Iron Deficiency

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

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 gastrointestinal abnormalities (eg, tumors, inflammatory bowel disease, gastritis)

It is important to identify the cause of iron deficiency when it is not clearly identifiable from the history. Middle-aged and older adults with iron deficiency should undergo an endoscopic bowel workup as chronic bleeding due to colon cancer is a serious cause in middle-aged and older adults.

Iron deficiency and iron deficiency anemia are common among elite runners and triathlon athletes (1).

Chronic kidney disease and inflammatory bowel disease are also associated with iron deficiency. In patients with chronic kidney disease, including those on hemodialysis, and those with inflammatory bowel disease or other chronic inflammatory conditions, hepatic synthesis of the hormone hepcidin is increased, interfering with iron absorption and leading to iron deficiency. However, chronic inflammation also increases serum iron by decreasing the use of iron to make red blood cells and thus causes anemia of chronic disease and complicates the assessment of iron status.

When iron 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.

Iron deficiency may exacerbate some types of heart failure; in such cases, patients may benefit from iron replacement (2–4).

Diagnosis of iron deficiency involves complete blood count, serum ferritin, and measurement of transferrin saturation (TSAT). In deficiency states, ferritin levels tend to be low (< 50 mcg/L), and transferrin saturation is often < 20% (5).

Rarely, when the diagnosis of iron deficiency remains uncertain, examination of bone marrow for iron may be necessary.

Treatment of iron deficiency involves correcting the cause if possible (eg, treatment of a bleeding intestinal tumor). All people with moderate or severe iron deficiency and some people with mild deficiency require iron supplementation.