Undiagnosed Hypothyroidism in Obstructive Sleep Apnea Syndrome

Abstract

Objective Lethargy, apathy, daytime sleepiness are common features of Obstructive sleep apnea syndrome (OSAS). These features are already seen in hypothyroidism. OSAS is more frequent in obese patients and overt hypothyroidism may substantially add to this risk. We aimed to evaluate the incidence of hypothyroidism in cases applying with OSAS symptoms who have no known clinical thyroid disease to evaluate the necessity of thyroid hormone screening in OSAS. Materials and Methods The study population consisted of patients with no known history of thyroid disease. All patients were screened in the sleep laboratory for one night and polysomnography. Serum thyroid-stimulating hormone (TSH) levels were measured by chemiluminescence method in patients referred to our sleep center for an overnight sleep study. Results Of 1473 subjects, 1406 (95.5%) were diagnosed as OSA (Apnea-hypopnea index (AHI)>5). Elevated TSH levels were detected in 3 cases in the nonapneic group (4.47%) and 54 cases in the OSAS group (3.90%). In mild-moderate OSAS group, the mean TSH value was 2.02 µU /ml and in patients with severe OSAS this value was 2.44 µU/ml, though the difference was not statistically significant (p=0.08). AHI was found to be weakly correlated with TSH values, though the correlation was statistically significant (r=0.05, p=0.04). Mean TSH values were not correlated with oxygen desaturation index (ODI) or lowest oxygen saturation values (r=0.02 and r=-0.02, respectively). Conclusion The measurement of TSH levels in suspected OSAS cases may help both differential diagnosis between OSAS and hypothyroidism, but subclinical hypothyroidism was not found more common in patients with OSAS.

Keywords

• Obstructive sleep apnea syndrome
• subclinical hypothyroidism
• thyroid-stimulating hormone