Zinc metabolism in thyroid disease.

This study was designed to evaluate the zinc metabolism in adults of both sexes with thyroid disease. Plasma and erythrocyte zinc concentration and urinary zinc excretion were investigated. The mean concentration of plasma zinc in hypothyroid patients and in euthyroid patients, previously either hyperthyroid or hypothyroid, was lower than that of control subjects, whereas no statistically significant differences were observed in plasma zinc values between hyperthyroid patients and control subjects. The average erythrocyte zinc level in patients with thyroid disease was significantly lower than that in control subjects. Erythrocyte zinc concentration was significantly decreased in hyperthyroidism compared with hypothyroidism, or patients previously either hyperthyroid or hypothyroid but now euthyroid. Increased urinary zinc excretion in hyperthyroidism was noticed compared to euthyroid and hypothyroid patients and to control subjects. Increased urinary zinc concentrations may result from increased tissue catabolism such as muscle. The results of this study suggest that abnormal zinc metabolism occurs commonly in patients with thyroid disease.