Contraception aims to prevent pregnancy. Historically, options for men have been limited to condoms and vasectomy. The development of male birth control seeks to broaden these choices, offering new ways for men to participate in family planning.
If a Male Takes Female Contraceptives
Hormonal birth control pills designed for females would not function as contraception for men. These pills, which typically contain estrogen and progestin, disrupt the female reproductive cycle by preventing ovulation and altering cervical mucus and the uterine lining. Since male reproductive biology differs fundamentally, these pills will not make a male infertile or prevent pregnancy.
Instead, female hormones would introduce undesirable physical effects in a male’s body. Estrogen exposure can lead to feminizing changes, such as breast tenderness and growth (gynecomastia), and potential fluid retention. Both estrogen and progestin can cause mood changes, decreased libido, and possibly contribute to weight gain. Prolonged exposure might also raise concerns about cardiovascular strain or liver issues.
How Male Contraception Works
Male contraception primarily functions by temporarily suppressing sperm production or function. Hormonal approaches typically involve interfering with brain signals that stimulate sperm production in the testes. This is achieved by administering exogenous hormones, such as testosterone combined with progestins, which suppress the release of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) from the pituitary gland. Lowered levels of LH and FSH then lead to a significant reduction in sperm count.
Non-hormonal methods, in contrast, target different stages of sperm development, maturation, or their ability to function. These approaches might involve blocking sperm transport, inhibiting their motility, or affecting their capacity to fertilize an egg. Some non-hormonal strategies aim to disrupt specific proteins essential for sperm function or development, or physically block sperm pathways. These diverse mechanisms provide multiple avenues for temporarily preventing male fertility without relying on hormonal manipulation.
Types of Male Contraceptives in Development
Several categories of male contraceptives are under research and development, aiming to provide varied options. Hormonal methods include oral pills, gels, and injections designed to suppress sperm production. For instance, dimethandrolone undecanoate (DMAU) is an investigational oral pill that combines androgenic and progestogenic activity to reduce sperm count. Another hormonal approach involves a daily transdermal gel containing Nestorone (a progestin) and testosterone, which aims to suppress sperm production when applied to the skin.
Non-hormonal methods are also being explored, focusing on mechanisms that do not involve sex hormones. These include compounds that target specific proteins in sperm, like those involved in motility or development, such as BRDT inhibitors or retinoic acid receptor antagonists. Physical barrier methods, such as RISUG (Reversible Inhibition of Sperm Under Guidance) and Vasalgel, involve injecting a polymer gel into the vas deferens to block sperm flow. RISUG, for example, creates a physical and chemical barrier that damages sperm membranes. Vasalgel, similar to RISUG, forms a hydrogel in the vas deferens to prevent sperm passage and is designed to be reversible.
Current Progress in Male Contraception
The field of male contraception is seeing advancements, with various methods progressing through clinical trials. Hormonal gels, such as the combination of Nestorone and testosterone, are in Phase II clinical trials, with studies evaluating their safety and efficacy in couples. Oral hormonal pills like DMAU are also undergoing clinical testing to assess their ability to suppress sperm production and their overall safety profile.
Non-hormonal approaches are also reaching human trials, marking a significant step in diversifying contraceptive options. For example, YCT-529, a hormone-free male contraceptive pill that interferes with vitamin A metabolism to stop sperm production, has successfully completed Phase 1 clinical trials for safety and is advancing to Phase 2 for efficacy testing. Additionally, injectable hydrogels like ADAM, a vas-occlusive contraceptive, are in early-stage clinical research. Bringing these methods to market involves rigorous testing phases to ensure both effectiveness and a favorable side effect profile.