Introduction: The aim of the present study is to evaluate the effect of alcoholic extract of Chelidonium majus concentration of cholesterol and thyroid hormone levels in the male rats having hypercholesterolemia. 

  Methods: In this study, 40 male Wistar rats were divided into five groups of control group (n=8) with normal diet, observing group with fat dietary, and three experimental groups receiving the same fat diet plus ethanol extract of the Chelidonium majus plant of 100, 200, 300 (mg/kg). After this period (21 days) blood samples were collected and after measuring the amount of thyroid hormones of T₃, T₄, TSH and also the amount of cholesterol, the data were analyzed by using SPSS software , ANOVA and t-test.

  Results: There was a significant increase in the amount of cholesterol, T₃ a nd T₄ serum level in observation group comparing with control group (P<0.05) and the amount of T₃ a nd T₄ in groups receiving the maximum dose of Chelidonium majus extract had the minimum decrease comparing to the group receiving moderate dose (P<0.05).

  Conclusions: The results demonstrate that Chelidonium majus alcoholic extract can reduce the concentrations of thyroid hormones and the amount of cholesterol and increase the amount of thyroid-stimulating hormones as well, which is probably due to the existence of plant’s alkaloids and flavonoids, as well as the negative feedback mechanism of thyroid hormones.