Natural course of Graves' disease after subtotal thyroidectomy and management of patients with postoperative thyroid dysfunction.

The Natural course of Graves' disease after subtotal thyroidectomy was studied in 67 patients who had subtotal thyroidectomy for Graves' disease and did not receive any medical treatment for 8 to 12 years after surgery. Postoperative thyroid status was determined by serum free thyroxine (T4), free triiodothyronine (T3), and thyrotropin (TSH) levels in the first period (1 year after surgery), second period (3.9 +/- 1.0 years), and third period (8.8 +/- 1.5 years). Serum thyroid stimulating antibody (TSAb) and TSH binding inhibitor immunoglobulin (TBII) activities were also measured. A total of 53 patients (79%) changed thyroid status during the observation period. One year after surgery, 50 percent of euthyroid subjects developed abnormal thyroid function in the next period. Reversible latent hypothyroidism was the most common type of thyroid dysfunction seen in up to 46% of patients. Interestingly, hyperthyroidism and hypothyroidism that developed in the postoperative period were temporary disorders in most cases. Serum TSAb and TBII activities did not help predict the postoperative changes of thyroid status. Our study indicates that the instability of the thyroid function is common after subtotal thyroidectomy.