Oral copper loading test in humans

There has been no report of normal responses of plasma copper and/or ceruloplasmin concentrations after an oral loading dose of unlabeled copper in humans. To establish a normal plasma response curve following an oral dose, we performed a copper-loading test (10 mg elemental copper as copper sulfate) in six healthy adult subjects and monitored plasma copper and ceruloplasmin concentrations for 3.5 h. We found that there were no significant changes in plasma copper and ceruloplasmin concentrations following the oral dose in the subjects. The test was originally intended to evaluate whether there was copper malabsorption in a female patient who developed signs of copper deficiency with her plasma copper levels below 3.0 μmol/l after multiple gastrointestinal surgeries. She did not respond to oral copper sulfate administration but responded to a sublingual application of copper glycinate. These findings suggest that she does not have adequate intestinal copper absorption. In conclusion, the use of unlabeled copper, such as copper sulfate, for an oral loading test, seemingly simple and economical, does not appear to be a suitable means to evaluate copper absorption in humans and is discouraged. In case of copper malabsorption, sublingual administration of copper may be worth trying. J. Trace Elem. Exp. Med. 16: 61–66, 2003. © 2003 Wiley-Liss, Inc.