Copper
Plasma Copper
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.
Serum Ceruloplasmin
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.
Erythrocyte Superoxide Dismutase Activity
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.
Hair Copper
The level of copper in hair varies under different conditions and is a poor
measure of copper status in the body.
Urinary Copper
Urinary copper excretion does not vary much with changes in copper intake and
therefore is not a useful measure of copper status.