Stored iron, which comprises about 27% of total body iron, provides a source of iron when physiologic demand is high, such as in blood loss, pregnancy, and periods of rapid growth.
Storage compounds include ferritin and hemosiderin. Ferritin is a protein-bound, water-soluble, mobilizable storage compound and is the major source of stored iron. Hemosiderin is a water-insoluble form that is less readily available for use. Men have approximately 1 g of stored iron and women have less than 1 g. (3)
When the amount of total body iron is relatively low, storage iron consists predominately of ferritin. When iron stores are increased, hemosiderin predominates. Unlike ferritin, hemosiderin stains with the Prussian blue stain (Perls reaction) and may be observed in tissues. The image on the right shows iron deposits in a liver section that was stained with Prussian blue.
Image is courtesy of John Woosley, MD.