Sources of Circulating 3,5,3′-Triiodothyronine in Hyperthyroidism Estimated after Blocking of Type 1 and Type 2 Iodothyronine Deiodinases

Abstract

Although thyroidal T(3) contributes only around 20% of total T(3) production in normal individuals, this is much higher in patients with a hyperactive thyroid, ranging up to two thirds. The major part is produced from T(4) deiodinated in the thyroid.