The Science of Male Birth Control

A new report was released this week in the Journal of Clinical Endocrinology & Metabolism detailing the results of a large-scale, global study of an injectable form of hormonal-based birth control for men.

The treatment, consisting of an intramuscular injection every 8 weeks of a mixture of 1000mg of testosterone (the main male sex hormone) and 200mg of norethisterone enanthate (basically a derivative of the female hormones progesterone and estrogen). The latter acts on the brain’s pituitary gland to stop the production of sperm and testosterone in the testicles, while the former helps to counteract the effects of the loss of natural testosterone production.

According to a press release put out by Contraception Research and Development (CONRAD), one of the research firms involved in the study, the treatment had a 96% success rate among the 320 male participants (and their non-pregnant partners), with over 75% of participants stating that they are satisfied with the treatment and would continue to use it, but came with some side effects:

“The regimen led to a near-complete and reversible suppression of spermatogenesis, or sperm production. The contraceptive efficacy compared favourably to other reversible methods available for men. However, the frequency of side effects was relatively high, which included: acne, injection site pain, increased libido, and mood disorders. Due to these adverse events, the study was terminated before its completion.”

The study was halted on the recommendation of the independent committee established by CONRAD and the World Health Organization. This has lead a number of media outlets to put forth the assertion that the research has been entirely halted because the men involved didn’t think that the side-effects were worth it, despite the fact that many female-only contraception options currently on the market have very similar side-effects. The resulting “men need to toughen up and deal with the side effects women already deal with” narrative has lead to a number of misconceptions I’d like to clear up:

First of all, the pill was originally approved for use in 1960 – a year before sweeping reforms in the FDA’s drug approval process lead to much tighter regulations on drug control trials. The number of women participating in the original trials, as well as the short length of time they were studied, has lead many to criticize the pill’s original approval as hasty. In the intervening timeframe we have seen a number of studies examining the potential health risks (notably blood clots and potential long-term susceptibility to mood disorders such as depression) associated with the pill.

Secondly, research in the area of male birth control has not been “halted” as a result of this study’s premature termination; the study was a Phase II trial (the second of the three phases of drug testing prior to release to a market), and was never meant to develop a marketable product in the first place, only to evaluate the effectiveness and safety of one currently in the middle of development. In fact, researchers have hailed the results as a great breakthrough in a field that has been largely stagnate for 40+ years, and the scientists involved hope that future research will continue these developments. The press release even states that “given the efficacy and acceptability of this method, despite side effects, there continues to be a strong rationale for continuing research.”

So although it is certainly unfair to have women continue to take a product with unpleasant and potentially unsafe side-effects while the male version receives additional safety reviews, this is the product of a very different historic and scientific climate than exists today, and this clinical trial is simply trying to avoid repeating the missteps of the past. Yes, there is an undeniable, unequal burden of contraception placed on women, but I find it unfair to disparage the results of a study which is being conducted with the express goal of eventually bridging this gap.