Abstract
Alterations of circulating thyroid hormones are frequently present in chronic nonthyroidal illnesses and may predict prognosis. Pulmonary tuberculosis, a common treatable debilitating disease, may provide a useful model for detailed evaluation of changes of thyroid hormones in relation to subsequent recovery or mortality. Over a period of 12 months, we performed a prospective study of 40 consecutive Chinese patients aged over 50 years and admitted with newly diagnosed pulmonary tuberculosis. Blood samples were drawn for serial thyroid function tests [free thyroxine (T4), free triiodothyronine (T3) and thyroid-stimulating hormone] before treatment and at 1, 2 and 4 months afterwards. Mortality was determined up to 12 months of follow-up. The euthyroid sick syndrome occurred in 63% of patients at presentation. Twelve of 25 euthyroid sick patients died as compared to one of 15 patients with normal baseline thyroid function tests (P < 0·02). Among euthyroid sick patients, those who died had significantly lower free T3 concentration at presentation than those who survived (P < 0·05). An undetectable free T3 concentration at presentation was associated with a subsequent mortality of 75% (9 of 12). Of the survivors, all patients demonstrated a significant rise in serum free T4 concentrations following treatment, which was apparent by 1 month. These data suggest that an undetectable free T3 concentration at presentation reflects severity of illness and predicts a subsequent high mortality.