Assessment of functional lung impairment in patients with thyroid disorders

Background and objective Many thyroid diseases can lead to pulmonary problems. Hypothyroidism reduces respiratory drive and can cause obstructive sleep apnea, pleural effusion, skeletal muscle myopathy, and decreased carbon monoxide diffusing capacity, whereas hyperthyroidism increases respiratory drive and can cause dyspnea on exertion. Thus, the aim of this study was to evaluate and compare the frequency of clinical presentations, the extent of lung functional endurance (spirometric and diffusion lung capacity), and arterial blood gases affection between patients with hypothyroidism and hyperthyroidism when compared with normal euthyroid volunteers and find out who could compromise the respiratory system more. Patients and methods This study included 90 participants (30 patients with hyperthyroidism, 30 patients with hypothyroidism, and the remaining 30 were normal healthy volunteers as control) referred from the Endocrinology and Internal Medicine Departments in Ain Shams University Hospitals and Misr University for Science and Technology according to their serum free thyroid hormone 3, free thyroid hormone 4, and thyroid-stimulating hormone values. Spirometric function tests and diffusing capacity of the lung for carbon monoxide evaluation were performed for all participants. Results Respiratory symptoms were more frequent in hypothyroid than in hyperthyroid patients, especially cough, sputum production, and chest wheezes. All spirometric functional parameters and respiratory muscle function were decreased (whether or not significant) among patients with hypothyroidism and hyperthyroidism compared with normal euthyroid controls. More statistically significant respiratory functional impairment was noticed among patients with hypothyroidism than among those with hyperthyroidism. Diffusion was more affected in the hypothyroidism group than in the hyperthyroid group, but it was statistically nonsignificant. A statistically significant increase in partial carbon dioxide pressure was observed among patients with hypothyroidism than in patients in hyperthyroidism (However, there was a statistically significant decrease in partial oxygen pressure and pH in patients with hypothyroidism than in those with hyperthyroidism.). Although oxygen saturation was lower in hypothyroidism, it was statistically nonsignificant. Conclusion Hypothyroidism causes greater respiratory system endurance compared with hyperthyroidism. Early diagnosis and hormonal replacement may be