Biochemical and Histopathological Investigation of Nasturtium officinale on Thyroid Function: an Experimental Study on Models of Hypothyroidism and Hyperthyroidism

Background and objectives: Nasturtium officinale, is a medicinal plant with antioxidant properties and is rich in iodine, glucosinolates, vitamins, and minerals. In Persian folk medicine, it is used for the management of thyroid conditions. This study aimed to evaluate the effects of watercress on the hypothyroidism and hyperthyroidism models. Methods: Seventy-eight rats divided into 13 groups were used. Hypothyroid groups (group 1-4) and hyperthyroid groups (group 10-13) were induced by methimazole (60 mg/kg/day) and levothyroxine (600 μg/kg/day), respectively. Groups 5-9 remained as normal groups without any intervention. After 6 weeks of induction, models were approved by measuring triiodothyronine (T3) and thyroxine (T4) serum levels. Afterward, hypothyroid rats received plant decoction 250 and 500 mg/kg/day, hyperthyroid rats received plant powder 250 and 500 mg/kg/day and normal rats received decoction and powder in both dosages. The treatment kept going for 4 weeks. T3, T4, and thyroid-stimulating hormone (TSH) serum levels, body weight, thyroid weight, thyroid histological parameters, and Thyroid peroxidase (TPO) activity were measured. Results: Plant decoction changed the serum levels of T3, T4, and TSH, body and thyroid weight, thyroid histological parameters, and TPO activity in hypothyroid rats in favour of hypothyroidism. Administering plant powder changed the mentioned factors toward normalization in hyperthyroid rats. In normal groups, both the powder and the decoction changed the factors toward hypothyroidism. These changes were not dose-dependent. Conclusion: Watercress seems to be a suitable complementary medicine or functional food for hyperthyroidism; however, it may worsen hypothyroidism. Clinical studies are required to achieve more reliable results.