Iron Deficiency Anemia Health Article

Definition

Iron deficiency anemia refers to anemia that is caused by lower than normal levels of iron. This type of anemia is caused by deficient erythropoiesis, the ongoing process of the bone marrow to produce healthy red blood cells (RBCs). It is characterized by the production of small (microcytic) RBCs. When examined under a microscope, the RBCs also appear pale or light colored from the absence of heme, the major component of hemoglobin, which is the iron-bearing protein and coloring pigment in RBCs. Anemia resulting from a deficiency of iron is also called microcytic anemia.

Description

Anemia is a blood disorder characterized by abnormally low levels of healthy RBCs or reduced levels of hemoglobin (Hgb), the iron-bearing protein in RBCs that delivers oxygen to tissues throughout the body. Blood cell volume (hematocrit) may also be reduced in some anemias, but not necessarily in iron deficiency anemia. The reduction of any or all of these blood parameters reduces the essential delivery of oxygen through the bloodstream to the organs of the body. Iron is a mineral found in the bloodstream that is essential for growth, enzyme development and function, a healthy immune system, energy levels, and muscle strength. It is an important component of hemoglobin and myoglobin, the type of hemoglobin in muscle tissue.

Iron deficiency anemia is the most common type of anemia throughout the world, although it occurs to a lesser extent in the United States because of the higher consumption of iron-rich red meat and the practice of food fortification (addition of iron to foods by manufacturers). In developing countries in tropical climates, the most common cause of iron deficiency anemia is infestation with hookworm.

The onset of iron deficiency anemia is gradual and may not have early symptoms. The deficiency begins when the body's store of iron is depleted and more iron is being lost through bleeding or malabsorption than is derived from food and other sources. Because depleted iron stores cannot meet the red blood cells' needs, fewer red blood cells develop. In this early stage of anemia, the red blood cells look normal, but they are reduced in number. Eventually the body tries to compensate for the iron deficiency by producing more red blood cells, which are characteristically small in size (spherocytosis). Symptoms of anemia, especially weakness and fatigue, develop at this stage.

Causes and symptoms

Iron is an essential component of the production of healthy RBCs, and iron stores must be maintained for the ongoing production of RBCs by the bone marrow. Iron deficiency anemia can develop as a result of depleted iron stores from chronic blood loss, increased demands for iron as seen in periods of growth (e.g., in infancy and adolescence), or malabsorption of iron even when foods or supplements are supplying adequate amounts. It is accepted that iron is hard to absorb; this, in combination with diets that may not meet daily requirements, is a common route to iron deficiency and iron deficiency anemia. Iron can also be lost through strenuous exercise and heavy perspiration, poor digestion, frequent consumption of antacids, long-term illness, heavy menstrual cycles, and other causes.

Infancy is a period of increased risk for iron deficiency because dietary iron may not be adequate for the rapid growth of the child in the first two years of life, an example of increased demand. The human infant is born with a built-in supply of iron, which can be tapped during periods of drinking low-iron milk or formula. Both human milk and cow milk contain rather low levels of iron (0.5–1.0 mg iron/liter). However, the iron in the mother's breast milk is about 50 percent absorbed by the infant, while the iron of cow milk is only 10 percent absorbed. During the first six months of life, growth of the infant is made possible by the milk in the diet and by the infant's built-in supply of iron. However, premature infants have a lower supply of iron and, for this reason, it is recommended that pre-term infants, beginning at two months of age, be given oral supplements of 7 mg iron/day, as ferrous sulfate. Iron deficiency can be provoked where infants are fed formulas based on unfortified cow milk. For example, unfortified cow milk is given free of charge to mothers in Chile. This practice has the fortunate result of preventing general malnutrition, but the unfortunate result of allowing the development of mild iron deficiency.

Children have a great need for iron as they grow, and in most cases, the diet will provide replacement iron for the iron used in growth. Children seem to stay in balance unless a bleeding disorder of some kind exists, either hereditary (hemophilia or von Willebrand's) or related to hookworm infection or another illness. In adolescence, girls have an increased requirement for iron because of increased growth and the start of menstruation. Adolescent boys also experience a major growth spurt that demands more iron; iron stores are worn thin especially when healthy red cell function is needed for adequate oxygenation of exercising muscles and developing organs. Teenagers are also not noted for making healthy food choices; often they are losing iron stores and not replenishing iron through diet.

Iron deficiency occurs most often through chronic blood loss, more often in adults than in children, although the sources of bleeding can apply to people of all ages. Blood losses from gastrointestinal bleeding, excessive menstrual bleeding, and infection with hookworm can deplete iron and lead to iron deficiency anemia. In hookworm infection, a parasitic worm that thrives in warm climates, including in the southern United States, enters the body through the skin, such as through bare feet. The hookworm then migrates to the small intestines where it attaches itself to small sausage-shaped structures in the intestines (villi) that help with the absorption of all nutrients. The hookworm damages the villi, resulting in blood loss; they simultaneously produce anti-coagulants that promote continued bleeding. Each worm can initiate losses of up to 0.25 ml of blood per day.

Chronic blood losses through gradual bleeding in the gastrointestinal tract can be provoked by other conditions such as hemorrhoids, bleeding ulcers, anal fissures, irritable bowel syndrome, aspirin-induced bleeding, blood clotting disorders, and diverticulosis (a condition caused by an abnormal opening from the intestine or bladder). Several genetic diseases also lead to bleeding disorders. These include the coagulation disorders hemophilia A and hemophilia B, and von Willebrand's disease, a bleeding disorder caused by a deficiency in von Willebrand factor, an essential component of the coagulation system. All three genetic diseases can produce symptoms and be diagnosed in childhood.

The symptoms of iron deficiency anemia appear slowly and typically include weakness and fatigue. These symptoms result because of the reduced oxygen carrying capacity of RBCs and the reduced ability of the RBCs to carry iron to working muscles. Iron deficiency can also affect other tissues, including the tongue and fingernails. Prolonged iron deficiency can result in a smooth, shiny, and reddened tongue, a condition called glossitis. The fingernails may grow abnormally and acquire a spoon-shaped appearance.