Testosterone levels in obese male patients with obstructive sleep apnea syndrome: relation to oxygen desaturation, body weight, fat distribution and the metabolic parameters

To investigate the impact of obstructive sleep apnea syndrome (OSAS) on testosterone levels and on the main parameters of the metabolic syndrome in abdominally obese men, 15 male subjects with abdominal obesity phenotype and polysomnographic diagnosis of OSAS (OB-OSAS) and 15 controls matched for age and anthropometric parameters (OB) were investigated. Anthropometry, SHBG, sex hormones and several parameters of the metabolic syndrome were measured. Only subjects with an Epworth Sleepiness Score greater than 10 underwent a polysomnographic study with calculation of the number of desaturation rates per sleeping hour (ODI), the minimal oxygen saturation during each desaturation episode (minSaO(2)) and the mean minimal arterial oxygen saturation for the whole night period (MminSaO(2)). Both total and free testosterone levels were lower in OB-OSAS than in OB patients. A negative correlation between polysomnographic parameters (ODI, minSaO(2) and MminSaO(2)) and testosterone levels was found. The relationship between total and free testosterone and ODI persisted after adjusting for body mass index (BMI) and waist (W) values. Triglyceride and uric acid levels were significantly higher in OB-OSAS than in OB patients. A negative correlation between testosterone and acid uric level and a positive correlation between testosterone and HDL-cholesterol level was found, regardless of BMI and W circumference, particularly in the OB-OSAS group. Our study suggests that, in patients with obesity and OSAS, the severity of hypoxia during sleeping hours may be an additional factor in reducing testosterone levels, regardless of BMI and abdominal fatness. This may contribute in worsening metabolic abnormalities which, in men with OSAS, exceed those expected on the basis of degree of obesity and pattern of fat distribution.