Male birth control shot found effective, but side effects cut study short

By Susan Scutti, CNN
7 minute read
Updated 2:33 PM EDT, Tue November 1, 2016
Women have many choices when it comes to avoiding pregnancy, but men have only two. According to the Centers for Disease Control and Prevention, 99% of sexually active women used at least one contraceptive method at some point between 2006 and 2010. Here's a look at a variety of birth control methods and how they each work.
A woman's choice —
Women have many choices when it comes to avoiding pregnancy, but men have only two. According to the Centers for Disease Control and Prevention, 99% of sexually active women used at least one contraceptive method at some point between 2006 and 2010. Here's a look at a variety of birth control methods and how they each work.
Photo Illustration/Thinkstock
A male condom is a thin covering worn on the penis during intercourse. It can prevent sexually transmitted diseases, and is about 82% effective at preventing pregnancy.
A male condom is a thin covering worn on the penis during intercourse. It can prevent sexually transmitted diseases, and is about 82% effective at preventing pregnancy.
Shutterstock
During a vasectomy, a surgeon cuts the vas deferens, the tubes that carry sperm from the testicles. It has a failure rate of about 0.15% and can be reversed, but the procedure is complicated.
During a vasectomy, a surgeon cuts the vas deferens, the tubes that carry sperm from the testicles. It has a failure rate of about 0.15% and can be reversed, but the procedure is complicated.
Shutterstock
An intrauterine device, or IUD, is a flexible T-shaped device that's inserted by a doctor into a woman's uterus. The devices block sperm and change the lining of the uterus, which may keep a fertilized egg from attaching. Pregnancy is prevented from three to 12 years, depending on the type.
IUD —
An intrauterine device, or IUD, is a flexible T-shaped device that's inserted by a doctor into a woman's uterus. The devices block sperm and change the lining of the uterus, which may keep a fertilized egg from attaching. Pregnancy is prevented from three to 12 years, depending on the type.
Photo Illustration/Thinkstock
Approved in 1960 by the Food and Drug Administration, oral contraceptives involve taking a daily pill with a combination of estrogen and a progestin. The hormones prevent ovulation and thicken a woman's cervical mucus, blocking sperm from fertilizing an egg.
The pill —
Approved in 1960 by the Food and Drug Administration, oral contraceptives involve taking a daily pill with a combination of estrogen and a progestin. The hormones prevent ovulation and thicken a woman's cervical mucus, blocking sperm from fertilizing an egg.
Condoms aren't just for men. The female condom fits inside the vagina with a ring at one end that covers the cervix. When used correctly all of the time, the National Institutes of Health says, it's 95% effective, with bonus protection from sexually transmitted infections.
Female condom —
Condoms aren't just for men. The female condom fits inside the vagina with a ring at one end that covers the cervix. When used correctly all of the time, the National Institutes of Health says, it's 95% effective, with bonus protection from sexually transmitted infections.
Keith Brofsky/Getty Images
The diaphragm also fits inside the vagina but covers only the cervix, where it blocks sperm from entering the uterus. It is made of silicone and can last up to two years. A spermicide must also be used for greatest effectiveness.
Diaphragm —
The diaphragm also fits inside the vagina but covers only the cervix, where it blocks sperm from entering the uterus. It is made of silicone and can last up to two years. A spermicide must also be used for greatest effectiveness.
Jenny Swanson/Getty Images
The cervical cap is similar to a diaphragm but smaller in size and made of rubber instead of silicone. It is useful for women who find it hard to keep a diaphragm in place.
Cervical cap —
The cervical cap is similar to a diaphragm but smaller in size and made of rubber instead of silicone. It is useful for women who find it hard to keep a diaphragm in place.
Dorling Kindersley/Getty Images
Implants are flexible matchstick-size devices that are surgically inserted into a woman's arm. They slowly release the hormone progestin into the body, preventing a woman's ovaries from releasing eggs. The protection can last several years.
Implant —
Implants are flexible matchstick-size devices that are surgically inserted into a woman's arm. They slowly release the hormone progestin into the body, preventing a woman's ovaries from releasing eggs. The protection can last several years.
Shutterstock
For women who don't want to take a pill or insert a device, the Ortho Evra birth control patch sticks to the body and releases pregnancy-preventing hormones through the skin. A woman must change her patch once a week for three weeks in a row. No patch is used in the fourth week, and then the cycle starts again.
The patch —
For women who don't want to take a pill or insert a device, the Ortho Evra birth control patch sticks to the body and releases pregnancy-preventing hormones through the skin. A woman must change her patch once a week for three weeks in a row. No patch is used in the fourth week, and then the cycle starts again.
NuvaRing, approved for use in the United States in 2001, is a small, flexible ring inserted into the vagina. It releases estrogen and progestin, the same pregnancy-preventing hormones found in most variations of the birth-control pill.
Vaginal ring —
NuvaRing, approved for use in the United States in 2001, is a small, flexible ring inserted into the vagina. It releases estrogen and progestin, the same pregnancy-preventing hormones found in most variations of the birth-control pill.
Introduced in 1983, the Today Sponge was pulled from the market after fears of toxic shock but returned in 2005 following design changes. The sponge contains spermicide and can be inserted into the vagina before sex, like a diaphragm, to prevent pregnancy.
Vaginal sponge —
Introduced in 1983, the Today Sponge was pulled from the market after fears of toxic shock but returned in 2005 following design changes. The sponge contains spermicide and can be inserted into the vagina before sex, like a diaphragm, to prevent pregnancy.
Meijer/Today Sponge
Depo-Provera, an injection form of birth control, provides protection for three months with hormones that prevent ovulation and block sperm. It doesn't contain estrogen, as do some other forms of birth control. As a result, it is a popular option for women who can't take estrogen or who are breastfeeding.
The shot —
Depo-Provera, an injection form of birth control, provides protection for three months with hormones that prevent ovulation and block sperm. It doesn't contain estrogen, as do some other forms of birth control. As a result, it is a popular option for women who can't take estrogen or who are breastfeeding.
Pfizer
Emergency contraception, frequently referred to as the morning-after pill, can be taken to prevent pregnancy up to five days after unprotected sex. It can prevent the ovaries from releasing eggs and thickens a woman's cervical mucus. The morning-after pill can also thin the uterus lining, which could prevent a fertilized egg from attaching.
Morning-after pill —
Emergency contraception, frequently referred to as the morning-after pill, can be taken to prevent pregnancy up to five days after unprotected sex. It can prevent the ovaries from releasing eggs and thickens a woman's cervical mucus. The morning-after pill can also thin the uterus lining, which could prevent a fertilized egg from attaching.
Birth control methods

Story highlights

A male hormonal birth control injection prevented pregnancy in female partners, a new study finds

The study was ended early because of side effects, particularly depression and mood disorders

CNN  — 

Both men and women are responsible for pregnancy, yet the burden of preventing it often falls on one gender. Women can choose from a variety of options to control fertility while for generations, men have been limited to withdrawal, condoms and sterilization. But someday soon, a new method may allow men to shoulder a greater share of responsibility.

A new hormonal birth control shot for men effectively prevented pregnancy in female partners, a new study found.

The study, co-sponsored by the United Nations and published Thursday in the Journal of Clinical Endocrinology and Metabolism, tested the safety and effectiveness of a contraceptive shot in 320 healthy men in monogamous relationships with female partners. Conducted at health centers around the world, enrollment began on a rolling basis in September 2008. The men, who ranged in age from 18 to 45, underwent testing to ensure that they had a normal sperm count at the start.

birth control pill
Shutterstock

How the 'male pill' could actually work

The injection, given every eight weeks, consisted of 1,000 milligrams of a synthetic form of testosterone and 200 milligrams of norethisterone enanthate, essentially a derivative of the female hormones progesterone and estrogen referred to as “progestin” in the synthetic form.

According to Dr. Seth Cohen, a urologist at NYU Langone Medical Center, when a man is given a shot of testosterone, “basically, the brain assumes the body is getting enough,” so the body shuts down its own production of testosterone – specifically “the testicle’s production of testosterone as well as the testicle’s production of sperm.”

The progestin “further drives the brain malfunction, so it stops the testicle’s production of both testosterone and sperm,” explained Cohen, who was not involved in the new study.

The researchers used a combination of hormones in order to reduce the testosterone dose to a level that they believed, based on previous studies, would effectively lower fertility yet still be safe.

Study terminated early

During the ramp-up pre-efficacy stage of the study, the couples were instructed to use non-hormonal birth control methods, while the men participants received shots and provided semen samples until their sperm counts dropped to less than 1 million per milliliter in two consecutive tests. At that point, couples relied on the injections as contraception.

Throughout the study, the men provided semen samples to ensure that their sperm counts stayed low. Once the participants stopped receiving the injections, they were monitored to see whether and how quickly their sperm counts recovered to levels described as “fertile” by the World Health Organization.

The researchers discovered that the shot effectively held the sperm count at 1 million per milliliter or less within 24 weeks for 274 of the participants. The contraceptive method was effective in nearly 96% of continuing users.

Four pregnancies (resulting in three live births) occurred among the men’s partners, all during the phase where other contraception was required. All the babies were normal, noted Doug Colvard, co-author of the study and deputy director for programs at the nonprofit research organization CONRAD, Eastern Virginia Medical School, a co-sponsor of the study.

birth control pill
Shutterstock

Birth control linked to depression, new study says

Serious negative effects resulting from the shots included one case of depression and one experience of an abnormally fast and irregular heartbeat after the injections stopped. The researchers considered one intentional overdose of acetaminophen possibly related.

“It is possible that the fluctuations in the circulating progestin following bimonthly injections could have resulted in the reported or observed mood swings, such as occurs in women, whether on a hormonal contraceptive or not,” Colvard speculated.

Overall, 20 men dropped out early due to side effects. A total of 1,491 adverse events were reported by participants, including injection site pain, muscle pain, increased libido and acne. The researchers say that nearly 39% of these symptoms – including one death by suicide – were unrelated to the shots.

However, due to side effects, particularly depression and other mood disorders, the researchers decided in March 2011 to stop the study earlier than planned, with the final participants completing in 2012.

“I immediately thought of the recent findings on female birth control,” Elisabeth Lloyd said of a study published last month in the journal JAMA Psychiatry. A faculty scholar at the Kinsey Institute, she is a professor of biology and an adju