An experimental type of male birth control that involves hormone injections to lower men’s sperm count has been found to be nearly as effective as female contraceptive pills at preventing pregnancy, according to a new trial study published last week in the Journal of Clinical Endocrinology & Metabolism. Male participants in the study were given a series of hormone shots that were shown to dramatically lower their sperm level by “switching off” the male reproductive system. However, the trial had to be stopped early because of the high rate of reported unpleasant side effects, including depression and other mood disorders.
Whereas hormonal birth control methods for women—including pills, patches, rings and intrauterine devices (IUDs)—have been available for years, men’s options for controlling their fertility have remained limited to condoms and withdrawal during intercourse, which are less effective than hormonal birth control. Men can also have a vasectomy, but this method is invasive and often not reversible.
And although some previous studies have looked at the effectiveness of hormonal birth control in men, efforts to develop a commercial product have stalled—until now.
The new study involved 320 healthy males, ages 18 to 45, from seven different countries. All participants were in monogamous, long-term relationships with women, and none of the couples had a condition that would prevent them from getting pregnant.
Every eight weeks for a year, the males in the study received injections of two hormones: a long-acting form of progestogen designed to act on the pituitary gland to switch off sperm production, and a form of testosterone to offset a drop in the male hormone triggered by the progestotogen. Both hormones suppress sperm production, and they are used together in order to reduce side effects.
During the first 26 weeks of the study, couples were told to use other forms of nonhormonal birth control in addition to receiving the injections while the men’s sperm counts lowered. After the 26-week mark, the couples were told to rely solely on the shots for contraception.
Results from the study found that the shots worked to effectively suppress sperm production in 96% of the male participants. Furthermore, only four pregnancies occurred among partners of the 274 men, which translates to a pregnancy rate of about 1.5 pregnancies per 100 people in the study.
The overall failure rate of the shots was 7.5%, indicating a similar level of efficacy as female contraceptive pills. According to the Centers for Disease Control and Prevention, about 9% of women who use birth control pills become pregnant during a given year.
After participants stopped receiving the shot injections, about 95% of the men saw their sperm count return to normal levels within a year. Richard Anderson, a professor of clinical reproductive science and author of the study, said: “If you’re comparing it to other reversible male methods, it’s far better than the condom and it puts it in the same ballpark as the pill.”
However, scientists stopped enrolling new participants into the study in 2011 due to the rate of reported negative side-effects, including acne, pain at the site of the injection, increased sex drive, depression and mood swings.
Despite the side effects, at the end of the trial more than 75% of the men in the study said they would be willing to use this method of contraception if it became available in the future. The scientists said it might be possible to reduce the side-effects by changing the dose of hormones or the way they are delivered.
While the promising results from the study have the potential to pave the way for men and women to share equal responsibility for birth control in the future, more research is needed before this method of contraception could become available to men, according to study co-author Dr. Mario Philip Reyes Festin. “Although the injections were effective in reducing the rate of pregnancy, the combination of hormones needs to be studied more to consider a good balance between efficacy and safety,” Festin said.
The study was funded by the United Nations/World Health Organization, and the nonprofit organization CONRAD (Contraception Research and Development), using funds from the Bill & Melinda Gates Foundation and the U.S. Agency for International Development.