Unresponsiveness to thyrotropin-releasing hormone (TRH) in treated Graves' hyperthyroidism and in euthyroid Graves' disease.

Abstract

ABSTRACT Sixteen euthyroid patients with Graves' disease were given 1000 μg of thyrotropinreleasing hormone (TRH) intravenously and changes in serum thyrotropin (TSH) concentrations were measured. In the same patients, before the time of TRH injection, serum thyroxine, serum free thyroxine, serum triiodothyronine and serum free triiodothyronine concentrations as well as thyroxine turnover were determined. Six patients had not previously been hyperthyroid as far as could be ascertained, and 10 had become euthyroid after treatment for hyperthyroidism. Five of the 16 patients did not respond to intravenous TRH with a rise in serum TSH concentration. The mean values for serum thyroxine, serum free thyroxine, serum triiodothyronine, serum free triiodothyronine and thyroxine turnover for the 5 TRH nonresponsive patients were not statistically different from those in the 11 TRH-responsive patients. In addition, a dissociation between thyroidal suppressibility and TRH responsiveness was observed in several patien...