Thyrotropin-Releasing Hormone Testing during Antithyroid Drug Treatment of Graves' Disease as an Indicator of Remission*

Abstract

In 74 patients with hyperthyroid Graves' disease, TRH tests were undertaken every third month during the course of a standardized antithyroid drug and T4 treatment program. The antithyroid drug dose was reduced gradually and finally withdrawn when persistently normal TSH responses were obtained. In 46 patients (62%), such normal responses occurred and therapy was discontinued after a mean treatment period of 13 months (range, 5-24 months). In the remaining unresponsive 28 patients (38%), therapy was gradually withdrawn after 2 yr of treatment (mean treatment period, 27 months; range, 25-36 months; P = 0.0001 vs. the other group). The mean overall follow-up period after cessation of treatment was 65 months (range, 32-100 months) and did not differ between the TRH-responsive and TRH-unresponsive group. In the TRH-responsive group, 12 relapses (26%) occurred 23 months (range, 6-45 months) after discontinuation of therapy, in contrast to 20 relapses (71%) after 6 months (range, 0-12 months) in the TRH-unresponsive group. The differences in relapse rates and time duration until relapse are highly significant (P = 0.0003 and P = 0.0001, respectively). Small but significant differences in serum T3 and T4 levels were found between the groups throughout the treatment periods, emphasizing the importance of thyroid hormone levels in regulating the pituitary responsiveness to TRH. It is concluded that regular TRH tests during antithyroid drug treatment are useful in deciding the dose and duration of therapy and in predicting the likelihood of remission.