ED usually has a physical cause, such as disease, injury, or side effects of drugs. Any disorder that causes injury to the nerves or impairs blood flow in the penis has the potential to cause ED.
Because 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.
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, high blood pressure, nerve disease or nerve damage, multiple sclerosis, atherosclerosis, and heart disease-account for the majority of ED cases. Patients should be thoroughly evaluated for these conditions before they begin any form of treatment for ED.
Lifestyle choices that contribute to heart disease and vascular problems also raise the risk of ED. Smoking, drinking alcohol excessively, being overweight, and not exercising are possible causes of ED.
Surgery-especially radical prostate and bladder surgery for cancer-can also 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 the fibrous tissues of the corpora cavernosa.
In addition, ED can be a side effect of many common medicines such as blood pressure drugs, antihistamines, antidepressants, tranquilizers, appetite suppressants, and cimetidine, an ulcer drug.
Psychological factors such as stress, anxiety, guilt, depression, low self-esteem, and fear of sexual failure can also cause ED. Even when ED has a physical cause, psychological factors may make the condition worse.
Hormonal abnormalities, such as low levels of testosterone, are a less frequent cause of ED.