Since an erection requires a precise sequence of events, (ED) 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 (two parallel chambers of the penis that, when filled with blood, produce an erection).

Damage to nerves, arteries, smooth muscles, and fibrous tissues, often as a result of disease, is the most common cause of ED. Diseases - such as diabetes, kidney disease, chronic alcoholism, multiple sclerosis, atherosclerosis, vascular disease, and neurologic disease - account for about 70 percent of ED cases. Between 35 and 50 percent of men with diabetes experience ED.

What is Erectile Dysfunction?

Erectile dysfunction means the same thing as impotence. Both erectile dysfunction and impotence mean the inability to have or keep an erection that is good enough for sexual intercourse. If you have erectile dysfunction, it does not mean that you have an inability to have orgasm or a decreased libido (sex drive) or have premature ejaculation; although if you have these other conditions, they can affect the extent of your erectile dysfunction.

What Is an Erection?

How your body actually produces an erection and then maintains it is a complicated process that depends on

  * blood flow
  * steroid (androgen) production
  * nervous system (neurological) stimulation
  * chemical signals from the brain (neurotransmitters)
  * enzymes

During an erection, small areas within the penis allow more blood in. This increase in blood causes the expansion/erection of the penis.

The increase in blood into the penis also compresses the blood vessels (veins) that allow blood to circulate back out of the penis. So once blood flows in, it is trapped and cannot flow out. This allows the erection to be maintained during sexual activity.

What Are the Causes of Erectile Dysfunction?

The causes of erectile dysfunction or impotence can be divided into two broad groups: organic and non-organic.

Organic
Organic causes are related to physical problems, problems involving your body. Examples include:

  * neurological deficits caused by diabetes, spinal cord injuries, or brain (cerebral) injuries
  * physical injury (trauma)
  * poor blood circulation caused by atherosclerotic disease often related to smoking
  * inadequate blood vessel compression, which does not allow the erection to be maintained
  * drug-induced changes that decrease erectile ability

Non-Organic
Non-organic causes are related to psychological factors.  The non-organic causes of erectile dysfunction are less well understood. Personal issues, such as marital problems, performance anxiety, or lack of desire, can and do affect erectile ability. (This is also called psychogenic impotence.)

Evaluation of Erectile Dysfunction

My evaluation of erectile dysfunction can be extensive but initially involves a careful history and physical examination. I often order blood tests to look at hormone levels and other elements in your blood. Some examples of the many possible tests that I might use include a test to measure the largeness and frequency of your night time erections (also called nocturnal penile tumescence), Doppler ultrasound to examine blood flow, and different forms of penile pressure measurements.

Also, surgery (especially radical prostate and bladder surgery for cancer) can injure nerves and arteries near the penis, causing ED. Injury to the penis, spinal cord, prostate, bladder, and pelvis can lead to ED 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 ED 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 ED cases. Men with a physical cause for ED 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.

SOURCE: National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)