In this week's BMJ, Walter and colleagues1 present a systematic review and meta-analysis of randomised controlled trials of the effects of antithyroid drugs on treatment with radioiodine. Radioiodine is perceived as a simple and cost effective treatment of hyperthyroidism.2 A β adrenergic blocker, such as propranolol (total daily dose of 80-160 mg), can usually provide appreciable relief of symptoms between the initial consultation and administration of radioiodine, and for the next six to eight weeks until treatment is effective.

In elderly patients and in those with severe thyrotoxicosis or cardiovascular complications, such as atrial fibrillation and heart failure, it is common practice to restore euthyroidism first with antithyroid drugs. This prevents the rare, but well recognised, worsening of hyperthyroidism caused by irradiation induced leakage of stored thyroid hormones seen within the first few days,3 an important consideration given the increased mortality in the early weeks after giving radioiodine.4

Antithyroid drugs do not prevent …