ferritiin

Ferritin is a ubiquitous iron-storage protein that plays a central role in iron metabolism. In humans, ferritin exists as a soluble serum form and as intracellular ferritin found mainly in the liver, spleen, bone marrow, and reticuloendothelial system. The protein shell is composed of 24 subunits, typically a mix of heavy (H) and light (L) chains, and encloses a ferric iron (ferrihydrite) mineral core that can store up to about 4,500 iron atoms. The primary biological function of ferritin is to sequester iron safely, protecting cells from iron-catalyzed free radical damage and providing a readily available iron reservoir for metabolic needs. Iron is released from ferritin through ferroportin when cells require it, a process integrated with systemic iron regulation involving hepcidin.

Serum ferritin is a widely used laboratory marker of total body iron stores, but it behaves as an acute-phase protein and can rise in infection, inflammation, liver disease, and malignancy. Because of this, ferritin interpretation should consider inflammatory or hepatic markers. Clinically, low ferritin generally indicates iron deficiency, while high ferritin can indicate iron overload conditions such as hereditary hemochromatosis or reflect inflammatory states. Very high ferritin levels may occur in conditions like hemophagocytic lymphohistiocytosis or adult Still’s disease.

Ferritin levels are measured by immunoassays and are interpreted alongside other iron indicators such as transferrin saturation, transferrin, and inflammatory markers. Reference ranges vary by laboratory and assay.