Assessment of pulmonary function by spirometry in hypothyroid children and adolescents

Background and objectives. Hypothyroidism affects the function of the respiratory system. Although this effect has been thoroughly studied in adults, it has not been extensively studied in children and adolescents. The aim of this study was to evaluate the pulmonary function in hypothyroid children and adolescents and its correlation with thyroid hormone levels. Methods. A case-control study was conducted with 65 subjects, aged 7–16 years. They were classified into three groups: the control (euthyroid) group (1st group, n = 25), the treated hypothyroid group (2nd group, n = 25), and the newly diagnosed hypothyroid group (3rd group, n = 15). Spirometry and thyroid function tests were performed for all participants. Results. All groups were comparable in terms of age, gender, and body mass index (BMI). Forced vital capacity percentage (FVC%) was significantly higher in the euthyroid group compared to the treated and newly diagnosed hypothyroid groups (p-value <0.05; p-value <0.001, respectively) and in the treated group compared to the newly diagnosed group (p-value <0.001). The percentage of forced expiratory volume in one second (FEV1%) was significantly lower in the 3rd group compared to the 2nd and 1st groups (p-value <0.01; p-value <0.001, respectively). The correlations of FVC% and FEV1% with thyroid-stimulating hormone (TSH) levels were significantly negative (p-value <0.00; p-value <0.05, respectively). Conversely, the correlation of FVC% with free thyroxine (fT4) levels was significantly positive (p-value <0.05). Conclusion. Hypothyroidism reduces pulmonary function in hypothyroid children and adolescents. The reduction in spirometric parameters improves with thyroxine therapy.