Follow-up of solitary autonomous thyroid nodules treated with 131I

We studied the long-term effects of 131I therapy for solitary autonomous thyroid nodules on the size of the nodule and on thyroid function. Twenty-three patients with autonomous thyroid adenomas that had been treated with 131I from 4 to 16.5 years earlier (mean, 8.5) were examined, and their thyroid function was tested. In 12 patients (54 per cent), the nodules were still palpable, and in 2 they had increased in size. Eight patients (36 per cent) had become hypothyroid. The incidence of hypothyroidism was not related to nodule size or the level of thyroid function before therapy with 131I or to the total dose of 131I that had been given. We conclude that 131I therapy for autonomous thyroid adenoma often causes hypothyroidism and in many cases does not eradicate the offending nodule.