Comparison of the outcome between the calculated dosimetry and the estimated dosimetry of ¹³¹I in the treatment of hyperthyroidism

To compare the outcomes of different methods in prescribing the optimal dose of radioactive iodine (¹³¹I) for the treatment of hyperthyroidism, we retrospectively analyzed 52 patients with toxic diffuse goiter. They received single dose of ¹³¹I for the treatment of hyperthyroidism. In addition, all of them met the following criteria: 1) symptoms and signs of hyperthyroidism; 2) elevated blood triiodothyronine (T3) and thyroxine (T4) by radioimmunoassay (RIA) method; 3) diffuse goiter with increase of uptake proved by thyroid scintiscan; 4) only one dose of ¹³¹I was given during the follow-up period; 5) well-documented thyroid function test in the medical chart during the follow-up period (6 months, 1 year, 2 years and 5 years after ¹³¹I therapy). The enrolled patients were divided into estimated and calculated group. The dose of ¹³¹I in the calculated group was obtained from the measurement of size and ¹³¹I uptake of thyroid gland. The dose of ¹³¹I in the estimated group was prescribed according to the size of thyroid gland by physical examination, and the association with cardiac arrhythmia, congestive heart failure, or ischemic heart disease. The mean doses of ¹³¹I were 4.8 ± 1.4 mCi and 7.0 ± 1.1 mCi in the calculated and estimated group respectively. In this study, there were no significant differences in the incidence of euthyroidism, hyperthyroidism, and hypothyroidism between these two groups in the follow-up period after ¹³¹I therapy. In view of simplicity and time-saving, it is a practical choice to prescribe the dose of ¹³¹I therapy for toxic diffuse goiter according to the size of thyroid gland and the associated cardiac condition. Copyright © 1995 Chang Gung Medical Journal.