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A randomized double-blind comparison of fixed versus calculated radioiodine dose in the treatment of Graves’ Hyperthyroidism


Elaine C. Cunanan,
Sjoberg A. Kho,
Leilani B. Mercado-Asis

Related Institution

Section of Endocrinology and Metabolism Diabetes Center - University of Santo Tomas Hospital

Department of Nuclear Medicine - University of Santo Tomas Hospital

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Publication Information

Publication Type
Philippine Journal of Internal Medicine
Publication Date
July-September 2014


Introduction: Radioactive iodine (I131) therapy is an established definitive treatment for Graves'
hyperthyroidism. However, the optimal method of determining the radioiodine treatment dose remains controversial.

Objective: To compare the efficacy of fixed dose versus calculated dose regimen in the treatment of Graves' hyperthyroidism among Filipinos Methodology: Diagnosed Graves' disease patients underwent thyroid ultrasound to estimate thyroid size. Patients were randomized to either fixed or calculated dose of radioiodine treatment. For fixed dose group, the WHO goiter grading was utilized: Grade 0 (5mCi), Grade 1 (7mCi), Grade2 (10mCi), Grade 3 (15mCi). For calculated dose group the following formula was used: Dose(mCi)=160uCi/g thyroid x thyroid gland weight in grams x 100 24-hour RAIU (%) Thyroid function test (TSH, FT4) was monitored every three months for one year.

Results: Of the 60 patients enrolled, 45 (fixed dose; n= 27, calculated dose; n= 18) completed the six months follow-up study. Analysis was done by application of the intention-to-treat principle.The percentage failure rate at third month in the fixed vs. calculated dose group was: 26 v. 28% with a relative risk (RR) value of 0.93. At six months posttherapy, there was a noted reduction in the failure rates for both study groups (11 vs. 22%, respectively), with a further reduction in the relative risk value (0.67), favoring the fixed dose group.

Conclusion: Fixed dose radioiodine therapy for Graves' disease is observed to have a lower risk of treatment failure (persistent hyperthyroidism) at three and six months post-therapy compared to the
calculated dose.

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