Tmprss6-/-Tfr2-/- double knock out animals develop iron deficiency with high hepcidin, a phenotype similar to Tmprss6-/- mice (Lee et al., 2012; Nai et al., 2014) and to Tmprss6-/-Hfe-/- animals (Finberg et al., 2011; Lee et al., 2012). Here, HAMP is linked to Iron deficiency anemia.