Cardiovascular Manifestations of Hyperthyroidism Before and After Antithyroid Therapy: A Matched Case-Control Study Faizel Osman, Jayne A. Franklyn, Roger L. Holder, Michael C. Sheppard, Michael D. Gammage Overt hyperthyroidism is associated with well-recognized cardiovascular effects believed to be reversed by antithyroid therapy; however, increasing data suggest significant long-term cardiovascular mortality. A total of 393 patients with overt hyperthyroidism were compared with 393 age- and gender-matched euthyroid control subjects. Cardiovascular symptoms and signs, abnormal blood pressure measurements, and rhythm disturbances were more prevalent in patients at presentation, during antithyroid therapy (when patients showed the biochemistry of subclinical hyperthyroidism), and after restoration of biochemical euthyroidism in hyperthyroid patients compared with control subjects.