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Updated 03 May 2013

Iron deficiency anaemia

Iron deficiency is the most common cause of anaemia.

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Summary

  • Iron deficiency is the most common cause of anaemia worldwide.
  • Iron deficiency causes microcytic hypochromic anaemia. (Other causes include: chronic disease, thalassaemia, and anaemia due to lead poisoning.)
  • Common causes of iron deficiency are nutritional, or as a result of chronic blood loss. Chronic blood loss usually occurs due to excessive menstruation or blood loss from the gastro-intestinal tract.
  • Nutritional iron deficiency may occur when there is an increased demand for iron. This occurs during periods such as foetal growth in pregnancy, as well as when children undergo rapid growth spurts in infancy and adolescence.
  • The symptoms of chronic iron deficiency anaemia include tiredness, weakness, shortness of breath, poor concentration and sometimes a fast heartbeat.
  • Laboratory investigation is the only reliable way of diagnosing iron deficiency anaemia.
  • Iron deficiency is treated by iron supplementation and treatment of the underlying cause.

Definition

Anaemia is defined as a haemoglobin concentration lower than normal for the age and sex of the person involved. (Haemoglobin is the molecule in red blood cells that carries oxygen; it is the substance that gives blood its red colour and is measured using specialised instruments).

Anaemia is not a diagnosis, and an underlying cause should always be sought. To aid in establishing the cause of the anaemia, the appearance of red blood cells under the microscope and the size of red blood cells, measured by laboratory instruments, are used. In iron deficiency the cells are small and contain very little haemoglobin and are called microcytic hypochromic cells.

This is therefore a chronic type of anaemia in which the red blood cells become small (microcytic) and pale (hypochromic) and the body’s iron stores are depleted. This is the most common form of anaemia.

Causes

Iron deficiency occurs when the rate of loss or use of iron exceeds its rate of uptake and assimilation. The reasons for this are:

  • Chronic blood loss: Most commonly due to excessive menstruation or due to bleeding into or from the gut as a result of a peptic ulcer, gastritis, haemorrhoids, or  worm infestation in children.
  • Increased need for iron: In pregnancy, due to the growth of the foetus, or in children undergoing rapid growth spurts in infancy and adolescence.
  • Nutritional: Inadequate intake of iron to meet the body’s requirements. This occurs because of diets with insufficient iron. It also occurs during the weaning period when babies are switched from breast milk to solids. Breast milk contains lactoferrin, a type of iron which is very easily absorbed.
  • Decreased absorption of iron:
    • After a partial or total removal of the stomach
    • Lack of stomach acid
    • Chronic diarrhoea  
    • Malabsorption  

Who gets it?

  • Women with excessive menstrual bleeding
  • People with peptic ulcers, gastritis, haemorrhoids or gastro-intestinal malignancies
  • Pregnant and breastfeeding women
  • Children undergoing rapid growth spurts in infancy and adolescence
  • Babies who are being weaned from breast or formula milk to solids. This usually occurs at 4-6 months to 2 years.
  • The elderly and the poor are prone to iron deficiency anaemia due to a poor diet.
  • Those living in countries where little meat is eaten (and grains form the basis of the diet).
  • Children with severe worm infestation.

Symptoms and signs

  • The usual symptoms of chronic anaemia (such as tiredness, weakness, shortness of breath and sometimes a fast heartbeat).
  • There may also be difficulty concentrating, and some neurocognitive deficits.
  • The tongue may be smooth, shiny and inflamed (called glossitis).
  • Angular stomatitis, the erosion, tenderness and swelling at the corners of the mouth, may also occur.
  • In some children there may be poor growth overall, and growth faltering.
  • Pica, a craving for strange foods such as starch, ice, and sand, may develop.
  • The symptoms of the underlying cause of the iron deficiency may be present, such as heavy menstrual bleeding or abdominal pain due to peptic ulceration.

Stages of development

The body has several requirements for the absorption of iron. These include having an adequate nutritional intake. Demands are increased during times of growth and when there is chronic blood loss. The body then requires an intact small intestine with sufficient specific iron carrier proteins for the iron to be absorbed. If the gastrointestinal surface is damaged from any cause, the iron may not be adequately absorbed. If there are insufficient proteins produced, this will also affect iron absorption. The body keeps the amount of iron in balance by regulating iron absorption in the gastro-intestinal tract. Red blood cells account for 90% of the body’s iron. When these cells die, the iron is carefully re-cycled by the body. There is a balance that the body needs to maintain, and  this is carefully regulated. However, the demands at some periods, e.g. growth, or when there is excess blood loss, may be far greater than the diet can provide. If this occurs, iron deficiency will develop. Iron deficiency develops slowly in stages. Initially the body utilises all existing stores. During the next stage the red blood cells become smaller (microcytic) and have less haemoglobin (hypochromic). This is followed by a decrease in the total number of red cells and a decrease in the haemoglobin, i.e. the development of anaemia itself. As iron is also required  for muscles, brain function, as well as for enzyme systems throughout the body, tiredness, lethargy, fatigue, difficulty concentrating and poor attention span also develop.  If you then add losses from menstruation (average 0,5 mg/day),  and blood loss due to disease or accident, iron deficiency readily develops. This loss takes place in sequential changes or stages.

Stage 1

Iron loss exceeds intake. As a result, there is a negative iron balance and the iron stored in the bone marrow is progressively depleted. As stored iron decreases, there is a compensatory increase in the absorption of iron in the diet and an increase in the iron binding capacity of the cells.

Stage 2

The exhausted iron stores cannot meet the needs of the bone marrow. This means that there is progressively less iron available for the formation of red blood cells.

Stage 3

By now anaemia has developed, but the red blood cells still look normal.

Stage 4

The red blood cells become smaller (microcytic) and pale (hypochromic).

Stage 5

Iron deficiency affects the tissues, resulting in the symptoms and signs of iron deficiency anaemia.

Diagnosis

A complete and thorough history, as well as review of diet and potential blood loss is critical in making the diagnosis.

Laboratory investigations are the only reliable way of diagnosing iron deficiency anaemia. There is a low haemoglobin concentration in the blood, and when the red blood cells are examined under a microscope, they are pale and small. The iron stores in the body are measured using serum iron, transferrin and percentage saturation of the cells. Ferritin levels are required to distinguish between iron deficiency anaemia and anaemia of chronic disease. In iron deficiency the serum iron is low, transferrin is increased and the percentage saturation is below 16%. Serum ferritin is also decreased in iron deficiency

As iron deficiency is extremely common in children, a full blood count will usually suffice, and  it is not necessary to do iron studies. If there is no response to iron supplementation after 6-9 months, additional tests and referral are required.

Prevention

A well-balanced diet is essential and there is proof that iron supplementation during times of increased demand such as pregnancy and weaning are vital for the prevention of iron deficiency.

Treating the underlying cause of iron deficiency will prevent the development of anaemia or the continuation of anaemia after treatment.

Treatment

Iron deficiency responds very well to oral iron sulphate tablets such as ferrous sulphate, taken in a dose of 300 mg three times a day in an adult. A dose of 300 mg once or twice a day may be effective for prophylaxis or mild iron deficiency. In children the dose is dependent on the child’s weight, and it is best for a doctor or pharmacist to advise on this.

The tablets should be taken between meals, as iron is absorbed better on an empty stomach. However, this form of iron has side effects such as bloating, fullness and sometimes stomach pain, and taking the tablets with meals may help to alleviate these side effects. Iron may result in constipation and black stools.

Ferrous gluconate or ferrous lactate may have fewer side effects. Vitamin C may be used to aid absorption of the iron tablets. Iron tablets should not be taken with tea, as this inhibits or decreases the absorption of the iron.

Iron-containing cocktails of vitamins should not be used alone to treat iron deficiency, as they contain insufficient amounts of iron. They can be used as a part of routine supplementation. Once iron deficiency occurs, specific iron supplements are required to provide sufficient iron for replacement. Drugs that reduce acid production by the stomach such as cimetidine (Tagamet) may inhibit iron absorption and these tablets should not be taken with iron supplements.

It is necessary to continue iron therapy for four to six months to correct anaemia and replenish stores.

If iron is not being absorbed in the gut, it may be given by injection into the vein. This is required in certain cases where there is insufficient absorption of iron due to problems with the gastro-intestinal tract, or where iron supplements are not tolerated. Intravenous iron should be used when a sufficient trial of oral iron has been given, and should be done with the guidance of a physician. There is a small possibility of reactions to the intravenous preparation and its should be administered with the necessary care, preferably in a hospital, doctor’s rooms or a clinic.

Outcome

Iron deficiency anaemia responds well to treatment with iron tablets and a change in diet.

When to see your doctor

  • If you have heavy and prolonged menstrual periods and show symptoms of iron deficiency anaemia.
  • If you develop strange food cravings, along with symptoms of tiredness and weakness.
  • If your stool becomes black and foul-smelling.
  • If you notice growth faltering or a fall-off in growth on the “road to health card” of your child.

Previously reviewed by Dr Betsie Lombard, MBChB (Pret), Mmed (Haem Path) (Stell)

Reviewed by Dr Yasmin Goga MBBCH (Wits), DCH (SA), FCPaeds (SA), Cert Clin Haem Paeds (SA), June 2011

 
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