LACK OF EFFECT OF THYROXINE ADMINISTRATION ON ELEVATED THYROID-STIMULATING HORMONE-RECEPTOR ANTIBODY-LEVELS IN TREATED GRAVES-DISEASE PATIENTS

Increased levels of antibodies to TSH receptors are thought to be a ma jor cause of active Graves' disease or recurrence following therapy. I t was recently reported that T-4 administration during antithyroid dru g treatment for Graves' disease resulted in a significant decrease of TSH receptor antibodies compared to drug therapy alone. It is known th at these antibodies may remain elevated long after patients become eut hyroid, so a large number of patients whose antibodies remained signif icantly elevated after 1 year of methimazole therapy were evaluated in the study. A total of 330 Graves' disease patients were treated with methimazole for 1 year. TSH receptor antibody titers remained persiste ntly elevated in 195 patients. Thirty-bye randomly selected patients w ere continued on maintenance doses of methimazole for a second year, a nd 160 patients were treated with a combination of methimazole and thy roxine for a second year. T-4 doses needed ranged from 75-100 mu g/day to maintain serum-free T-4 and free T-3 within the normal range. Afte r 6 months of combined therapy, 35 patients were found to have suppres sed serum TSH levels. The patients were divided after 18 months into t hree groups: A, B, and C. Group C, consisting of 35 randomly selected patients (8 males and 27 females) whose ages ranged from 12-62 years a nd who had been maintained on methimazole alone, served as controls. G roup B, whose serum TSH levels were suppressed after 6 months of combi ned therapy, consisted of 9 males and 26 females whose ages were 15-66 years. Group A, 35 randomly selected patients with normal serum TSH l evels after methimazole and thyroxine therapy for 6 months, consisted of 8 males and 27 females whose ages were 10-63 years. TSH receptor an tibody titers gradually decreased in all three groups with drug therap y, and there was no significant difference in the titers at correspond ing times, i.e. 0, 1.0, 1.5, and 2.0 years. After treatment for 2.0 ye ars, all patients of the three groups were followed for a further 12 m onths. Rates of recurrence among the above three groups were not signi ficantly different during the observation period. In the present study , T-4 administration in combination with antithyroidal drugs had no ef fect on levels of antibodies to TSH receptors and no effect on rates o f recurrence. The reason for the discrepant results in the present stu dy from previous reports is not known.