Airway function and markers of airway inflammation in patients with treated hypothyroidism

Background: There is increasing evidence of an association between organ specific autoimmune diseases, particularly autoimmune thyroid disease and respiratory morbidity. A study was undertaken to determine whether patients with autoimmune thyroid disease have objective evidence of airway inflammation and dysfunction. Methods: Twenty six non-smoking women with treated hypothyroidism and 19 non-smoking controls completed a symptom questionnaire and underwent full lung function tests, capsaicin cough reflex sensitivity measurement, methacholine challenge test, and sputum induction over two visits. Results: Symptoms of cough (p = 0.01), dyspnoea (p = 0.01), sputum production (p = 0.004), and wheeze (p = 0.04) were reported more commonly in patients than controls. Patients with hypothyroidism had heightened cough reflex sensitivity compared with controls (geometric mean concentration of capsaicin causing five coughs: 40 v 108 mmol/l; mean difference 1.4 doubling doses; 95% confidence interval of difference 0.4 to 2.5; p = 0.008) and a significantly higher proportion of patients had airway hyperresponsiveness (methacholine provocative concentration (PC20)