Iron Deficiency and Iron Overload.

Iron is essential to most, if not all, living organisms, and the higher animals and man have employed it for many purposes essential to life. The readiness with which iron undergoes oxidation and reduction is utilized in many of the enzymes of electron transport, and in a number of other enzymes whose function is not understood. Furthermore, the combination of iron with porphyrin and protein leads to complexes that have the property of binding large amounts of oxygen in a readily reversible fashion. Haemoglobin and myoglobin are complexes of this nature, which serve the function of oxygen transport and storage. About three-quarters of the iron in a normal man (between 4 g. and 5 g.) is incorporated in circulating haemoglobin. Less than 5% is present in myoglobin, various enzymes, or in transport in the plasma. The remainder, about 20% of the total, is present in the tissue stores, much of it as the iron-protein complex ferritin (Drabkin, 1951). Very little iron is excreted, as the iron from broken-down aged red cells is returned to the marrow for re-use in haemoglobin synthesis. The iron content of the body is achieved during periods of growth, and maintained thereafter at a steady level, through control of the amount absorbed. As the amount of iron utilized in haemoglobin synthesis is so much greater than the quantity of new iron absorbed, it is perhaps not surprising that iron deficiency is so common. It is the most frequent cause of anaemia, and the most important deficiency state in countries with good economic means. Iron deficiency is particularly common in early infancy, as the requirements of rapid growth exceed the infant's capacity to absorb enough iron from food. Iron in excess is toxic: acute iron poisoning follows ingestion of large amounts of iron salts, and is one of the most common