The effect of the enhanced metabolic rate over antioxidant status was
investigated in hyperthyroid individuals. Serum total T3 and T4 levels
were measured by radioimmunoassay in 45 patients and 25 controls. The
serum vitamin E was assayed fluorometrically in the hexane extract of
serum. Serum ceruloplasmin activity was measured spectrophotometrical
ly. Statistical significance was asessed by correlation regression ana
lysis and paired t-test. The serum vitamin E levels decreased signific
antly as the levels of the thyroid hormones increased. For ceruloplasm
in the opposite changes were observed: mean serum ceruloplasmin of hyp
erthyroid patients was greater than that of control group. Although th
e changes in vitamin E and ceruloplasmin concentrations did correlate
with the levels of thyroid hormones in hyperthyroid patients, we obser
ved no associations between these parameters in the euthyroid state. A
s these two parameters are the measure of oxidation potential, it may
be suggested that raised free radical activity in hyperthyroidism caus
e the increased oxidative stress and increased general radical scaveng
ing. The present data may indicate a direct effect of thyroid hormones
on vitamin E and ceruloplasmin metabolism.