Posttherapeutic Myxedema: Relative Occurrence After Treatment of Hyperthyroidism by Radioactive Iodine (131I) or Subtotal Thyroidectomy

The interval from treatment of hyperthyroidism to diagnosis of myxedema was determined for 53 patients after subtotal thyroidectomy and 39 patients with myxedema following treatment with radioactive iodine ( 131 l) observed between 1950 and 1965. The existence of a cumulative incidence of myxedema after treatment of hyperthyroidism by subtotal thyroidectomy as well as by 131 l is confirmed. Accrual rates which are reported to be lower following the former may be explained by differences in patient selection and are not necessarily due to inherent differences in the effects of these forms of treatment. Requirements for valid statistical analysis of the absolute and relative incidence of posttherapeutic myxedema have not been met in this or other published studies. Until these requirements are met, definitive statements about the magnitude of the risk of myxedema following treatment of hyperthyroidism cannot be made.