SHBG and obstructive sleep apnea syndrome: In the present meta-analysis, excepting Grunstein and colleague [29] early in 1989 suggested that CPAP can improve testosterone in 43 OSA men, the remaining 6 studies (including 2 RCTs) with 8 cohorts elucidated that there is no influence of CPAP on serum total testosterone, free testosterone and SHBG in men with OSA.