Metabolic Activity of 3,3'-Diiodothyronine and 3,3'-Diiodo-5-Bromothyronine

¹ From the Department of Pharmacology, School of Medicine, University of Virginia, Charlottesville, Virginia

Following the preparation of (±) 3,3'-diiodothyronine and of (±) 3,3'-diiodo-5-bromothyronine, these compounds were tested for metabolic activity. It was found that 3,3'-diiodothyronine had only slight activity in the antigoiter test and in the oxygen consumption test in thyroidectomized rats. In contrast, (±) 3,3'-diiodo-5-bromothyronine had marked activity as compared with (–) 3,3',5-triiodothyronine. It is apparent from these results that iodine in position 5 is important for the activity of 3,3',5-triiodothyronine and it may be replaced by bromine with retention of metabolic activity.