Metabolism of L-Thyroxine and L-Triiodothyronine in the Absence of the Liver

¹ From the Sections of Biochemistry, Surgical Research, and Biophysics and Biophysical Research, Mayo Clinic and Mayo Foundation, Rochester, Minnesota

The total amount of I¹³¹-containing compounds excreted in the urine of the dehepatized dog receiving either radioactive thyroxine or triiodothyronine is similar to that of the normal dog receiving similar injections. The important role of the liver in the deiodination of thyroxine and triiodothyronine is indicated by the failure of the liverless animal to convert these compounds to inorganic iodide as completely as does the normal dog. Only a small percentage of the I¹³¹ compounds excreted by the liverless dog appears as inorganic iodide. The most abundant iodine compound in the urine of the dehepatized dog is a conjugate of thyroxine when thyroxine is injected, and an unidentified compound, b, when triiodothyronine is injected.