The effects of levonorgestrel on various sperm functions

Department of Obstetrics and Gynaecology, The University of Hong Kong, Hong Kong, China.
Contraception (Impact Factor: 2.34). 01/2003; 66(6):453-7. DOI: 10.1016/S0010-7824(02)00408-0
Source: PubMed


Two doses of 750-microg levonorgestrel at 12 h apart is one of the regimens for emergency contraception. The mechanism of action of this regimen is not fully known. We investigated whether levonorgestrel influences sperm functions and thereby, exerts contraceptive activity. The motility, acrosome reaction, zona binding capacity, and oocyte fusion capacity of human spermatozoa treated with 1, 10, and 100 ng/mL levonorgestrel for 3 h were evaluated. Levonorgestrel decreased the curvilinear velocity of the treated spermatozoa in a dose-dependent manner. A significant decrease in straight-line velocity, average path velocity and linearity were also found with 100 ng/mL levonorgestrel treatment. This concentration of levonorgestrel, but not others, also marginally decreased (p = 0.045) the zona binding capacity of the treated spermatozoa. The steroid had no effect on acrosome reaction but had a dose-dependent inhibition on spermatozoa-oocyte fusion. These data show that levonorgestrel affects sperm function only at high concentration and the contribution of these effects to emergency contraception is unlikely to be significant.

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    • "It inhibits spermatozoa–oocyte fusion as well as decreases the curvilinear velocity of spermatozoa only at high concentration, and the contribution of these effects to EC is unlikely to be significant [38]. In vitro data indicate that LNG or mifepristone in doses relevant for EC has no direct effect on sperm function [38] [40] [41]. The observations described by Kesserü et al. [42] on LNG effects on cervical and intrauterine mucus are probably of importance when LNG is used as a regular contraceptive but unlikely to be the main mechanism of action of LNG used for EC since sperm can be retrieved from the fallopian tube within 5 min after insemination of semen in the vagina [42] [43]. "
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    ABSTRACT: Concerns regarding the mechanisms of action of emergency contraception (EC) create major barriers to widespread use and could also lead to incorrect use of EC and overestimation of its effectiveness. While the copper intrauterine device (Cu-IUD) is the most effective method available for EC, the hormonal methods are frequently considered to be more convenient and acceptable. Today, the most commonly used method for hormonal EC is levonorgestrel (LNG). More recently, the progesterone receptor modulator ulipristal acetate (UPA) has been shown to be more effective than LNG to prevent an unwanted pregnancy. The main mechanism of action of both LNG and UPA for EC is delaying or inhibiting ovulation. However, UPA appears to have a direct inhibitory effect on follicular rupture which allows it to be effective even when administered shortly before ovulation, a time period when use of LNG is no longer effective. The main mechanism of action of the Cu-IUD is to prevent fertilization through the effect of Cu ions on sperm function. In addition, if fertilization has already occurred, Cu ions influence the female reproductive tract and prevent endometrial receptivity. Based on this review of the published literature, it can be concluded that existing methods used today for EC act mainly through inhibition of ovulation or prevention of fertilization. An additional effect on the endometrium as occurs for the Cu-IUD, but not for the hormonal alternatives, seems to increase the efficacy of the method.
    Full-text · Article · Oct 2012 · Contraception
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    • "However, when the spermatozoa were exposed to LNG concentrations similar to those observed in serum after intake for EC [16], no effect was observed [17]. Additionally, when human spermatozoa were treated in vitro with LNG at doses of 1 ng/mL, 10 ng/mL and 100 ng/mL, representing lower, similar and higher levels than those observed in serum after LNG intake for EC, motility was found to be impaired with the 10 ng/mL dose; however, no effect was observed on the AR [7]. Otherwise, administration of 1.5 mg of LNG to sterilized women at different moments following coitus failed to have any effect on the quality of cervical mucus, sperm penetration to the uterine cavity or AR [18]. "
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    ABSTRACT: The mechanism of action of levonorgestrel (LNG) as emergency contraception (EC) remains a subject of debate and its effect on sperm function has been only partially explained. The aim of this study was to assess whether LNG at a similar dose to those found in serum following oral intake for EC could affect spermatozoa when exposed to human fallopian tubes in vitro. Fifteen mini-laparotomies were performed, the side on which ovulation occurred was recorded, and both tubes were removed and perfused with a suspension containing 1 × 10(6) motile spermatozoa, with or without LNG. Following 4-hour incubation, the tubes were sectioned to separate the isthmus and the ampulla. Each segment was flushed and the material was evaluated to quantify the number of motile sperm, the number of spermatozoa adhering to the oviductal epithelium and the acrosome reaction (AR) rate. The addition of LNG did not significantly alter the number of recovered motile spermatozoa either at the isthmus or at the ampulla, nor did it have any effect on the number of recovered spermatozoa adhered to the human tubal epithelium. Furthermore, LNG did not affect the AR rate. No significant differences were found even when the side on which ovulation occurred was taken into account. In a similar dose to that observed in serum following oral intake for EC, LNG had no effect on the number of motile spermatozoa recovered from the human fallopian tubes in vitro, on their adhesion to the tubal epithelium, distribution or AR rate. The possible effect of LNG as EC on sperm function remains poorly understood.
    Full-text · Article · Jan 2012 · Reproductive Biology and Endocrinology
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