THYROID SUPRESSION TESTS DURING DRUG TREATIMENT OF HYPERTHYROIDISM

Abstract
In 15 hyperthyroid patients treated for 5 or more consecutive years with propylthiouracil, 4 or more yearly prognostic suppression tests (Cassidy and VanderLaan, 1960) were done. In 9 of the 15 patients there was a progressive diminution over a period of 3-6 yr in the values of these suppressed uptakes to 20% or below. Eight of these 9 patients remained euthyroid off therapy for 1-8 yr (average 3.1 yr). None became hypothyroid. The data suggest a gradual continuing change in thyroid function over the course of years in some hyperthyroid patients on antithyroid therapy. This may be a long-term effect of the drug and may have prognostic significance.