In this study, we investigated thyroid hormones, thyroid stimulating hormone (TSH), prostaglandin D-2 (PGD(2)) and prostaglandin E-2 (PGE(2)) levels in rapid-eye-movement (REM) sleep-deprived rats compared with controls. The aim of the present study was to detect the effect of REM sleep deprivation (RSD) especially on hypothalamic prostaglandin levels. Twenty-seven male rats were randomly assigned in three groups as dry cage control, yoked control, and RSD. RSD rats were sleep deprived for 10 consecutive days. At the end of 10th day all rats were sacrificed for measurement. Our results indicated that total triiodothyronine (T-3) and thyroxine (T-4) decreased in the RSD group while there was no change in TSH. We also measured hypothalamic PGD(2) and PGE2 levels, but we could not find any significant change between groups. (c) 2005 Elsevier Ltd. All rights reserved.