MORTALITY AFTER THE TREATMENT OF HYPERTHYROIDISM WITH RADIOACTIVE IODINE

Background Hyperthyroidism affects many organ systems, but the effects are usually considered reversible. The long-term effects of hyperthyr oidism on mortality are not known. Methods We conducted a population-b ased study of mortality in a cohort of 7209 subjects with hyper thyroi dism who were treated with radioactive iodine in Birmingham, United Ki ngdom, between 1950 and 1989. The vital status of the subjects was det ermined on March 1, 1996, and causes of death were ascertained for tho se who had died. The data on the causes of death were compared with da ta on age-specific mortality in England and Wales. The standardized mo rtality ratio was used as a measure of relative risk, and the effect o f covariates on mortality was assessed by regression analysis. Results During 105,028 person-years of follow-up, 3611 subjects died; the exp ected number of deaths was 3186 (standardized mortality ratio, 1.1; 95 percent confidence interval, 1.1 to 1.2; P<0.001). The risk was incre ased for deaths due to thyroid disease (106 excess deaths; standardize d mortality ratio, 24.8; 95 percent confidence interval, 20.4 to 29.9) , cardiovascular disease (240 excess deaths; standardized mortality ra tio, 1.2; 95 percent confidence interval, 1.2 to 1.3), and cerebrovasc ular disease (159 excess deaths; standardized mortality ratio, 1.4; 95 percent confidence interval, 1.2 to 1.5), as well as fracture of the femur (26 excess deaths; standardized mortality ratio, 2.9; 95 percent confidence interval, 2.0 to 3.9). The excess mortality was most evide nt in the first year after radioiodine therapy and declined thereafter . Conclusions Among patients with hyperthyroidism treated with radioio dine, mortality from all causes and mortality due to cardiovascular an d cerebrovascular disease and fracture are increased. (C)1998, Massach usetts Medical Society.