For decades, contraceptive responsibility has largely fallen on women. While multiple hormonal birth control methods exist for females, options for men remain limited to condoms or vasectomy. With vasectomy being considered a more permanent choice, the tubes are charged with moving the sperm from the testes to the head of the penis. This imbalance has prompted researchers to explore hormonal contraceptives for men that temporarily suppress sperm production without permanently affecting fertility. One promising approach involves injectable hormone combinations that can reduce sperm counts while maintaining normal hormone levels in the body.
Male hormonal contraceptives work by disrupting the hormonal signals that regulate sperm production. Under normal conditions, the hypothalamus and pituitary release luteinizing hormone (LH)(What Is Luteinizing Hormone?) and follicle-stimulating hormone (FSH) (Follicle-Stimulating Hormone (FSH): What It Is & Function), which stimulate the testes to produce testosterone and sperm. Introducing external hormones interferes with this process through negative feedback. The higher levels of hormones inhibit further production. Gu et al. , used testosterone undecanoate (TU), a long-acting form of testosterone, together with depot medroxyprogesterone acetate (DMPA), a progestin that further suppresses gonadotropin production. The DMPA is the same hormone found in the commonly used female contraceptive known as the depot shot (Depot Medroxyprogesterone Acetate and Bone Effects). This dual-hormone strategy reduces sperm production while maintaining circulating testosterone levels necessary for normal male physiology.
Gu et al. investigated whether combining TU and DMPA could provide an effective injectable contraceptive. Their Phase I open-label clinical trial included 30 healthy Chinese men, divided into three treatment groups: TU alone, TU with a low dose of DMPA, and TU with a higher dose of DMPA. The study took place over an eight-week baseline period, followed by 24 weeks of hormone treatment, and finally a 24-week recovery phase after treatment ended. During this time, researchers monitored sperm counts and hormone levels to assess both effectiveness and safety.
To evaluate whether the treatment could function as a contraceptive, researchers monitored sperm concentration for slightly over a year. Azoospermia refers to the complete absence of sperm in semen, while severe oligozoospermia describes extremely low sperm counts. Both conditions significantly reduce the likelihood of fertilization and are commonly used as indicators of contraceptive effectiveness.
The results showed that the combination of TU and DMPA suppressed sperm production more effectively than testosterone alone. Nearly all participants receiving the dual-hormone regimen reached azoospermia or severe oligozoospermia, while two individuals in the TU-only group experienced a rebound in sperm concentration. Importantly, sperm production returned to normal levels during the recovery phase, suggesting that the contraceptive effect was reversible.
These findings support the growing interest in dual-hormone male contraceptive strategies, mirroring the already existing female contraceptives. By combining an androgen with a progestin, researchers were able to suppress sperm production more consistently than with testosterone alone. The eight-week injection interval may also make this approach practical, as longer dosing intervals are generally easier for patients to maintain.
However, several limitations remain. The small sample size restricts the ability to generalize the results, and the relatively short duration prevents researchers from fully evaluating long-term safety. The study also did not track pregnancy outcomes directly, and instead relied on sperm counts as a proxy for contraceptive effectiveness. Additionally, because the participants were drawn from a single demographic group, hormonal responses may differ in more diverse populations.
Despite these limitations, the study represents an important step toward expanding male contraceptive options. A reliable injectable contraceptive lasting several weeks could help shift contraceptive responsibility toward a more equitable model of family planning. Consequent research will likely focus on larger clinical trials, optimizing hormone dosages, and testing alternative progestins to further improve effectiveness and acceptability.
Ultimately, advances in male hormonal contraception could transform how couples approach birth control. By providing men with a safe and reversible contraceptive option, these approaches may move reproductive decision-making toward a more shared responsibility.
This article is based on Yi-qun Gu’s Male Hormonal Contraception: Effects of Injections of Testosterone Undecanoate and Depot Medroxyprogesterone Acetate at Eight-Week Intervals in Chinese Men.
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Gu, Y., Tong, J., Ma, D., Wang, X., Yuan, D., Tang, W., & Bremner, W. J. (2004). Male Hormonal Contraception: Effects of Injections of Testosterone Undecanoate and Depot Medroxyprogesterone Acetate at Eight-Week Intervals in Chinese Men. The Journal of Clinical Endocrinology & Metabolism, 89(5), 2254–2262. https://doi.org/10.1210/jc.2003-031307
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