New Male Birth-Control Options May Be on the Way
One approach that has been tested uses the hormone testosterone by itself, injected once a week or once a month. This suppresses sperm counts, but the effect varies, so a small percentage of men remain fertile. For unexplained reasons, testosterone alone appears to be more effective in Asian men than in men studied in the U.S., Europe, and Australia.
"The Chinese are interested in this approach and likely to be the first to introduce it on a non-experimental basis, using longer-acting testosterone that can be injected once a month," Amory says.
The most promising hormonal approaches for non-Asian men combine testosterone with another substance to enhance its effect. One possibility is combining testosterone with a chemical called gonadotropin-releasing hormone antagonists, which block another type of hormone involved in sperm production. But these chemicals are expensive and must be injected under the skin.
Another possibility is combining testosterone and progestin hormones. Many researchers believe this combination is the most likely to work in non-Asian populations, the study's authors write.
In the latest tests of male hormonal contraceptives, men have remained on the methods for up to a year. "In all of them, once they stopped taking it, their sperm count come up to normal within six months of stopping, and several have had children," Baird says. "However, if you ask me, 'What will happen if I take it for 30 years?,' we can't know that until enough men have taken it for 30 years."
How soon could male hormonal contraceptives reach drugstore shelves? "Twenty years ago, people were saying 'in five years' and they turned out to be wrong, so I'm hesitant to make predictions," Amory says. "There are technical hurdles that need to be overcome. Conservatively, let's estimate 10 to 15 years. Or if there were a major breakthrough, it could be five years."
- Researchers are continuing work on developing more birth-control options for men.
- Early studies have been conducted with injections of testosterone, alone or in combination with other substances.
- The hope is to find male birth control that has positive side effects, such as reducing the risk of prostate and testicular cancer, acne, benign enlarged prostate, and male pattern baldness.