Women have always endured the brunt of responsibility when it comes to arranging for pharmacological birth control methods, with drug companies slow to provide options for men. Attempts like an injectable gel or an implant that inhibits sperm cell production are in various stages of development, but it appears one contender might be closer—and more practical—than the rest.
A new study published in The Journal of Endocrinology and Metabolism [PDF] found that men who were given injections of the hormones testosterone and norethisterone enanthate every eight weeks had a reduced sperm count within six months that was sufficient to prevent pregnancy 96 percent of the time.
Exogenous testosterone—meaning testosterone that has been added to, not produced by, the body—inhibits sperm production, although past attempts to use it as a form of birth control have been mixed: Too much of it can result in long-term endocrine issues. By using it alongside the norethisterone, researchers could reduce the dose and still be successful in suppressing sperm count below 1 million per milliliter.
While the numbers are promising, researchers still have their work cut out for them. Although the amount of testosterone administered was reduced, it can still affect numerous functions in the body, and subjects experienced a cascade of side effects: depression, irritability, and libido changes. Nearly half of participants complained of acne.
Some of these unwanted symptoms were severe enough for subjects to drop out, although the study’s authors maintain the effects were usually mild in nature and not dissimilar to those experienced by women, who have long struggled with the hormonal roulette that birth control can ignite. But with the vast majority of the male enrollees—75 percent—saying they were satisfied and would use the method if it became commercially available, they may not have to endure it for much longer.