Concentrations of thyroid hormones in serum and activity of hepatic 5′ monodeiodinase in copper-deficient rats

The aim of the present study was to investigate the effect of copper deficiency on thyroid hormone metabolism in rats. Therefore, an experiment with growing male Sprague-Dawley rats was carried out, consisting of two groups of rats fed either a copper-deficient (0.06 mg Cu/kg) or a copper-adequate diet (16 mg Cu/kg). Both groups of rats were fed identical quantities of diet by pair-feeding. Copper deficiency decreased the final body weight of the rats by 5% compared to copper-adequate control rats. A severe copper-deficient state in the rats fed the copper-deficient diet was proved by a large decrease of ceruloplasmin activity in serum (by 97%) and hematological changes. For estimation of thyroid hormone metabolism, the concentrations of total and free thyroxine (T4) and triiodothyronine (T3) in serum and the activity of hepatic 5'monodeiodinase (5'D) were determined. Copper-deficient rats had an increased concentration of T3 in serum, whereas the concentrations of total and free T4 as well as the activity of hepatic 5'D were not different compared with copper-adequate control rats. Therefore, the study shows that copper deficiency has only slight effects on thyroid hormone metabolism in growing rats.