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Image of a sperm with the midpiece highlighted and the caption "Target area of the proposed male contraceptive."

New Birth Control for Men

A study was recently completed that lays the groundwork for a form of male contraception that is easily reversible and doesn’t impact men’s hormones like the pill impacts women’s hormones. The media got it wrong and made it sound like this new form of birth control is just around the corner.

Fortunately, if the many hurdles that lie ahead are overcome, this new birth control for men could be much more elegant and far less invasive than the pill is for women.

The new form of contraception doesn’t stop or even decrease the production of sperm. Instead, it works by making a small part of the sperm tail rigid rather than flexible. As a result, sperm aren’t able to penetrate through the outer layer of the egg, which is called the zona pellucida. They have no problem getting there, but they are helpless to wiggle their way through the outer coating of an egg as long as their midpiece can’t flex.

When scientists remove the zona pellucida from the outer part of an egg, these same sperm are able to make a female pregnant and the offspring are perfectly normal. This means that the only part of the sperm that’s impacted is the midpiece.

This new male birth control method works by targeting two calcium-dependent proteins that are only found in the testes. The downside is that calcium-dependent proteins are necessary for the functioning of most cells in the body. So the challenge will be in creating an inhibitor that targets only the kind of calcium-dependent protein that is needed to create a flexible midpiece in sperm.

To achieve the desired result, scientists have used a medication that is used to suppress a person’s immune system after receiving an organ transplant. So the current medication suppresses the entire immune system instead of just impacting sperm.

It could be years before science creates a medication that can safely and effectively target the calcium-dependent protein that’s specific to sperm and leaves the rest of the body alone.

Another issue is that the research is currently being done on mice, but that’s not as big of a problem as you might think. Immune suppressing drugs have the same contraceptive effect on the sperm of human males as they do on mice. Also, within a week after humans and mice stop taking the drug, their sperm are back to normal and conception can occur. So the effects are the same on mice and men.

As for what’s at stake, the human population has tripled since the birth control pill first became available (from 3 billion to 7.6 billion). So the pill, condoms and other forms of birth control are not having the impact that we need for effective population control. (Even in the US, 50% of all women have had a pregnancy that is unplanned.)

While many men will be happy to use contraception that is easily reversible and does not mess up their sex drive or make them feel strange, we don’t yet know how many men would use it regularly, or how many women would trust that their male partners were actually using it.

But it certainly would be nice if men and women had the option.

CITATIONS: H. Miyata et al., Science 350, 442 (2015) and “Toward a rapid and reversible male pill” by Castanada and Matzuk, Science Magazine, 23 October 2015 • VOL 350 ISSUE 6259

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