Introduction
The yearly growth rate of non-toxic multinodular goiter has been estimated at 10-20%.1 Suppressive treatment with thyroxine or triiodothyronine reduces the thyroid volume in diffuse non-toxic goiter by up to 30%,2 but it is disputed whether such an effect can be achieved in multinodular glands.'34 The growing nodular non-toxic goiter is traditionally treated by subtotal thyroidectomy. At least 10% of patients have a recurrence after subtotal thyroidectomy for non-toxic multinodular goitre.56 In these patients, as well as in others with a high surgical risk, a non-operative reduction in thyroid size would be desirable. Treatment of hyperthyroidism with radioactive iodine (1311) is well accepted and usually results in a substantial decrease in the size of the thyroid.78 The possibility of '31I treatment of non-toxic multinodular goitre is less accepted, but recently we found a 41% reduction in ultrasonically determined thyroid volume within one year of treating such patients with "3'I.9 The present study investigated the long term consequences of 1'3I treatment on thyroid function and thyroid volume in a large group of patients with non-toxic multinodular goitre to clarify the future role of this treatment.