INSECTICIDE-INDUCED CHANGES IN SECRETORY ACTIVITY OF THE THYROID-GLAND IN RATS

The present study was conducted to examine the effect of organochlorin e (Heptachlor, Benzene hexachloride (BHC)), organophosphorus (Malathio n, Monitor) and pyrethroid (Karate, Talstar) insecticides on the thyro id secretory function in rats. Heptachlor (0.5 mg per rat), BHC (0.66 mg per rat) Malathion (0.06 mg per rat), Monitor (0.2 mg per rat), Kar ate (0.2 mg per rat), Talstar (0.5 mg per rat) were orally administere d to young adult rats for 21 days. Serum concentrations of triiodothyr onine (T-3), thyroxine (T-4) and thyrotrophin (TSH) were determined by using specific radioimmunoassays. Body weight was not affected by tre atment with any insecticide except Talstar (P < 0.01). Among organochl orine and organophosphorus insecticides, treatment with BHC and Malath ion, respectively, led to a significant decrease (P < 0.01) in serum c oncentration of T-3 and T-4. Administration of BHC and Malathion also increased (P < 0.01) TSH secretion. Treatment with both of the pyrethr oid insecticides similarly induced significant suppression (P < 0.01) of serum T-3 and T-4 levels, and concomitant stimulation (P < 0.01) of TSH concentrations. The T-4 / T-3 ratio was decreased (P < 0.05) in r ats treated with Karate but not with any other insecticide. These data indicate that immense care is warranted in the use of insecticides, b ecause they not only affect the liver, kidney and other organs but als o may alter the activity of the endocrine glands.