Okewole Idris A, Arowojolu Ayodele O, Odusoga Okanlawon L, Oloyede Olufemi A, Adeleye Olufemi A, Salu Jide, Dada Olukayode A
Department of Obstetrics and Gynaecology, Olabisi Onabanjo University Teaching Hospital, Sagamu, P.M.B. 2001, Sagamu, Ogun State, Nigeria.
Contraception. 2007 May;75(5):372-7. doi: 10.1016/j.contraception.2007.01.019. Epub 2007 Mar 29.
Levonorgestrel (LNG) 1.5 mg administered within 72 h of unprotected coitus is an established method of emergency contraception. Currently, there is some, although incomplete, knowledge about the mechanism of action.
We administered 1.5 mg LNG peri-ovulatory to determine the effects on serum gonadotrophins, estradiol and progesterone levels. Fourteen women were studied in a pretreatment and treatment cycle; eight women (Group A) took LNG 3 days before the expected day of ovulation, while 6 (Group B) took LNG a day before the expected day of ovulation.
The women in Group A had a significant delay in their LH peak and onset of the next menses compared with their pretreatment cycles (26.4 vs. 39.1 days, p<.05). Those in Group B had no significant changes in the endocrine parameters but there was a significant shortening of the mean cycle length in comparison with their pretreatment cycles (25.1 vs. 20.2 days).
Levonorgestrel 1.5 mg acts as an emergency contraception by delaying the LH surge and interfering with ovulation. It may also disrupt corpus luteum formation causing premature luteinization of unruptured follicles.
在无保护性交72小时内服用1.5毫克左炔诺孕酮（LNG）是一种既定的紧急避孕方法。目前，虽然对其作用机制的了解并不完整，但已有一些相关认识。
我们在排卵期前后给予1.5毫克LNG，以确定其对血清促性腺激素、雌二醇和孕酮水平的影响。对14名女性进行了预处理周期和治疗周期的研究；8名女性（A组）在预计排卵日的前3天服用LNG，而6名女性（B组）在预计排卵日的前1天服用LNG。
与预处理周期相比，A组女性的促黄体生成素（LH）峰值和下次月经来潮时间显著延迟（26.4天对39.1天，p<0.05）。B组女性的内分泌参数无显著变化，但与预处理周期相比，平均周期长度显著缩短（25.1天对20.2天）。
1.5毫克左炔诺孕酮通过延迟LH峰和干扰排卵起到紧急避孕作用。它还可能破坏黄体形成，导致未破裂卵泡过早黄素化。
