Thyroid function in pulmonary tuberculosis.

OBJECTIVE: To evaluate the thyroid hormone economy in pulmonary tuberculosis (PTB). DESIGN: Cohort comparative study. PLACE AND DURATION OF STUDY: Multan Institute of Radiotherapy and Nuclear Medicine (MINAR) from January 2003 to June 2005. PATIENTS AND METHODS: The study included 266 confirmed cases of pulmonary tuberculosis (PTB), aged between 11 and 65 years, who had completed short course of chemotherapy. Two samples were collected from each patient, first after final diagnosis and second after completion of the treatment. Initial analysis of samples showed that 31 samples had both T3 (triiodothyronine) and T4 (thyroxine) in lower than normal range. One more sample in the middle of treatment was collected for these patients. Radioimmunoassays and immunoradiometeric assays were applied to estimate mean TT3, TT4 and TSH (thyroid stimulating hormone) levels. Students t-test was used to compare patient and normal values derived from 713 volunteers. RESULTS: The age had no effect on levels of T3, T4 and TSH in normal persons. Mean T3 and T4 values (0.74 nmol/l and 91.9 nmol/l) in PTB patients were significantly decreased (p < 0.001) with 50% and 11.6 % cases in lower than normal range respectively. Follow-up data on subgroup of 31 patients showed that both T3 and T4 levels improved after chemotherapy. TSH levels remained unaffected throughout. CONCLUSION: Both T3 and T4 levels were decreased in PTB but T4 levels were less affected. TSH was found unaffected by the disease. This confirms that PTB produces euthyroid sick syndrome (SES) i.e., decreased T3 and T4, and no change affected by 5'deiodinase (an enzyme that causes deiodination of T4). The levels improved after chemotherapy.