In VivoDeiodination of Labeledl-Thyroxine tol-3,5,3′-Triiodothyronine in Mouse and Human Pituitaries

Abstract

L-Thyroxine labeled with I¹³¹ (T4*) was injected into normal and radiothyroidectomized mice, and also into 2 patients undergoing pituitary surgery. Four hours after injection, up to 27 % of the radioactivity found in the mouse pituitaries was in the form of 3,5,3′-triiodothyronine (T3*). In the human pituitaries, 5 and 10 % of the radioactivity was present as T3*. Labeled iodide (I*) and unchanged T4* constituted the remainder of the radioactivity.