The testes hang outside the body for a reason: They need to keep cool to function properly. Intentionally warming them with an ultrasound machine could kill off sperm cells permanently.
Contraception has had a rough couple of months. There was the great condom debacle in South Africa in January, when millions of government-supplied condoms leaked "like sieves." There was the oral contraceptive recall in the United States, in which one million packs of birth control pills were called into question after inert pills were thought to have taken the place of active ones. And then there was the Aspirin method that gained so much awareness last month.
Birth control is a real concern, not only because of the number of unwanted pregnancies in both developed and developing nations, but because it hasn't evolved much in the last few decades. For men, the evolution has been even more stalled; they have few options, aside from condoms, which can be unreliable, and vasectomy, which is not always reversible.
There's another technique, though, with a funny history but some serious possibility. In the 1970s, researcher Mostafa S. Fahim realized that ultrasound might be a possibility for male contraception, by "zapping" the testes past the point of functionality. The testes hang outside of the body for a reason: They need to be kept cooler than the internal body temperature to work properly. Too-tight underwear or excessive laptop use can cause a decrease in sperm production, enough to affect the odds of conception. In this vein, intentionally warming the sensitive testes with ultrasound might render them more clinically defunct.
Fahim had shown that ultrasound applied to the testicles could significantly diminish sperm production in a number of species, including rats, dogs, and monkeys. Its benefits were that it was effective and, apparently, reversible. A few humans (scheduled to undergo testes removal for prostate cancer anyway) even underwent the procedure, and reported only a "gentle feeling of warmth" during application. But because follow-up studies couldn't replicate the findings, interest in the technique waned, and it was largely abandoned by the medical community.
But a recent study in rats may bring renewed hope for the procedure -- and for men willing to undergo it. Commissioned by the Male Contraception Information Project, researchers at the University of North Carolina put to the test the type of ultrasound machine commonly used in medical practices to restore damaged joints. The trick here was that the team, led by James Tsuruta, used the ultrasound to generate damage to healthy testicles.
The researchers applied several variations of the technique, altering the intensity of the ultrasound, the addition of "regular" heat, the distance of the ultrasound from the scrotum, and the number of applications. They found that when ultrasound was applied twice at high frequency, two days apart, for 15-minutes at a time, the success rate was highest. The rats' sperm production was drastically reduced and the sperm that did exist were virtually immotile. The insides of the testes' "seminiferous tubules," which are normally rife with germ cells destined to become sperm cells, were eerily vacant in the treated testes, leaving a large empty space where there would normally be none.
A couple of years ago, another team had shown that a similar procedure was effective in dogs; and newer research, also commissioned by the Male Contraception Information Project, has shown it to work in monkeys, although the application can be awkward (PDF), at least for the humans applying it. "The monkeys didn't seem to mind the treatment a bit, but we were having a rough time of it," said University of California, Davis, researcher Catherine VandeVoort. "Thirty minutes of treatment three times a week is a lot of monkey testicular massage. We felt pretty silly, and it didn't help when the techs would come around and wonder what kind of research we were doing! We were relieved when we finally saw an effect."
One of the major lingering questions is how long-lasting the technique could be, and then, how reversible. The study in dogs showed permanent contraceptive potential, but the study in monkeys found the method to be just temporary. And it's less clear whether the rats in the study mentioned above would be able to procreate after the treatment was stopped, since follow up lasted only two weeks in the rodents (though sperm counts were still low after this period). Exposing the testes to the zap of an ultrasound would probably produce some anxiety in men, unless the safety, longevity, and reversibility of the treatment were extremely well mapped.
In any case, it would likely take recurring applications of the method for it to have a true contraceptive effect. And how often the treatment would need reapplication will affect its potential adoption. For people in developing countries, it's easy to hand out condoms, but it's not so easy to have men return to a clinic for testicle ultrasounds every few months.
More research will be needed in animals and, eventually, in humans to learn more about the long-term effects, both desired and undesired. But Tsuruta and team say that "a permanent or reversible method of contraception based on therapeutic ultrasound treatment could encourage more men to share greater responsibility for family planning." Time will tell whether ultrasound will present a viable alternative to the current methods, or whether the endeavor will simply end up an example of science shooting blanks.