Abstract
Fifty-three thyroid suppression tests were carried out at the end of a year of treatment of hyperthyroidism with antithyroid drugs. Two to 7 years later (average 47 months), 27 patients were well and 26 patients had relapsed or had experienced a recurrence within periods ranging from a few days to 69 months (average 7 months) after antithyroid drugs were discontinued. The average value of 24-hr I131 uptake after the test for those who remained well was 23%, in contrast to 58% for those in whom hyperthyroidism recurred (p<.001). The test indicates the likelihood of a prompt relapse of hyperthyroidism after treatment is discontinued if the value is 50% or more and a prolonged or permanent remission when it is 30% or less.