Altered thyroid hormone status and dichlorvos toxicity in rats.

The effects of altered thyroid function upon serum cholin-esterase levels and dichlorvos toxicity were studied in adult male and female rats. No sexual dimorphism was observed in the base level of serum cholinesterase, however, oral administration of dichlorvos (52.5 mg/kg) resulted in 30% mortality to intact female rats. Hypothyroidism significantly elevated while hyperthyroidism decreased serum cholinesterase enzyme activity in both sexes of rats. Hyperthyroid females were more susceptible than males to dichlorvos challenge even with similar decrease in serum cholinesterase activity.