Association of free thyroxine with obstructive lung pattern in euthyroid middle-aged subjects: A population-based study.

Abstract

BackgroundThe association between thyroid hormone levels and pulmonary function in euthyroid population is still unclear. We aimed to examine the relationship between thyroid function and lung function in a large cohort study of euthyroid subjects.MethodsWe analyzed biochemical and spirometry data from a nationwide, population-based, cross-sectional survey (KNHANES VI). A total of 1,261 middle-aged participants aged 45-65 years with spirometry tests and normal thyroid function were included in this study. The subjects were grouped according to free thyroxine (fT4) (ng/dL) quartiles (Q1, 0.89-1.09; Q2, 1.10-1.19; Q3, 1.20-1.30; Q4, 1.31-1.76). Obstructive lung pattern was defined as forced expiratory volume in one second (FEV1)/forced vital capacity (FVC) ResultsOverall, 10.9% of the subjects had an obstructive lung pattern. The mean fT4 levels were significantly higher in those with obstructive lung pattern than in those with normal lung function (1.26 vs. 1.20 ng/dL, pConclusionHigh fT4 levels are an independent predictor of obstructive lung pattern in euthyroid middle-aged subjects. Further prospective studies are needed to confirm these findings.