Ferritin

Overview
Ferritin is a globular protein complex consisting of 24 protein subunits and is the main intracellular iron storage protein in both prokaryotes and eukaryotes, keeping it in a soluble and non-toxic form. Ferritin which is not combined with iron is called apoferritin.

Description
The ferritin protein consists of 24 protein subunits. In vertebrates, these are both the light (L) and the heavy (H) type with a molecular weight of 19 kDA or 21 kDA respectively. In plants and bacteria the complex only consists of the H-chain type. Inside the ferritin shell, iron ions form crystallites together with phosphate and hydroxide ions. The resulting particle is similar to the mineral ferrihydrite. Each ferritin complex can store about 4500 iron (Fe3+) ions.

Some ferritin complexes in vertebrates are hetero-oligomers of two highly-related gene products with slightly different physiological properties. The ratio of the two homologous proteins in the complex depends on the relative expression levels of the two genes.

Uses
Serum ferritin levels are measured in patients as part of the iron studies workup for anemia and for restless leg syndrome. The ferritin levels measured have a direct correlation with the total amount of iron stored in the body. If ferritin is high there is iron in excess, which would be excreted in the stool. If ferritin is low there is a risk for lack in iron which sooner or later could lead to anemia. Low ferritin levels have been associated with symptoms of restless leg syndrome even in the absence of anemia.

In the setting of anemia, serum ferritin is the most sensitive lab test for iron deficiency anemia.

Ferritin is also used as a marker for iron overload disorders, such as hemochromatosis and porphyria in which the ferritin level may be abnormally raised.

As ferritin is also an acute-phase reactant, it is often elevated in the course of disease. A normal C-reactive protein can be used to exclude elevated ferritin caused by acute phase reactions.

Ferritin can be elevated during periods of acute malnourishment.

Free iron is toxic to cells, and the body has an elaborate set of protective mechanisms to bind iron in various tissue compartments. Within cells, iron is stored complexed to protein as ferritin or hemosiderin. Apoferritin binds to free ferrous iron and stores it in the ferric state. As ferritin accumulates within cells of the reticuloendothelial system, protein aggregates are formed as hemosiderin. Iron in ferritin or hemosiderin can be extracted for release by the RE cells although hemosiderin is less readily available. Under steady state conditions, the serum ferritin level correlates with total body iron stores; thus, the serum ferritin level is the most convenient laboratory test to estimate iron stores.

Ferritin is also used in materials science as a precursor in making iron nanoparticles for carbon nanotube growth by chemical vapor deposition.

Hematology diagnostic test
Normal blood levels are 12-300ng/mL for males and 12-150ng/mL for females.

How to lower/raise: avoid or eat foods rich in iron: eggs, liver, red meat, soy products. Also cook or avoid cooking with a cast iron skillet.