A randomized trial evaluating a block-replacement regimen during radioiodine therapy

Area of Science:

• Endocrinology
• Nuclear Medicine
• Thyroidology

Background:

• Lack of consensus on optimal antithyroid drug regimens before radioiodine therapy for hyperthyroidism.
• Two distinct strategies were compared in a randomized trial.

Purpose of the Study:

• To compare two antithyroid drug regimens in patients undergoing radioiodine therapy for hyperthyroidism.
• To evaluate the impact of these regimens on treatment outcomes and thyroid function.

Main Methods:

• Randomized trial involving 100 patients with Graves' disease or toxic nodular goiter.
• Patients received radioiodine therapy either after methimazole discontinuation or during a continuous block-replacement regimen.
• Radioactivity doses and thyroid function were monitored.

Main Results:

• The group discontinuing methimazole showed higher cure rates (61%) compared to the block-replacement group (48%) one year post-therapy.
• The block-replacement regimen required higher radioactivity doses and maintained stable thyroid function initially.
• Treatment failure in Graves' disease was unpredictable, while in toxic nodular goiter, it correlated with radiation dose, methimazole dose, and TSH levels.

Conclusions:

• Discontinuing antithyroid drugs before radioiodine therapy may lead to better outcomes in hyperthyroidism, particularly for Graves' disease.
• A continuous block-replacement regimen stabilizes thyroid function but necessitates higher radioactivity.
• Predicting treatment success in Graves' disease remains challenging, unlike toxic nodular goiter where several factors correlate with failure.