 9), global ablation of Tmprss6 gene (Tmprss6−/−) or a deletion of the Mt2 catalytic domain (mask) in mice (10, 11, 12, 13), because they all result in an inappropriately high hepcidin and iron-deficiency anemia. The gene discussed is TMPRSS6; the disease is Iron deficiency anemia.