Ovarian function during low-dose oral contraceptive use

Abstract

Lowering the total steroid dose in modern oral contraceptives (OCs) has been connected with a higher incidence of ovarian follicle and cyst formation. To investigate the presence of ovarian follicles and cysts by means of vaginal ultrasonography and serum hormone determinations during use of two low-dose OCs, 65 volunteers were randomized to receive either 20 micrograms ethinylestradiol (EE) + 150 micrograms desogestrel (group A) or 35 micrograms EE + 250 micrograms norgestimate (group B) for a 2-month study period. At baseline, 39% of women in group A and 31% in group B exhibited at least one follicle < 35 mm in diameter. By the end of the second treatment cycle, the frequency of these follicles had decreased to 14% in each group. Only one subject in the higher estrogen group developed an ovarian cyst > 35 mm. One subject in each group demonstrated hormone levels characteristic of ovulation; no pregnancy occurred in either group. The 20 micrograms EE preparation was not found to lead more often to ovarian follicles or cysts when compared with a 35 micrograms EE preparation, possibly because of the type and dose of the progestogen used.

PIP: In Austria, health workers randomly allocated 28 women to the group using the low-dose oral contraceptive (OC) Mercilon (20 mcg ethinyl estradiol [EE] + 150 mcg desogestrel) and 35 women to the group using the low-dose OC Cilest (35 mcg EE + 250 mcg norgestimate). No one had used OCs for at least one month before the study. Clinicians used vaginal ultrasonography and serum hormone levels to learn the degree of ovarian suppression during use of these two low-dose OCs by looking for ovarian follicles and cysts. Before beginning to use the OCs, 39% of women in the Mercilon group and 31% of those in the Cilest group had at least one ovarian follicle. By the second treatment cycle, the frequency of ovarian follicles (35 mm) had fallen significantly to 14% in both groups as compared to baseline (p 0.05). No one in the Mercilon group developed a follicle larger than 35 mm in diameter that remained for more than 4 weeks (i.e., ovarian cyst). One woman in the Cilest group did develop an ovarian cyst (46 mm), however. It appeared during the pill-free week after the first pill cycle and steadily decreased to 40 mm during the second pill cycle. One woman in each group had hormone levels indicative of ovulation. No one in either group became pregnant. These findings suggest that the type and dose of progestogen in the Mercilon OC (desogestrel) were responsible for the lower frequency of ovarian follicles and cysts in the lower-dose OC group than that in the higher-dose OC.