The value of T3 suppression test for the prediction of longterm medical treatment was studied in 166 unselected patients with Graves disease treated with thionamide. 72 patients

out of 166 satisfied criteria for suppression (suppression rate

43.37%)

of these

45 patients (after 12-29months of treatment) were followed for 1-5 years and relapse occurred in 18 patients 2-36 months after stopping treatment(relapse incidence

43.9%)

27 patients(after 30 -64 months of treatment) were followed for the same period and relapse occurred in only 3 patients 9-24 months after stopping treatment (relapse incidence

13.64%). In 19 of 94 nonsuppressed patients interrupted medication and 11 experienced relapse 2-18 months after stopping treatment (relapse incidence

57.89%). Comparison of suppressed group with the nonsuppressed group of (patients in respect to several clinical parameters (age

sex

goiter size

eye sign

serum T3

T4

T3RU

and 24 hour 131 uptake) yielded no clinical means for distinguishing the two groups with high reliability. As to the time course of suppression

it wasobserved that about two-thirds of the suppressed patients satisfied the criteria for suppression within 3 years of starting treatment. The time course of suppression in each patient could not be predicted from the result of initial thyroid tests. The overall remission rate among the 72 suppressed patients followed for 1-5 years was 60.98%. Our results confirm the usefulness of T3 suppression test for predicting sustained remission of Graves’ disease after treatment

and clearly indicate that long-term medical therapy could increase the number of remission in the patients with Graves’ disease.