Thyroid function and histology in forty-five patients with hyperthyroid Graves' disease in clinical remission more than ten years after thionamide drug treatment.

Thyroid function was determined in 45 patients with hyperthyroidism due to Graves' disease who had been diagnosed and treated with thionamide drugs between 1965 and 1971 and had remained clinically euthyroid for greater than 10 yr after discontinuation of therapy. Physical examination revealed that only 2 patients had signs of mild hyperthyroidism; all others were euthyroid. Measurements of serum concentrations of thyroid hormones and TSH revealed elevated free T4 index values and serum T3 in 3 (6.7%), T3 toxicosis in 4 (8.9%), and subclinical hypothyroidism in 2 patients (4.4%). The remaining 36 patients were biochemically euthyroid. TRH tests were performed in these 36 patients, and hyporesponsiveness was found in 3 and hyperresponsiveness in 5 patients. T3 suppression tests were performed in 15 of the 36 patients; 10 were suppressible and 5 were nonsuppressible. All suppressible patients responded to TRH. Large needle biopsies performed in 8 biochemically euthyroid patients and 1 patient with subclinical hypothyroidism revealed chronic lymphocytic thyroiditis in 7 and normal biopsies in 2 patients. Diffuse epithelial hyperplasia was not found in any of the specimens. Antithyroid antibody titers were significantly higher than in 1972 at the time of discontinuation of therapy using the same methods. These results suggest that Graves' disease may evolve into chronic thyroiditis in some patients who are in permanent remission, and some patients in apparent permanent remission have hyperthyroidism and concomitant chronic thyroiditis.