Abstract
In 50 patients with uncomplicated thyrotoxicosis whose eeg''s were compared before and after radioactive I131, there was a small but significant decrease in QRS duration. The mean amplitude of R-II and the maximum R amplitude of thyrotoxic patients was significantly higher than comparable controls and decreased following therapy. Left ventricular hypertrophy, judged to be present in 14 of the thyrotoxic patients, disappeared in 9 after therapy.