HAMP and hereditary hemochromatosis: Mice underexpressing hepcidin are severely iron-overloaded (Nicolas et al., 2001), mimicking the human genetic disorder hereditary hemochromatosis, which (in rare cases) is caused by genetic lesions in the hepcidin gene itself (Roetto et al., 2003), in genes that encode hepcidin-regulatory factors (Bridle et al., 2003), or by mutations in ferroportin that render it resistant to hepcidin control (Drakesmith et al., 2005).