Endocrine Abstracts

Background: Obstructive sleep apnoea syndrome (OSAS) is common; disproportionately affecting the overweight and obese. Continuous positive airway pressure (CPAP) is the first-line treatment for moderate to severe OSAS. Clinical equipoise exists as to whether CPAP treatment directly affects pituitary-gonadal hormone synthesis.

Study Aim: This study aimed to determine the effect of CPAP treatment on gonadotropins, prolactin, sex-hormone binding-globulin (SHBG), total testosterone (TT) and calculated free testosterone (cFT) in newly diagnosed male OSAS patients. 2018 European Health Research Compliance. Ethical approval was sought from the Bon Secours Health System Clinical Ethics Committee (CEC) and granted on the 08/03/2019. All participants in the research gave informed consent, obtained in accordance with guidelines provided by the CEC, Trinity College Dublin and the Royal College of Surgeons Ireland.

Methods: OSAS was diagnosed via gold standard in-house polysomnography studies. Participants provided venous blood samples before and twice after (first night CPAP, n=25 and 3 months CPAP, n=13) commencing CPAP treatment. At each time-point, concentrations of TT, SHBG, prolactin and gonadotropins were measured. In total, 53 males with a diagnosis of OSAS confirmed by polysomnography were prospectively enrolled to this study.

Results: Hypogonadism in the cohort was low (n= 2). Hyperprolactinaemia was prevalent (n= 25). TT and cFT were significantly negatively correlated with obesity. cFT was correlated with OSAS severity, but not TT. Significant reductions were observed in TT (pre 16.6 nmol/l, post 13.5 nmol/l, P= 0.003), cFT (pre 332 pmol/l, post 250 pmol/l, P= 0.001) and prolactin (pre 360 mIU/l, post 225 mIU/l, P= 0.006) after 3-months of CPAP (n=13). No significant change was observed in other pituitary hormones or SHBG.

Conclusions: The prevalence of hypogonadism is low in this cohort. CPAP treatment reduced testosterone and prolactin in eugonadal males with OSAS. The benefits of CPAP treatment for OSAS may be independent to change in serum testosterone levels. Hypogonadal OSAS patients should be managed via strategies other than CPAP alone.