Radioiodine (long term effects of treatment)

• Franklyn et al (1) undertook a population-based study describing a cohort of over 7000 patients treated with radioactive iodine over a 40 year period. The study examined data on both specific and all-cause mortality - the study compared rates with national figures for the general population for England and Wales. The findings included:
  
  
• all-cause mortality was 13% higher in the radioactive iodine treated group than in the general population
• excess mortality was most prominent in the first year after radioactive iodine treatment - the difference in mortality rates declined thereafter
• cardiovascular and cerebrovascular disease were the major causes of excess mortality in the radioactive iodine treated group - the mortality associated with these causes was greatest in the first year after treatment - the excess mortality was seen in the over-50s age group - of note, is that hyperthyroidism is itself associated with cardiovascular problems and the excess deaths may be explained by the presence of hyperthyroidism itself, rather than radioiodine
• the study also revealed an increased risk of death from thyroid disease in the radioiodine group - this was most evident in the first year after treatment and disappeared after nine years follow-up. This may be explained that the higher probability of receiving treatment with radio-iodine during the period of most severe hyperthyroidism

Reference:

• 1) Franklyn JA, Maisonneuve P, Sheppard MC et al (1998). Mortality after the treatment of hyperthyroidism: a population-based cohort study. NEJM, 341 (12), 879-884.