Empirical 131 Iodine therapy in thyrotoxicosis based on 99mTechnetium thyroid scan and gamma camera based uptake values

This is the authors' abstract. We don't add key points for this paper.

Objective: Radioactive iodine-131 (RAI) has been established in the treatment of patients with various etiologies of hyperthyroidism. However, the short term and long term clinical outcome of patients receiving RAI is different in various studies. The aim of this study was to assess clinical outcome one year after RAI therapy and identify factors associated with a good response. Materials and Methods: In this experimental study among patients with Graves' disease, referred to the Nuclear Medicine Department and had indication for RAI therapy, 164 consecutive subjects were enrolled for the study. Radioiodine dose was calculated based on the uptake of the thyroid gland by routine pertechnetate thyroid scan done on a gamma camera. Patients with less than 10% uptake of injected dose were given 10 mCi of oral Na-I 131 and if uptake was higher than 10%, a dose of 15 mCi was administered. Patients were monitored closely clinically and with blood investigations after treatment for one year. Results: Among the 158 patients, who completed follow-up, 96.2% recovered and 3.8% remained thyrotoxic. Among patients who recovered, 77.6% became hypothyroid and 22.4% euthyroid. The incidence of hypothyroidism was 32.2% in first trimester, 58.5% in second trimester, 5.1% in third trimester and 4.2% in fourth trimester. Conclusion: In our study, a good result was seen in more patients than other studies and it might relate to higher absorption of radioactive iodine in our region . According to our result, incidence of hypothyroidism was the most in second trimester, and so patients should be carefully followed in this period.