Is triiodothyronine capable of ameliorating pyrethroid‐induced thyroid dysfunction and lipid peroxidation?

A study on the effect of triiodothyronine (T3) in the regulation of pyrethroid (fenvalerate)‐induced thyroid dysfunction and lipid peroxidation was carried out in male mice. Fenvalerate (120 mg kg−1 body wt. daily for 15 days) administration led to a decrease in the serum concentration of thyroid hormones and the activity of hepatic type I iodothyronine 5′‐monodeiodinase (5′D‐I) and an increase in the level of lipid peroxidation. The decrease in the activity of hepatic 5′D‐I due to the administration of fenvalerate was restored with the administration of T3 (7 μg kg−1 body wt. on alternate days). The increased level of lipid peroxidation was also ameliorated by T3. However, T3 could not restore the serum concentration of thyroxine (T4), only that of T3. We suggest that the ameliorating role of T3 in the fenvalerate‐intoxicated mice could be the result of the lipogenic action of the thyroid hormone, which in turn led to the restoration of 5′D‐I activity. © 1998 John Wiley & Sons, Ltd.