Ferritine

Ferritin, sometimes referred to as ferritine in some languages, is a ubiquitous intracellular protein complex that stores iron and releases it in a controlled manner. It forms a hollow nanocage capable of sequestering up to about 4,500 iron atoms as ferrihydrite. By buffering cellular iron, ferritin helps prevent iron-catalyzed oxidative damage and maintains iron homeostasis.

In vertebrates, ferritin is a 24-subunit complex composed of heavy (H) and light (L) chains. The H subunit provides ferroxidase activity that converts Fe2+ to Fe3+, initiating mineralization; the L subunit supports long-term storage and nucleation of iron. The shell interior is mineralized with ferrihydrite, while the exterior surface permits iron exchange through channels. The relative abundance of H and L subunits varies by tissue and physiological conditions.

Ferritin is present in most cell types, with particularly high levels in the liver, spleen, and bone marrow. Cytosolic ferritin is the main form, though a mitochondrial ferritin (FTMT) exists in some cells. Serum ferritin largely reflects body iron stores but is also an acute-phase protein that can rise with inflammation, infection, or liver disease independent of iron status. Its synthesis is regulated by iron regulatory proteins binding to iron-responsive elements in its mRNA, linking production to cellular iron availability.

Clinically, serum ferritin measurement is a common test for assessing iron status. Low ferritin indicates iron deficiency; very high ferritin can indicate iron overload or inflammatory states. Because ferritin can be elevated during inflammation, interpretation often considers C-reactive protein and other iron indices such as transferrin saturation. See also: iron metabolism, ferritin heavy chain, ferritin light chain, ferritinophagy, ferroptosis.