Impotence
Impotence is a consistent inability to sustain an erection
sufficient for sexual intercourse. Medical professionals often
use the term "erectile dysfunction" to describe this
disorder and to differentiate it from other problems that interfere
with sexual intercourse, such as lack of sexual desire and problems
with ejaculation and orgasm. This fact sheet focuses on impotence
defined as erectile dysfunction.
Impotence can be a total inability to achieve erection, an
inconsistent ability to do so, or a tendency to sustain only
brief erections. These variations make defining impotence and
estimating its incidence difficult. Experts believe impotence
affects between 10 and 15 million American men. In 1985, the
National Ambulatory Medical Care Survey counted 525,000 doctor-office
visits for erectile dysfunction.
Impotence usually has a physical cause, such as disease, injury,
or drug side-effects. Any disorder that impairs blood flow in
the penis has the potential to cause impotence. Incidence rises
with age: about 5 percent of men at the age of 40 and between
15 and 25 percent of men at the age of 65 experience impotence.
Yet, it is not an inevitable part of aging.
Impotence is treatable in all age groups, and awareness of
this fact has been growing. More men have been seeking help
and returning to near-normal sexual activity because of improved,
successful treatments for impotence. Urologists, who specialize
in problems of the urinary tract, have traditionally treated
impotence--especially complications of impotence.
How Does an Erection Occur? 
The penis contains two chambers, called the corpora cavernosa,
which run the length of the organ (see figure 1). A spongy
tissue fills the chambers. The corpora cavernosa are
surrounded by a membrane, called the tunica albuginea.
The spongy tissue contains smooth muscles, fibrous tissues,
spaces, veins, and arteries. The urethra, which is the channel
for urine and ejaculate, runs along the underside of the corpora
cavernosa .
Erection begins with sensory and mental stimulation. Impulses
from the brain and local nerves cause the muscles of the corpora
cavernosa to relax, allowing blood to flow in and fill the
open spaces. The blood creates pressure in the corpora cavernosa,
making the penis expand. The tunica albuginea helps
to trap the blood in the corpora cavernosa, thereby sustaining
erection. Erection is reversed when muscles in the penis contract,
stopping the inflow of blood and opening outflow channels.
What Causes Impotence?
Since an erection requires a sequence of events, impotence
can occur when any of the events is disrupted. The sequence
includes nerve impulses in the brain, spinal column, and area
of the penis, and response in muscles, fibrous tissues, veins,
and arteries in and near the corpora cavernosa.
Damage to arteries, smooth muscles, and fibrous tissues, often
as a result of disease, is the most common cause of impotence.
Diseases--including diabetes, kidney disease, chronic alcoholism,
multiple sclerosis, atherosclerosis, and vascular disease--account
for about 70 percent of cases of impotence. Between 35 and 50
percent of men with diabetes experience impotence.
Surgery (for example, prostate surgery) can injure nerves
and arteries near the penis, causing impotence. Injury to the
penis, spinal cord, prostate, bladder, and pelvis can lead to
impotence by harming nerves, smooth muscles, arteries, and fibrous
tissues of the corpora cavernosa.
Also, many common medicines produce impotence as a side effect.
These include high blood pressure drugs, antihistamines, antidepressants,
tranquilizers, appetite suppressants, and cimetidine (an ulcer
drug).
Experts believe that psychological factors cause 10 to 20
percent of cases of impotence. These factors include stress,
anxiety, guilt, depression, low self-esteem, and fear of sexual
failure. Such factors are broadly associated with more than
80 percent of cases of impotence, usually as secondary reactions
to underlying physical causes.
Other possible causes of impotence are smoking, which affects
blood flow in veins and arteries, and hormonal abnormalities,
such as insufficient testosterone.
How Is Impotence Diagnosed? 
Patient History
Medical and sexual histories help define the degree and nature
of impotence. A medical history can disclose diseases that lead
to impotence. A simple recounting of sexual activity might distinguish
between problems with erection, ejaculation, orgasm, or sexual
desire.
A history of using certain prescription drugs or illegal drugs
can suggest a chemical cause. Drug effects account for 25 percent
of cases of impotence. Cutting back on or substituting certain
medications often can alleviate the problem.
Physical Examination
A physical examination can give clues for systemic problems.
For example, if the penis does not respond as expected to certain
touching, a problem in the nervous system may be a cause. Abnormal
secondary sex characteristics, such as hair pattern, can point
to hormonal problems, which would mean the endocrine system
is involved. A circulatory problem might be indicated by, for
example, an aneurysm in the abdomen. And unusual characteristics
of the penis itself could suggest the root of the impotence--for
example, bending of the penis during erection could be the result
of Peyronie's disease.
Laboratory Tests
Several laboratory tests can help diagnose impotence. Tests
for systemic diseases include blood counts, urinalysis, lipid
profile, and measurements of creatinine and liver enzymes. For
cases of low sexual desire, measurement of testosterone in the
blood can yield information about problems with the endocrine
system.
Other Tests
Monitoring erections that occur during sleep (nocturnal penile
tumescence) can help rule out certain psychological causes of
impotence. Healthy men have involuntary erections during sleep.
If nocturnal erections do not occur, then the cause of impotence
is likely to be physical rather than psychological. Tests of
nocturnal erections are not completely reliable, however. Scientists
have not standardized such tests and have not determined when
they should be applied for best results.
Psychosocial Examination
A psychosocial examination, using an interview and questionnaire,
reveals psychological factors. The man's sexual partner also
may be interviewed to determine expectations and perceptions
encountered during sexual intercourse.
How Is Impotence Treated?
Most physicians suggest that treatments for impotence proceed
along a path moving from least invasive to most invasive. This
means cutting back on any harmful drugs is considered first.
Psychotherapy and behavior modifications are considered next,
followed by vacuum devices, oral drugs, locally injected drugs,
and surgically implanted devices (and, in rare cases, surgery
involving veins or arteries).
Psychotherapy
Experts often treat psychologically based impotence using
techniques that decrease anxiety associated with intercourse.
The patient's partner can help apply the techniques, which include
gradual development of intimacy and stimulation. Such techniques
also can help relieve anxiety when physical impotence is being
treated.
Drug Therapy
Drugs for treating impotence can be taken orally or injected
directly into the penis. Oral testosterone can reduce impotence
in some men with low levels of natural testosterone. Patients
also have claimed effectiveness of other oral drugs, including
yohimbine hydrochloride, dopamine and serotonin agonists, and
trazodone--but no scientific studies have proved the effectiveness
of these drugs in relieving impotence. Some observed improvements
following their use may be examples of the placebo effect, that
is, a change that results simply from the patient's believing
that an improvement will occur.
Many men gain potency by injecting drugs into the penis, causing
it to become engorged with blood. Drugs such as papaverine hydrochloride,
phentolamine, and prostaglandin E1 widen blood vessels. These
drugs may create unwanted side effects, however, including persistent
erection (known as priapism) and scarring. Nitroglycerin, a
muscle relaxant, sometimes can enhance erection when rubbed
on the surface of the penis.
Research on drugs for treating impotence is expanding rapidly.
Patients should ask their doctors about the latest advances.
Vacuum Devices
Mechanical vacuum devices cause erection by creating a partial
vacuum around the penis, which draws blood into the penis, engorging
it and expanding it. The devices have three components: a plastic
cylinder, in which the penis is placed; a pump, which draws
air out of the cylinder; and an elastic band, which is placed
around the base of the penis, to maintain the erection after
the cylinder is removed and during intercourse by preventing
blood from flowing back into the body (see figure 2).
One variation of the vacuum device involves a semirigid rubber
sheath that is placed on the penis and remains there after
attaining erection and during intercourse. 
Surgery
Surgery usually has one of three goals:
- to implant a device that can cause the penis to become
erect;
- to reconstruct arteries to increase flow of blood to
the penis;
- to block off veins that allow blood to leak from the
penile tissues.
Implanted devices, known as prostheses, can restore erection
in many men with impotence. Possible problems with implants
include mechanical breakdown and infection. Mechanical problems
have diminished in recent years because of technological advances.
Malleable implants usually consist of paired rods, which are
inserted surgically into the corpora cavernosa, the twin
chambers running the length of the penis. The user manually
adjusts the position of the penis and, therefore, the rods.
Adjustment does not affect the width or length of the penis.
Inflatable implants consist of paired cylinders, which are
surgically inserted inside the penis and can be expanded using
pressurized fluid (see figure 3). Tubes connect the cylinders
to a fluid reservoir and pump, which also are surgically implanted.
The patient inflates the cylinders by pressing on the small
pump, located under the skin in the scrotum. Inflatable implants
can expand the length and width of the penis somewhat. They
also leave the penis in a more natural state when not inflated.
Surgery to repair arteries can reduce impotence caused by
obstructions that block the flow of blood to the penis. The
best candidates for such surgery are young men with discrete
blockage of an artery because of an injury to the crotch area
or fracture of the pelvis. The procedure is less successful
in older men with widespread blockage.
Surgery to veins that allow blood to leave the penis usually
involves an opposite procedure--intentional blockage. Blocking
off veins (ligation) can reduce the leakage of blood that diminishes
rigidity of the penis during erection. However, experts have
raised questions about this procedure's long-term effectiveness.
What Will the Future Bring?
Advances in injectable medications, implants, and vacuum devices
have expanded the options for men seeking treatment for impotence.
These advances also have helped increase the number of men seeking
treatment.
One possible new treatment, currently in experimental stages,
is a small pellet that a man can insert in the end of his penis.
The pellet releases a drug that migrates into the erectile tissue
and causes a temporary erection. There is no need for a needle.
Whether or not this method proves to be safe and effective,
ongoing improvements in traditional methods should continue
to create more successful and widespread treatment of impotence.
Points to Remember
- Impotence is a consistent inability to sustain an erection
sufficient for sexual intercourse.
- Impotence affects 10 to 15 million American men.
- Impotence usually has a physical cause.
- Impotence is treatable in all age groups.
- Treatments include psychotherapy, drug therapy, vacuum devices,
and surgery.
NIH Publication No. 95-3923
September 1995
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