A comparative randomized trial on the impact of two low-dose oral contraceptives on ovarian activity, cervical permeability, and endometrial receptivity.

In a double-blind randomized study, the suppression of ovarian activity and anti-conceptive effects on the cervix and endometrium were assessed during administration of two low-dose monophasic oral contraceptives (20 micrograms ethinyl estradiol [EE], 500 micrograms norethisterone--Eve 20 [Grünenthal, Aachen, Germany]; 20 micrograms EE, 150 micrograms desogestrel --Lovelle [Organon, Munich, Germany]). One hundred eighteen healthy women (ages: 18-35 years) were studied in 10 investigation centers during medication with either Eve 20 (n = 59) or Lovelle (n = 59). During three treatment cycles, ovarian activity was evaluated by sonographic determination of follicle-like structures (FLS) and by simultaneous assessment of serum endocrine profiles (gonadotropins LH and FSH, ovarian steroids estradiol [E2] and progesterone [P]). While on either treatment, no ovarian activity (as judged by no FLS and/or reduced sex steroid levels) was found in 90.8% (Eve 20) and 97.2% (Lovelle) of all investigated cycles. Follicular activity or cyst formation were detected in 18 of 173 cycles (Eve 20) and in 5 of 175 cycles (Lovelle), respectively. Gonadotropin levels were suppressed (LH < 6 IU/L, FSH < 8 IU/L) in most treatment cycles (Eve 20 76.6% vs. Lovelle: 84.8%). Serum E2 concentrations exceeding 0.1 nmol/L indicated residual follicular activity in 19.3% (Eve 20) versus 12.2% (Lovelle) of all cycles. An estimated by serum P levels over 5 nmol/L, ovulation had presumably occurred in 4.1% (Eve 20) versus 2.9% (Lovelle) of treatment cycles. However, when the sonographical and endocrinological data were combined, no ovulation was documented in any pill cycle. The quality and quantity of the cervical mucus was found to be minimal in the majority of women. Moreover, the endometrial layer was determined to be low by ultrasound during most pill cycles, indicating equally strong suppressive effects on endometrial receptivity by the two contraceptives. These observations suggest that ovarian activity is suppressed in the majority of cycles during use of low-dose contraceptives. This effect may mainly be medicated by pronounced suppression of serum gonadotropin levels. Strong anti-conceptive effects of these formulations on both cervical permeability and endometrial receptivity are additional factors ensuring the contraceptive efficacy of these formulations.