Blood loss is the most common cause of iron deficiency. Menstruation is the most likely reason in women ages 15 to 45 years. Iron deficiency anemia in adult men and postmenopausal women is most likely due to chronic gastrointestinal blood loss. Lack of dietary iron may cause anemia in infancy when the daily need for iron is not met by milk alone. This is why iron supplements are given to infants.
Iron deficiency is a major cause of anemia in pregnancy.
Malabsorption of iron is a rare cause of iron deficiency but is seen in patients who have had a partial gastrectomy or who have a malabsorption disorder. Small amounts of ferritin, derived from iron stores, circulate in the plasma. The amount of serum ferritin closely reflects iron stores, thus providing a readily measured assessment of body iron stores. Transferrin, the major iron transport protein, is synthesized by the liver and macrophages. Each molecule of transferrin can bind two atoms of iron.