Sleep apnea syndrome among patients with hypothyroidism

There is an association of sleep apnea among patients with untreated hypothyroidism. Thyroxine therapy is considered to reduce AHI (apnea-hypopnea index) significantly. A study of 20 successive hypothyroid patients was undertaken to investigate the occurrence of sleep apneas, and response to thyroxine therapy after achieving euthyroid state.

Sleep studies were conducted in 20 consecutive hypothyroid patients at our sleep centre while they were hypothyroid. All were restudied during euthyroid state subsequent to three months of thyroxine therapy.

Nine (45%) of untreated 20 patients had obstructive sleep apnea syndrome (OSAS). Restudy of them during euthyroid state showed complete recovery in six, partial improvement in two and no change in one. Besides them, three other patients developed sleep apnea syndrome of central origin after euthyroid state was achieved. Central respiratory drive improved in 17 patients, while it was reduced among three of nine patients with OSAS who did not show recovery.

Our experience suggests that there is high incidence of sleep apnea among hypothyroid patients. Thyroxine treatment could achieve disappearance of these apneas in majority of them. Few hypothyroids may develop sleep apnea despite the achievement of euthyroid state. Central respiratory drive probably plays an insignificant role in the pathogenesis of sleep apnea among hypothyroids.