Use with caution

Ophthalmopathy is a characteristic feature of Graves' disease, although it is usually mild or subclinical. Enlargement of the extraocular muscle can be shown by computed tomography or magnetic resonance scanning in most patients with autoimmune hyperthyroidism, but only in 10-25% of cases does this result in clinically important problems such as proptosis, conjunctival oedema, or ophthalmoplegia—and the dreaded complication of optic nerve compression is mercifully rare.1 When it does occur, however, severe thyroid eye disease is difficult to treat and may result in disfigurement, diplopia, or visual loss. Radioactive iodine (I-131) is widely used to treat the thyrotoxicosis of Graves' disease, but, despite its demonstrable efficacy and safety,2 there have long been concerns about its possible adverse effect on thyroid eye disease. Recently definitive evidence for this link has been presented.3 As a result, all doctors should now be aware that radioiodine should be used with caution in patients with ophthalmopathy.

In their large, well designed …