Prevalence of thyroid disease in patients with obstructive sleep apnea

Background: Previous studies have reported conflicting results with regard to thyroid disease in obstructive sleep apnea (OSA) patients. Objectives: To determine the prevalence and predictors of thyroid disease in OSA patients. Methods: Consecutive patients who were referred for an overnight polysomnography (PSG) in the study period underwent serum TSH and thyroxine (FT4) measurement within 4 weeks of PSG using the electrochemiluminescence immunoassay method. Standard definitions were used to define clinical hypothyroidism, subclinical hypothyroidism, clinical hyperthyroidism and subclinical hyperthyroidism. Results: During the study period, 271 patients with OSA and a mean age of 48.7±14.1yr, body mass index (BMI) of 37.7±9.6 kg/m 2 and apnea hypopnea index (AHI) of 55.2±37/hr and 76 non-OSA patient (control group) with a mean age of 40.8±14.9yr and BMI of 33.7±8.9kg/m 2 and AHI of 3.8±3.1/hr were included. Among OSA patients, a total of 26 (9.6%) were known cases of clinical hypothyroidism. The prevalence of newly diagnosed clinical hypothyroidism was 0.4% and the prevalence of newly diagnosed subclinical hypothyroidism was 11.1% in OSA patients. In the non-OSA patients, the prevalence of newly diagnosed clinical hypothyroidism was 1.4%, and the prevalence of newly diagnosed subclinical hypothyroidism was 5%. There were no cases of clinical or subclinical hyperthyroidism in the studied group. Female gender was the only predictor of clinical hypothyroidism. Conclusion: The prevalence of newly diagnosed clinical hypothyroidism was very low in OSA patients to warrant routine testing for thyroid function. On the other hand, subclinical hypothyroidism was common among patients with OSA.