THE PROGNOSTIC VALUE OF THYROTROPIN RECEPTOR ANTIBODY MEASUREMENT IN THE EARLY STAGES OF TREATMENT OF GRAVES-DISEASE WITH ANTITHYROID DRUGS

In most trials, at least 50% of patients with Graves' disease treated with antithyroid drugs (ATD) relapse after achieving euthyroidism. At present, there are no definitive prognostic parameters available early in treatment to indicate those likely to achieve long-term remission. Because thyrotropin receptor antibodies (TRAb) are specific for Grave s' disease, the possibility that their rate of change early in treatme nt (0 to 6 months) might be such an indicator was explored. TRAb were measured both as thyrotropin binding inhibitory immunoglobulins (TBII) and as thyroid-stimulating antibodies (TSAb) in 85 patients with untr eated Graves' disease at 6-month intervals throughout their ATD treatm ent. The patients in the study were treated for a minimum period of 12 months and were categorized retrospectively into two groups depending on whether or not they remained in remission after ATD treatment. Rem ission was deemed as reached in patients who remained euthyroid for a minimum period of 15 months after cessation of ATD. The mean initial T BII and TSAb values in the nonremission group were significantly highe r than in the remission group (p < 0.001 for both parameters). The rat es of fall in mean TBII levels were similar for each group in the firs t 6 months of treatment, but while they continued to fall in the remis sion group over the next 6 to 12 months, mean values for the nonremiss ion group plateaued and failed to fall to control levels within that p eriod. These results indicate that changes in TRAb levels, measured ei ther as TBII or TSAb, occur more rapidly in the second 6 months of tre atment in patients who ultimately achieve remission than those who do not. If TBII fall to control levels by 12 months, the patient has at l east a 70% chance of ultimately achieving remission with ATD treatment alone.