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Reducing iodine intake does not alter the efficacy of methimazole
The background of the study. Among patients with hyperthyroidismantithyroid drug therapy may be moreeffective in patients whose iodine intake is relatively low than in those whose iodine intake is higher. In thisstudy, the short-term efficacy of methimazole was compared in patients in whom iodine intake was relativelyhigh and those in whom it was restricted.
How the study was done. The study was done in 70 Japanese patients with hyperthyroidism caused by Graves’ disease. Thirty-one patients agreed to reduce their dietary iodine intake, by excluding iodine-rich foods such as kelp, seaweed, and seafood, and 39 continued their usual diet. Serum free thyroxine (T4) and urinary iodine and creatinine were measured at base line and after treatment with methimazole, 15 mg daily, for 4 and 8 weeks.
The results of the study. At base line, the patients in the iodine-restricted group and the control group had similar serum free T4 concentrations and urine iodine/creatinine values. During methimazole therapy, serum free T4 concentrations decreased similarly in both groups. The median urinary iodine/creatinine ratio decreased from 220 µg/g at base line to 150 µg/g at 8 weeks in the iodine-restricted group, and it increased from 195 to 339 µg/g in the control group.
The conclusions of the study. In patients with hyperthyroidism caused by Graves’ disease, decreasing dietary iodine intake when antithyroid drug (methimazole) therapy is started does not alter the short-term efficacy of the drug.
The original article. Hiraiwa T, Ito M, Imagawa A, Takamatsu J, Kuma K, Miyauchi A, Hanafusa T. Restriction of dietary iodine does not ameliorate the early effect of anti-thyroid drug therapy for Graves’ disease in an area of excessive iodine intake. J Endocrinol Invest 2006;29:380-4.
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| Thyroid Digest Index | | | November 2006 Thyroid Digest |
