Respiratory dysfunction in hypothyroidism

Hypothyroidism is one of the most common endocrine disorders in adults. While it affects almost all systems of the body, little attention has been paid to the involvement of the respiratory system and its function in hypothyroidism. The present review summarises the available literature on respiratory function in patients with hypothyroidism. Hypothyroidism has myriad effects on respiratory function. It is known to cause upper airway obstruction during sleep causing sleep disordered breathing (obstructive sleep apnoea). It affects the respiratory drive causing reduced responsiveness to hypoxia or hypercapnia, potentially causing life-threatening hypoventilation on rare occasions. Pleural effusions solely attributable to hypothyroidism are a relatively uncommon occurrence. Deficiency of thyroid hormones reduces the strength of the respiratory muscles. A reduction in diffusion lung capacity for carbon monoxide points to lung parenchymal involvement as well. These two changes lead to a predominantly restrictive pulmonary physiology on spirometry. Studies show that the restrictive pattern improves after thyroxin replacement. Since pulmonary involvement is a relatively underevaluated aspect of hypothyroidism, more studies in this area are the need of the hour, to fill the current lacunae in our knowledge and understanding.