Physical Causes

A number of conditions share a common problem with erectile dysfunction--the impaired ability of blood vessels to open and allow normal blood flow. Such conditions include diabetes, hypertension, coronary artery disease, kidney failure, peripheral artery disease, and stroke. Increasingly, researchers are studying the role of nitric oxide, which plays a major role in keeping blood vessels open, in all of these disorders.

The following diseases are highly associated with erectile dysfunction:

• Heart Disease. Erectile problems may be a warning sign of heart disease. Several important studies in 2005 and 2006 firmly established this link. The studies indicated that men with ED are more likely to have coronary artery disease (CAD) and high blood pressure, and more severe forms of heart disease, than men without erectile problems. In fact, the studies suggested that ED is a stronger predictor of CAD than smoking, family history, cholesterol levels, or high blood pressure. Men who experience ED are at greater risk for angina, heart attack, or stroke. Many experts now recommend that men with erectile dysfunction undergo a complete cardiovascular evaluation.
• High Blood Pressure (Hypertension). Erectile dysfunction is a very common problem in men with high blood pressure. More than 40 percent of men with erectile dysfunction have hypertension. The disease process is the major contributor to impotence, but many of the drugs used to treat hypertension also cause it. Newer anti-hypertensive drugs, including angiotensin-converting enzyme (ACE) inhibitors and angiotensin-receptor blockers (ARBs) are less likely to cause erectile dysfunction. In fact, ARBs may be particularly effective in restoring erectile function in men with high blood pressure who suffer from impotence.
• Diabetes. Diabetes is a major risk factor for erectile dysfunction. It may increase the risk for ED by as much as 169% and contribute to as many as 40% of impotence cases. Between a third and a half of all men with diabetes report some form of sexual difficulty. Blocked arteries and nerve damage are both common complications of diabetes. When the blood vessels or nerves of the penis are involved, erectile dysfunction can result. Diabetes is also associated with heart disease, another risk factor for ED.
• Obesity. Obesity increases the risk for diabetes, heart disease, and erectile dysfunction. According to a 2006 study, obese men are 60% more likely to develop ED than normal weight men.

Other Common Medical Conditions That Contribute to Erectile Dysfunction

Parkinson's Disease. As a risk factor for impotence, Parkinson's disease (PD) is an under-appreciated problem. It is estimated that about a third of men with PD experience impotence. The physical cause of PD-related impotence is most likely an impaired nervous system. Depression and lowered self-esteem also contribute to erectile dysfunction in these patients.

Multiple Sclerosis. Multiple sclerosis (MS), which affects the central nervous system, also precipitates sexual dysfunction in as many as 78% of male patients. (Corticosteroids, which are common treatments for MS, may improve sexual function.)

Other Common Medical Conditions. Other medical conditions that have been associated with erectile dysfunction include allergies, thyroid problems, lung disease, and epilepsy.

Prostate Cancer and Its Treatments

Advanced prostate cancer can damage nerves needed for erectile function. Prostate surgery and surgical and radiation treatments for prostate cancer can also cause impotence. A number of treatments for sexual dysfunction are available that may help some men. [For more information, see In-Depth Report #33: Prostate cancer.]

Prostate Cancer Surgery (Radical Prostatectomy). The first nationally representative study to evaluate long-term outcomes after radical prostatectomy concluded that impotence occurs far more frequently than previously reported. Those who have so-called nerve-sparing surgeries have better results than those whose surgeries affect the nerves around the prostate. Some evidence also suggests that sexual function rates might improve if the nerve-sparing prostate surgeries also spare the ducts that carry semen.

Some studies suggest that impotence after prostate surgery may in part be due to injury to the smooth muscles in the blood vessels. Early treatments to maintain penile blood flow, particularly alprostadil injections, may helpful in restoring erectile function. In one study, men administered injections every other night for 6 months. They then started taking sildenafil (Viagra) 3 months after surgery. At 6 months, 82% of these men achieved penetration compared to 52% of men who took Viagra only. The vacuum pump may serve a similar purpose as the injections.

Radiation. Although it is generally believed that radiation poses a lower risk for impotence than does surgery, studies have reported similar rates after 3 years. Experts suggest radiation injures the blood vessels and so lead to erectile dysfunction over time. Some studies report a lower risk for impotence from brachytherapy, a radiation technique that involves the implantation of radioactive "seeds" compared to external-beam radiation. Still, there have been very few studies that have lasted more than 2 years. One 5-year study reported a high long-term rate of impotence (53%) with brachytherapy, which is close to that of standard externally administered radiation. Early use of alprostadil injections and Viagra may help these men as well as those who had surgery.

Drug Treatments. Prostate cancer medical treatments commonly employ androgen-suppressive treatments, which cause erectile dysfunction.

Surgical Treatments that Affect Intestinal Tracts

Surgery for Colon and Rectal Cancers. Surgical and radiation treatments for colorectal cancers can cause impotence in some patients. In general, colostomy does not usually affect sexual function. However, wide rectal surgery can cause short term or long-term sexual dysfunction. Total mesorectal excision (TME) may pose fewer risks than standard surgery. Sildenafil (Viagra) may help many men who experience this after surgery.

Surgical Treatment of Inflammatory Bowel Disease. Rectal excision for inflammatory bowel disease (IBD) can cause impotence, but rates are low (2 - 4%). Sildenafil (Viagra) is very effective in restoring potency after IBD surgery.

Operations for Fistulas. Surgery to repair anal fistulas can affect the muscles that control the rectum (external anal sphincter muscles), sometimes causing impotence. (Repair of these muscles may restore erectile function.)

Treatments for Benign Prostatic Hyperplasia (BPH)

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 - 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 6 - 19% of patients. Anti-androgen drugs used to treat BPH can 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 experts think that nearly every drug, prescription or nonprescription, can be a cause of temporary erectile dysfunction.

Drugs that commonly cause impotence may include:

• 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.
• Anti-androgens, including drugs known as gonadotropin-releasing hormone agonists. They are used in prostate cancer and also for treating BPH.

Drugs that sometimes cause impotence include:

• Older anti-ulcer medications (cimetidine)
• Anticholinergic drugs (including some antihistamines)
• Antinausea drugs, particularly metoclopramide (Reglan)
• Antifungal drugs (especially ketoconazole)
• Nonsteroidal anti-inflammatory drugs (NSAIDs), when used on a daily basis

Physical Trauma, Stress, or Injury

Injury to the Spine. Spinal cord injury and pelvic trauma, such as a pelvic fracture, can cause nerve damage that results in impotence. Other conditions that can injure the spine and effect impotence include spinal cord tumors, spina bifida, and a history of polio.

Orthopedic surgery. Erectile dysfunction can sometimes result from orthopedic surgery. A study of young men who underwent surgical repair (“intramedullary nailing”) for a broken thighbone reported that about 40% of these patients experienced erectile dysfunction after surgery. The researchers theorized that the surgery affected pelvic nerves that play a key role in erection. Patients who received a higher dose of muscle relaxant during surgery had better sexual function outcomes.

Bicycling. Studies have indicated that frequent bicycling may pose a risk for erectile dysfunction by reducing blood flow to the penis. The greatest risk is in cyclers who sit upright while cycling. In addition, a 2004 report in the Journal of Urology found that long distance cyclers may reduce their risk by riding a road bike instead of a mountain bike and by choosing saddles without a cutout.

Note: 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 - 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:

• 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. Some researchers believe, however, that 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 fractures.

Low Testosterone Levels. Only about 5% of men who see a doctor 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.

Other Hormonal Abnormalities. Other hormonal abnormalities that can lead to erectile dysfunction include:

• High levels of the female hormone estrogen (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 an underactive or overactive thyroid or adrenal gland abnormalities.

Varicoceles

A varicocele is an enlarged (varicose) vein in the cord that connects to the testicle. Varicoceles are found in 15 - 20% of all men and in 25 - 40% of infertile men. When varicoceles occur in both testicles, they may contribute to hormone imbalances that cause erectile dysfunction.