Page last reviewed: 13/07/2011
In the past 50 years, there have been few changes in male contraception compared to the range of options available to women. The only two options currently available for men are:
- condoms - a form of barrier contraception that stops sperm from reaching an egg
- vasectomy- a minor surgical procedure that stops sperm from being ejaculated from a man's penis during sex (it is usually permanent)
There are many ongoing research projects into different methods of male contraception. Researchers are optimistic that a safe, effective method of male contraception will eventually become a reality, although this is still several years away.
Types of research
There are two main areas of research into male contraception:
- hormonal contraception - where synthetic hormones are used to temporarily stop the development of healthy sperm
- non-hormonal methods - where other techniques are used to stop healthy sperm from entering a woman's vagina
These are explained further below.
In fertile men, new sperm cells are constantly created in the testicles. This process is triggered by the hormone testosterone.
The goal of hormonal contraception research is to find a way of temporarily blocking the effects of testosterone so that the testicles stop producing healthy sperm cells. However, this needs to be achieved without lowering testosterone levels to such an extent that it triggers side effects, such as a loss of sexual desire.
One way that this may be done is by giving men a synthetic version of testosterone. The synthetic testosterone would stop the body producing natural testosterone, so no new sperm cells would be produced. At the same time, testosterone levels in the body would be kept high enough to prevent side effects.
During clinical trials, researchers found that testosterone alone did not always stop the body producing sperm. Other synthetic hormones were also needed.
Researchers then looked at using progestogens as well as testosterone. Progestogens are synthetic versions of a female sex hormone that is often found in female hormonal contraceptives.
Research is now focusing on different combinations of synthetic testosterone and progestogens. Several trials in different countries are looking at the effectiveness and long-term safety of hormonal contraceptives for men, including some phase III trials. Phase III trials are the last clinical trials that are carried out before a medicine is given a marketing licence.
An important drawback of using synthetic testosterone is that sperm production is suppressed at different rates in men of different ethnic origins.
These differences may be due to genetic, dietary or environmental factors but the exact reasons are unknown. Understanding the reasons may lead to new ways of providing an effective form of contraception for all men of diverse ethnic backgrounds.
Many of the non-hormonal methods of contraception currently being studied involve the vas deferens. The vas deferens is the tube that sperm pass through on their way to the penis. This tube is cut during a vasectomy.
RISUG and the IVD
One promising avenue of research is a technique called Reversible Inhibition of Sperm Under Guidance (RISUG). During this technique, a non-toxic synthetic chemical is injected into the vas deferens. The chemical reacts and blocks the vas deferens. The chemical also kills sperm when they come into contact with it. The chemical is effective almost immediately after it is injected.
The chemical stays in place until a man decides that he wants to have children. It can then be washed out using another injection which dissolves it and flushes it out of the vas deferens.
A variation of this technique is the intra-vas device (IVD). It involves injecting a "plug" into the vas deferens which can be removed later. The IVD filters out the sperm as it passes though the vas deferens.
Initial results of RISUG and IVD are promising, but further research is needed to assess the long-term effectiveness and safety of both techniques.
Other research is focusing on the epididymis. The epididymis is a long, coiled tube behind the testicles that stores and helps transport sperm.
Attempts have been made to interfere with the way that the sperm matures inside the epididymis and to interfere with the way that the epididymis works. However, so far neither approach has been successful.
Testosterone is a male sex hormone that is involved in making sperm and developing male sexual characteristics, such as a deeper voice. Testosterone is also found in small amounts in women.
The testicles are part of the male reproductive system. They produce sperm and are located within the scrotum (a loose bag of skin) hanging down behind the penis.