Changes in Thyroid Functions in Patients with Euthyroid Graves' Disease*

Abstract

Studies were performed in 57 patients with euthyroid Graves' disease. All of them had exophthalmos and other eye signs of classes II-IV in th American Thyroid Association classification. T₃ suppression tests, TRHtests, and measurements of antithyroid antibodies were performed in all of them, and needle biopsy was carried out in 9 patients. Twenty-seven among 57 patients were followed for 6 months to 3 yr. When patients were divided into subgroups according to the results of T₃ suppression tests and TRH tests, 35 patients (61.4%) were T₃ nonsuppressive and TRH nonresponsive (group I), 6 (10.5%) were T₃ nonsuppressive and TRH responsive (group II), 1 patient (1.8%) was T₃ suppressible and TRH nonresponsive(group III), and 15 (26.3%) were T3 suppressible and TRH responsive (group IV) at the first tests. During the period of observation of 17 patients in group I, 8 became clinically and biochemically thyrotoxic and 4 patients remained in group I, but 2 moved to group II and 3 moved to group IV. Of 2 patients in group II, 1 became hypothyroid and 1 moved to group I. Of 7 patients in group IV, 1 became thyrotoxic and 1 became hypothyroid. Three patients remained in group IV, but patient moved to group I and the other moved to group II during the period of observation. Clinical course and thyroid function test agreed well with histologica findings in 2 patients with diffuse epithelial hyperplasia and in 1 with the fibrous variant of chronic lymphocytic thyroiditis. However, 5 of 6 patients with chronic lymphocytic thyroiditis were T₃ nonsuppressible and TRH nonresponsive during the period of observation. These results suggest that thyroid function tests in euthyroid Graves' disease are variable and unstable and that euthyroid Graves' disease, Graves' disease, and Hashimoto's disease are closely related to each other and cannot be separated before the clear onset of each disease