Male Birth Control Pill Blocks 'Sperm Hormones,' But Will It Work?The largest clinical trial to date on hormonal male contraception is slated to begin in the first half ofand aims hormonap enroll more than couples in six countries around the world. The experimental gel contains a synthetic progestin called nestorone—which blocks the testes from making enough testosterone to produce sperm—and a synthetic testosterone, which will counteract subsequent psychiatric side effects of steroids imbalances. A different combination of progestin and testosterone was previously tested in a smaller clinical trial published last year, in which men got hormone injections male hormonal contraceptive pill two months. Min Lee, program officer on the upcoming trial and a researcher hormonak the National Hormoal of Child Health and Human Development, says that the contraceptive gel contains male hormonal contraceptive pill less synthetic testosterone than the injectable formula did—which will hopefully prevent many of those problems. Over the last few years, he says, contraceeptive at the NIH and the Population Council have reformulated the gels into one product. The women in the trial will also use a form of female birth control for about the first four months their male partners are using the contraceptive gel. The gel has male hormonal contraceptive pill shown to suppress sperm levels for about 72 hours.
Male Birth Control Pill Blocks 'Sperm Hormones,' But Will It Work?
Then, after lab testing indicates their sperm counts have been suppressed to extremely low levels which could take two to three months , the couples will be tracked for a year while they use the gel as their lone form of contraception. The project, led by the U. National Institutes of Health and the Population Council , is expected to begin signing up couples in early , along with collaborating partners at nine locations in the U.
Once these sites get institutional and national review board sign-offs, the study will test whether the latest version of a hormonal birth control system for men can overcome the myriad obstacles that have sidelined earlier efforts. Just last year a clinical trial of a hormonal male contraceptive shot was shut down after some participants suffered concerning side effects.
Yet vasectomy requires surgery and is not always reversible, condoms are often used inconsistently and withdrawal is unreliable. It introduces into the bloodstream a combination of the hormones progestin—which suppresses sperm creation in the body—and testosterone. An earlier version of this approach appeared promising in a small, six-month pilot trial, in which gel application reduced sperm production while maintaining healthy testosterone levels.
In about 89 percent of users, sperm counts were reduced to one million per milliliter or less a point typically considered to indicate successful sperm suppression. By way of comparison, among women the typical failure rate for oral contraceptives hovers around 9 percent due to noncompliance and imperfect use, putting it in striking distance of the male gel sperm-suppression numbers.
Researchers have been trying for decades to deliver on male hormonal birth control. But in practice it is far more complex. In women the Pill essentially tricks the body into acting as though it already is pregnant, making it temporarily infertile. Among men a hormonal contraceptive could inhibit testosterone production in the testes, reducing sperm levels. It would, however, simultaneously decrease testosterone in the blood—which would cause intolerable side effects that include impeded ejaculation as well as altered libido and muscle mass.
So the biggest hurdle to developing a male contraceptive pill has been the difficulty of providing replacement testosterone in oral form, Blithe says. The hormone would leave the body too quickly, rendering such a pill impractical because men would have to take it too many times a day. Last year a study headed by the World Health Organization and a reproductive health institute called CONRAD reported a hormone injection suppressing sperm production in men was about 96 percent effective.
The NIH had no role in that project. The shot—which men needed to receive every two months—included testosterone and progestin. Twenty of the participants in that trial dropped out citing problems such as mood changes, erectile dysfunction or pain.
Yet even with those side effects there was still a lot of interest in the product. The remaining trial participants mostly praised the injections and said they were still interested in continuing to use them, even after the scientists brought the test to a halt. Blithe and her team expect their approach to be largely free of the side effects seen with the injection, because the daily gel applications would release the hormones more consistently.
The most common side effect would likely be acne, according to Blithe. In the pilot work a small number of men reported acne, increased appetite, decreased libido, mood swings, headaches or insomnia—side effects also seen among women who take oral contraception. Unlike the gel, Blithe notes, the shots contained large levels of hormones that were introduced every eight weeks and then decreased in the body at varying rates until the next injection, likely contributing to the negative side effects.
Colvard, who is not involved with the gel effort, says it seems promising. For now his group is analyzing links between some of the mood swings seen in its study and hormonal fluctuations in the weeks following the injections, he says.
Aaron Hamlin, executive director of the Male Contraception Initiative—a nonprofit organization that funds and advocates for nonhormonal male birth control—says a gel that continuously delivers a hormone makes sense.
But he cautions that reversible nonhormonal methods—those that block sperm from fertilizing eggs without introducing hormones into the body—would still be preferable, because any hormone-based intervention would be subject to months-long delays between when a man starts using it and when his sperm production is sufficiently suppressed. The body, Hamlin notes, must also clear a reserve of sperm that existed before the treatment began.
He is also concerned about the side effects of hormonal birth control, and the consideration that it may not adequately suppress sperm count in all men. Yet nonhormonal methods beyond vasectomies and condoms that seek to impede egg fertilization have yet to reach the same level of testing in men. Researchers published promising results with Vasalgel in rabbits and monkeys earlier this year but its maker says it has no timeline for human clinical trials.
Yet another product, Gendarussa, was created by researchers at Airlangga University in Indonesia. Gendarussa has, however, received clearance from the Indonesian equivalent of the U. Despite their different methods, all these products have one thing in common: They are designed to fill the massive need for more contraceptive options.
In , 40 percent of all pregnancies worldwide were unintended, according to the Guttmacher Institute. New forms of birth control, reproductive specialists hope, could help slash those numbers.
Dina Fine Maron is an award-winning journalist and an editor at Scientific American covering medicine and health. She is based in Washington, D. Sign up for our email newsletter.