Iron deficiency

Esa Soppi, adjunct professor, internal medicine

According to estimations in the USA, 1–2% of the adult population has iron deficiency anemia. It is estimated that iron deficiency without anemia occurs among approximately 11% of females and 4% of males. Some 40% of women have experienced iron deficiency at some point during their life. Clearly, iron deficiency is a very common condition, but it is poorly known and identified. One may even claim that iron deficiency, being so common, is a national disease.

Only a minute bleeding of just a few milliliters of blood per day (1 mL of blood contains about 0.5 mg of iron) may lead to iron deficiency, since the daily absorption of iron may be less than what is lost in this volume of blood. In this case, iron is first depleted from the body’s iron stores, which is reflected in a decrease in the ferritin concentration.  Only when the iron stores are sufficiently depleted, anemia ensues.  Anemia is defined as a blood hemoglobin concentration of less than 117 g/L for females and less than 134 g/L for males. Importantly, however, a notable proportion of people with iron deficiency may develop severe deficiency without any reductions in the hemoglobin value or a reduction that is too small to qualify as anemia.  

The best measure of iron deficiency is the ferritin concentration.  When the value is below 30 mg/L, iron deficiency is almost invariably present. However, the ferritin concentration is affected by similar factors as the CRP concentration and the sedimentation rate and may increase substantially when there is, for instance, an infection.  Occasionally, it may be exquisitely difficult to identify iron deficiency and much “detective work” is needed.

The usual causes of iron deficiency are heavy or prolonged menstrual bleeding, pregnancy, blood donations and other instances of blood loss and celiac disease. Iron deficiency may develop slowly, and the underlying causes, like marked menstrual blood loss and pregnancies, may have occurred 10–30 years earlier. Nevertheless, when iron deficiency is diagnosed, it is very important that the cause for the deficiency is established clearly.

Iron deficiency may give rise to a multitude of various symptoms, and clinically the symptoms may mimic, for example, those of hypothyroidism.

Among the most common symptoms the following may occur:  fatigue, languor, poor performance capacity, weight gain, chilliness, disturbed bowel function, body temperature changes and sweats, headache, joint pain, feeling a lump in the throat, dry skin and restless legs.

The universal primary treatment of iron deficiency is a suitable iron preparation by mouth (at least 100 mg per day). Oral iron treatment needs to be continued for about 6–9 months after the anemia has been corrected. Among the side effects of oral iron treatment are nausea, constipation, diarrhea and stomach aches. The teeth may become discolored. The degree of iron deficiency and/or the symptoms of some patients may so severe that it is not possible to correct the iron deficiency at all or within a reasonable time with oral iron supplementation alone. There are also patients who do not tolerate oral iron supplementation at all. In such situations it may be possible to administer an iron preparation by the intravenous route. However, such therapy may have serious side effects.

Taking iron supplementation without the guidance of a physician is discouraged. Liquid iron supplementation products do not usually provide enough iron to correct for the iron deficiency.  A standard dose of a liquid iron preparation contains only about 20 mg of iron.

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