Fatemeh Abdolhosseinipoor
1, Masoud Sadeghi-Dinani
2, Ali Hosseini-Sharifabad
1* 
1 Department of Pharmacology and Toxicology, School of Pharmacy and Pharmaceutical Sciences, Isfahan University of Medical Sciences, Isfahan, Iran
2 Department of Pharmacognosy, School of Pharmacy and Pharmaceutical Sciences, Isfahan University of Medical Sciences, Isfahan, Iran
Abstract
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 7 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 0.1% W/V PTU and then injected saline (control group) or 25, 50, 100, 150 mg/kg UDHAE, respectively for 4 weeks. Positive control group was fed levothyroxine 0.5 mg/kg during the PTU treatment. Then, the blood samples were collected and the levels of thyroxine (T4), triiodothyronine (T3), free triiodothyronine (FT3) 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 50 or 100 mg/kg doses of UDHAE remarkably increased the blood level of T3 and FT3. The 50 mg/kg doses of UDHAE increased the blood level of T4. None of the UDHAE doses showed significant change in the TSH levels. 25 and 150 mg/kg doses of UDHAE did not change the PTU- diminished level of thyroid related hormones.Conclusion: The findings suggest that 50 mg/kg dose of UDHAE has stimulatory effect on thyroid gland function and raises plasma T3 & T4 & FT3 levels. UDHAE at the dose of 50 or 100 mg/kg could enhance blood level of T3 and FT3 perhaps by increase in T4 to T3 transformation. Higher doses of UDHAE could not increase the level of these hormones probably due to the presence of inhibitory materials.