Effect of hydroalcoholic extract of caraway on thyroid gland structure and hormones in female rat

Caraway is one of the medicinal plants used for digestion problems, however, it has been reported that the long term use of this plant in large doses might cause hyperthyroidism symptoms such as leanness, hair loss, severe sweating and tremulousness. Therefore, the aim of this study was to evaluate the effect of hydroalcoholic extract of caraway on the level of thyroid hormones and morphologic changes of thyroid gland in rats. For this purpose, 60 rats were divided into 5 experimental and control groups. Experimental groups were orally given 100, 400, 800 and 1600 mg/kg of extract for 45 days by gavage. The same volume of saline was given to the control group. Blood samples were taken before and after the experiments for the measurement of hormones. The rats were dissected under deep anesthesia and their thyroid glands were removed, processed and stained with H&E. Results show that T3 and T4 were increased and TSH was decreased significantly at high doses compared to those in the control group, but no change was observed in the structure of the gland and the size of follicles. It seems that caraway can temporally increase thyroid hormones and cause hyperthyroidism, but further studies are required to clarify the issue.