[Zn-content of erythrocytes in overt and subclinical hyperthyroidism]

Assaying the markers in blood reflecting thyroid hormone effect at peripheral tissue level previous data revealing a significantly decreased red-blood cell Zn-content in overt hyperthyroidism compared to euthyroid controls could be confirmed (p < 0.001). In patients with thyrotoxicosis during Metothyrin treatment the Zn-concentration of red-blood-cells normalised about 8 weeks later than the abnormally elevated serum thyroxine and triiodothyronine levels. On the basis of the present findings it is assumed that the Zn-concentration of red-blood cells reflects to a certain degree the circulating levels of thyroid hormones 2 to 3 months prior to the performed examination. The measurement of red-blood cell Zn-content does not seem to be a reliable method for the detection of a possible "tissue"-thyrotoxicosis in cases of subclinical hyperthyroidism.