Relapse of Graves' disease after medical therapy: predictive value of thyroidal technetium-99m uptake and serum thyroid stimulating hormone receptor antibody levels.

In 49 patients with Graves' disease, the 20-min thyroidal uptake of 99mTc and serum levels of thyroid stimulating hormone (TSH) receptor antibody were estimated at presentation and at intervals during a 1-yr course of carbimazole and triiodothyronine. In the 12 mo after cessation of therapy, 29 patients developed recurrent thyrotoxicosis. Thyroidal 99mTc uptake had a poor predictive value for recurrence of thyrotoxicosis, both at presentation and during therapy. A very high level of TSH receptor antibody was present in seven patients at presentation, all of whom relapsed on withdrawing therapy. An abnormal value of TSH receptor antibody at the end of the course of medical therapy was present in 24/29 (83%) patients who relapsed and in 1/20 (5%) patients who remained euthyroid 1 yr after stopping antithyroid drugs.