Surgery and drug treatments for benign prostatic hyperplasia (BPH) can also increase the risk for impotence, although to a much lesser degree than surgery for prostate cancer.

 
• Between 4% and 10% of patients who have transurethral resection of the prostate (TURP) and open prostatectomy for BPH report impotence afterward. The risk is very low, however, in men who were functioning normally before surgery.  
• Finasteride (Proscar) has been associated with impotence in between 6% and 19% of patients. Anti-androgen agents used in BPH also cause erectile dysfunction.

Medications
About a quarter of all cases of impotence can be attributed to medications. Many drugs pose a risk for erectile dysfunction. Some authorities go so far as to say that nearly every drug, prescription or nonprescription, can be a cause of temporary erectile dysfunction.

Among the drugs that are common causes of impotence are the following:

 
• Drugs used in chemotherapy.  
• Many drugs taken for high blood pressure, particularly diuretics and beta blockers.  
• Most drugs used for psychological disorders, including anti-anxiety drugs, anti-psychotic drugs, and antidepressants, especially selective serotonin reuptake inhibitors (SSRIs). Newer antidepressants pose fewer problems.

Drugs that sometimes cause impotence include:

 
• Older anti-ulcer medications (cimetidine).  
• Anticholinergic drugs (including some antihistamines).

Physical Trauma, Stress or Injury
Injury. Spinal cord injury and pelvic trauma, such as a pelvic fracture, can cause nerve damage that results in impotence.

Bicycling. Studies have indicated that regular bicycling may pose a risk for erectile dysfunction by reducing blood flow to the penis.

Vasectomy. Vasectomy does not cause erectile dysfunction. When impotence occurs after this procedure, it is often in men whose female partners were unable to accept the operation.

Hormonal Abnormalities
Hypogonadism (Testicular Failure). Hypogonadism in men is a deficiency in male hormones, usually due to an abnormality in the testicles, which secrete these hormones. It affects 4 to 5 million men in the United States. In addition to impotence, hypogonadism causes reductions in energy, sex drive, lean body mass, and bone density. Hypogonadism can be caused by a number of different conditions. Among them are the following:

 
• Disorders in the pituitary or hypothalamus glands.  
• Malnutrition.  
• Genetic factors.  
• Myotonic dystrophy.  
• Orchitis (inflammation of the testicles).  
• Physical injury.  
• Mumps.  
• Radiation treatments.  
• Exercise-induced hypogonadism. Only a few cases of exercise-induced hypogonadism have been identified in men, but some researchers believe certain athletes may be at risk, including those who began endurance training before full sexual maturity, have very low body weight, and have a history of stress fracture.

Low Testosterone Levels. Only about 5% of men who see a physician about erectile dysfunction have low levels of testosterone, the primary male hormone. In general, lower testosterone levels appear to reduce sexual interest, not cause impotence. A 1999 study, however, suggests that testosterone levels are not an accurate reflection of sexual drive.

Other Hormonal Abnormalities. Other hormonal abnormalities that can lead to erectile dysfunction in men are the following:

 
• High levels of the female hormone estrogen may cause impotence (which may occur in men with liver disease).  
• Abnormalities of the pituitary gland that cause high levels of the hormone prolactin are particularly likely to cause impotence.

Other, uncommon hormonal causes of impotence include abnormalities of the thyroid gland and the adrenal glands.

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American Urological Association