BACKGROUND: Half of pregnancies in the United States are unintended. However, there are several effective methods of contraception available. Since the year 2000, there have been many new methods of birth control in the U.S., including the levonorgestrel-releasing intrauterine system, the hormonal contraceptive ring, the patch, the 91-day regimen of oral contraceptives, the hormonal implant, and a new form of female sterilization. The most popular method used by over ten million women in the US between 2006 and 2008, was the oral contraceptive pill. (Source: www.cdc.gov) However, male contraception is becoming more popular.
INTERESTING FACTS ABOUT CONTRACEPTION: Between 2006 and 2008, 99% of women who had ever had sexual intercourse had used at least one method of birth control. Some interesting facts are:
· 7.3% of women who were currently at risk of unintended pregnancy were not using a contraceptive method.
· Hormonal implants for women are 99% effective.
· Injections for women are 91-99% effective.
· Both the pill and the patch for women are 91-99% effective.
· Male condoms are 82-98% effective. Female condoms are 79-95% effective.
· Spermicides are 72-85% effective.
· Female sterilization, trans cervical sterilization, and male sterilization are all over 99% effective. (Source: www.cdc.gov)
TYPES OF MALE CONTRACEPTION: The two most common male contraceptive methods are vasectomies and condoms. They have obvious draw backs (not being reversible and condoms have a high failure rate). A study found that over 60% of men in Spain, Brazil, Mexico, and Germany were willing to use a new method of male contraception. A heat-based method could offer easily implemented birth control. Researchers have used different sources of heat to disrupt fertility: hot water, incandescent light bulbs, saunas, and ultrasounds. Optimal sperm production (spermatogenesis) requires temperatures to be below average body temperature. By warming the testicles above average, it disrupts spermatogenesis. RISUG is an option that is effective immediately right after injection procedures and lasts for ten years unless reversed. (Source: www.malecontraceptives.org)
NEW TECHNOLOGY: Oral contraceptives have been available for women since the 1960s, but for men this option has been limited. Some have tried using testosterone to decrease sperm production, but they come with a list of side effects (acne, increase risk of heart disease and prostate cancer). Spermatogenesis relies on vitamin A to allow the production of normal numbers of sperm. Researchers are developing a way to use vitamin A metabolism in the testis to regulate spermatogenesis. One recent study found that a compound that interferes with the body’s ability to use vitamin A made male mice sterile (they were receiving 8 to 16 week courses). Once they stopped giving it to the mice, they resumed making sperm. So far, the researchers have not found side effects and testosterone remained stable. Another study is working with a drug that interferes with the action of an enzyme that converts vitamin A to its biologically active form in the testis, hoping it will render men temporarily sterile. Testing is still under way. (Source: www.ncbi.nlm.nih.gov)
John Amory, MD, MPH, Physician of Internal Medicine at the University of Washington, talks about a new idea of male contraception.
Tell me about this?
Dr. Amory: The group of endocrinologists here at the University of Washington has been interested in developing a male contraceptive for over 40 years; really since the advent of the female contraceptive. The approach that has been taken historically is to use hormones to suppress spermatogenesis or sperm production. It is very analogous actually to the female pill. The female pill uses estrogen and progesterone to suppress ovulation or egg production. Male hormonal contraceptive approach uses the male hormones, testosterone plus progesterone to suppress sperm production.
What is your research?
Dr. Amory: That research has been ongoing for about 25 or 30 years. About 5 years ago, I decided to explore ways of suppressing sperm without using hormones or steroids. So, I have actually been looking at an idea to develop a male contraceptive that involves blocking the function of vitamin A in the testicle. It may surprise you to know that if you make a mouse or a rabbit vitamin A deficient, two things will happen; it will get night blindness which most people are familiar with and it will become infertile. Starting from that we decided if we could block the function of vitamin A just in the test is leaving its function intact in other tissues, maybe we could have a reversible male contraceptive that did not rely on the use of steroids such as testosterone.
What about the safety of testosterone? Are there some serious downsides?
Dr. Amory: There are concerns and the debate about whether or not to use it in older men whose testosterone may be getting lower is one thing. When you are thinking about developing a contraceptive, it has to be extraordinarily safe because there is the potential to be giving it to tens of millions of young men and they could be taking it for a long period of time. So, there are some advantages to thinking about approaches to male contraceptive development that do not rely on testosterone and that was one of my motivations for studying vitamin A.
What is the danger of taking testosterone?
Dr. Amory: The answer is we don’t know. So, there is a paradox here because most men make testosterone their entire lives from the time they go through puberty until the day they die. Whether or not it is associated with harmful outcomes is really unknown. There is concern about whether or not it might increase the risk of heart disease because it lowers the good or HDL cholesterol and then there is this association with prostate cancer, but there is a lot of uncertainty about this. So, when you see the ads for testosterone in the news, we really don’t know whether or not we are doing more good than harm. Certainly, there are short term benefits in terms of muscle mass and sex drive and those things, but what about the long term implications; it is unknown. We really need male health initiative analogous to the women’s health initiative study that was done to define the risks of testosterone.
So, I know testosterone can come in shots and you can also do a gel for men. How would you block vitamin A through a pill?
Dr. Amory: Yes, it would be a pill. Actually we have new compounds that do block and they are not just blocking vitamin A. Tissues take up vitamin A and turn it into something called retinoic acid. What we would be blocking is the conversion of vitamin A, or retinol to retinoic acid in the tissue. This would be a pill; probably a daily pill and eventually we could develop a 3 monthly formulation similar to Depo-Provera which is very popular for women.
Which comes to the fact, and I have said this to women, and they respond, “we would never trust a man to take a pill.” What is your response to that?
Dr. Amory: I think that is a valid point. The pill would be good for some men. There are some men who probably take a pill religiously. Once we get the pill developed, we will be looking at longer acting injectable forms and maybe even implants. There are two yearly implants that women take and those are ideal because they take remembering to take your pill out of the equation. So the hope is that we could develop the pill that we are working on into something that would be longer acting for men. I will tell you a funny story… So we have done studies with hormonal contraceptives using implants and the men really like the implants because they can show them off at cocktail parties. They are put on the inner aspect of the upper arm and so it is kind of an excuse to point out their bicep to women. Also it is nice because the women can feel the implant; rest assured that the man was actually using contraception.