NATURAL-HISTORY OF HYPER-THYROIDISM DUE TO GRAVES-DISEASE IN REMISSION - SEQUENTIAL STUDIES OF PITUITARY-THYROID REGULATION AND VARIOUS SERUM PARAMETERS

A previous study of pituitary-thyroid regulation in 20 patients with hyperthyroidism due to Graves' disease who had remained in remission for at least 6 months after cessation of antithyroid therapy revealed that 13 of the 20 had subnormal serum TSH responses to TRH and/or abnormal thyroid suppressibility (J Clin Endocrinol Metab 43: 419, 1976). These results were interpreted as indicating the persistence of subclinical Graves' disease in these 13 patients. Three years later, all 20 patients were restudied. Serum thyroglobulin (Tg) and TSH displacement activity were also measured in serum samples from both times. Four patients developed recurrent hyperthyroidism; three initially had both subnormal TSH responses to TRH and abnormal thyroid suppression. In the others, TSH responses to TRH and thyroid suppressibility were normal more often on restudy than they were originally. Serum Tg concentrations were initially elevated in six patients; three remained euthyroid and had little change in their serum Tg levels. Serum TSH displacement activity was similarly a poor predictor of recurrent hyperthyroidism. These results indicate that recurrent hyperthyroidism is most likely to occur in those patients with both subnormal TSH responses to TRH and abnormal thyroid suppression. If only one test is abnormal, recurrent hyperthyroidism is unlikely. In those patients who remained euthyroid, the later return to normality in the TRH or suppression tests suggests that subclinical Graves' disease had gradually disappeared. © 1979 by The Endocrine Society.