Kinin-enhancing drugs for unexplained subfertility in men
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abstract
BACKGROUND: Oligo-astheno-teratospermia (sperm of low concentration, reduced motility and increased abnormal morphology) of unknown cause is common and the need for treatment is felt by patients and doctors alike. As a result, a variety of empirical, non-specific treatments have been used in an attempt to improve semen characteristics and fertility. One suggested treatment for idiopathic oligo- and/or asthenospermia is the administration of kallikrein (kallidinogenase), a kinin-releasing enzyme (or kininogenase). The kinin biological system is complex and involves kininogen (the substrate), kininogenases (the activating enzymes), kinins (the effectors) and kininases (the inactivating enzymes). All four components of the kinin system have been found in the genitalia and in semen. Kallikrein releases 2 major kinins, kallidin and bradykinin, from seminal plasma kininogens. Activated kinins in semen affect sperm motility and metabolism. In vitro addition of kallikrein to semen has been shown to have a positive effect on sperm motility, sperm velocity, cervical mucus penetration, penetration of zona-free hamster eggs and post-thaw survival and motility rate after semen cryopreservation. The latter observation, however, was not confirmed in a more recent comparison of motility stimulants for cryopreserved semen using computerised sperm motion analysis. In vitro treatment of semen with kallikrein has been employed in a clinical context during sperm preparation prior to insemination. Although the kinin system may also be involved in the regulation of spermatogenesis in vivo, a clear mechanism of action is missing. Multiple suggestions on how an increase in kinin levels in the genital tract influences spermatogenesis at the testicular levels have been made by various authors. OBJECTIVES: To determine whether treatment of the male with drugs enhancing kinin levles increases pregnancy rates among couples where failure to conceive has been attributed to idiopathic oligo- and/or asthenospermia. Effects on sperm parameters and sex hormones were studied as secondary outcomes. SEARCH STRATEGY: The Cochrane Subfertility Review Group specialised register of controlled trials was searched". SELECTION CRITERIA: SIxteen RCTs on the therapeutic use of androgens (clomiphene citrate or tamoxifen) in subfertile men were identified. Six trials were excluded. DATA COLLECTION AND ANALYSIS: Methodological characteristics of trials Baseline characteristics of the studied groups Outcomes: Pregnancy rates, semen parameters (sperm concentration, motility and morphology), endocrinology (serum FSH, testosterone and oestradiol)
