Chapter 9: Iron Deficiency and Iron Overload

INTRODUCTION

• Iron deficiency is one of the most common chronic maladies in humans. One-third to one-half of healthy women of reproductive age in the United States have absent iron stores, and 10% have iron-deficiency anemia. Iron deficiency is also common in infants and adolescents.

• Iron overload denotes an excess of iron in the body.

DEVELOPMENTAL STAGES OF IRON DEFICIENCY

• The normal 70-kg male has about 3.0 g of total body iron.

  — 1 g is in the storage compartment in men and a few hundred milligrams are present in women of childbearing age in the form of ferritin.

  — 2.0 g are in hemoglobin in red cells.

  — 0.13 g is in myoglobin.

  — Very small amounts (~11 mg) are in plasma bound to transferrin and iron-containing enzymes in all organs.

• Iron depletion: In the case of negative iron balance (eg, surreptitious blood loss), initially, storage iron decreases until absent. This loss of stores has no impact on erythropoiesis.

• One of the most frequent causes of surreptitious iron loss is menstrual bleeding each month in women of childbearing age. In addition, with pregnancy, iron is transferred to the fetus and some loss occurs in the placental blood at childbirth (see “Pregnancy and Lactation,” below). This results in women of childbearing age frequently having diminished or absent iron stores and being at high risk of developing iron-deficiency anemia from continued negative iron balance as a result of menometrorrhagia. Even without anemia, the nonanemic iron deficiency can have a significant impact on quality of life.

• Iron deficiency: Storage iron absent with low serum iron concentration and transferrin saturation.

• Iron-deficiency anemia: Storage iron absent, low serum iron concentration and transferrin saturation, and low hemoglobin level.

CAUSES OF IRON DEFICIENCY

• Chronic blood loss

• Diversion of maternal iron to fetus/infant during pregnancy/lactation

• Inadequate dietary intake of iron, primarily in infants and children

• Chronic malabsorption of iron

• Intravascular hemolysis with hemoglobinuria and or hemosiderinuria

• Combinations of the above

Dietary Causes

• Infants most often develop iron deficiency because milk is a poor source of dietary iron and the additional requirements for iron imposed by rapid growth are not satisfied.

• In children, poor dietary iron intake plus intestinal parasites and/or bleeding gastrointestinal lesions are the usual causes.

• In the United States, average iron intake is 12 to 20 mg/d, varying by age and gender. Children and menstruating women are in precarious iron balance and at higher risk for iron deficiency.

Malabsorption

• Iron absorption is decreased in the malabsorption syndromes.

• After subtotal gastrectomy, malabsorption of dietary iron occurs in 50% of patients because of rapid gastrointestinal transit and because food bypasses the site of maximal absorption due to the anastomosis. In contrast, medicinal iron is well absorbed after partial gastrectomy.

• In postgastrectomy anemia, there may be bleeding ...