Iron Deficiency Anemia

Iron deficiency anemia is the most common form of anemia.  Iron is an essential component of the hemoglobin molecule: without iron the bone marrow is unable to produce hemoglobin.  The red cell count falls and those which do enter circulation are smaller than normal (microcytic) and lacking in hemoglobin, hence they are pale (hypochromic).

The deficiency of iron may be absolute (there is no iron available for the production of hemoglobin – this is true iron deficiency anemia) or relative (the iron is present in storage in the marrow but other reasons prevent its incorporation into red blood cells).

Causes and Development

Red blood cells deliver oxygen to where it is needed. The hemoglobin molecules inside make blood red and bind with oxygen.

The average amount of iron in the average adult male is 4gm and in the average adult female 2.5gm.  The normal North American diet contains approximately 15-20mg of iron per day.  Most is present in meat and green vegetables; approximately 1.0mg is absorbed each day and just about an equal amount is lost in feces and sweat.  As a result, the average adult's iron intake is in delicate balance, but is of little consequence as there is slightly more iron absorbed than lost and a store of iron is gradually accumulated.  If, for some reason, the rate of iron loss increases, these stores can be depleted and an absolute iron deficiency develops.  Such a deficiency requires large doses of supplemental iron to resupply the body stores and sufficient monitoring to prevent iron overload.

Causes of iron deficiency include:

• Diet – uncommon except in children
• Failure to absorb
• Increased utilization (for example pregnancy, adolescent growth)
• Atransferrinemia
• Failure to utilize (for example lead poisoning, chronic diseases)
• Blood loss.

Chronic blood loss is the most common cause of iron deficiency anemia.  It must be remembered that anemia in iron deficiency develops slowly.  The type and severity of the anemia varies with time.  The development stages are:

1. Depletion of iron stores, decreased ferritin levels, no anemia
2. Increased transferrin levels, no anemia
3. Fall in serum iron, no anemia
4. Development of normocytic, normochromic anemia
5. Development of microcytic, hypochromic anemia.

Signs and Symptoms

Along with those mentioned below, symptoms often include malaise (a vague feeling of physical discomfort or uneasiness).

Diagnosis and Tests

Laboratory Diagnosis of Iron Deficiency

Half of a hemoglobin molecule, with two iron atoms shown in green.

Routine procedures. Hgb, Hct and RBC count are all decreased.  The degree of decrease depends upon the length of time the marrow has been without sufficient supplies of iron.  Because marrow can continue to produce empty cells, the red cell number will not be proportionately as low as the Hgb and Hct values.  Serum ferritin is a better measure of body iron stores than any value in the complete blood count, as it will begin dropping long before other signs appear in the blood.

Indices. MCV – decreased, MCH – decreased, MCHC – decreased.  The MCHC is the last to become lowered because as the marrow becomes more and more depleted of iron it produces smaller cells with a smaller amount of hemoglobin in each in an attempt to keep the concentration of hemoglobin in each normal.  The RDW is increased, reflecting the anisocytosis characteristic of iron deficiency.

Treatment and Prevention

Treatment depends on the underlying cause.  Iron deficiency anemia is usually easy to resolve; an anemia that does not respond as expected may require the help of a hematologist and additional testing.