Chemistry Reference
In-Depth Information
For example, one of the main functions of iron is the movement of oxygen from
the environment to body tissues (Beard, 2006). As a result, approximately 66%
of iron in the body is found in hemoglobin of circulating erythrocytes. Another
25% is in the readily mobilizable iron store and the remaining 15% is contained
in the myoglobin of muscle tissue and a variety of enzymes required for
oxidative metabolism and other functions in cells. In humans, there are four
major classes of iron-containing proteins: heme proteins (hemoglobin,
myoglobin, cytochromes), iron-sulfur enzymes (flavoproteins, heme-flavopro-
teins), iron transport and storage proteins (lactoferrin, transferrin, ferritin,
hemosiderin) and other iron-containing or activated enzymes (sulfur, non-
heme enzymes). Iron is critical for the regulation of genes, cell growth and
differentiation, hematopoiesis and
cognitive
development
during
infancy
(Kelleher and Lonnerdal, 2005).
Iron-deficiency anemia is the late stage of negative iron balance and is
diagnosed as low serum transferrin saturation (
<
15%), a low serum ferritin
concentration (
<
12 mg/l) and an elevated soluble transferrin receptor (
>
6 mg/
dL) in a background of microcytic anemia. The physical symptoms of iron-
deficiency anemia are tiredness, listlessness, apathy and general feelings of
lack of energy. Endurance exercise is markedly impaired. These symptoms
represent true reductions in muscle functioning but may also reflect patholo-
gical changes in central nervous system functioning (Beard, 2001). Iron-
deficiency anemia affects an estimated 20-25% of infants worldwide and
appears to cause irreversible developmental delays (Lozoff et al., 2003).
Other clinical signs of iron deficiency include inflammation or infection of
the tongue (glossitis), fissuring in the corners of the lips (angular stomatitis),
spoon nails (koilonchyia), blue sclera, esophageal webbing and behavior
disturbances (pica, the abnormal consumption of non-food items) (Beard,
2006).
Ferritin and hemosiderin (a water-insoluble degradation product of
ferritin) comprise 95 and 5%, respectively, of the storage forms of iron in the
liver (Beard, 2006). Because both the human host and most pathogens
require iron, the host must meet cellular demands while simultaneously
preventing excess accumulation. Iron overload can be induced by several
factors including blood transfusions, hereditary hemochromatosis or parti-
cular forms of food and their preparation (i.e., consuming beer cooked in
iron pots). In iron overload, there is gross cellular accumulation of both
ferritin and hemosiderin in several tissues but particularly in the liver where
therateofincreaseofhemosiderinis10 times that of ferritin (Miyazaki
et al., 2002).
Iron requirements are highest during pregnancy (Table 10.2). On the
other hand, the requirement for exogenous iron is virtually zero for the
normal
full-term
infant
at
birth
because
of
the
normally
very
high
