Iron
is transported in plasma complexed to the metal-binding globulin, transferrin,
which is synthesized in the liver. Total iron binding capacity is calculated
from transferrin levels measured immunologically. Each molecule of transferrin
has two iron-binding sites, so its iron binding capacity is 1.47 mg/g. Normally,
transferrin carries an amount of iron representing about 16?60% of its capacity
to bind iron, ie, % saturation of iron binding capacity is 16-60%.
Normal
Range: 250-460 µg/dL
increased
in: Iron deficiency anemia, late pregnancy, infancy, hepatitis. Drugs: oral
contraceptives.
Decreased in: Hypoproteinemic
states (eg, nephrotic syndrome, starvation, malnutrition, cancer), chronic
inflammatory disorders, chronic disease, chronic liver disease.
Additional: Increased
% transferrin saturation with iron: in iron overload (iron poisoning,
hemolytic anemia, sideroblastic anemia, thalassemia, hemochromatosis,
pyridoxine deficiency, aplastic anemias). Decreased % transferrin saturation
with iron: in iron deficiency (usually saturation <16%). Transferrin
levels can also be used to assess nutritional status.
