What is
it?
Erectile
dysfunction, sometimes called "impotence," is the
repeated inability to get or keep an erection firm enough
for sexual intercourse. The word "impotence" may also be used
to describe other problems that interfere with sexual intercourse
and reproduction, such as lack of sexual desire and problems
with ejaculation or orgasm. Using the term erectile dysfunction
makes it clear that those other problems are not involved.
Erectile
dysfunction, or ED, 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
ED and estimating its incidence difficult. Estimates range
from 15 million to 30 million, depending on the definition
used. According to the National Ambulatory Medical Care Survey
(NAMCS), for every 1,000 men in the United States, 7.7 physician
office visits were made for ED in 1985. By 1999, that rate
had nearly tripled to 22.3. The increase happened gradually,
presumably as treatments such as vacuum devices and injectable
drugs became more widely available and discussing erectile
function became accepted. Perhaps the most publicized advance
was the introduction of the oral drug sildenafil citrate (Viagra)
in March 1998. NAMCS data on new drugs show an estimated 2.6
million mentions of Viagra at physician office visits in 1999,
and one-third of those mentions occurred during visits for
a diagnosis other than ED.
In older
men, Erectile Dysfunction usually has a physical cause, such
as disease, injury, or side effects of drugs. Any disorder
that causes injury to the nerves or impairs blood flow in
the penis has the potential to cause ED. Incidence increases
with age: About 5 percent of 40-year-old men and between 15
and 25 percent of 65-year-old men experience Erectile
Dysfunction. But it is not an inevitable part of
aging.
ED is
treatable at any age, and awareness of this fact has been
growing. More men have been seeking help and returning to
normal sexual activity because of improved, successful treatments
for Erectile Dysfunction. Urologists, who
specialize in problems of the urinary tract, have traditionally
treated ED; however, urologists accounted for only 25 percent
of Viagra mentions in 1999.
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
and is surrounded by the corpus spongiosum.
Erection
begins with sensory or mental stimulation, or both. Impulses
from the brain and local nerves cause the muscles of the corpora
cavernosa to relax, allowing blood to flow in and fill the
spaces. The blood creates pressure in the corpora cavernosa,
making the penis expand. The tunica albuginea helps trap the
blood in the corpora cavernosa, thereby sustaining erection.
When muscles in the penis contract to stop the inflow of blood
and open outflow channels, erection is reversed.
What
causes Erectile Dysfunction ?
Since
an erection requires a precise sequence of events, Erectile
Dysfunction can occur when any of the events is disrupted.
The sequence includes nerve impulses in the brain, spinal
column, and area around the penis, and response in muscles,
fibrous tissues, veins, and arteries in and near the corpora
cavernosa.
Damage
to nerves, arteries, smooth muscles, and fibrous tissues,
often as a result of disease, is the most common cause of
ED. Diseases--such as diabetes, kidney disease, chronic alcoholism,
multiple sclerosis, atherosclerosis, vascular disease, and
neurologic disease--account for about 70 percent of Erectile
Dysfunction cases. Between 35 and 50 percent of men with diabetes
experience ED.
Also,
surgery (especially radical prostate and bladder surgery for
cancer) can injure nerves and arteries near the penis, causing
Erectile Dysfunction. Injury to the penis,
spinal cord, prostate, bladder, and pelvis can lead to ED
by harming nerves, smooth muscles, arteries, and fibrous tissues
of the corpora cavernosa.
In addition,
many common medicines--blood pressure drugs, antihistamines,
antidepressants, tranquilizers, appetite suppressants, and
cimetidine (an ulcer drug)--can produce ED as a side effect.
Experts
believe that psychological factors such as stress, anxiety,
guilt, depression, low self-esteem, and fear of sexual failure
cause 10 to 20 percent of ED cases. Men with a physical cause
for ED frequently experience the same sort of psychological
reactions (stress, anxiety, guilt, depression).
Other
possible causes are smoking, which affects blood flow in veins
and arteries, and hormonal abnormalities, such as not enough
testosterone.
How is
Erectile Dysfunction diagnosed?
Patient
History
Medical
and sexual histories help define the degree and nature of
ED. A medical history can disclose diseases that lead to ED,
while a simple recounting of sexual activity might distinguish
among problems with sexual desire, erection, ejaculation,
or orgasm.
Using
certain prescription or illegal drugs can suggest a chemical
cause, since drug effects account for 25 percent of ED cases.
Cutting back on or substituting certain medications can often
alleviate the problem.
Physical
Examination
A physical
examination can give clues to systemic problems. For example,
if the penis is not sensitive to touching, a problem in the
nervous system may be the cause. Abnormal secondary sex characteristics,
such as hair pattern or breast enlargement, can point to hormonal
problems, which would mean that the endocrine system is involved.
The examiner might discover a circulatory problem by observing
decreased pulses in the wrist or ankles. And unusual characteristics
of the penis itself could suggest the source of the problem--for
example, a penis that bends or curves when erect could be
the result of Peyronie's disease.
Laboratory
Tests
Several
laboratory tests can help diagnose Erectile Dysfunction. Tests
for systemic diseases include blood counts, urinalysis, lipid
profile, and measurements of creatinine and liver enzymes.
Measuring the amount of free testosterone in the blood can
yield information about problems with the endocrine system
and is indicated especially in patients with decreased sexual
desire.
Other
Tests
Monitoring
erections that occur during sleep (nocturnal penile tumescence)
can help rule out certain psychological causes of erectile
dysfunction. Healthy men have involuntary erections
during sleep. If nocturnal erections do not occur, then ED
is likely to have a physical rather than psychological cause.
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 a questionnaire, reveals
psychological factors. A man's sexual partner may also be
interviewed to determine expectations and perceptions during
sexual intercourse.
How is
Erectile Dysfunction treated?
Most physicians
suggest that treatments proceed from least to most invasive.
Cutting back on any drugs with harmful side effects is considered
first. For example, drugs for high blood pressure work in
different ways. If you think a particular drug is causing
problems with erection, tell your doctor and ask whether you
can try a different class of blood pressure medicine.
Psychotherapy
and behavior modifications in selected patients are considered
next if indicated, followed by oral or locally injected drugs,
vacuum devices, and surgically implanted devices. In rare
cases, surgery involving veins or arteries may be considered.
Psychotherapy
Experts
often treat psychologically based ED using techniques that
decrease the anxiety associated with intercourse. The patient's
partner can help with the techniques, which include gradual
development of intimacy and stimulation. Such techniques also
can help relieve anxiety when ED from physical causes is being
treated.
Drug
Therapy
Drugs
for treating ED can be taken orally, injected directly into
the penis, or inserted into the urethra at the tip of the
penis. In March 1998, the Food and Drug Administration (FDA)
approved Viagra, the first pill to treat Erectile Dysfunction.
In August 2003, the FDA gave approval to a second oral medicine,
vardenafil hydrochloride (Levitra). Additional oral medicines
are being tested for safety and effectiveness.
Taken
an hour before sexual activity, Viagra and Levitra work by
enhancing the effects of nitric oxide, a chemical that relaxes
smooth muscles in the penis during sexual stimulation and
allows increased blood flow.
While
oral medicines improve the response to sexual stimulation,
they do not trigger an automatic erection as injections do.
The recommended dose for Viagra is 50 mg, and the physician
may adjust this dose to 100 mg or 25 mg, depending on the
patient. The recommended dose for Levitra is 10 mg, and the
physician may adjust this dose to 20 mg if 10 mg is insufficient.
Lower doses of 5 mg and 2.5 mg are available for patients
who take other medicines or have conditions that may decrease
the body's ability to use Levitra.
Neither
Viagra nor Levitra should be used more than once a day. Men
who take nitrate-based drugs such as nitroglycerin for heart
problems should not use either drug because the combination
can cause a sudden drop in blood pressure. Also, Levitra should
not be taken with any of the drugs called alpha-blockers,
which are used to treat prostate enlargement or high blood
pressure.
Oral testosterone
can reduce ED in some men with low levels of natural testosterone,
but it is often ineffective and may cause liver damage. Patients
also have claimed that other oral drugs--including yohimbine
hydrochloride, dopamine and serotonin agonists, and trazodone--are
effective, but the results of scientific studies to substantiate
these claims have been inconsistent. Improvements observed
following use of these drugs 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
achieve stronger erections by injecting drugs into the penis,
causing it to become engorged with blood. Drugs such as papaverine
hydrochloride, phentolamine, and alprostadil (marketed as
Caverject) widen blood vessels. These drugs may create unwanted
side effects, however, including persistent erection (known
as priapism) and scarring. Nitroglycerin, a muscle relaxant,
can sometimes enhance erection when rubbed on the penis.
A system
for inserting a pellet of alprostadil into the urethra is
marketed as Muse. The system uses a prefilled applicator to
deliver the pellet about an inch deep into the urethra. An
erection will begin within 8 to 10 minutes and may last 30
to 60 minutes. The most common side effects are aching in
the penis, testicles, and area between the penis and rectum;
warmth or burning sensation in the urethra; redness from increased
blood flow to the penis; and minor urethral bleeding or spotting.
Research
on drugs for treating ED is expanding rapidly. Patients should
ask their doctor about the latest advances.
Vacuum
Devices
Mechanical
vacuum devices cause erection by creating a partial vacuum,
which draws blood into the penis, engorging and expanding
it. The devices have three components: a plastic cylinder,
into 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 .
One variation
of the vacuum device involves a semirigid rubber sheath that
is placed on the penis and remains there after erection is
attained 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 ED. Possible problems with implants include mechanical
breakdown and infection, although 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 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 a pump, which are also 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 ED caused by obstructions that
block the flow of blood. The best candidates for such surgery
are young men with discrete blockage of an artery because
of an injury to the crotch or fracture of the pelvis. The
procedure is almost never 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
the rigidity of the penis during erection. However, experts
have raised questions about the long-term effectiveness of
this procedure, and it is rarely done.
Hope
Through Research
Advances
in suppositories, injectable medications, implants, and vacuum
devices have expanded the options for men seeking treatment
for ED. These advances have also helped increase the number
of men seeking treatment. Gene therapy for ED is now being
tested in several centers and may offer a long-lasting therapeutic
approach for ED.
The National
Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
sponsors programs aimed at understanding the causes of erectile
dysfunction and finding treatments to reverse its
effects. NIDDK's Division of Kidney, Urologic, and Hematologic
Diseases supported the researchers who developed Viagra and
continue to support basic research into the mechanisms of
erection and the diseases that impair normal function at the
cellular and molecular levels, including diabetes and high
blood pressure.
| kidney.niddk.nih.gov
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