What Causes Erectile Dysfunction (Impotence)?

What is erectile dysfunction and how does a normal erection occur?

Erectile dysfunction (ED) is defined as the persistent inability to achieve or maintain a penile erection sufficient for satisfactory sexual performance. A breakdown occurs in the normal physiology that allows the penis to fill with blood, become firm and erect, and then become flaccid after ejaculation or because sexual stimulation has stopped. Impotence is a term no longer used to describe the inability to maintain an erection.

Erectile dysfunction can cause stress and relationship troubles and can be the sign of an underlying medical condition. Although many men find it uncomfortable or awkward to discuss erectile dysfunction with their health-care professional, persistent erectile dysfunction should trigger a visit to a doctor.

For a normal erection to occur, the arteries to the penis must be able to deliver blood, hormone levels need to be optimized, and there needs to be an appropriate psychological state. If any of these systems do not function properly, an erection may not occur.

There are two spongy areas within the penis, called the corpus cavernosum, that are capable of becoming engorged with blood. With proper sexual stimulation, either physical or emotional, hormones trigger the release of nitrous oxide at nerve endings in the penis to dilate blood vessels and allow arterial blood to be pumped into these spongy tissues causing the penis to become erect. With continued sexual stimulation, the muscles at the base of the penis start to contract, preventing blood from entering or escaping the penis and increasing its firmness. Once either ejaculation occurs or stimulation stops, the muscles relax, allowing the blood to leave the penis.

What causes erectile dysfunction?

Before an erection can occur, numerous organ systems in the body need to function properly. Should any or all systems fail, erectile dysfunction may result. These systems include the brain, hormone release, muscles, nerves, arteries, veins, and emotional response.

The hypothalamus and pituitary glands in the brain need to function to stimulate the testes to produce the testosterone required for libido (sexual drive or desire). Injury, stroke, or a tumor may affect brain function. Hypogonadism (hypo=less + gonad=testicle), trauma, or surgery may result in failure of the testes to produce testosterone.

Nerve supply to the penis needs to be intact. Nerves can be damaged by trauma or surgery, especially after prostate surgery. Poorly controlled diabetes can lead to peripheral neuropathy and failure of nerves that support an erection. Multiple sclerosis is associated with erectile dysfunction.

Adequate blood supply needs to be delivered to the penis. Blood supply can be affected by trauma or surgery. More commonly, blood supply is restricted because of peripheral vascular disease or hardening of the arteries, the same scenario that can lead to heart attack and stroke. Patients with erectile dysfunction have a high likelihood of also having coronary artery disease. Risk factors include high blood pressure, high cholesterol, smoking, and diabetes.

The muscles and tissues of the penis need to be capable of accepting the increased blood supply required to produce an erection. Damage due to trauma or surgery may be the underlying cause of a flaccid penis.

An appropriate emotional and psychological state is required to achieve an erection. Mental and emotional problems that could lead to erectile dysfunction include depression, mental disorders, stress, and performance anxiety. Side effects from selective serotonin reuptake inhibitors (SSRI antidepressants) like fluoxetine (Prozac), sertraline (Zoloft), paroxetine (Paxil), citalopram (Celexa), and escitalopram (Lexapro) can also be a factor in erectile dysfunction.

What are the risk factors for erectile dysfunction?

Perhaps the most important risk factors that can be controlled for erectile dysfunction are those related to peripheral artery disease or hardening of the arteries. High blood pressure, high cholesterol, smoking, and poorly controlled diabetes all contribute to narrowing of arteries in the body. Not only can blood flow to the penis be affected but so can blood supply to all the major organs in the body. Erectile dysfunction is associated with coronary artery disease, stroke, and claudication (pain during exercise, especially in the legs). Drug and alcohol use are risk factors for erectile dysfunction. Repeat local trauma -- such as bicycling -- affects the nerves and blood flow to the penis, which may cause erectile dysfunction.

Can young men get erectile dysfunction?

The likelihood of developing erectile dysfunction tends to increase with age and affects more than 30 million men in the United States. However, younger men can also be affected but the cause is most often psychological and related to stress or performance anxiety. Alcohol and drug abuse may also be contributing factors.

It is important to remember that erectile dysfunction shares the same risk factors as heart disease, and it is appropriate to seek medical care to assess the potential for heart attack. It may be appropriate to be screened for high blood pressure, high cholesterol, and diabetes.


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Vlachopoulos, C.V., et al. "Prediction of cardiovascular events and all-cause mortality with erectile dysfunction: a systematic review and meta-analysis of cohort studies." Circulation: Cardiovascular Quality and Outcomes 6.1 (2013): 99-109.