Spirometry in adult hypothyroid patients: a comparative study

Hypothyroidism adversely affects pulmonary function, which may improve by thyroxine therapy. Limited studies about the effect of hypothyroidism on spirometric parameters in adult patients were conducted in Basra, south of Iraq. Moreover, the effect of thyroxine therapy on spirometric parameters was not covered by these studies. In this study, pulmonary function in adult's hypothyroid patients was evaluated by spirometry to detect any impairment, type of impairment, and to evaluate the effect of thyroxine therapy.

A comparative study was conducted in Al-Faiha Specialized Diabetes, Endocrine, and Metabolism Center (FDEMC) in Al-Faiha teaching hospital, Basrah, Iraq. Subjects are divided into four groups: uncontrolled hypothyroid group (n=72), controlled hypothyroid group (n=60), newly diagnosed hypothyroid group (n=52), and control group (n=110). Spirometry was done to all subjects in sitting position, it's repeated at least three times and the best result was recorded.

A significantly (p<0.05) less spirometric parameters and more abnormal pulmonary function test (PFT) were noticed in hypothyroid groups, the reduction were more pronounced in the uncontrolled hypothyroid group. The abnormality in PFT was mostly of restrictive type. A significantly (p<0.05) negative correlation has been found between thyroid-stimulating hormone (TSH) and spirometric parameters, while the correlation of fT4 is significantly (p<0.05) positive with FVC% and FEV%.

In hypothyroidism, high TSH and low fT4 are recognized causes of a reduction in spirometric parameters. Therefore, spirometry can be used to detect pulmonary function changes in hypothyroidism.