title: Pesticide-induced changes in peripheral thyroid hormone levels during different reproductive phases in Heteropneustes fossilis.
abstract: Effects of gamma-BHC (an organochlorine) and malathion (an organophosphorus) exposure on plasma triiodothyronine (T3) and thyroxine (T4) levels have been studied in the freshwater catfish, Heteropneustes fossilis, during its annual reproductive cycle. After 4 weeks exposure of gamma-BHC (8 and 16 ppm) and malathion (10 and 20 ppm), the effects on plasma T3, T4, and T3/T4 ratio varied during different reproductive phases. Malathion seems to have a stimulatory effect, while gamma-BHC seems to have an inhibitory effect on extrathyroidal conversion of T4 to T3. Changes in levels of various thyroid hormones during different reproductive phases occurred most probably due either to inhibited (in response to gamma-BHC) or to stimulated (in response to malathion) extrathyroidal T4 monodeiodination and their altered excretion or consumption rate.
mesh_terms: D000818:Animals; D002397:Catfishes / Q000502:physiology*; D005260:Female; D010575:Pesticides / Q000633:toxicity*; D012098:Reproduction / Q000187:drug effects*; D013963:Thyroid Hormones / Q000097:blood*; D013974:Thyroxine / Q000097:blood; D014284:Triiodothyronine / Q000097:blood; D014873:Water Pollutants / Q000633:toxicity*; D014874:Water Pollutants, Chemical / Q000633:toxicity*
chemical_list: D010575:Pesticides; D013963:Thyroid Hormones; D014873:Water Pollutants; D014874:Water Pollutants, Chemical; D014284:Triiodothyronine; D013974:Thyroxine