The ability to achieve and sustain erections require:
A healthy nervous system that conducts nerve impulses in the brain, spinal column, and penis,
Healthy arteries in and near the corpora cavernosa,
Healthy smooth muscles and fibrous tissues within the corpora cavernosa,
Adequate levels of nitric oxide in the penis.
Erectile dysfunction can occur if one or more of these requirements are not met. The causes of erectile dysfunction include:
Aging:
There are two reasons why older men are more likely to experience erectile dysfunction than younger men. First, older men are more likely to develop diseases (such as heart attacks, angina, strokes, diabetes mellitus, and high blood pressure) that are associated with erectile dysfunction. Second, the aging process alone can cause erectile dysfunction in some men; primarily by decreasing the compliance of the tissues in the corpora cavernosa, although it has been suggested, but not proven, that there is also decreased production of nitric oxide in the nerves that innervate the corporal smooth muscle within the penis.
Diabetes mellitus:
Erectile dysfunction tends to develop 10-15 years earlier in diabetic men than among nondiabetic men. In a population study of men with type I diabetes for more than 10 years, erectile dysfunction was reported by 55% of men between the ages of 50 to 60 years. The increased risk of erectile dysfunction among men with diabetes mellitus may be due to the earlier onset and greater severity of atherosclerosis that narrows the arteries and thereby reduces the delivery of blood to the penis. When insufficient blood is delivered to the penis, it is not possible to achieve an erection. Diabetes mellitus also causes erectile dysfunction by damaging both sensory and autonomic nerves, a condition called diabetic neuropathy. Smoking cigarettes, obesity, poor control of blood glucose levels, and having diabetes mellitus for a long time further increases the risk of erectile dysfunction in diabetes. In addition to atherosclerosis and/or neuropathy causing ED in diabetes, many diabetic men develop a myopathy (muscle disease) as their cause of ED in which the compliance of the muscle in the corpora cavernosa is decreased and clinically this presents as an inability to maintain the erection.
Hypertension (high blood pressure):
Patients with essential hypertension or arteriosclerosis have an increased risk of developing erectile dysfunction. Essential hypertension is the most common form of hypertension; it is called essential hypertension because it is not caused by another disease, (for example, by kidney disease). It is not clearly known how essential hypertension causes erectile dysfunction; however, patients with essential hypertension have been found to have low production of nitric oxide by the arteries of the body, including the arteries in the penis. Scientists now suspect that the decreased levels of nitric oxide in patients with essential hypertension may contribute to erectile dysfunction.
Cardiovascular diseases:
The most common cause of cardiovascular diseases in the United States is atherosclerosis, the narrowing and hardening of arteries that reduces blood flow. Atherosclerosis typically affects arteries throughout the body and is aggravated by hypertension, high blood cholesterol levels, cigarette smoking, and diabetes mellitus. When coronary arteries (arteries that supply blood to the heart muscle) are narrowed by atherosclerosis, heart attacks and angina occur. When cerebral arteries (arteries that supply blood to the brain) are narrowed by atherosclerosis, strokes occur. Similarly, when arteries to the penis and the pelvic organs are narrowed by atherosclerosis, insufficient blood is delivered to the penis to achieve an erection. There is a close correlation between the severity of atherosclerosis in the coronary arteries and erectile dysfunction. For example, men with more severe coronary artery atherosclerosis also tend to have more erectile dysfunction than men with mild or no coronary artery atherosclerosis. Some doctors suggest that men with new onset erectile dysfunction should be evaluated for silent coronary artery diseases (advanced coronary artery atherosclerosis that has not yet caused angina or heart attacks). For more information, please read the Heart Attack Prevention article.
Cigarette smoking:
Cigarette smoking aggravates atherosclerosis and thereby increases the risk for erectile dysfunction. For more information, please read the Smoking and Quitting Smoking article.
Nerve or spinal cord damage:
Damage to the spinal cord and nerves in the pelvis can cause erectile dysfunction. Nerve damage can be due to disease, trauma, or surgical procedures. Examples include injury to the spinal cord from automobile accidents, injury to the pelvic nerves from prostate surgery, multiple sclerosis (a neurological disease with the potential to cause widespread damage to nerves), and long-term diabetes mellitus.
Substance abuse:
Marijuana, heroin, cocaine, and alcohol abuse contribute to erectile dysfunction. Alcoholism, in addition to causing nerve damage, can lead to atrophy of the testicles and lower testosterone levels. For more information, please visit the Drug Abuse Center.
Low testosterone levels:
Testosterone (the primary sex hormone in men) is not only necessary for sex drive (libido) but also is necessary to maintain nitric oxide levels in the penis. Therefore, men with hypogonadism (diminished function of the testes resulting in low testosterone production) can have low sex drive and erectile dysfunction.
Medications:
Many common medicines produce erectile dysfunction as a side effect. Medicines that can cause erectile dysfunction include many used to treat high blood pressure, antihistamines, antidepressants, tranquilizers, and appetite suppressants. Examples of common medicines that can cause erectile dysfunction include beta-blockers such as propranolol (Inderal), hydrochlorothiazide, digoxin (Lanoxin), amitriptyline (Elavil), famotidine (Pepcid), cimetidine (Tagamet), metoclopramide (Reglan), indomethacin (Indocin), lithium (Eskalith; Lithobid), verapamil (Calan, Verelan, Isoptin), phenytoin (Dilantin), and gemfibrozil (Lopid).
Depression and anxiety:
Psychological factors may be responsible for erectile dysfunction. These factors include stress, anxiety, guilt, depression, low self-esteem, and fear of sexual failure. For more information, please visit the Depression Center.
