Why Is Transferrin Decreased In Iron Deficiency Anemia?

Iron is a mineral nutrient that is required for producing red blood cells in all mammals. Your body usually conserves and recycles iron fairly efficiently, but your iron stores can be depleted if your diet lacks iron or if you lose more iron than your intestine can absorb. Without enough iron to make new red blood cells, you can develop a condition called iron-deficiency anemia. Transferrin is a protein that transports iron throughout your body, and its concentration in your bloodstream usually changes when you are iron deficient.

Hemoglobin

In order to function normally, your cells and organs must have an adequate supply of oxygen. Your red blood cells, by virtue of their hemoglobin content, are uniquely adapted to deliver oxygen to the remotest corner of your body. The iron held within the hemoglobin molecule allows it to quickly pick up oxygen in your lungs, efficiently transport it through your bloodstream and release it in your peripheral tissues where it is needed for metabolism. According to "The Merck Manual of Diagnosis and Therapy," about two-thirds of your iron stores are found in hemoglobin, while less than 0.1 percent is held by the iron-transport protein, transferrin.

Transferrin

Iron absorption from your intestine is fairly tightly regulated, increasing when your need for iron increases and decreasing when your iron stores are sufficient. Iron absorbed from your intestine is bound to transferrin, a protein manufactured in your liver, and transported to tissues where it is needed. Iron that is not immediately utilized is deposited by transferrin into your iron "storage pool," which consists of the proteins ferritin and hemosiderin. Normally, when you are iron deficient your liver manufactures more transferrin to enhance iron absorption from your intestine.

Chronic Disease

In some chronic diseases, such as rheumatoid arthritis, osteoarthritis, kidney failure or certain forms of cancer, your liver's ability to manufacture transferrin is impaired, and iron is retained in your storage pool. This interferes with your ability to transfer iron to your bone marrow, where red blood cells are produced. As red blood cell production declines, you develop an anemia that resembles iron-deficiency anemia. However, according to an October 2000 review in "American Family Physician," your iron stores are usually normal or even slightly elevated in anemia of chronic disease; your body is just unable to access its iron due to low transferrin levels.

Considerations

The Linus Pauling Institute at Oregon State University reports that iron deficiency is the most common nutrient deficiency in the world. Iron-deficiency anemia has a characteristic appearance that resembles anemia of chronic disease, even though the latter is not caused by true iron deficiency. Iron-deficiency anemia typically causes an increase in transferrin levels, while anemia of chronic disease is associated with low transferrin levels. Measurement of a serum ferritin level, which is decreased in iron-deficiency anemia, will help to distinguish between the two in 70 percent of cases. Check with your doctor to see if you have iron-deficiency anemia or anemia of chronic disease.