Are thyroid function tests necessary in patients with suspected sleep apnea?
Thyroid evaluation is frequently performed in patients with sleep apnea because of a suspected causal relationship between hypothyroidism and obstructive sleep apnea (OSA). The aim of this study was to determine the actual prevalence of hypothyroidism in patients referred for polysomnography and evaluate whether its rate was higher in patients with OSA than those without OSA. Ultrasensitive thyroid stimulating hormone (TSH) was performed on 255 of 279 consecutive patients referred for polysomnography from the neurology service of a large HMO. Hypothyroidism was detected in 1.6% (4/243) of all patients, 1.5% (3/194) of patients referred to evaluate OSA, and 2.0% of patients referred to evaluate the presence of periodic leg movement disorder (PLMD)/narcolepsy/parasomnia. There was no significant difference in rates of hypothyroidism in patients with documented OSA (2.9%, 3/103) compared to those without OSA (0.7%, 1/135). Two of the four patients with elevated TSHs had previously documen
