The body contains approximately 80 mg of copper, most of which resides in tissues. Plasma contains only a small amount of the total body store of copper, and so plasma copper is not a very good indicator of body stores; while plasma copper does detect severe copper deficiency, it is not sensitive to marginal copper status. Factors that can increase plasma levels include oral contraceptive use, pregnancy, stress, and infections. Plasma copper levels can decrease in nephrosis, Wilson's disease, and protein-energy malnutrition.
Ceruloplasmin is the primary copper-containing protein in the serum and serves as a transporter of copper. It functions as ferroxidase, an enzyme that oxidizes ferrous to ferric ion and influences the flow of iron from cells to plasma. In copper deficiency, ceruloplasmin levels fall, and there is a decrease in iron mobilization resulting in a microcytic anemia. Ceruloplasmin levels increase with estrogens, and decrease in Wilson's disease, uremia, and nephrosis.
The enzyme erythrocyte superoxide dismutase is a free-radical scavenger. Levels of this enzyme fall during copper deficiency; thus testing for the enzyme's activity is considered a sensitive indicator of copper depletion.
The level of copper in hair varies under different conditions and is a poor measure of copper status in the body.
Urinary copper excretion does not vary much with changes in copper intake and therefore is not a useful measure of copper status.
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