Copper, 24 Hour, Urine
Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test
The biliary system is the major pathway of copper excretion. Biliary excretion of copper requires an adenosine triphosphate (ATP)-dependent transporter protein. Mutations in the gene for the transporter protein cause hepatolenticular degeneration (Wilson disease). Ceruloplasmin, the primary copper-carrying protein in the blood, is also reduced in Wilson disease. Urine copper excretion is increased in Wilson disease due to a decreased serum binding of copper to ceruloplasmin, or due to allelic variances in cellular metal ion transporters.
Hypercupriuria is also found in Menkes disease (kinky hair disease), hemochromatosis, biliary cirrhosis, thyrotoxicosis, various infections, and a variety of other acute, chronic, and malignant diseases (including leukemia). Urine copper concentrations are also elevated in patients taking contraceptives or estrogens and during pregnancy.
Low urine copper levels are seen in malnutrition, hypoproteinemias, malabsorption, and nephrotic syndrome. Increased zinc consumption interferes with normal copper absorption from the gastrointestinal tract causing hypocupremia.
Investigation of Wilson disease and obstructive liver disease
Humans normally excrete less than 60 mcg/day of copper in the urine.
Urinary copper excretion greater than 60 mcg/day may be seen in:
-Obstructive biliary disease (eg, primary biliary cirrhosis, primary sclerosing cholangitis)
-Nephrotic syndrome (due to leakage through the kidney)
-Mega-dosing of zinc-containing vitamins
Because ceruloplasmin is an acute phase reactant, urine copper is elevated during acute inflammation. During the recovery phase, urine copper is usually below normal, reflecting the expected physiologic response to replace the copper that was depleted during inflammation.
Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances
No significant cautionary statements
Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.
0-17 years: not established
> or =18 years: < or =60 mcg/24h
Clinical References Provides recommendations for further in-depth reading of a clinical nature
1. Zorbas YG, Kakuris KK, Deogenov VA et al: Copper homeostasis during hypokinesia in healthy subjects with higher and lower copper consumption. Trace Elements and Electrolytes 2008;25:169-178
2. Lech T, Sadlik JK: Contribution to the data on copper concentration in blood and urine in patients with Wilson's disease and in normal subjects. Biol Trace Elem Res 2007 July;118(1):16-20