Ferritin is a protein with a capacity of about 4500 iron (III) ions per protein molecule. This is the major form of iron storage.
If the capacity for storage of iron in ferritin is exceeded, a complex of iron with phosphate and hydroxide forms. This is called hemosiderin; it is physiologically available.
As the body burden of iron increases beyond normal levels, excess hemosiderin is deposited in the liver and heart. This can reach the point that the function of these organs is impaired, and death ensues.
Several conditions can lead to excess body iron.
Idiopathic hemochromatosis is a condition in which control of iron absorption is defective, and excess iron is absorbed.
Multiple transfusions can also lead to an excess body burden of iron. This is a serious problem for persons with beta-thalassemia, a disease in which hemoglobin is not made normally, and is supplied by blood transfusion as needed.
Treatment of excess iron storage involves artificial removal of iron from the body.
Bleeding is the treatment of choice for idiopathic hemochromatosis.
For beta-thalassemia bleeding would be inappropriate since the disease consists of inability of the body to synthesize a blood component, hemoglobin. In this case chelators are administered which bind iron. The complex of chelator with iron is excreted in the urine.
A commonly used chelator is deferoxamine.
Although it is effective, it must be administered by an inconvenient process of overnight infusion.
More unfortunately, treatment becomes critical as the patients reach their teenage years, a period of life associated with rebelliousness and feelings of invulnerability. These patients tend to be unreceptive to the treatment.