What is erectile dysfunction?
Erectile dysfunction (ED), also known as
impotence, is the inability to achieve or sustain an erection for satisfactory
sexual activity. Erectile dysfunction is different from other conditions that
interfere with male sexual intercourse, such as lack of sexual desire (decreased
libido) and problems with ejaculation and orgasm (ejaculatory dysfunction). This
article focuses on the evaluation and treatment of erectile dysfunction.
How common is erectile dysfunction?
Erectile dysfunction (ED, impotence) varies in severity; some men have a
total inability to achieve an erection, others have an inconsistent ability to
achieve an erection, and still others can sustain only brief erections. The
variations in severity of erectile dysfunction make estimating its frequency
difficult. Many men also are reluctant to discuss erectile dysfunction with
their doctors due to embarrassment, and thus the condition is underdiagnosed.
Nevertheless, experts have estimated that erectile dysfunction affects 30
million men in the United States.
While erectile dysfunction can occur at any age, it is uncommon among young
men and more common in the elderly. By age 45, most men have experienced
erectile dysfunction at least some of the time. According to the Massachusetts
Male Aging Study, complete impotence increases from 5% among men 40 years of age
to 15% among men 70 years and older. Population studies conducted in the
Netherlands found that some degree of erectile dysfunction occurred in 20% of
men between ages 50-54, and in 50% of men between ages 70-78. In 1999, the
National Ambulatory Medical Care Survey counted 1,520,000 doctor-office visits
for erectile dysfunction. Other studies have noted that approximately 35% of men
40-70 years of age suffer from moderate to severe ED, and an additional 15% may
have milder forms.
What are some of the risk factors for erectile dysfunction?
The common risk factors for ED include the following:
- Advanced age
- Cardiovascular disease
- Diabetes mellitus
- High cholesterol
- Cigarette smoking
- Recreational drug use
- Depression or other psychiatric diseases
How is erectile dysfunction diagnosed?
A diagnosis of erectile dysfunction is made in men who have repeated inability
to achieve and/or maintain an erection for satisfactory sexual performance for
at least three months. Candid communication between the patient and the doctor
is important in establishing the diagnosis of erectile dysfunction, assessing
its severity, and determining the cause. During patient interviews, doctors try
to answer the following questions:
- Is the patient suffering from erectile dysfunction or from loss of
libido or a disorder of ejaculation (for example, premature ejaculation)?
- Is erectile dysfunction due to psychological or physical factors?
Healthy men have involuntary erections in the early morning and during REM
sleep (a stage in the sleep cycle with rapid eye movements). Men with
psychogenic erectile dysfunction (erectile dysfunction due to psychological
factors such as stress and anxiety rather than physical factors) usually
maintain these involuntary erections. Men with physical causes of erectile
dysfunction (for example, atherosclerosis, smoking, and diabetes) usually do
not have these involuntary erections.
- Are there physical causes of erectile dysfunction? A prior history of
cigarette smoking, heart attacks, strokes, and poor circulation in the
extremities suggest atherosclerosis as the cause of the erectile
- Diminished sensation of the penis and the testicles, bladder
dysfunction, and decreased sweating in the lower extremities may suggest
diabetic nerve damage. Loss of sexual desire and drive, lack of sexual
fantasies, gynecomastia (enlargement of breasts), and diminished facial hair
suggest low testosterone levels.
- Is the patient taking medications that can contribute to erectile
The physical examination can reveal clues for physical causes of erectile
dysfunction. For example, if the penis does not respond as expected to touching,
a problem in the nervous system may be the cause. Small testicles, lack of
facial hair, and enlarged breasts (gynecomastia) can point to hormonal problems
such as hypogonadism with low testosterone levels. A reduced flow of blood as a
result of atherosclerosis can sometimes be diagnosed by finding diminished
arterial pulses in the legs or listening with a stethoscope for bruits (the
sound of blood flowing through narrowed arteries). Unusual characteristics of
the penis itself could suggest the root of the erectile dysfunction, for
example, bending of the penis with painful erection could be the result of
Peyronie's disease. Particular attention is paid to any underlying risk factors
for erectile dysfunction.
The following are common laboratory tests to evaluate erectile dysfunction:
- Complete blood counts
- Urinalysis: An abnormal urinalysis may be a sign of diabetes mellitus
and kidney damage.
- Lipid profile: High levels of LDL cholesterol (bad cholesterol) in the
blood promotes atherosclerosis.
- Blood glucose levels: Abnormally high blood glucose levels may be a sign
of diabetes mellitus.
- Blood hemoglobin A 1c: Abnormally high levels of blood hemoglobin A 1c
in patients with diabetes mellitus establish that there is poor control of
blood glucose levels.
- Serum creatinine: An abnormal serum creatinine may be the result of
kidney damage due to diabetes.
- Liver enzymes and liver function tests: Advanced liver disease
(cirrhosis) can result in hormonal imbalance and gonad dysfunction leading
to low testosterone levels. Thus, evaluation for liver disease may be
necessary in cases of erectile dysfunction.
- Total testosterone levels: Blood samples for total testosterone levels
should be obtained in the early morning (before 8 a.m.) because of wide
fluctuations in the testosterone levels throughout the day. A low total
testosterone level suggests hypogonadism. Measurement of bio-available
testosterone may be a better measurement than total testosterone, especially
in obese men and men with liver disease, but measurement of bio-available
testosterone is not widely available.
- Other hormone levels: Measurement of other hormones beside testosterone
(luteinizing hormone (LH), prolactin level, and cortisol level) may provide
clues to other underlying causes of testosterone deficiency and erectile
problems, such as pituitary disease or adrenal gland abnormalities. Thyroid
levels may be routinely checked as both hypothyroidism and hyperthyroidism
can contribute to erectile dysfunction.
PSA levels: PSA (prostate specific antigen) blood levels and prostate
examination to exclude prostate cancer is important before starting
testosterone treatment since testosterone can aggravate prostate cancer.
Other blood tests: Evaluation for hemochromatosis, lupus, scleroderma, zinc
deficiency, sickle cell anemia, cancers (leukemia, colon cancer) are some of
the other potential tests that may be performed based on each individual's
history and symptoms.
In a setting of a previous pelvic trauma, X-rays may be performed to assess
various bony abnormalities. Ultrasound of the penis and testicles is done
occasionally to check for testicular size and structural abnormalities.
Ultrasound with Doppler imaging can provide additional information about blood
flow of the penis. Rarely, an angiogram may be performed in cases in which
possible vascular surgery could be beneficial.
Prostaglandin E1 injection test is sometimes performed to determine the penile
blood flow. Prostaglandin is directly injected into the corpora cavernosa in
order to cause dilation of blood vessels and promote blood flow into the penis.
If erection ensues, it confirms normal or adequate blood flow to the penis. This
can also provide information about possible therapeutic options.
Monitoring erections that occur during sleep (nocturnal penile tumescence)
can help distinguish between erectile dysfunction of psychological and physical
causes. A band is worn around the penis for two to three successive nights and
it can signal intensity and duration of erections if they occur. If nocturnal
erections do not occur, then the cause of erectile dysfunction is likely to be
physical rather than psychological, however, tests of nocturnal erections are
not completely reliable. Scientists have not standardized the tests and have not
determined in whom they should be done.
Direct vibrational stimulation (biothesiometry) is occasionally done to
evaluate penile nerve function. Small electromagnetic electrodes are placed on
the shaft of the penis and vibration amplitude is slightly adjusted until
sensation is noted by the patient. Although this test does not measure the exact
nerve function, it serves as a screening method to detect any sensory nerve
deficit as the cause of ED.
A psychosocial examination using an interview and questionnaire may reveal
psychological factors contributing to erectile dysfunction. The sexual partner
also may be interviewed to determine expectations and perceptions encountered
during sexual intercourse.