Increasing Men’s Birth Control Options
Contraception allows couples to prevent pregnancy or better control the timing of when they conceive. The NICHD’s Contraceptive Discovery and Development Branch (CDDB) supports research on new contraceptive methods, for women and for men, to meet the diverse needs of individuals throughout their reproductive lives.
Except for condoms and vasectomies, most contraceptive methods target the female reproductive system to prevent the woman’s egg from being fertilized by the man’s sperm. Accordingly, the burden often falls on women to take the initiative to ensure that contraception is used during sex to prevent pregnancy. However, NICHD research on the mechanisms of sperm development may lead to new contraceptive methods that target the male reproductive system—and so, one day, may bring more options for men and their partners.
We recently consulted Diana Blithe, Ph.D., Program Director for the CDDB’s Male Contraceptive Development Program, to learn more about this research and emerging possibilities for male contraception.
What are the main differences between male and female contraception?
What kinds of male contraception are currently available to the public? How do they work, and how are they delivered?
What kinds of new male contraceptives are currently under research or in development?
Why might someone prefer using one form rather than another?
Are hormonal forms of male contraception easily reversible? Do they have other long-term health effects?
What are the barriers to increased development and promotion of male contraception?
What kind of research still needs to be done on male reproductive behavior, to better understand men’s contraceptive preferences and willingness to use male contraceptives?
What avenues of research in male contraception overall do you find most promising for the future?
Diana Blithe, Ph.D.
- What are the main differences between male and female contraception?
Although women produce one, sometimes two, eggs per month and men produce millions of sperm per ejaculate, the hormonal mechanisms regulating fertility are actually very similar between the sexes. Hormones called gonadotropins stimulate testosterone production in men to develop sperm in the testes and, in women, stimulate estradiol production to develop an egg in the ovary. In both men and women, other hormones called progestins can tell the brain to stop producing gonadotropins, which ultimately will prevent sperm and egg production, respectively, in each sex.
- What kinds of male contraception are currently available to the public? How do they work, and how are they delivered?
Currently, the only contraceptive methods available to men are condoms, withdrawal, or vasectomy.
Small studies have shown that hormonal therapy using progestins normally prescribed for women (DMPA, desogestrel, levonorgestrel, and others) combined with testosterone replacement products for men (including gels, implantable pellets, and injections) can result in effective contraception for men. However, progestins can be taken orally, while testosterone cannot, since it clears the body too quickly to be effective as a once-a-day pill. Thus, it would be difficult to develop a pill that would combine all of the currently available hormonal therapies required for this contraceptive approach to work.
- What kinds of new male contraceptives are currently under research or in development?
The NICHD is currently testing new hormonal methods of contraception for men in clinical trials. The most developed approach is a combination of two gels applied to the skin: one containing a progestin called Nestorone, and the other containing testosterone. Studies show that using these gels once daily will stop sperm production so that conception is completely prevented. Next steps are to combine Nestorone and testosterone into one gel, demonstrate that they do not interfere with one another, and then test the product in couples.
Researchers are also working to develop new synthetic androgens (hormones similar to testosterone that are important in reproductive activity, among other functions) that have both progestin activity and androgenic activity and could be formulated in a once-a-day pill for men. Clinical studies to prove safety and effectiveness are currently in progress.
In addition, the Institute supports studies of non-hormonal approaches to male contraception. Researchers have identified many possible mechanisms through which drug therapies can prevent sperm development and production in animal models. The CDDB is providing resources for medicinal chemistry and biological testing to support further work by the investigators who have identified candidate drugs. Several of these drugs appear to be very promising and will undergo pre-clinical testing to demonstrate the safety and effectiveness that are required before subsequent studies in humans.
- Why might someone prefer using one form rather than another?
Surveys show that men are very willing to try a new method of male contraception. When asked about preference for one formulation over another, many men say they would prefer a pill, but a large number also say they would prefer an injection or an implant.
It is well known that the most highly effective methods for women are implants or IUDs, which provide continuous contraceptive protection without further effort by the woman (such as taking pills or inserting and removing barrier devices). It is likely that the most effective male contraceptive methods will similarly provide continuous protection with little or no maintenance (such as implants or injections).
- Are hormonal forms of male contraception easily reversible? Do they have other long-term health effects?
Hormonal male contraception methods have been shown to be fully reversible in all cases, but some men return to fertility faster than others. The long-term safety has not been demonstrated because there is no hormonal contraception method currently in use for men.
Studies in women have shown that those who have used hormonal contraceptives have a longer lifespan than those who do not. Hormonal contraceptives also lower women’s risk of colon cancer and ovarian cancer. And recent studies have shown that some progestins may provide neurological benefits.
- What are the barriers to increased development and promotion of male contraception?
Funding and commercial interest greatly influence the development of new male contraception methods. Pharmaceutical companies have largely discontinued efforts to develop contraceptive methods for men (or new methods for women). The NICHD continues to make progress, within the resources we have. Eventually, a commercial partner will be needed to take a promising product through the regulatory approval and marketing processes required by all new drugs.
- What kind of research still needs to be done on male reproductive behavior to better understand men’s contraceptive preferences and willingness to use male contraceptives?
There has been a great deal of research demonstrating men’s willingness to use, and preferences for, male contraceptive methods. Until a product is available commercially, all research remains hypothetical. If a product is developed that is safe and effective, it remains to be seen whether it will gain popularity. If it does, then additional companies will likely try to develop similar products.
- What avenues of research in male contraception overall do you find most promising for the future?
Hormonal forms of male contraception are likely to reach the marketplace soonest because they are, scientifically, the best understood, and long-term safety has already been demonstrated in women.
For me, though, the most exciting approaches involve non-hormonal mechanisms to prevent sperm development. If we can show that they work well with little or no undesirable side effects, it would be an exciting advance for the field. I think we will do that eventually, but the process of new drug development normally takes about 25 years, and safety requirements are tougher when treating healthy individuals, rather than those with life-threatening conditions.
We have made remarkable progress, but it takes tremendous patience and perseverance in the face of many challenges. However, the objective is important for the future of both men and women.
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Originally Posted: June 23, 2014
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