With hormonal male contraception likely to be available in the near future, results of a study in this week's issue of THE LANCET highlight how such contraception is reversible within a few months.

Currently available male contraceptive methods (condoms, withdrawal, and vasectomy) are not acceptable to many couples because they are either not sufficiently reliable or not easily reversible. In a similar way to ovulation suppression by hormone treatment in women, sperm production can be fully inhibited by androgen or androgen-progestagen treatment combinations in men. With such hormone treatment, azoospermia (no sperm in ejaculate) or severe oligozoospermia (less than 3 million sperm per mL of semen), which is sufficient for contraceptive purposes, can be achieved. Currently, a large phase III study with an androgen treatment and a large, multicentre phase II study of androgen-progestagen combinations are being completed in China and Europe, respectively.

Peter Liu from the Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center (LA BioMed), who is currently located at the ANZAC Research Institute, University of Sydney, Australia, and colleagues analysed data from individual participants in 30 studies published in 1990-2005, in which sperm output was monitored every month until recovery. The primary outcome was the time for the sperm concentration to recover to a threshold of 20 million per mL, an indicator of fertility.

Data were available for around 1500 men. The average time for sperm recovery to 20 million/mL was 3•4 months. Various factors were associated with higher rates of recovery including older age, Asian origin, shorter treatment duration, and higher sperm concentrations at baseline. Although these factors modulated the speed of recovery, spermatogenesis recovered to levels compatible with fertility in all men.

Dr Liu and colleagues comment: "Our data provide strong assurance that the previously described efficacy of hormonal male contraceptives is coupled with highly predictable recovery to semen characteristics that are compatible with fertility. These findings thereby increase the promise of new contraceptive drugs allowing men to share more fairly the satisfaction and burden of family planning."

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Contacts: Dr Peter Y Liu, Department of Andrology, Concord Hospital and ANZAC Research Institute, University of Sydney, Sydney 2139, NSW, Australia; T) + 61 2 9767 9100; pliu@mail.usyd.edu.au, or Professor Christina Wang, General Clinical Research Center, Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, 90509, Torrance, CA, USA; 310 222 2503; wang@labiomed.org

The Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center (LA BioMed) is one of the largest independent, not-for-profit biomedical research institutes in Los Angeles County. Affiliated with both the David Geffen School of Medicine at UCLA and the Harbor-UCLA Medical Center, the Institute has an annual budget of over $72 million and currently supports more than 1,000 research studies in areas such as cardiology, emerging infections, cancer, women's health, reproductive health, vaccine research, respiratory physiology, neonatology, molecular biology, and genetics.