Thyroxine replacement therapy reverses sleep-disordered breathing in patients with primary hypothyroidism

Anecdotal reports suggest that sleep-disordered breathing (SDB) is common among patients with primary hypothyroidism. This study was undertaken to determine the prevalence of SDB and to evaluate the effect of thyroxine replacement therapy on SDB in patients with primary hypothyroidism.

Fifty consecutive newly diagnosed, untreated symptomatic patients with primary hypothyroidism (age: 34+/-11 years; males: 21 [42%]) were prospectively studied. Physical examination, anthropometry, fasting blood glucose and serum lipids were performed in all patients at baseline. Polysomnography was done at baseline in all patients and was repeated after adequate thyroxine replacement in those who had SDB.

SDB defined as apnea-hypopnea index (AHI) > or =5 was present in 15 patients (30%) at baseline and was reversible in 10 of the 12 patients evaluated following thyroxine replacement therapy (P=0.006). Thyroxine replacement therapy was associated with improvement in findings that reflect a compromised upper airway, such as macroglossia (4 [33%] vs. 1 [8%]; P=0.083), myoedema (5 [42%] vs. 1 [8%]; P=0.046) and facial puffiness (10 [83%] vs. 1 [8%]; P=0.003).

Reversible SDB is common among patients with primary hypothyroidism. Changes in upper airway anatomy resulting from hypothyroidism probably contribute to the development of SDB in these patients.