Effects of a monophasic combined oral contraceptive containing nomegestrol acetate and 17ß-oestradiol in comparison to one containing levonorgestrel and ethinylestradiol on markers of endocrine function.

OBJECTIVES: To compare the effects of two monophasic combined oral contraceptives, containing either nomegestrol acetate/17ß-oestradiol (NOMAC/E2) or levonorgestrel/ ethinylestradiol (LNG/EE) on endocrine function, androgens, and sex hormone-binding globulin (SHBG). METHODS: Randomised, open-label, multi-centre trial involving 121 healthy women, aged 18-50 years old. Participants received NOMAC/E2 (2.5 mg/1.5 mg) in a 24/4-day regimen (n=60) or LNG/EE (150 µg/30 µg) in a 21/7-day regimen (n=61) for six cycles. The primary outcome was the change from baseline to cycle 6 in markers of adrenal and thyroid function, androgens, and SHBG. RESULTS: Total cortisol, corticosteroid-binding globulin (CBG), and thyroxine-binding globulin (TBG) increased from baseline in both groups, with significantly greater increases in the LNG/EE group. No relevant changes from baseline or differences between the groups were observed for thyroid-stimulating hormone (TSH) and free thyroxine (T4). Androgens and androgen precursors decreased from baseline in both groups, with significantly greater decreases in the LNG/EE group (except for free testosterone). A greater increase in SHBG was observed with NOMAC/E2 than with LNG/EE. CONCLUSIONS: NOMAC/E2 has significantly less influence on markers of adrenal and thyroid function and androgens than LNG/EE. The clinical relevance of these findings requires further study.