To Study changes of cerebral function and cerebrovascular hemodynamics in patients with hyperthyrodism before and after treatment. Methods Electroencephalogram (EEG) and transcranial Doppler (TCD) were performed in 60 patients with hyperthyroidism. Results The abnormal rate of EEG and TCD before treatment was 70% (42/60), 89% (51/57) respectively. Twenty one patients after treatment had normal EEG and TCD; There was significant correlation between the levels of plasma thyroid hormones and the abnormal rate...