Fatemeh Abdolhosseinipoor
Masoud Sadeghi-Dinani
Ali Hosseini-Sharifabad

Introduction: Hypothyroidism is an important endocrine disorder determined by some depressed symptoms. Urtica dioica (Urticaceae) is a medicinal plant which has been traditionally used for treatment of a wide range of decreased functions of different organs. In the current study, we aimed to evaluate the effect of hydroalcoholic extract of aerial parts of U. dioica on thyroid hormones in propylthiouracil (PTU)-induced hypothyroidism in rats.Methods: Forty-two male Wistar rats were randomly divided into ۷ groups including control, PTU, different doses of Urtica dioica hydroalcoholic extract (UDHAE) treated and levothyroxine treated groups. The animals in various groups received water (control group) or water containing ۰.۱% W/V PTU and then injected saline (control group) or ۲۵, ۵۰, ۱۰۰, ۱۵۰ mg/kg UDHAE, respectively for ۴ weeks. Positive control group was fed levothyroxine ۰.۵ mg/kg during the PTU treatment. Then, the blood samples were collected and the levels of thyroxine (T۴), triiodothyronine (T۳), free triiodothyronine (FT۳) and thyroid-stimulating hormone (TSH) measured via the Elisa method.Results: The data showed that PTU decreased the blood level of thyroid hormones but increased TSH, significantly. The ۵۰ or ۱۰۰ mg/kg doses of UDHAE remarkably increased the blood level of T۳ and FT۳. The ۵۰ mg/kg doses of UDHAE increased the blood level of T۴. None of the UDHAE doses showed significant change in the TSH levels. ۲۵ and ۱۵۰ mg/kg doses of UDHAE did not change the PTU- diminished level of thyroid related hormones.Conclusion: The findings suggest that ۵۰ mg/kg dose of UDHAE has stimulatory effect on thyroid gland function and raises plasma T۳ & T۴ & FT۳ levels. UDHAE at the dose of ۵۰ or ۱۰۰ mg/kg could enhance blood level of T۳ and FT۳ perhaps by increase in T۴ to T۳ transformation. Higher doses of UDHAE could not increase the level of these hormones probably due to the presence of inhibitory materials.