Ferritin is a highly specialized protein whose main function is to store excess iron intracellularly. It is widely distributed throughout the animal and plant kingdoms. In mammalian tissues, ferritin is present in concentrated form in spleen, liver and the intestinal mucosa. Ferritin is not a structurally homogeneous protein since purified preparations, when examined by polyacrylamide gel electrophoresis, show multiple bands. Immunologically, ferritins appear to be species specific but not organ specific.

Addison and co-workers have developed a sensitive immunoradiometric assay for detection of serum ferritin (Addison, G.M., Beamish, M.R., Hales, C.N., Hodgkins, M., Jacobs, A. and Llewellin, P., J. Clin. Pathol., 25, 326, 1972). Serum ferritin is markedly lowered in iron deficiency anemia and its levels are elevated in an iron overload (Jacobs, A., Miller, F., Worwood, M., Beamish, M.R. and Wardrop, C.A., Brit. Med. J., 4, 206, 1972). Therefore, from a clinical standpoint, serum ferritin level can serve as a convenient and sensitive index for diagnosis of iron deficiency and iron overload. Serum ferritin level is markedly elevated in patients with acute and chronic liver diseases (Prieto, J., Barry, M. and Sherlock, S., Gastroenterology, 68, 525, 1975). This observation has applications in clinical medicine.