What causes erectile dysfunction (ED)?

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 erectile dysfunction. 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 erectile dysfunction.

Lifestyle choices that contribute to heart disease and vascular problems also raise the risk of erectile dysfunction. Smoking, being overweight, and avoiding exercise are possible causes of erectile dysfunction.

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 erectile dysfunction 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 erectile dysfunction 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 erectile dysfunction cases. Men with a physical cause for erectile dysfunction 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 (ED) diagnosed?

Patient History

Medical and sexual histories help define the degree and nature of erectile dysfunction. A medical history can disclose diseases that lead to erectile dysfunction, 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 erectile dysfunction 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 erectile dysfunction 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.

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Source: NIDDK, NIH USA. NIH Publication No. 06–3923. December 2005. This publication was reviewed by Arnold Melman, M.D., Montefiore Medical Center, Bronx, NY; and Mark Hirsch, M.D., U.S. Food and Drug Administration.

Disclaimer: The U.S. Government does not endorse or favor any specific commercial product or company. Trade, proprietary, or company names appearing in this document are used only because they are considered necessary in the context of the information provided. If a product is not mentioned, the omission does not mean or imply that the product is unsatisfactory.