Objective：To observe the clinical efficacy of oral levothyroxine plus intrathyroidal injection of dexamethasone in conversion of overt hypothyroidism （OH） caused by Hashimoto＇ thyroiditis. Methods： Totally 356 patients with overt hypothyroidism caused by Hashimoto＇ thyroiditis were evenly randomized into 2 groups. Patients in levothyroxine group were treated with oral levothyroxine for 12 months to maintain the normal serum levels of free T4, free T3, and sensitive thyroid-stimulating hormone （TSH） ; patients in dexamethasone group were treated with oral levothyroxine plus intrathyroidal injection of dexamethasone （5 rng each time, once a week for 8 times, followed by once in 2 weeks for 4 times, finally once in 4 weeks for another 4 times）. Serum FT4, FT3, sensitive TSH, thyroglobulin antibody, thyroid peroxidase antibody, cortisol, and adrenocorticotropic hormone were determined before and 12 months after treatment. FT4 and sensitive TSH levels were regularly examined in patients. The recurrence of OH was deemed as the endpoint of the study and LT4 treatment was restored; if OH did not recur the patients were reevaluated till the end of the 16th weeks. Results： Sixteen weeks after the treatment, 12 （7 % ） patients in levothyroxine group had normal thyroid function, 21 （12 % ） had subclinical hypothyroidism, 141 （81%） had OH, and 4 patients withdrew from the study; in dexamethasone group the numbers were 35 （20%）, 32 （18 % ）, 108 （62 % ）, and 3, respectively. Compared with levothyroxine group, patients in dexamethasone group had an absolute benefit increase （ABI） of 6% from overt to subclinical hypothyroidism with a number need to treat （NNT） of 17, and had an ABI of 13% and an NNT of 8 from OH to normal thyroid function. Levothyroxine plus dexamethasone therapy was more effective in reducing goiter and lowering the levels of thyroid autoantibodies in serum. There were not serious side effects in both groups. Conelsion： Oral levothyroxine plus intrathyroidal injection of dexamethasone therapy is superior to oral levothyroxine thyerapy in conversing OH to subclinical hypothyroidism or normal thyroid function.[著者文摘]