SLC40A1 may be involved in iron export from duodenal epithelial cells and also in transfer of iron between maternal and fetal circulation. It mediates iron efflux in the presence of a ferroxidase (hephaestin and/or ceruloplasmin). Defects in SLC40A1 are the cause of hemochromatosis type 4, an autosomal dominant iron-loading disorder characterized by early iron accumulation in reticuloendothelial cells and a marked increase in serum ferritin.