Trinidad Express / Injecting men with two different hormones every eight weeks suppressed their sperm production enough to act as birth control, according to a new study. The study had to be stopped due to safety concerns, however. An independent safety board found that side effects, including depression and other mood disorders, outweighed the potential benefits of the injections. “Researchers are trying to identify a hormonal male contraceptive that is effective, reversible, safe, acceptable, affordable, and available,” the study’s technical team wrote in an e-mail to Reuters Health. The researchers, led by Dr Hermann Behre of Martin Luther University of Halle-Wittenberg in Germany, recruited 320 healthy men ages 18 to 45 from several countries. All had been in monogamous relationships for at least a year with women between 18 and 38 years old. The couples did not want to get pregnant within the next two years. Every eight weeks, the men received injections of long-acting testosterone and progestin. Suppressing sperm count “Giving testosterone in high doses suppresses sperm production in the male reproductive organ or the testes over several weeks,” according to the researchers. Adding another hormone, “usually a progestin, helps increase the suppression of sperm production to lower levels, in more numbers of men,” they continued. “It will also help to sustain it, so that injections may be given less frequently.” In 274 men, or 86 per cent, sperm counts dropped to the target of less than 1 million per millilitre of semen after 24 weeks. Normal sperm counts range from 40 to 300 million per millilitre, according to the National Infertility Association. Four pregnancies occurred among 266 couples over 56 weeks of follow up, the researchers report in the Journal of Clinical Endocrinology and Metabolism. Nearly 1,500 adverse events were reported during the study. About 39 per cent were not related to the injections, however. In addition to safety concerns, there are other unknowns about this approach to birth control, said Dr Landon Trost, who is head of andrology and male infertility at the Mayo Clinic in Rochester, Minnesota. For example, in most participants, sperm production rebounded after the injections stopped—but the study only included men with healthy sperm counts.