Background: A common insecticide made of organophosphates is chlorpyrifos (CPF). The purpose of this study was to
identify the effects of chlorpyrifos on the thyroid gland's microscopic structure and to assess how well montelukast protected
the gland from these harmful effects.
Materials and Methods: There are three main groups made up of forty mature male albino rats. groups I (Control), II
(Chlorpyrifos-treated), and III (Chlorpyrifos-treated plus montelukast). Chlorpyrifos was given to Group II (5.4 mg/kg/day).
Group III got the same dose of chlorpyrifos as before plus 10 mg/kg/day of montelukast. The experiment extended for six
weeks. Measurement of serum thyroid hormone levels and oxidant and antioxidant markers in thyroid tissue, light and electron
microscopic studies, immunohistochemistry labelling to look for caspase-3 and calcitonin, morphometric and statistical studies
were conducted.
Results: Chlorpyrifos treated group revealed significantly decreased mean serum T3 and T4 and higher mean serum TSH.
Also, Mean values of MDA in thyroid tissue were increased and mean values of GSH were decreased. In addition, CPF
treated group showed histological changes including many follicular cells with cytoplasmic vacuolation and some follicles
had multiple layers of follicular cells lining them and increased colloid vacuolation. Dilated blood capillaries were crowded in
between the follicles. Caspase-3 and calcitonin immunoexpression were markedly elevated. Electron microscopic examination
revealed dilated cisternae of rough endoplasmic reticulum, electron dense mitochondria and few microvilli protruding into the
colloid. Eosinophils were seen in between the follicles.
Conclusion: Montelukast ameliorated the effects induced by Chlorpyrifos on thyroid gland structure and function.