Development of Thyroidal Suppression by Triiodothyronine During Six Months' Treatment of Thyrotoxicosis with Antithyroid Drugs

Abstract

Forty-one thyrotoxic patients were treated with carbimazole, and thyroidal suppression (fall in uptake of 50% of pretreatment uptake value) by exogenous triiodothyronine had developed in 22 of the patients by 6 months. Both in the group showing suppression and in that showing no suppression adequate control of hormone production as shown by serum PBI, triiodothyronine resin uptake and free thyroxine index was achieved. The 2 groups showed no difference with regard to age, sex and indices of thyroid function before treatment was started. Differences between the 2 groups included significantly smaller goiters, with a tendency for the goiter to become smaller during treatment, in the group which suppressed. It is concluded that from the viewpoint of suppressibility there may be 2 kinds of Graves' disease. Antithyroid drugs rapidly influence suppressibility in a proportion of patients, and in these at least the drug possibly influences the disease process.