search for


Graves’ Disease Patients with Large Goiters Respond Best to Radioactive Iodine Doses of at Least 15 mCi: a Sonographic Volumetric Study
Int J Thyroidol 2018;11(2):137-142
Published online November 30, 2018;
© 2018 Korean Thyroid Association.

Yun Ah Jeong, Jee Hee Yoon, Hee Kyung Kim and Ho-Cheol Kang

Department of Internal Medicine, Chonnam National University Medical School, Gwangju, Korea
Correspondence to: Hee Kyung Kim, MD, PhD, Department of Internal Medicine, Chonnam National University Medical School, 160 Baekseo-ro, Dong-gu, Gwangju 61469, Korea
Tel: 82-61-379-7621, Fax: 82-61-379-7628, E-mail:
Received June 18, 2018; Revised September 27, 2018; Accepted October 15, 2018.
This is an open-access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (, which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
Background and Objectives: Radioactive iodine therapy (RAI) is an important treatment modality of Graves’ disease (GD), but there is still not a consensus on the optimal dosage regimen. We studied the treatment success rate of different RAI doses, and examined which clinical markers were useful for determining the optimal RAI dosage for successful therapy in Korean patients. Materials and Methods: We retrospectively studied 123 patients with GD treated with RAI between 2004 and 2014 at Chonnam National University Hwasun Hospital. The responder group was defined as patients who developed hypothyroidism requiring levothyroxine replacement following RAI, regardless of the RAI dosage. Results: A total of 54 patients (43.9%) became hypothyroid after the first dose, and 31 needed two to four additional doses to achieve hypothyroidism. In the responder group as a whole (85 patients), the mean total dose of RAI was 15.5±7.0 mCi and the mean thyroid volume (TV) was 35.4±23.4 mL. When divided into low dose (<15 mCi, n=46) and high dose (≥15 mCi, n=39) responder groups, TV was significantly lower in the low-dose responder group (25.7±11.4 vs. 48.4±31.3, p<0.001). The optimal cut-off TV for the low-dose responder group was <32.37 mL (sensitivity 80.9%, specificity 76.7%). Conclusion: TV had significant effects on the outcome of RAI in GD patients. The optimal fixed RAI dose for Korean GD patients with a large goiter (≥33 mL) should be at least 15 mCi to achieve the best outcome.
Keywords : Graves’ disease, Radiotherapy, Iodine-131, Diagnostic imaging

November 2018, 11 (2)