Assessment of Factors Affecting the Treatment Efficacy of Radioactive Iodine (I-131) Therapy in Patients with Hyperthyroidism

Abstract

Objective: Hyperthyroidism is an increase in hormone production in the thyroid gland and the exposure of tissues to the hormones of the thyroid glands in the circulation. The most common causes encountered are Graves’ Disease, Toxic Multinodular Goiter and Toxic Adenoma. The purpose of radioactive iodine treatment is to make patients become euthyroid or hypothyroid. Despite adequate treatment, hyperthyroidism persists or reccurs in some patients. The aim of our study is to investigate the factors affecting the efficacy of radioactive iodine treatment in hyperthyroidism. Methods: In this retrospective study, relevant clinical and laboratory data were recorded in database of Kayseri Training and Research Hospital, Endocrinology and Metabolism Diseases Outpatient Unit between 2013-2016. Results: A total of 79 cases including 17 (21%) male, and 62 (79%) female patients were enrolled in the study. There were 33 (42%) Graves’ disease 9 (11%) Toxic Multinodular Goitre and 37 (47%) Toxic Adenoma patients when grouped according to diagnoses. Mean age was 56.5 ± 16,80. Development of hypothyroidism or euthyroidism were accepted as efficient treatment, hyperthyroidism or recurrence were considered as treatment failure. In 71 (89%) patients, treatment efficiently resulted in hypothyroidism or euthyroidism, whereas in 8 (11%) patients, the treatment failed due to recurrence or persistent disease. Treatment was 100 % effective in Toxic Multinodular Goitre and Toxic Adenoma groups, while it was effective in 75.7 of patients with Graves’ Disease. Patients who did not use antithyroid drugs recovered faster than patients who did. Conclusion: Radioactive iodine therapy is an efficient treatment in patients with hyperthyroidism. It was determined that 1 mm increase in nodule size decreased the treatment efficacy by 1.07 times (p<0,05). However, there are many factors that affect the efficacy of this treatment. To elucidate these factors and improve clinical practice, prospective long-term studies providing more reliable data with larger samples needed.