Hepcidin expression can be downregulated directly by HIF in iron deficiency,64 but hepcidin is indirectly downregulated by hypoxia65 during EPO‐mediated expansion of marrow erythroid cells66, 67 through their production of erythroferrone (ERFE), a hormone that suppresses liver hepcidin production.68 This evidence concerns the gene HAMP and Iron deficiency anemia.