Ferritin excretion and iron balance in humans

Under normal circumstances, most of the lumenal iron taken into the intestinal mucosal cell is stored within the cell as ferritin and subsequently is lost in the faeces when the cell exfoliates at the end of its lifespan. To evaluate whether faecal iron proteins reflect mucosal cell iron as well as whole body iron and to examine further the kinetics of gastrointestinal iron transport, faecal H-rich and L-rich ferritin were measured in normal subjects and patients with iron deficiency and genetic haemochromatosis. In normal and iron-deficient subjects, the concentration of L-rich but not H-rich faecal ferritin correlated closely with body iron status. In genetic haemochromatosis, the faecal L-rich and H-rich ferritin concentrations were lower than expected for their body iron status. The administration of oral iron to normal subjects led to a rise in L-rich ferritin. Administration of oral or parenteral iron to patients with iron deficiency led to a prompt rise in both forms of faecal ferritin, although the relative increase of L-rich ferritin was greater than that of H-rich ferritin with oral iron administration. Faecal ferritin correlated closely with iron stores in normals and patients with iron deficiency but faecal ferritin levels were lower than expected in genetic haemochromatosis, similar to that previously noted in the duodenal mucosal cells of these patients.