Hapangama D, Glasier A F, Baird D T
Contraceptive Development Network, Department of Reproductive and Development Sciences, The University of Edinburgh, Centre of Reproductive Biology, EH3 9ET, Edinburgh, Scotland, United Kingdom.
Contraception. 2001 Mar;63(3):123-9. doi: 10.1016/s0010-7824(01)00186-x.
Levonorgestrel (LNG) 0.75 mg administered 12 h apart within 72 h of unprotected coitus, is an established method of emergency contraception (EC). The mechanism of action of LNG used in this manner is unknown. We administered LNG 0.75 mg twice immediately before ovulation, to test the hypothesis that LNG acts as an emergency contraceptive by abolishing the pre-ovulatory lutenizing hormone (LH) surge and thereby delaying ovulation. Twelve women took LNG on or before the day of the first significant rise in urinary LH in 12 cycles. In four women, the LH peak and the onset of next menses were significantly delayed (delay of 16.8 days (SD +/- 8.7) from the day of mean LH peak in placebo cycles). One woman did not ovulate at all, despite a normal LH peak and cycle length. In the remaining eight women, LNG did not affect ovulation or the cycle length, but the length of the luteal phase and the total luteal phase LH concentrations were significantly reduced. We suggest that LNG acts as an emergency contraceptive by other mechanisms as well as delaying the LH surge and interfering with ovulation.
左炔诺孕酮（LNG）0.75毫克在无保护性交72小时内每隔12小时给药一次，是一种既定的紧急避孕（EC）方法。以这种方式使用的LNG的作用机制尚不清楚。我们在排卵前立即给予0.75毫克LNG两次，以检验LNG通过消除排卵前促黄体生成素（LH）高峰从而延迟排卵来发挥紧急避孕作用的假设。12名女性在12个周期中于尿LH首次显著升高之日或之前服用LNG。在4名女性中，LH高峰和下次月经来潮明显延迟（比安慰剂周期中平均LH高峰日延迟16.8天（标准差±8.7））。1名女性尽管LH高峰和周期长度正常，但根本没有排卵。在其余8名女性中，LNG未影响排卵或周期长度，但黄体期长度和黄体期LH总浓度显著降低。我们认为，LNG除了延迟LH高峰和干扰排卵外，还通过其他机制发挥紧急避孕作用。
