Recent methodological advances in male hormonal contraception.

Landmark WHO-sponsored trials showed decades ago that male hormonal contraception (MHC) is an effective male-directed contraceptive approach. Considerable progress has been made particularly in the last 5 years, establishing for the first time the reversibility of MHC and its short-term safety. Methodological advances in recent years include the pooling of information and individual-level integrated analysis; the first-time use of centralized semen analysis and fluorescence to detect low sperm concentrations; the establishment of sperm quality reference ranges in fertile men; the measurement of blood steroid concentrations by gas chromatography/mass spectrometry; and the inclusion of placebo groups to delineate clearly possible adverse effects of androgens and progestins in men. We report integrated analyses of factors that are important in predicting suppression and recovery of spermatogenesis after MHC clinical trials for the past 15 years. These are the best data available and will provide guidance and reassurance for the larger-scale Phase III specific regimen efficacy studies that will be required to bring MHC to the population (market).