Objectives : This study was done to investigate the effects of JMT on hypothyroidism in rats. Materials and Methods : After pretreatment with 50mg/kg thiouracil for 30 days, the experimental group was treated with 0.56g/kg JMT orally and the control group was treated with 0.56g/kg of normal saline instead for 20 days. The various indicators related to hypothyroidism were measured, such as T3-uptake content, T3 content, T4 content, TSH content, hematological values, enzyme activity, total cholesterol content, Na+ content change in the serum and body weight of rats induced by thiouracil. Results : The JMT-treated group showed significant increase in comparison with the control group in serum T3-uptake and T4 content. The JMT-treated group also showed significant decrease in comparison with the control group in serum TSH content. However, the JMT-treated group did not show significant increase in comparison with the control group in serum T3 content. The JMT-treated group showed significant increase in comparison with the control group in serum RBC. The JMT-treated group showed significant decrease in comparison with the control group in serum CPK, ALP, LDH content and serum total cholesterol content. The JMT-treated group did not show significant increase in comparison with the control group in serum Na+ content. The JMT-treated group showed significant decrease in comparison with the control group in body weight. Conclusions : These results suggest that JMT is useful in treatment of hypothyroidism.