LACK OF EFFECT OF THYROXINE IN PATIENTS WITH GRAVES HYPERTHYROIDISM WHO ARE TREATED WITH AN ANTITHYROID DRUG

Background. Antithyroid drugs are effective in patients with hyperthyr oidism due to Graves' disease, but the rate of recurrence after treatm ent is high. In a recent Japanese study, adjunctive treatment with thy roxine (T-4) was associated with a recurrence rate 20 times lower than that among patients who received only an antithyroid drug. If these r esults are confirmed, combined therapy with an antithyroid drug and T- 4 might become the treatment of choice for all patients with Graves' h yperthyroidism. Methods. We treated 111 patients (89 women and 22 men) who had Graves' hyperthyroidism. All patients initially received 40 m g of carbimazole daily for one month. Then one group received carbimaz ole alone for 17 months (52 patients), and the other group received ca rbimazole plus T-4 for 17 months and T-4 alone for 18 months (59 patie nts). In the carbimazole group, the dose was adjusted after one month to maintain a normal serum thyrotropin concentration. in the carbimazo le-T-4 group, the dose of carbimazole was not changed, but 100 mu g of T-4 per day was added to the regimen and the dose was adjusted to mai ntain an undetectable serum thyrotropin concentration (<0.04 mu U per milliliter). Results. At the time of our analysis, 53 of the 111 patie nts had completed at least 3 months of follow-up (median, 12 months) a fter carbimazole was withdrawn. Hyperthyroidism recurred in eight pati ents in each group after a mean (+/-SD) of 6+/-4 months in the carbima zole group and 7+/-4 months in the carbimazole-T-4 group. There was no difference between the recurrence rates in the two groups, despite th e fact that serum thyrotropin concentrations were undetectable in 73 p ercent of patients in the carbimazole-T-4 group on at least 75 percent of their visits. Conclusions. The administration of T-4 to patients w ith Graves' disease during carbimazole treatment and after its withdra wal neither delays nor prevents the recurrence of hyperthyroidism. (C) 1996, Massachusetts Medical Society.