Approximately one-third of the number of U.S. citizens that have an iron deficiency may be affected by an iron overload due to a condition called hemochromatosis. Normally, the amount of iron in the human body is regulated by gastrointestinal absorption; excess iron simply passes through. Hemochromatosis results in excessive absorption; the tissue stores iron to the point of injury. The consequences of this condition normally show up between the ages of 40 and 60, and may include cirrhosis, hepatomas, diabetes, cardiamyopathy, arthritis or athropathy, or hypopituitarism with hypogonadism. There is no evidence that iron fortification of foods, or the taking of iron dietary supplements during pregnancy, increases the risk of disease due to hemochromatosis. This condition will require phlebotomy, even if the iron intake of the person who has it is only average.
My source for this writeup was www.cdc.gov/epo/mmwr/preview/mmwrhtml/0051880.htm, which goes into far more detail through medical terminology than my layman's brain could handle.