This study was conducted to evaluate the protective potential of the polyphenols curcumin and quercetin on thyroid function in sodium fluoride intoxicated rats. Seventy eight-week-old male Wistar rats receiving a standard diet and regular drinking water were divided into seven groups of 10 each. Group I served as the untreated control. Groups II, III, IV, and V were treated intraperitoneally for 7 days, respectively, with 10 or 20 mg/kg body weight of curcumin or quercetin, followed by 600 mg/L of sodium fluoride in their drinking water for 7 days. Group VI rats were administered 10 mg/kg body weight of vitamin C intraperitoneally for 7 days followed by 600 mg NaF/L in their drinking water for 7 days as a comparison group. Group VII rats were treated only with the same concentration of NaF in their drinking water for 7 days as a further control. After fatal anesthesia with ketamine and xylazine, blood samples were collected by retro-orbital puncture, and the serum levels of thyroxine and triiodothyronine were measured by radioimmunoassay. Pretreatment especially with the higher dosages of curcumin and quercetin, and also vitamin C prior to fluoride exposure effectively kept the serum thyroid hormone levels near the normal range
