Therapeutic Effect of Scutellaria baicalensis on L-Thyroxine-Induced Hyperthyroidism Rats

BACKGROUND: This study was performed to evaluate the anti-hyperthyroidal effects and action mechanism of Scutellaria baicalensis Georgi (SB), a medicinal herb, on levothyroxine (LT4)-induced hyperthyroidal rats. METHODS: Male Wistar rats were divided into five groups, namely, euthyroidal normal group (Normal), hyperthyroidism control group (Control), hyperthyroidism plus PTU-treated group (PTU) as a positive control, hyperthyroidism plus 400 mg/kg SB-treated group (SB400), and hyperthyroidism plus 800 mg/kg SB-treated group (SB800). The rats in groups other than Normal were injected with LT4 for 2 weeks to induce hyperthyroidism and then were administrated each treatment for 2 weeks. Clinical symptoms and biomarkers related to hyperthyroidism were examined, and the gene expressions related to the regulation of thyroid hormone were determined. RESULTS: Compared with the Control group, pulse rate, serum T3, T4, triglyceride, thyroid follicle size, and the deiodinase 1 (Dio1) gene expression were significantly reduced in the SB and PTU groups. Serum TSH and the thyroxine-binding globulin (Tbg) gene expression were significantly increased in the SB and PTU groups. CONCLUSIONS: These results suggest that SB might suppress T3, T4, and adrenergic activity by modulating Dio1 and Tbg expression, and therefore, SB could be an alternative therapy for hyperthyroidism.