Rapid changes in thyroid function tests upon treatment of tuberculosis.
METHODS
Inpatient service and tuberculosis (TB) clinic of a public hospital.


OBJECTIVE
(1) To test the hypothesis that an hepatic effect of antituberculosis drugs increases serum thyroxine-binding globulin (TBG); (2) to resolve conflicting reports on thyroid function in TB.


METHODS
Measurement of serum thyroid hormones, thyroid hormone binding (T3RU) and binding proteins (TBG, transthyretin [TTR] and albumin) in 38 patients with active TB and in 29 healthy tuberculin-positive controls, before and about 10 days into therapy.


RESULTS
With therapy of TB (with isoniazid [INH], rifampin [RIF], ethambutol and/or pyrazinamide), TBG increased above control values and T3RU decreased (P < 0.001). These changes were weakly correlated with liver enzyme activities but did not predict clinical hepatitis, which developed in only 1 patient. T3 was initially subnormal in 61% of 38 TB patients, while T4, thyrotropin (TSH) and TBG were normal. T3, TTR and albumin, all negative acute phase reactants, increased towards normal by day 10 (P < 0.001). Thyroid function remained unaltered in 14 control patients taking INH, whereas T3RU decreased (binding increased) and T3 increased in 15 taking INH and RIF (P < 0.001).


CONCLUSIONS
TB patients manifest the expected low T3 of non-thyroid illness, but, unlike most sick patients, usually have normal or increased serum binding of thyroid hormones. Chemotherapy further increases binding by increasing TBG, an effect probably due to RIF.
Hill
A R
AR
Department of Medicine, State University of New York Health Science Center, Brooklyn 11203, USA.
Schmidt
M F
MF
Schussler
G C
GC
D000995:Antitubercular Agents / Q000627:therapeutic use*; D006801:Humans; D008111:Liver Function Tests; D011446:Prospective Studies; D011863:Radioimmunoassay; D013960:Thyroid Function Tests; D013974:Thyroxine / Q000378:metabolism*; D013975:Thyroxine-Binding Proteins / Q000378:metabolism*; D014284:Triiodothyronine / Q000378:metabolism*; D014397:Tuberculosis, Pulmonary / Q000188:drug therapy* / Q000378:metabolism
D000995:Antitubercular Agents; D013975:Thyroxine-Binding Proteins; D014284:Triiodothyronine; D013974:Thyroxine