Treatment's results of hyperthyroid patients with Iodine-131

Introduction: radioiodine (131 I) is an effective and inexpensive alternative to surgery in the treatment of thyroid hyper function. The debate today concerns the maximum and minimum ablative doses, and factors leading to hypothyroidism. Patients and method: 1035 hyperthyroid patients treated with weight-adjusted ablative doses of 131 I were retrospectively assessed for treatment outcome or correlated with sex, age, underlying pathology, and administrated dose of 131 I . Results: Thyroid hyper function was more common in women. The greatest proportions of patients were in the 31-40 years age group and the smallest proportion over -70. The commonest underlying pathology was Grave's disease. Men had a lower response rate to 131 I therapy, with 2.4-fold greater probability of persistent hyperthyroidism (P<0.0001). The probability of post-131 I hypothyroidism decreased with increasing age (P<0.0001). The best response to 131 I therapy was seen in patients with toxic adenoma, (P=0.0001). The incidence of hypothyroidism did not show a positive correction with increased administered dose of 131 I (P<0.001). Average time to develop clinical hypothyroidism was 7.1 months. 131 I was effective in reducing thyroid nodule size. There were 18 cases of temporary hyperthyroidism, all of which recovered to euthyroid status within 12 months. Conclusion: one dose of radioiodine was effective in treatment of hyperthyroid patients in 91.2 % of cases. Age, sex and underlying pathology were determining factors. In most cases the average time to hypothyroidism was reasonably short, obviating the need for long time follow up in these patients