Advances in male contraception

Abstract

Despite significant advances in contraceptive options for women over the last 50 yr, world population continues to grow rapidly. Scientists and activists alike point to the devastating environmental impacts that population pressures have caused, including global warming from the developed world and hunger and disease in less developed areas. Moreover, almost half of all pregnancies are still unwanted or unplanned. Clearly, there is a need for expanded, reversible, contraceptive options. Multicultural surveys demonstrate the willingness of men to participate in contraception and their female partners to trust them to do so. Notwithstanding their paucity of options, male methods including vasectomy and condoms account for almost one third of contraceptive use in the United States and other countries. Recent international clinical research efforts have demonstrated high efficacy rates (90-95%) for hormonally based male contraceptives. Current barriers to expanded use include limited delivery methods and perceived regulatory obstacles, which stymie introduction to the marketplace. However, advances in oral and injectable androgen delivery are cause for optimism that these hurdles may be overcome. Nonhormonal methods, such as compounds that target sperm motility, are attractive in their theoretical promise of specificity for the reproductive tract. Gene and protein array technologies continue to identify potential targets for this approach. Such nonhormonal agents will likely reach clinical trials in the near future. Great strides have been made in understanding male reproductive physiology; the combined efforts of scientists, clinicians, industry and governmental funding agencies could make an effective, reversible, male contraceptive an option for family planning over the next decade.

Figure 1

The endocrinology of spermatogenesis and male hormonal contraception. Open arrows denote promotion of spermatogenesis; dashed lines denote inhibition of spermatogenesis and hormone production. A, Diagram of the naturally occurring, normal state. B, Diagram of the impact of hormonal contraceptive interventions on the reproductive axis.

Figure 2

Rate and extent of gonadotropin suppression with various hormonal interventions. Normal healthy men ages 18–55 given TE alone (100 mg im every week), TE plus oral levonorgestrel (LNG, 125 mg oral, daily), TE + acyline (300 μg/kg sc on day 0 only), or TE + LNG + acyline (n = 7 per group). Error bars represent ± sem. Rates of suppression were compared using time-to-event analysis with the event defined as suppression of LH or FSH to <1 IU/liter. Suppression of both LH and FSH was accelerated in both groups receiving acyline (P < 0.05) compared with the other two groups. [Data printed with permission of A. D. Coviello and W. J. Bremner.]