Simple and reliable method for predicting the remission of Graves' disease: revised triiodothyronine-suppression test, indexed by serum thyroxine.

To find a simple and reliable method for predicting the long-term remission of Graves' disease, we studied the outcome of 182 methimazole-treated patients with Graves' disease, whose thyroidal RAIU became < 12% after T3 administration. The patients were treated with methimazole over 2 years. T3 suppression test was done 6 months after the disappearance of TSH-receptor antibody (TRAb); the patients took T3 for 14 days, and on the 14th day, blood was obtained for serum T3, T4, and TSH determination, and RAIU was measured. These 182 patients were followed for 5 years after methimazole withdrawal. We divided the 182 methimazole-treated patients, whose thyroidal RAIU became < 12% after T3 administration, into two groups based on the outcome after the discontinuation of methimazole; 40 patients (22%) had an overt recurrence (group A) and the other 142 (78%) did not (group B). The degree of serum T4 suppressibility by T3 was less in group A than in group B. In group A, the number of the patients with a serum T4 < 60% of the pre-T3 levels is less than that with a serum T4 > or = 60%, but, in group B the former is more than the latter. The serum T4 < 60% of the pre-T3 level was significantly associated with the remission.(ABSTRACT TRUNCATED AT 250 WORDS)