1980 Volume 132 Issue 1 Pages 1-10
To evaluate the long-term results of 131I treatment for Graves' disease, the thyroid function was studied in 331 patients 5-17 years after this therapy. Twenty-five patients were hypothyroid and had already been on thyroid medication. Among the remaining 306 patients without any treatment for thyroid disorder, 188 patients (61.4%) had a normal thyroid-stimulating hormone (TSH) level (less than 10μU/ml) of whom 151 were euthyroid with normal thyroxine (T4) and triiodothyronine (T3) level. 118 patients (38.6%) had a high TSH level, of whom 22 were hypothyroid with low T4 and T3 levels and 38 were with normal T3 and low T4 levels, and 14 patients out of this 38 were clinically hypothyroid. Although all of the patients with high TSH levels do not per se require the replacement therapy for hypothyroidism, the overt hypothyroidism seems to occur sooner or later in patients with a lower T4 level. Among 331 patients studied, 61 (18.4%) were clinically hypothyroid. The incidence of hypothyroidism was 20.7% after 10 years of 131I treatment and 33% after 15-17 years. The incidence of patients with high TSH levels was 50% after 10 years of 131I treatment and 60% after 15-17 years. Both of cumulative incidence of hypothyroidism and patients with high TSH levels increased linearly with years after the treatment, which coincided with the linear decrease of mean T4 and T3 levels and linear increase of mean TSH level with years after the treatment. The difference of positive incidence of antithyroid antibodies between cases of normal TSH level and high TSII, level was not significant.
