Abstract： Objective To evaluate the efficacy of low-dose levothyroxine sodium in treatment of severe pulmonary tuberculosis with euthyroid sick syndrome(ESS). Methods One hundred and twenty inpatients with severe pulmonary tuberculosis and ESS were randomly divided into treatment group and control group by gender, age, disease duration and severity. Both groups were given anti- tuberculosis, antiinfection treatment and nutritional support for 2 weeks; patients in treatment group were given low-dose levothyroxine sodium additionally. Thyroid function, clinical improvements, increase of albumin, reduction of acid-fast bacilli, improvements on images and the mortality rates were compared between the groups.Results After 2 weeks of treatment, symptoms including fever, cough and night sweats were improved in both groups. Marked improvements were observed in 19 patients(31.7%)of treatment group and 8 patients (13.3%)of control group(χ2 = 5. 73, P ＜ 0.05). Clearance rate of acid-fast bacilli in treatment group was 25.0%(15/60), but that in the control was only 6.7%(4/60)(χ2 = 7. 50, P ＜ 0.01). Serum albumin in the treatment group was increased to(34.2 ±0.4)g/L after the treatment, and that in the control group was(29.1 ±0.6)g/L(t =2.42, P＜0.05). T3 and FT3 were significantly increased in both groups, but more significant difference was observed in the treatment group(t = 59. 42 and 50. 66, P ＜ 0. 01). No empty closed after treatment in both groups, but the effective rate in treatment group was significantly higher than that in the control group(93.3% vs. 76.7%, χ2 =6. 54, P＜0.05). Two patients in control group died(2/60, 3. 3%), while no death was reported in treatment group. Conclusions Low-dose levothyroxine sodium treatment is effective for ESS in patients with severe pulmonary tuberculosis.Improvement on low T3 syndrome may be an important indicator for the overall improvement or recovery.