ACUTE TOXICITY OF CYPERMETHRIN EXPOSURE ON THYROID HORMONE LEVELS IN JUVENILE Clarias gariepinus (Burchell, 1822)

This study was conducted to investigate the dose relationship between thyroid hormone parameters in exposed juveniles of Clarias gariepinus and Cypermethrin using Thyroid function tests. Measuring the levels of Triiodothyronine (T3), Thyroxine (T4), and Thyroid Stimulating Hormone (TSH) are not only critical for diagnosing thyroid problems, but also in differentiating between a primary and secondary cause of a thyroid condition, for instance, an exposure to cypermethrin leading to hypothyroidism. The experimental fishes were exposed to 0, 15, 30, and 45µg/l of Cypermethrin fo96 hours in an acute toxicity experiment. At the end of the 96 hours, muscle tissue samples were harvested and prepared for biochemical analyses using standard procedures. Findings from this study confirm that cypermethrin is an Endocrine Disrupting Chemical (EDC) in fish and alters the thyroid hormone levels in C. gariepinus by targeting the hypothalamus-pituitary-thyroid axis. Furthermore, it provokes the inhibition of thyroid function in the fish so that the activity levels of T3 and T4 reduced significantly (p < 0.05). The levels of TSH increased in a dose-dependent trend, CYP 3 (0.85±0.05) > CYP 2 (0.81±0.01) > CYP 1 (0.75±0.05). A disruption in the normal thyroid function of the fish could impede the regulation of liver glycogen, protein metabolism, cell respiration, antioxidant system and the excitability of neurons and muscles, ultimately leading to deformities in juvenile fish and eventual death