Celecoxib is an effective agent in the treatment of signs and symptoms of inflammation, rheumatoid arthritis and osteoarthritis. The purpose of this study is to assess the effects of two different doses of celecoxib on some hormones and endocrine glands of male rats. In this study, the doses of 10 and 50 mg/kg/day of celecoxib were given to male rats orally for 28 days. At the end of the study, serum total triiodothyronine (T-3), total thyroxine (T-4), thyroid stimulating hormone (TSH), testosterone and luteinizing hormone (LH) levels of rats were analyzed by radioimmunoassay technique using RIA kits. Thyroid and testis tissues of male rats were examined histopathologically. While there was no a change in serum T3, T4 and LH levels of celecoxib-treated rats, there were differences in serum TSH and testosterone levels of rats treated with 50 mg/kg/day celecoxib for 28 days compared with those of control rats. In histopathological examinations, celecoxib-related changes were found in thyroid glands of the rats. (c) 2006 Elsevier B.V. All rights reserved.