THE ROLE OF THE GASTROINTESTINAL TRACT, INCLUDING THE LIVER, IN THE METABOLISM OF RADIOTHYROXINE*

Abstract

introduction THE role of the gastrointestinal tract, including the liver, in the metabolism of thyroid hormone has been debated for years. Older experiments on biliary excretion and gastrointestinal reabsorption of thyroidal substances have been summarized by Elmer (1938), and more recent studies, some with more refined and others with newer technics, by Monroe and Turner (1949). From these studies has arisen the concept that the “liver rids the body of excess thyroxine.” Certain doubts concerning the validity of this idea have been raised by recent observations with minute amounts of radioactive thyroxine and other radioactive thyroidal materials in the human and the rat (Hamilton et at., 1949; Albert and Keating, 1949; Albert et al., 1949; Albert and Keating, 1951). Considerable radioactivity was constantly found to be localized in the region of the liver in the human. Direct analysis of tissues in the rat disclosed that the liver and gastrointestinal tract concentrated large amounts of. I131 after the injection of radiothyroxine (Gross and Leblond, 1947).