Effects of Salicylates on the Distribution and Early Plasma Disappearance of Thyroxine in Man¹

The early curve of plasma distribution, the hepatic volume of distribution and the hepatic clearance of 131I-thyroxine were measured before and after the intravenous administration of 2 g of sodium salicylate in 8 normal humans. Salicylates increased the rate of disappearance of thyroxine from the plasma in all subjects. The fraction of radioactivity entering the liver was not changed by salicylate but the fraction entering the nonhepatic tissues was significantly increased. Hepatic volume of distribution and clearance of thyroxine increased in all subjects. These distributional changes cannot be explained solely on the basis of an altered concentration of dialyzable thyroxine.