Studies of plasma zinc, copper, caeruloplasmin, and growth hormone

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Abstract
The levels of plasma zinc, copper, caeruloplasmin, and growth hormone were determined in a group of normal people and in four groups of patients who were suffering from carcinoma of the bronchus, other forms of malignancy, chest illnesses, and diseases other than chest illness or malignancy. The plasma zinc was higher, and the plasma copper lower, in people without malignancy below the age of 30 years than they were in other age groups. It was confirmed that about 66% of patients with carcinoma of the bronchus had plasma zinc levels less than 11·5 μmol/l but low levels were also found in 23% of other cases of malignancy and in 9% of the other patients. In carcinoma of the bronchus the low plasma zinc was found to be associated with epidermoid and anaplastic tumours and was to some extent related to the duration of the disease. In carcinoma of the bronchus the plasma copper was found to be higher than in all other groups, and values higher than 26·5 μmol/l were considered to support a diagnosis of carcinoma of the bronchus. There was, however, no relationship between the increase in the plasma copper and the decrease in the plasma zinc. Raised caeruloplasmin levels above 420 mg/l were found in 65% of cases of carcinoma of the bronchus, and these high levels were usually associated with raised plasma copper. Growth hormone was normal in all groups except six patients with carcinoma of the bronchus with secondary carcinoma of the liver, in whom it was raised. Surgical operations lowered plasma zinc and raised growth hormone but did not affect plasma copper. A plasma zinc below 11·5 μmol/l is helpful in the diagnosis of carcinoma of the bronchus, but by itself it is not sufficiently specific to be considered diagnostic or to form a reliable screening test. A raised plasma copper and a raised plasma caeruloplasmin were useful supportive findings.