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.
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.
