The majority of iron in the blood is bound to hemoglobin, the oxygen-transporting protein. Blood iron that is not in hemoglobin may be in transit and bound to the protein transferrin. Iron that comes from body stores is in the form of a protein called ferritin. Determining total blood iron and what forms are present indicates whether body iron is low, normal, or overloaded. The medical term for iron overload is hemochromatosis, a potentially toxic condition. Excess iron not in the form of hemoglobin or other proteins can lead to organ damage.
Video of the Day
Two thirds or more of body iron circulates in the blood in the form of hemoglobin. Given its importance, the body tends to hold on to iron, with no pathway for getting rid of any excess. Unless blood is lost, only about 1 percent of your iron leaves the body each day. Iron absorbed from food replaces normal iron loss. As red cells die, iron from hemoglobin is recycled into storage for later use. Stored iron is mostly in the liver, spleen, bone marrow and muscle in the form of ferritin or hemosiderin. Ferritin levels in the blood usually reflect overall levels of iron in the body, and are often measured along with blood iron. Inflammation, obesity, liver or kidney disease and some forms of cancer can cause release of ferritin into the bloodstream. Particularly with inflammation, this may be a short-term effect that reverses on its own.
Iron from Food
Consuming large amounts of iron in food or water is usually not the cause of iron overload, since your body can normally increase or decrease the amount absorbed as needed. Sources of excess dietary iron include well water, water passing through iron pipes, or food, especially acidic food, cooked in iron pans. In some cases, iron tablets or iron injections may have been prescribed and may be the cause of overload. Drinking excessive alcohol or having hereditary hemochromatosis, a genetic disease, increases body iron stores by interfering with the normal control of iron uptake from food. Alcoholism and primary hemochromatosis are two of the most common causes of iron overload.
Other Causes of High Iron
Secondary hemochromatosis is the term for another disease or condition leading to increased iron levels in the blood and body. Alcoholic cirrhosis, fatty liver, other liver diseases, diabetes or kidney disease can be the cause. People with conditions that lead to premature red cell aging or destruction such as thalassemia or sickle cell anemia often develop high iron levels, in part due to requiring blood transfusions. People whose bone marrow is not functioning efficiently in making red cells, such in cancer patients or people with aplastic anemia or myelodysplastic syndrome are also commonly transfused. Recurrent transfusions add large amounts of iron to the body and are another common cause of overload.
Iron Build Up
Chronic iron overload can lead to diabetes, heart muscle damage, loss of sex drive, cirrhosis of the liver, and kidney disease. Iron stores generally increase slowly over time in the absence of transfusion. Even people with hereditary hemochromatosis or who drink will not show signs of iron overload for many years. However, damage from iron overload can be irreversible. People with a family history of iron overload should discuss their risk with their doctor.
REFERENCES & RESOURCES
- National Heart, Lung and Blood Institue: What is Hemochromatosis?
- The American Journal of Clinical Nutrition: Iron Bioavailability and Daily Reference Values
- The American Journal of Pathology: Iron Kinetics With Emphasis on Iron Overload
- Medline Plus: Iron in the Diet
- Iron Disorders Institute: Iron Overload with Anemia
- GP Online: Raised Ferritin Levels
- The American Journal of Clinical Nutrition: Body Iron Stores and Their Determinants in Healthy Postmenopausal US Women
- MedlinePlus: Ferritin