• Summary
• Credits

1. The Long Road of Contraceptive Development
2. Vaginal Rings
3. Transdermal Contraception
4. Contraceptive Implants
5. Combined Injectables
6. Condoms
7. Fertility Awareness-Based Methods
8. Oral Contraceptives
9. Intrauterine Devices
10. Transcervical Female Sterilization
11. Male Hormonal Contraception
• Landmark Trials Provide Proof
• Testosterone-Only Formulations
• Combined Formulations
• Acceptability
12. Bibliography
13. Web Supplements

• Clinical trials assess effectiveness and safety of new contraceptives
• New low-dose DMPA formulation
• More long-term choices for men

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Male Hormonal Contraception

Male Hormonal Contraception Description: Most likely a monthly or bimonthly injection or implant delivering a combination of testosterone and a progestin. Stage of development: In phase II and III clinical trials. Effectiveness: Probably fewer than 1.4 pregnancies among partners of every 100 men per year of use. How they work: Prevent sperm production. What’s new? Provide men with another reversible, effective method to control fertility.

Hormonal contraception for men has been in clinical stages of development for almost two decades and is now in phase III clinical trials in China (253). This approach works by using testosterone or a combination of testosterone and a progestin to suppress sperm production. When testosterone is added to a man’s system, testosterone levels are lowered in the testes, resulting in reduced sperm production (6).

Pills, patches, injections, and implants have been tested to deliver various formulations of testosterone (159). In clinical trials injected formulations appear to be most effective in suppressing sperm production (159, 172, 257).

If clinical trials prove successful, a hormonal contraceptive method for men may be available in China by 2006 and in other countries several years later (171). Once on the market, this new hormonal approach would give men a choice of effective reversible contraception beyond just condoms. Also in development are long-term but potentially reversible male contraceptives, which focus on accessing the vas deferens to block sperm (see box below).

Two large-scale international clinical trials provided the initial evidence that testosterone can sufficiently suppress sperm production to serve as a viable contraceptive. The first study, in seven countries between 1986 and 1990, involved 271 men who received weekly injections of 200 mg of the hormone compound testosterone enanthate (275). The second study, in nine countries in 1994, involved 399 men who received testosterone enanthate on the same schedule (276).

These studies, which were sponsored by WHO in collaboration with CONRAD, established that hormonal methods would work for men and also defined the level to which sperm counts must decline in order to prevent men’s partners from becoming pregnant. Also, the second study established that a hormonal contraceptive could be effective—about one pregnancy among the partners of every 100 men per year of use when sperm production is adequately suppressed (276).

If the phase III clinical trials underway in China confirm phase II results (90), China could become the first country to register a hormonal male contraceptive method and to offer it in the national family planning program (253). One thousand Chinese men in 10 centers are receiving an initial dose of 1,000 mg of a testosterone formulation, testosterone undecanoate (TU), followed by 500 mg of it in doses given either every four or every six weeks for two years. Testosterone undecanoate is among the newest and most successful testosterone preparations. It is longer acting than other compounds such as testosterone enanthate, and it allows men to receive injections bimonthly or monthly instead of weekly (284).

Testosterone by itself does not suppress sperm production in non-Asian men as well as it does in Asian men, and therefore in other regions a male hormonal contraceptive would most likely combine a testosterone with another hormonal compound to improve effectiveness (276). Studies have been unable to pinpoint the cause for the difference in effectiveness between Asian men and other men (120, 156, 256).

The two primary challenges remaining for developing other male hormonal contraceptives are the need for frequent injections and the inability to uniformly supress sperm production in all users (89). Researchers are looking into longer-acting formulations of testosterone and combined hormonal formulations to overcome these challenges.

Combining testosterone with such compounds as progestins or gonadotropin-releasing hormone (GnRH) analogs speeds and improves suppression of sperm production and allows use of less testosterone, thus reducing testosterone-induced side effects (172, 257). To find the best contraceptive effect, researchers in several countries around the world are conducting small-scale clinical trials of combined formulas. Progestins appear to be the most promising. The studies are testing various delivery systems, separate from the delivery system for testosterone, to deliver the progestin, including a pill, patch, injection, and implant (10, 43, 85, 130, 158).

Major organizations involved in researching these compounds include WHO, CONRAD, the Institute of Reproductive Medicine of the University in Germany, Schering AG, Organon, and the Population Council, which is investigating a more potent synthetic hormone, MENT^®, as a substitute for testosterone (192, 203, 239).

Side effects. In small clinical trials combined testosterone and progestin formulas caused no serious side effects or medical complications. Male hormonal contraception is likely to have little impact on men’s sex drive or aggressive behavior, study results suggest (122).

Combining progestin with a testosterone appears to reduce, although not eliminate, the side effects of testosterone (7, 9, 31, 157). Side effects of testosterone alone have included pain at the injection site, acne, weight gain, and suppression of high density lipoprotein (HDL) cholesterol—the healthy type of cholesterol that has been associated with reduced risk of atherosclerosis (hardening of the arteries). HDL returns to normal levels after discontinuation of testosterone use (160, 277). Large, long-term studies are needed to assess all of the side effects of combined formulas (172).

Effectiveness. The contraceptive effectiveness of any male hormonal formulation of course depends on how well it can suppress sperm production. Researchers are aiming to develop a combined formulation that will reduce sperm counts to fewer than 1 million per milliliter of ejaculate, a level that would result in an effectiveness rate of 1.4 pregnancies per year among partners of 100 men using it (113, 276).

Several combinations of progestins and testosterone have been able to produce either low sperm counts or no sperm in nearly 100% of the study participants in small clinical trials. All progestins tested appear promising in suppressing sperm production, and no one progestin seems superior to the others (89, 257). Larger clinical trials, in which subjects will be treated for longer periods of time, are planned (159).

Advances in male hormonal contraception have lagged behind advances in female hormonal contraception (204). One reason is that contraception has been seen as the woman’s responsibility. Also, researchers have been cautious about the potential effects of hormone use on men’s emotional and sexual well-being (98, 197).

When developing female contraceptives, potential side effects can appear minor in comparison with the large health benefits of avoiding unintended pregnancy and childbearing. In contrast, when developing contraceptive methods for healthy men who do not face the risks of pregnancy and childbirth, the impacts of side effects can appear relatively large (123, 197).

Studies suggest, however, that many men are willing to take on the side effects and health risks of contraceptive use (102, 195, 196, 259). Many men and women in surveys, focus groups, and interviews say that they want to share the responsibility for contraception. Studies of the potential acceptability of male hormonal contraception also suggest that women would trust their partners to use the method reliably (88).

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