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Antithyroid drug therapy decreases the efficacy of radioiodine in patients with hyperthyroidism
The background of the study. Many patients with hyperthyroidism who are treated with radioactive iodine (I-131) are also treated with an antithyroid drug before or after I-131. This study was done to determine the effect of antithyroid drug therapy on the efficacy of I-131 therapy.
How the study was done. Studies of combined antithyroid drug and I-131 therapy in patients with hyperthyroidism were identified by a review of the literature. For inclusion in this analysis, the study patients had to have been randomly assigned to receive an antithyroid drug and I-131 or I-131 alone and followed for at least six months after I-131 was given. The outcomes evaluated were persistent or recurrent hyperthyroidism and hypothyroidism.
The results of the study. Fourteen studies met the criteria for inclusion in the analysis. They included 1306 patients, of whom 51 percent were treated with an antithyroid drug and I-131 and 49 percent with I-131 alone. Their average age ranged from 37 to 60 years, most were women, and most had hyperthyroidism caused by Graves’ disease.
The antithyroid drug was given before I-131 in five trials, at the same time as or after I-131 in seven, and before and after I-131 in two. Methimazole was given in six trials, carbimazole in three, propylthiouracil in four, and methimazole and propylthiouracil in one. The mean dose of I-131 was 8.9 mCi (329 MBq).
Persistent or recurrent hyperthyroidism was more common in the antithyroid-drug and I-131-therapy group than in the group given I-131 alone (Table). Conversely, hypothyroidism was less common in the antithyroid-drug and I-131-therapy group.
| Table. Frequency of Persistent or Recurrent Hyperthyroidism and Hypothyroidism after I-131 Therapy in Patients with Hyperthyroidism Treated with an Antithyroid Drug and I-131 or I-131 Alone. | ||
Persistent or Recurrent Hyperthyroidism |
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| Drug | No Drug | |
| Before I-131 | 28% | 19% |
| At or after I-131 | 23% | 19% |
| Hypothyroidism | ||
| Before I-131 | 25% | 32% |
| At or after I-131 | 14% | 24% |
The frequency of successful treatment and of hypothyroidism was similar in the patients treated with each of the three antithyroid drugs.
The conclusions of the study. The frequency of persistent or recurrent hyperthyroidism is higher and that of hypothyroidism is lower in patients with hyperthyroidism given an antithyroid drug before or after I-131 therapy, as compared with those treated with I-131 alone.
The original article. Walter MA, Briel M, Christ-Crain M, Bonnema SJ, Connell J, Cooper DS, Bucher HC, Muller-Brand J, Muller B. Effects of antithyroid drugs on radioiodine treatment: systematic review and meta-analysis of randomised controlled trials. BMJ 2007;334:514-20.
 Next Article: Serum C-reactive protein concentrations increase after radioiodine therapy in patients with hyperthyroidism |
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| Thyroid Digest Index | | | July 2007 Thyroid Digest |
