Ratsula K, Toivonen J, Lähteenmäki P, Luukkainen T
Department of Medical Chemistry, University of Helsinki, Finland.
Contraception. 1989 Feb;39(2):195-204. doi: 10.1016/s0010-7824(89)80008-3.
Levonorgestrel, estradiol and progesterone plasma concentrations were measured over four years of use of a 20 micrograms/day levonorgestrel-releasing intracervical device (LNG-ICD). The mean levonorgestrel concentration showed a slight decline, being 142 + 46 (SD) pg/ml in the third month and 81 +/- 22 pg/ml in the 48th month of LNG-ICD use. However, considerable interindividual variation in levonorgestrel plasma levels between study subjects was observed. In 77% of the monitored cycles, ovulation or a luteinized follicle was observed when judged by a plasma progesterone elevation of over 5 ng/ml. Some follicular function was also noted in anovulatory cycles. Inhibition of ovulatory ovarian function is not the mode of contraceptive action of the LNG-ICD.
在使用每日释放20微克左炔诺孕酮的宫颈内装置（LNG-ICD）的四年期间，对血浆中的左炔诺孕酮、雌二醇和孕酮浓度进行了测量。左炔诺孕酮的平均浓度略有下降，在使用LNG-ICD的第三个月为142 + 46（标准差）皮克/毫升，在第48个月为81 +/- 22皮克/毫升。然而，研究对象之间左炔诺孕酮血浆水平存在相当大的个体差异。在77%的监测周期中，当血浆孕酮升高超过5纳克/毫升时，观察到排卵或黄素化卵泡。在无排卵周期中也注意到一些卵泡功能。抑制排卵的卵巢功能不是LNG-ICD的避孕作用方式。
