Inhibition by Propylthiouracil of the Peripheral Metabolism of Radiothyroxine

Abstract

Treatment with propylthiouracil of euthyroid, hyperthyroid or hypothyroid patients previously given radiothyroxine (and, in one instance, thyroid extract) resulted in a diminution in the rate of disappearance of body radioactivity and serum protein-bound radioiodine. The findings suggest that propylthiouracil interferes with the extrathyroidal metabolism of thyroxine.