Pantarhei Bioscience BV

This is an open study in 50 young, healthy, female volunteers. Women who want to participate and who are using hormonal contraception stop using their hormonal contraceptive and wait for their first spontaneous menstruation (i.e. after a wash-out cycle). Women who do not use hormonal contraception wait for their next menstruation. From the 9th day after start of the menstruation onwards follicle growth will be monitored by ultrasonography until ovulation occurs or until day 24 after start of their menses. Women who ovulate within 24 days after start of their menses will be eligible to participate and will be stratified in one of 4 groups: 10 mg estetrol (E4) alone, 20 mg E4 alone, 20 mg E4 combined with 150 mcg desogestrel and 20 mg E4 combined with 200 mg progesterone. The subjects will be treated for 28 days. Treatment will start on the first day of their menses after the pre-treatment cycle.
During the study period (28 days) the activity of the hypothalamic-pituitary-ovarian (HPO) axis will be investigated by measuring follicular development using ultrasonography and by determining serum concentrations of Follicle Stimulating Hormone (FSH), Luteinising Hormone (LH), estradiol (E2) and Progesterone (P).