[Use of 131 iodine for the treatment of hyperthyroidism in adults]

The authors report on their experience with the treatment of hyperthyroidism using radioiodine (RI) over a period of 15 years in 516 patients. RI dosimetry was calculated from thyroid 24 hr uptake and weight, using linearly increasing RI doses (from 40 to 100 microCi/g) with increasing thyroid weight (between 10 and 100 g) for both diffuse (D) and multinodular (MN) toxic goiters. For solitary toxic (ST) nodules, a fixed dose of 250 microCi/g was used. In severe hyperthyroidism, antithyroid drugs (ATD) and KI (15 mg/d) were added 24 hours after RI and given during 1-4 months and 21 days, respectively. Combining RI + ATD/KI therapy allowed for a reduction of RI recirculation and release from the gland and also for more rapid return to a euthyroid status. The results showed that 88% of patients with ST, 68% with D, and 55% with MN were cured with a single dose of RI. Furthermore, the incidence of late hypothyroidism was relatively low, reaching 7% in ST, 36% in D, and 28% in MN after a follow-up period of fifteen years. Annual follow-up, however, showed that an additional 2.7% of patients (3.5% of D; 1.6% of MN; 2.4% of ST) exhibited--per year--an exaggerated TSH response to TRH even though these patients remained clinically and biochemically euthyroid (normal circulating basal hormones and TSH levels). In conclusion, 1) low doses RI combined with ATD/KI yielded a high success rate: less than 30% of patients required more than 1 dose and only 30% became hypothyroid after prolonged follow-up; 2) abnormalities of TRH test were not infrequent in patients with D and MN goiters, as well as ST nodules, thereby fully justifying the need for careful and prolonged follow-up of all hyperthyroid patients receiving RI therapy.