Exclusion criteria are: the presence of cardiovascular, liver, biliary or renal disease; hyperlipidemia; uncontrolled high blood pressure; endocrinological disorder; oligomenorrhea (menstrual intervals of more than 6 weeks) or amenorrhea (no menstruation for at least 3 months); pregnancy; a history of thromboembolic disorder; any malignancy; and intake of hormonal contraception the last two months prior to the study.