What are the functions of ferritin?

Ferritin plays a key role in iron homeostasis, storing iron in the cells and releasing it in a controlled manner when needed for crucial cellular processes. It also serves a protective function, protecting DNA, proteins, and lipids from the potentially noxious effects of iron. 

Ferritin is also used as a serum marker of total iron stores in the body. Serum ferritin serves a vital role in diagnosing and managing iron deficiency as well as iron overload.