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by Larry E. Johnson, MD, PhD

Iron (Fe) is a component of hemoglobin, myoglobin, and many enzymes in the body. Heme iron, contained mainly in animal products, is absorbed much better than nonheme iron (eg, in plants and grains), which accounts for > 85% of iron in the average diet. However, absorption of nonheme iron is increased when it is consumed with animal protein and vitamin C.

Iron Deficiency

Iron deficiency is one of the most common mineral deficiencies in the world. It may result from the following:

  • Inadequate iron intake, common in infants, adolescent girls, and pregnant women

  • Malabsorption (eg, celiac disease)

  • Chronic bleeding, including heavy menses and bleeding from GI lesions

Chronic bleeding due to colon cancer is a serious cause in middle-aged people and the elderly.

When deficiency is advanced, microcytic anemia develops.

In addition to anemia, iron deficiency may cause pica (a craving for nonfoods) and spoon nails and is associated with restless leg syndrome. Rarely, iron deficiency causes dysphagia due to postcricoid esophageal web.

Diagnosis of iron deficiency involves CBC, serum ferritin and iron levels, and possibly measurement of transferrin saturation (iron-binding capacity). In deficiency states, iron and ferritin levels tend to be low, and iron-binding capacity tends to be high.

All people with moderate or severe iron deficiency and some people with mild deficiency require iron supplementation.

Iron Toxicity

Iron may accumulate in the body because of

  • Iron therapy given in excessive amounts or for too long

  • Repeated blood transfusions

  • Chronic alcoholism

  • Overdose of iron

Iron overload can also result from an inherited iron overload disease ( hemochromatosis), a potentially fatal but easily treatable genetic disorder in which too much iron is absorbed. Hemochromatosis affects > 1 million Americans.

An overdose of iron is toxic, causing vomiting, diarrhea, and damage to the intestine and other organs.

Diagnosis of iron toxicity is similar to that for iron deficiency.

Treatment of iron toxicity often involves deferoxamine, which binds with iron and is excreted in urine.

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