Comparative Evaluation of Two Different Dosage Calculation Protocols of Iodine-131 in the Treatment of Hyperthyroidism
Tanyaluck Thientunyakit MD*, Suchitra Thongmak MD**, Teerapon Premprapha MD**
Affiliation : * Division of Nuclear Medicine, Department of Radiology, Siriraj Hospital, Faculty of Medicine, Mahidol University, Bangkok, Thailand ** Division of Nuclear M edicine, Department of Radiology, Songklanagarind hospital, Faculty of Medicine, Prince of Songkla University, Hat Yai, Thailand
Objective : To compare the effectiveness of radioiodine therapy with estimated dose and calculated dose in hyperthyroid
patients.
Material and Method: A prospective randomized study in 144 hyperthyroid patients referred for 131I treatment was performed
between June and December 2007. The patients were divided into two groups according to the 131I dose administered,
estimated group using dose based on gland size and calculated group using dose based on both gland size and 24-hour 131I
uptake. Outcome assessment was done at 12 months post-treatment.
Results : Eleven of 144 patients were excluded due to loss to follow-up and five became euthyroid before 131I treatment.
Fifty-six of 128 patients (45.3%) experienced persistent/recurrent hyperthyroidism, 26 (20.3%) developed hypothyroidism,
and 44 (34.4%) were euthyroid. Outcome was unrelated to the methods of I-131 dosing. Only gender and goiter size were
found to be correlated with the clinical outcomes.
Conclusion : An estimated I-131 dosing method using gland size determined by palpation is as effective as calculated method
using 131I uptake. This method is more cost effective and brings greater patient convenience.
Keywords : Hyperthyroidism, Radioiodine, Iodine-131, Radio-iodine uptake
