Hormone-specific alterations of T4, T3, and reverse T3 metabolism with recent ethanol abstinence in humans

Effects of recent alcoholic withdrawal on thyroxine (T4), 3,5,3'-triiodothyronine (T3), and reverse T3 (rT3) metabolism were determined by serum tracer kinetic studies in recently abstinent alcoholics without overt hepatocellular injury or caloric deprivation. Data were compared with those of normal subjects using a three-pool model, with rapidly and slowly equilibrating pools exchanging with serum. Significant differences included 1) reduced serum total rT3 levels (to 69% of normal) and rT3 degradation rates (to 61%); 2) increased rT3 binding in rapidly (to 557%) but reduced binding in slowly (to 13%) equilibrating tissues, with opposite effects on rT3 fractional transfer rates to serum from rapidly (to 7.5%) and slowly equilibrating sites (to 669%); 3) increased T4 fractional transfer rates from serum to rapidly equilibrating tissues (to 122%); and 4) increased T4 binding to both rapidly (to 195%) and slowly (to 190%) equilibrating tissues. T3 kinetics were not significantly altered. Thus recently abstinent alcoholics have hormone-specific alterations of T4, T3, and rT3 transfer, distribution, and metabolism distinct from other nonthyroidal illnesses or caloric deprivation. Furthermore, these data indicate separate transfer processes for T4, T3, and rT3 from serum to tissue sites and hormone-specific tissue binding characteristics in humans in vivo.