Amelioration of metformin-induced hypothyroidism by Withania somnifera and Bauhinia purpurea extracts in Type 2 diabetic mice.

An investigation was carried out to reveal the possible ameliorative role of two plant extracts on an antidiabetic drug-induced hypothyroidism in Type 2 diabetic animals. Dexamethasone (1.0 mg/kg, i.m.) administration caused hyperglycemia with a parallel increase in renal lipid peroxidation (LPO), relative risk ratio (RR), and the concentrations of serum insulin; total cholesterol (TC); low-density lipoprotein cholesterol (LDL-C); very low-density lipoprotein cholesterol (VLDL-C) and triglycerides (TG). It decreased serum triiodothyronine (T3), thyroxine (T4) and high-density lipoprotein cholesterol (HDL-C) levels as well as renal superoxide dismutase (SOD); catalase (CAT) and reduced glutathione (GSH) content. Administration with metformin (150 mg/kg, orally) to diabetic animals further reduced circulating T4 level and caused severe hypothyroidism. It also reduced renal LPO, RR, serum concentrations of insulin; glucose and LDL-C with a parallel increase in cellular antioxidants. While oral administration with either Withania somnifera (1.4 g/kg) or Bauhinia purpurea (2.5 mg/kg) extract along with dexamethasone and metformin elevated the concentrations of circulating T3 and T4 to euthyroid level. The plant extracts also corrected RR ratio and serum concentration of lipids. The findings of the present study, for the first time, reveal that the evaluated plant extracts have a potential to ameliorate metformin-induced hypothyroidism in Type 2 diabetic subjects. Copyright 2009 John Wiley & Sons, Ltd.