Sleep apnea and hypothyroidism.

Thyroid deficiency states are now a well recognized cause of the sleep apnea syndrome. The spectrum of disease ranges from mild, asymptomatic hypothyroidism to severe myxedema, and the disorder is associated with both obstructive and central types of sleep apnea. A variety of factors may be involved, including upper airway obstruction with or without obesity, and alterations in ventilatory drive. The definitive therapy is thyroid hormone replacement, which has been shown to diminish or completely eliminate apneic episodes and arterial oxygen desaturation, as well as to effect many improvements in sleep patterns and overall sleep efficiency. The incidence of thyroid deficiency states in patients with sleep apnea syndrome is not known, but it seems reasonable to evaluate thyroid function in all patients. Thyroid replacement therapy seems logical for the treatment of sleep apnea in patients with previously unrecognized subclinical hypothyroidism. Much remains to be learned about the diagnosis and treatment of sleep apnea syndromes associated with thyroid hormone deficiency, and further studies are needed.