Background:  Pituitary and thyroid hormones have important roles on homeostasis control. The aim of this study was to investigate  the effect of Tragopogon pratensis L. hydroethanolic extract (TPE) on serum levels of  thyroid hormones in male rats induced with lead acetate.

Methods: In this study, 36 male Wistar rats (weighing 220-250 gr) divided in 6 groups (n=6): control, lead acetate (in tap water, 500ppm), treatment groups : (Lead acetate 500 ppm, and 200mg/kg, 400mg/kg and 800mg/kg TPE), and positive control group ( 400mg/kg TPE). All data were expressed by mean±SEM and analyzed by ANOVA and Tukey's test. The statistical differences was significant by P<0.05.

Results: Lead acetate significantly (P<0.001) decreased T₃,T₄,TSH serum levels. Tragopogon pratensis L. extract increased thyroid hormones in rats induced with lead acetate. It  seems that the Tragopogon pratensis L. extract can  protect thyroid gland against oxidative stress caused by lead acetate.

Conclusion: The results of this study showed that lead acetate have toxic effects on thyroid hormones and Tragopogon pratensis L. hydroalcoholic extract may have protective role on thyroid function.