Logistic multiple regression analysis of factors predicting recurrence of hyperthyroidism after medical treatment of...

In order to determine which factors predict the outcome of short term antithyroid drug treatment we studied 42 patients with diffuse goitre in whom 43 instances of thyrotoxicosis were treated. Treatment duration ranged from 24 to 61 wk (median 30 wk). All patients received high-dose carbimazole and thyroid hormone substitution. Patients in remission were followed for 39 to 134 wk (median 73 wk). The relapse rate at 1 yr and at 2 yr after cessation of antithyroid drug treatment was 51%. Of the parameters studied presence or absence of eye signs and initial serum levels of thyroxine, triiodothyronine and immunoglobulin-G in the relapse group and in the remission group showed significant differences in univariate analysis. No significant differences were found for age, sex, family history of thyroid disease, thyroid gland volume or TSH-receptor stimulating autoantibodies. Linear discriminant analysis shows that of the four remaining factors thyroxine is not important in separating both groups. Cox analysis yields only initial serum triiodothyronine and eye signs as significant prognostic factors. With these two factors 18 out of 23 predictions of remission and 16 out of 18 predictions of relapse in the 41 patients with known initial serum triiodothyronine concentrations are correct. Such predictions can be used in the choice of therapy, short-term medical treatment for patients with a low risk and long-term medical treatment or, at the appropriate time, a destructive form of therapy for patients with a high risk of relapse.