RESPONSE TO TRIIODOTHYRONINE AS INDEX OF PERSISTENCE OF DISEASE IN THE THYROID REMNANT OF PATIENTS IN REMISSION FROM HYPERTHYROIDISM 1

Abstract

Duration of activity of disease in the thyroid remnant was studied in patients in sustained remission from hyperthyroidism subsequent to treatment by the usual modalities. An abnormal response of I-131 uptake by the thyroid following administration of triiodothyronine was taken to indicate such activity. Evidence of active disease within the gland was found 20 years after onset of remission and subsidence of disease occurred as early as 4 months after therapy as shown by a return to normal of the I-131 uptake response to triiodothyronine. The majority of patients tested showed evidence of activity of disease within the gland for the first 5 years after I-131 therapy and of subsidence of disease thereafter. To the contrary, in the majority of a small group of patients after surgery, subsidence of disease was evidenced by 1 to 2 years. A few patients treated previously by chronic anti-thyroid drug therapy, 1 patient treated by roentgen therapy and 2 patients in spontaneous remission were also studied. The possibility that the response to triiodothyronine may be abnormal despite euthyroidism in patients previously treated for hyperthyroidism must be taken into account when the triiodothyronine test is used in the diagnosis of recurrent hyperthyroidism.