Endocrinol Metab.  2016 Mar;31(1):168-173. 10.3803/EnM.2016.31.1.168.

Comparison of Fixed versus Calculated Activity of Radioiodine for the Treatment of Graves Disease in Adults

• Canto AU
• Dominguez
• Jimeno CA
• Obaldo JM
• Ogbac RV

• KMID: 2169709
• DOI: http://doi.org/10.3803/EnM.2016.31.1.168

Abstract

BACKGROUND
Radioactive iodine as a treatment modality has been shown in several studies to be a safe and effective therapy for Graves disease. However, there is still no uniformity regarding optimal dosing method. The aim of this study is to compare the efficacy of calculated and fixed dosing of radioiodine for the treatment of Graves disease.
METHODS
A hundred twenty-two patients diagnosed with Graves disease were randomized to receive either fixed or calculated dose of radioiodine. Those randomized to fixed activity received either low fixed activity at 9.9 mCi for thyroid gland size <40 g or high fixed activity at 14.9 mCi for thyroid gland size 40 to 80 g, and those grouped to calculated activity received 160 µCi/g of thyroid tissue adjusted for 24 hours radioiodine uptake. Thyroid function tests (free thyroxine [T4] and thyroid stimulating hormone [TSH]) were monitored at 10, 16, and 24 weeks after radioactive iodine therapy. The primary outcome, treatment failure was defined as persistently elevated free T4 and low TSH.
RESULTS
Of the 122 patients randomized, 56 in the fixed dose group and 56 in the calculated dose group completed the follow-up. At the end of 6 months, the percentage of treatment failure was 37.50% in the calculated dose group versus 19.64% in the fixed dose group with a relative risk of 0.53 (95% confidence interval, 0.28 to 0.98) favoring the fixed dose group.
CONCLUSION
Fixed dose radioiodine has a significantly lower incidence of persistent hyperthyroidism at 6 months post-radioactive therapy.

Keyword

Graves disease; Radioactive iodine; Hyperthyroidism

MeSH Terms

Adult*
Follow-Up Studies
Graves Disease*
Humans
Hyperthyroidism
Incidence
Iodine
Thyroid Function Tests
Thyroid Gland
Thyrotropin
Thyroxine
Treatment Failure
Treatment Outcome
Iodine
Thyrotropin
Thyroxine