Antithyroid drugs have mixed effects on radioiodine treatment for hyperthyroidism

Antithyroid drugs given in association with radioiodine therapy for hyperthyroidism tend to increase the rate of treatment failure but reduce rates of subsequent hypothyroidism, according to a meta-analysis of randomised controlled trials on the issue.The interactions between medication and radioiodine could affect morbidity and mortality in the year after treatment. "Failures of treatment include persistent and recurrent hyperthyroidism, which increases the cardiovascular risk and necessitates further treatment," the report stated. "Conversely, hypothyroidism requires regular and lifelong follow-up and consumption of healthcare resources for titration of the optimal dose of levothyroxine."The influence of antithyroid drugs on the effects of radioiodine therapy had been debated for decades, but most trials had been insufficiently powered to detect significant effects. One important issue was the rate of acute increases in thyroid activity in the few days after radioiodine therapy, experienced by about 10% of patients. About 0.3% had a 'thyroid storm' which had a mortality of about 25%, and was a common justification for the use of adjunctive antithyroid medication.There had also been continuing discussion about the relative merits of propylthiouracil and the imidazoles (carbimazole and methimazole), but the analysis found no difference between them in the rates of treatment failure or hypothyroidism.Results from the trials did not provide enough information to define the optimal period for interrupting antithyroid medication. In some patients, long-term monitoring for hypothyroidism might not be guaranteed and therefore withholding antithyroid drugs to allow for early development and identification of hypothyroidism might be a reasonable option.Despite the efforts so far, more trials were needed to define the best combinations of medication and antithyroid medication. Effects on quality of life and cardiovascular morbidity and mortality should also be addressed....