Ultrasonographic monitoring of ovarian follicles in women using norethisterone for contraception

Objective: The purpose of this study was to examine the effect of intranasal and oral norethisterone (NET) on ovarian folliculogenesis. Methods: Sixteen healthy, sterilized women with regular menstrual cycles were recruited to the study. NET 300 mu g per day was administered orally (n = 8) or intranasally (n = 8) for two consecutive menstrual cycles. Serial pelvic ultrasonography was performed to monitor ovarian follicular growth. Results: Ultrasonographic evidence of normal follicular growth and ovulation was observed in 10 cycles whilst 22 cycles were anovulatory. Formation of follicular cysts was seen in 14 cycles, 13 of which were anovulatory and in one ovulation was observed in the opposite ovary. The size of the cysts varied between 27 and 44 mm. The cysts disappeared when NET treatment was discontinued. A positive correlation between cyst size and estradiol levels was observed with intranasal NET in 50% of cyst cycles. In three cycles, although normal follicular growth and endocrine profile were observed, the follicles failed to rupture. These were classified as luteinized unruptured follicles. Immature follicles <10 mm were seen in six cycles. Conclusion: The study showed that NET administered either orally or intranasally evidently disturbs normal follicular growth and rupture.