Serum Vitamin D and Parathyroid Hormone Levels in Patients with Obstructive Sleep Apnea Syndrome

Introduction: An increase in sympathetic activity caused by intermittent hypoxia and reoxygenation that develops an obstruction of the upper respiratory tract in obstructive sleep apnea syndrome (OSAS) results in cardiovascular and metabolic changes. This study aimed to assess the effects of OSAS on serum vitamin D and parathyroid hormone (PTH) levels. Methods: The study population comprised 103 male patients with newly diagnosed OSAS and 58 male non-apnoeic controls matched for age, sex, and body mass index (BMI). Serum calcium, phosphorus, vitamin D, and PTH levels were measured. Results: There were no significant differences between patients with OSAS and the controls in terms of age, sex, BMI, smoking status, hypertension, and hyperlipidemia. Serum vitamin D levels were significantly lower in the OSAS group than in the control group (22.4+/-7.5 ng/mL vs. 31+/-7.9 ng/mL, respectively; p< 0.001), whereas PTH levels were significantly higher in the OSAS group than in the control group (56.6+/-18.8 pg/mL vs. 42.3+/-17.6 pg/mL, respectively; p< 0.001). On subgroup analysis, vitamin D levels were significantly lower in patients with severe OSAS than in those with mild/moderate OSAS (p< 0.001). Vitamin D levels significantly correlated with the apnea-hypopnea index, oxygen desaturation index, PTH levels, and mean oxygen saturation. Conclusion: These results showed that OSAS is associated with low vitamin D levels and elevated PTH levels, which is related severity of OSAS.