en Endocrinology Endocrinology Original Research: Clinical Science Original Research: Clinical Science <strong>Background: </strong>Multinodular goiter (MNG) is regarded as one of the most common causes of hyperthyroidism, particularly in areas of mild-to-moderate iodine deficiency. The present study aims to explore the effects of the radioactive iodine (RAI) therapy on benign non-toxic MNG and evaluate its side effects.<br> <strong>&nbsp;&nbsp;&nbsp; Methods:</strong> Patients with benign non-toxic MNG entered the study. Ultrasonography was applied to calculate the percentage of the decrease in the size of the thyroid before and six months minimum after the treatment. Chi-square, Mann-Whiteny-U and T-test were done using SPSS v.18.0 (p<0.05).&nbsp;<br> <strong>&nbsp;&nbsp;&nbsp; Results:</strong> The volumes of the thyroid lobes and nodules decreased significantly due to RAI therapy (p<0.001). The total volume of the thyroid, volume of the right nodule, and volume of the left nodule decreased by 77.8%, 40.7%, and 34.6% respectively.<br> <strong>&nbsp;&nbsp; Conclusion:</strong> According to the results of the current study, RAI therapy is an effective treatment method although it has short-term side effects. This treatment option is recommended for patients with benign non-toxic MNG, notably those who cannot be a candidate for surgery. This treatment affects the size of the thyroid and its nodules significantly and decreases almost all of the complications.<br> &nbsp; <div> <div><div id="_com_4" uage="JavaScript"></div></div> </div> Multinodular goiter, Nodule, Radioactive iodine therapy, Thyroid 769 772 http://mjiri.iums.ac.ir/browse.php?a_code=A-10-3607-2&slc_lang=en&sid=1 Iraj Heydari heydari.i@iums.ac.ir 200319475328460042344 200319475328460042344 No Endocrine Research Center, Institute of Endocrinology and Metabolism, Iran University of Medical Sciences, Tehran, Iran Maryam Honardoost marymail79@gmail.com 200319475328460042345 200319475328460042345 No Endocrine Research Center, Institute of Endocrinology and Metabolism, Iran University of Medical Sciences, Tehran, Iran Sedighe Moradi moradi.s@iums.ac.ir 200319475328460042346 200319475328460042346 No Endocrine Research Center, Institute of Endocrinology and Metabolism, Iran University of Medical Sciences, Tehran, Iran Fatemeh Golgiri golgiri.f@iums.ac.ir 200319475328460042347 200319475328460042347 No Endocrine Research Center, Institute of Endocrinology and Metabolism, Iran University of Medical Sciences, Tehran, Iran Hamidreza Dehnad alirezadehband@yahoo.com 200319475328460042348 200319475328460042348 No Endocrine Research Center, Institute of Endocrinology and Metabolism, Iran University of Medical Sciences, Tehran, Iran Saba Moradi Sabamoradi1358@gmail.com 200319475328460042349 200319475328460042349 No Shahid Beheshti University of Medical Sciences, Tehran, Iran Amir Ziaee Aziaee1963@yahoo.com 200319475328460042350 200319475328460042350 Yes Pediatric Growth and Development Research Center, Institute of Endocrinology and Metabolism ,Iran University of Medical Sciences Tehran, Iran