Clinical Significance

Ferritin is a large spherical protein consisting of 24 non-covalently linked subunits and having a molecular weight of approximately 450,000. The subunits form a shell surrounding a central core containing variable amounts of ferric hydroxyphosphate. One molecule of ferritin is capable of binding between 4,000 and 5,000 atoms of iron, making ferritin the major iron storage protein of the body.

Found chiefly in the cytoplasm of cells of the reticuloendothelial system, it once was thought that ferritin did not appear in plasma or extracellular fluid under normal conditions. However, the development of a sensitive immunoradiometric technique by Addison, et al., in 1972, resulted in the discovery that ferritin is a constituent of all normal human serum. Through this and other work, it was determined that the concentration of ferritin levels becoming a common diagnostic tool in the evaluation of iron status.

In most normal adults serum ferritin levels ranges from 10-300 ng/mL, but concentrations vary with age and sex. There is a sharp rise in serum ferritin levels in the first month of life, coinciding with the depression of bone marrow erythropoiesis. Within two or three months, erythropoiesis becomes reactivated and there is a drop in the concentration of serum ferritin. By six months, the concentration is reduced to fairly low levels where they remain throughout childhood. There is no sex difference until the onset of puberty, at which time ferritin levels rise, particularly in males. There is a significant positive correlation between age and serum ferritin levels in females, but not in males.

_{Source: Access Ferritin IFU #33020, 12/7/16}