Post-thyroidectomy thyrotoxicosis

94 patients with postoperative recurrent hyperthyroidism were evaluated for duration of remission, goitre size, and response to radio-iodine (131I). 6 patients required 131I therapy within twelve months of operation--5 had large remnants because of inadequate surgery. 57% of patients relapsed within 5 years, but 16% relapsed after 20 years and 8% after more than 30 years. Estimated goitre weights ranged from 4 g to 65 g, and goitre size was unrelated to the duration of remission. All patients were treated with 131I. 23% of the patients became hypothyroid in the first postoperative year and 10% in the second year. The results indicate that postoperative thyrotoxicosis can recur decades after operation. Operation seems to sensitise the thyroid to the early effects of radiation by 131I.