Effects of commercial formulations of deltamethrin and/or thiacloprid on thyroid hormone levels in rat serum

Deltamethrin (DEL) and thiacloprid (THIA) are the two commonly used synthetic insecticides applied either separately or as a mixture. The aim of this study was to assess thyroid stimulating hormone (TSH) and the serum levels of thyroid hormones exposure to these compounds in rats. The animals were orally gavaged with a single dose of DEL (15 mg/kg), THIA (112.5 mg/kg) or DEL + THIA (15 + 112.5 mg/kg) for 24 h (acute treatments) or DEL (3 mg/kg per day), THIA (22.5 mg/kg per day) or DEL + THIA (3 + 22.5 mg/kg per day) for 30 days (subacute treatments). Although all independent and combined treatments with DEL and THIA changed the levels of TSH, these alterations were not significant. Statistically significant increases in free triiodothyronine (FT3) and free thyroxine (FT4) serum hormone levels were observed in the independent treatment with THIA and the combined treatment with DEL and THIA for 30 days. The results of this study suggest that in vivo exposure to subacute treatments of commercial formulations of THI and mixture of DEL + THIA increased serum FT3 and FT4 levels in rats. Further studies are required to determine the effects of endocrine disruptors and potential health risks of these insecticides in human, especially in children because of the importance of these hormones during growth and development.