Effect of Ethanol on the Peripheral Metabolism of Thyroxine

Abstract

To determime the effect of ethanol on peripheral metabolism of T₄, deiodinative clearance of T₄ and serum concentration of T₄, T₃ and rT₃ were measured in rats isotopically equilibrated with T₄. Ethanol 8g/Kg body weight/day was given for 3 days to fasted rats and the results were compared with those normally fed or totally fasted animals. In fasted rats, deiodinative clearance of T₄ and serum T₄ and T₃ concentration, and T₃/T₄ ratio, were decreased significantly, while serum rT₃ concentration and serum rT₃/T₄ ratio was increased significantly when compared to those in normal rats.
When ethanol was administered to fasted rats, deiodinative clearance of T₄, serum T₄ and T₃ concentration and serum T₃/T₄ returned to normal level while serum rT₃ concentration and rT₃/T₄ ratio remained at higher levels than in normally fed animals. These results could not be interpreted on the basis of shift of 5 monodeiodinase to 5' form or vise versa, and imply that the two deionative process may be independent each other.