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Medical Author:

Dennis Lee, MD

Dennis Lee, MD

Dr. Lee was born in Shanghai, China, and received his college and medical training in the United States. He is fluent in English and three Chinese dialects. He graduated with chemistry departmental honors from Harvey Mudd College. He was appointed president of AOA society at UCLA School of Medicine. He underwent internal medicine residency and gastroenterology fellowship training at Cedars Sinai Medical Center.

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Medical Author:

Siamak T. Nabili, MD, MPH

Siamak T. Nabili, MD, MPH

Dr. Nabili received his undergraduate degree from the University of California, San Diego (UCSD), majoring in chemistry and biochemistry. He then completed his graduate degree at the University of California, Los Angeles (UCLA). His graduate training included a specialized fellowship in public health where his research focused on environmental health and health-care delivery and management.

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Medical Editor:

Jay W. Marks, MD

Jay W. Marks, MD

Jay W. Marks, MD, is a board-certified internist and gastroenterologist. He graduated from Yale University School of Medicine and trained in internal medicine and gastroenterology at UCLA/Cedars-Sinai Medical Center in Los Angeles.

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Medical Editor:

Melissa Conrad Stöppler, MD

Melissa Conrad Stöppler, MD

Melissa Conrad Stöppler, MD, is a U.S. board-certified Anatomic Pathologist with subspecialty training in the fields of Experimental and Molecular Pathology. Dr. Stöppler's educational background includes a BA with Highest Distinction from the University of Virginia and an MD from the University of North Carolina. She completed residency training in Anatomic Pathology at Georgetown University followed by subspecialty fellowship training in molecular diagnostics and experimental pathology.

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In this Article

• What is erectile dysfunction?
• How common is erectile dysfunction?
• What is normal penis anatomy?
• How does erection occur?
• How is erection sustained?
• What are some of the risk factors for erectile dysfunction?
• What are the causes of erectile dysfunction?
• How is erectile dysfunction diagnosed?
• What are the treatments for erectile dysfunction?
• What medications are used to treat erectile dysfunction?
• Oral phosphodiesterase type 5 (PDE5) inhibitors
• Sildenafil (Viagra)
• Vardenafil (Levitra)
• Tadalafil (Cialis)
• Intracavernosal injections
• Intraurethral suppositories
• How effective is testosterone in treating erectile dysfunction?
• Can low testosterone level be replaced?
• Vacuum devices
• Surgery for erectile dysfunction
• What will the future bring for erectile dysfunction?
• Erectile Dysfunction At A Glance
• Impotence (Erectile Dysfunction, ED) FAQs
• Patient Comments: Erectile Dysfunction (Impotence) - Treatments
• Patient Comments: Erectile Dysfunction (Impotence) - Share Your Experience
• Find a local Urologist in your town
• Impotence (ED) Index

Patient history

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:

1. Is the patient suffering from erectile dysfunction or from loss of libido or a disorder of ejaculation (for example, premature ejaculation)?



2. 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.



3. 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 dysfunction. 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.



4. Is the patient taking medications that can contribute to erectile dysfunction?

Physical examination

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.

Laboratory tests

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.

Imaging tests

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.

Other tests

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.

Psychosocial examination

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.