Ensuring that the stork doesn't bring any unexpected parcels of joy has mostly been the lot of women, but researchers are working to get men more involved through a long-term, reversible contraceptive for males.
Currently, the list of commonly available contraceptives for men is pitifully short: condoms and vasectomy.
Contrast that with the options for women. There's the diaphragm, the sponge, IUDs, the pill, cervical caps, "morning after" pills, Norplant, Depo-Provera, ovulation detectors, the female condom, foams, jellies, suppositories and sterilization, to name but a few.
But the choices for men are about to expand. An implanted male hormonal contraceptive is now being tested.
It works in much the same way as its female counterpart, which uses the hormones estrogen and progestin to shut off the release of eggs to prevent pregnancy. In the male version, testosterone and progestin are used to turn off sperm production.
"The hormones work by suppressing the production of two other hormones from the brain – LH (luteinizing hormone) and FSH (follicle-stimulating hormone)," said Dr. Christina Wang, professor at Harbor-UCLA Research & Education Institute.
"Suppressing these two hormones in turn suppresses the function of the testes and the production of sperm," she said.
"The two hormones are in separate implants," Wang said. "It's not possible to mix them because you have to make sure the two won't counteract each other."
The two rods – measuring about 2 mm in diameter and 45 mm in length – are inserted just under the skin of the arm. Insertion takes about 15 minutes and is done with a local anesthetic.
"It takes around 12 weeks for the implants to start working and another 12 weeks for the sperm count to return to normal once they have been removed," Wang said.
The testosterone implant can last up to a year before it needs replacing; the progestin rod can last up to five years.
One stumbling block Wang encountered was ensuring that men using the contraceptive received enough testosterone to maintain muscle and libido levels.
"With this method you are stopping the production of testosterone at the source so that sperm production is halted. But you still need to replace the testosterone that should be circulating throughout the body," said Doug Colvard, director of extramural research at the Contraceptive Research and Development Program, a sponsor of Wang's research.
"The amount of testosterone needed is around 7 milligrams a day – roughly what the man would be making – so for an implant to produce this using natural testosterone is impossible," Wang said.
To overcome this problem, Wang uses a more concentrated, synthetic version of the natural testosterone called MENT (7a-methyl-19-nortestosterone).
So far the trial results have been very promising, Wang said, with sperm count suppressed to very low numbers. Wang believes the rods could be as effective at preventing pregnancy as the pill is for women.
Not everyone, however, is so confident about the use of hormones.
"Any time you deal with hormones, you are going to have to deal with problems of possible toxicity and side effects," said Don Waller, a contraceptives expert and professor of pharmacology and toxicology at the University of Illinois at Chicago.
"Hormones are very difficult to control – it's a matter of directing them. They tend to not just interact with just one tissue but many tissues, and it is very difficult to get them to target just the area you want," Waller said.
Dr. Ronald Weiss, assistant professor of medicine at the University of Ottawa's Faculty of Medicine, agrees.
"When you take a pill or if you have an implant – any treatment that uses hormones that has to travel through the body – it's going to have an effect on the whole of the body's system," Weiss said.
Wang said that aside from acne and weight gain, there have been no significant side effects, but she admits so far it has only been a short-term study.
"The goal is to establish the lowest dose that is still effective – to use the minimum amount of testosterone and progestin while still at adequate levels to suppress sperm production," Wang said.
Waller agreed: "A lot has to do with the dosage and duration. An implant may be better than a pill because they release more slowly over a period of time."
Dr. Cappy Rothman, a male infertility expert and medical director of the California Cryobank, a Los Angeles sperm bank, pointed out that women have been taking hormones for years and they seem to have worked fine.
"Using hormones may put some guys off, but the alternative is that the wife takes them – so either you do or she does," Rothman said. "The answer may be you take them for one year, and she does the next."
But women shouldn't consign those pills to the trash just yet. The male implant is still under study as researchers try to find the optimal dose of the hormones. Wang said it could be another seven years before the implants are ready for prescription.
