Evaluation of the effects of chronic exposure to organophosphorus pesticides on thyroid function

Background: Organophosphorus (OP) compounds are considered among the most common insecticides. The major mechanism of organophosphorus toxicants includes inhibiting cholinesterase enzyme. organophosphorus toxicants cause impaired thyroid hormones through affecting different parts of the hypothalamus-pituitary-thyroid axis. The aim of this study is to determine the effects of chronic exposure to organophosphorus pesticides on thyroid function. Methods: The present descriptive-analytical study was conducted cross-sectionally on male workers employed in a factory producing OP as the exposure group as well as the personnel of the administrative department of the same factory as the control group chosen through census method. According to Helsinki declaration, 5 ml of venous blood was collected, and the activity of TT3, TT4, FT3, FT4, and TSH hormones was measured through CLIA method, while the activity of serum cholinesterase enzyme (CHE) was measured through colorimetry. Results: T-test indicated that there was no significant difference in the mean of activity of hormones and enzyme studied between exposure and control groups (p>0.05). Nevertheless, the activity of TT3, TT4, FT3, FT4 hormones, and CHE enzyme was lower in the exposure group, while that of TSH was higher than in the control group. Pearson correlation test indicated that there was no significant correlation between the activity of all studied hormones and CHE enzyme (p>0.05). Conclusions: In the present study, the workers employed in the factory producing OP did not suffer thyroid disorders. Further, OP did not have a considerable effect on the activity of CHE enzyme.