The influence of sleep deprivation on thyroid hormone metabolism in rat frontal cortex

The effects of 24 h sleep deprivation (SD) on central thyroid hormone metabolism were investigated in rat frontal cortex. SD induced a significant rise in the activity of iodothyronine type II 5'-deiodinase (5'D-II), which catalyzes the conversion of thyroxine (T4) to triiodothyronine (T3) in the rat central nervous system (CNS). Tissue concentrations of T4 remained unchanged, whereas levels of T3 increased to more than 150% of the corresponding levels measured in control rats. Serum concentrations of T4 and T3 were also significantly enhanced by SD--an effect that has previously been described in depressed patients having undergone the same procedure. These results suggest that SD can dramatically increase T3 concentrations (and possibly function) in rat CNS. Whether or not these findings are of relevance in regard to the well-known antidepressant effect of SD in psychiatric patients with major depressive disorders remains to be established.