What Is Iron Deficiency Anemia?

[dropcap]I[/dropcap]ron deficiency anemia is a blood cell disorder that is characterized by formation of small, pale red blood cells, causing tissue hypoxia. Hypoxia is the inability to meet the demands of the body for oxygen.

Q: Why do small, pale red blood cells cause tissue hypoxia?

A: Small, pale red blood cells (erythrocytes) cause tissue hypoxia because they are not able, as do normal erythrocytes, to pick up adequate oxygen from the lungs and carry it to cells that use oxygen.

Red blood cell production and function are dependent on a sufficient level of iron in the body and also the ability to use available iron to make hemoglobin in red blood cells.

Hemoglobin is a protein that binds oxygen in red blood cells to be carried by the bloodstream to cells throughout the body. In iron deficiency anemia,  hemoglobin in females is below 12.5g/dl (normal range is 12.5 to 16g/dl) and in males it is below 13.5g/dl (normal range is 13.5 to 17.5g/dl).

Iron must be obtained from the diet, since the body cannot make it, but there are various factors that can interfere with absorption and use in the body, causing anemia. Iron absorption from the gut first requires ionization, or gaining a positive electrical charge, in the strongly acidic environment of stomach juice. Ionized iron, only, can be absorbed in the duodenum, which receives the acidic contents of the stomach before it is neutralized further along.

Dietary iron can be heme or non-heme depending on the food source. Heme iron obtained only from animal food sources is absorbed into the bloodstream by active transport across the brush border (microvilli) which cover the multitudinous villi of the small intestinal lining.

Non-heme iron obtained from plants must bind with apoprotein after entering the enterocyte (surface cell of small intestinal lining) to be ferried to the underlying basolateral membrane and exited by active transport into the bloodstream.

Frequently, chronic anemia due to iron deficiency is accompanied by increased platelets, and this thrombocytosis resolves with iron repletion (normal iron level). Conversely, in severe iron deficiency anemia, patients may have thrombocytopenia (low platelets), which also resolves with iron therapy.¹

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Sources:

1. Koury M and Rhodes M. How to approach chronic anemia. Hematology Am Soc Hematol Educ Program. 2012;2012:183-90. doi: 10.1182/asheducation-2012.1.183. [↩]