Endocrine Abstracts

Radioactive iodine (RAI) is a common treatment for hyperthyroidism, but the dosage and cure rates vary between centres. We administer 370 MBq ¹³¹I in all cases unless a large goitre is present, and repeat the dose until hyperthyroidism is cured. Patients are considered cured if euthyroid or hypothyroid one year after the last dose of RAI.

We audited the outcome of RAI treatment in our institution between January 2000 and March 2002 to 112 patients (13 male) whose records were available. We excluded 12 patients who received larger doses of RAI for large goitres. Average patient age was 51. The cause of hyperthyroidism was toxic nodular goitre (TNG) in 35%, Graves’ disease in 23%, and undetermined in 41%. Average time from diagnosis to RAI was 19 months.

Of 87 patients followed until they were cured, 15 (17%) required more than one dose, 9 patients needed 2, 3 needed 3, 2 needed 4, and 1 needed 6 doses. There was no association between aetiology of hyperthyroidism, time from diagnosis to treatment or previous medication and the need for more than one dose of RAI. One year after successful treatment 40 patients (46%) required thyroxine replacement (66.7% of those with Graves’ disease and 17% of those with TNG).

Of 17 cases of thyroid eye disease 4 deteriorated after RAI. One further patient developed ophthalmopathy, and one developed atrial fibrillation. There were no other complications.

RAI was well-tolerated, but 17% of patients required more than one dose. 46% of patients required thyroxine replacement after one year, 66.7% of those with Graves’ disease versus 17% with Toxic Nodular Goitre.