Causes of Erectile Dysfunction

To understand what causes erectile dysfunction (ED) or impotence, it is important to first review how an erection occurs. For a man to have an erection, a complex process takes place within the body. Erectile dysfunction is a term related to male sexual dysfunction and will be the only subject covered in this article.

• Sexual dysfunction includes problems with sexual interest (libido), erectile problems, orgasmic problems, and ejaculatory problems. ED is one component of sexual dysfunction and may occur by itself or in association with other sexual dysfunctions.
• An erection is a "neurovascular event" meaning that in order to have an erection there needs to be proper function of nerves, arteries, and veins. An erection involves the central nervous system, the peripheral nervous system, physiologic and psychological factors, local factors with the erection bodies or the penis itself, as well as hormonal and vascular (blood flow or circulation) components. The penile portion of the process leading to an erection represents only a single component of a very complex process.
• Erections occur in response to touch, smell, auditory, and visual stimuli that trigger pathways in the brain. Information travels from the brain to the nerve centers at the base of the spine, where primary nerve fibers connect to the penis and regulate blood flow during erections and afterward.
• The penis is composed of three cylinders: two on the top, the corpora cavernosa and one on the bottom, the corpus spongiosum. All of these are involved in the process of an erection. The corpora cavernosa are composed of potential spaces that can distend with blood, causing rigidity of the penile shaft. The corpus spongiosum is important for rigidity of the glans of the penis. When aroused, stimulated chemicals are released from the nervous system (nitric oxide is one) that stimulate the arteries to the penis to relax and increase blood flow into the penis. These potential spaces, like a sponge, can expand when more blood flow comes in the penis. Each corpora cavernosa is surrounded by an outer coating the tunica albuginea. When the penis fills with blood, these potential spaces, the sinusoids, compress the veins in the corpora against the side of the tunica albuginea, thus preventing blood from leaving the penis. It is this compression of the veins that allows for the erection to become fully rigid.
• Erections occur in response to touch, smell, auditory, and visual stimuli that trigger pathways in the brain. Information travels from the brain to the nerve centers at the base of the spine, where primary nerve fibers connect to the penis and regulate blood flow during erections and afterward.
• Detumescence (the process by which the penis becomes flaccid) results when muscle-relaxing chemicals are no longer released. The muscles contract, blood flow to the penis decreases, and the sinusoids get smaller, allowing blood to drain from the penis.

If one or more of the above physical and/or psychological processes is disrupted, erectile dysfunction can result. Erectile dysfunction (ED)/impotence is defined as the inability to achieve and maintain an erection that is satisfactory for the completion of sexual activity.

In general, the cause of erectile dysfunction is divided into two types. Many men will have both

• psychological (mental) causes and
• physical or organic (having to do with a bodily organ or an organ system) causes.

The normal erection process.

Psychogenic ED was thought to be the most common cause of ED, however, psychologic causes often coexist with physical or functional causes of ED.

Erection problems usually produce a significant psychological and emotional reaction in most men. This is often described as a pattern of anxiety, low self-esteem, and stress that can further interfere with normal sexual performance. This "performance anxiety" needs to be recognized and addressed by your health care provider.

There are several areas of the brain involved in sexual behavior and erections. In psychogenic ED, the brain may send messages that prevent (inhibit) erections or psychogenic ED may be related to the body's response to stressors and the release of chemicals (catecholamines) that tighten the penile muscles, preventing them from relaxing.

Certain feelings can interfere with normal sexual function, including feeling nervous about or self-conscious about sex, feeling stressed either at home or at work, or feeling troubled in your current sexual relationship. In these cases, treatment incorporating psychological counseling with you and your sexual partner may be successful. One episode of failure, regardless of cause, may propagate further psychological distress, leading to further erectile failure. Los of desire or interest in sexual activity can be psychological or due to low testosterone levels.

Individuals suffering from psychogenic ED may benefit from psychotherapy, treatment of the ED, or a combination of the two. Also, medications used to treat psychologic troubles may cause ED; however, it is best to consult with your physician prior to stopping any medications that you are taking.

Physical causes of impotence are thought to be more common than psychological causes. However, as stated before, they often coexist. The inability to achieve an adequate erection can cause psychologic troubles, which then make it even more difficult to achieve an erection the next time.

Erectile dysfunction related to medical/physical causes is often treatable but less commonly curable. In some cases of medication-induced erectile dysfunction, changes in medication may improve erections. Similarly, in men with a history of arterial trauma, surgical intervention can restore erectile dysfunction. In most cases of ED associated with a medical condition, treatment allows one to have an erection "on demand" or with the aid of medications/device (but not spontaneous).

In the evaluation of physical causes of ED, the health care provider is assessing for conditions that may affect the nerves, arteries, veins, and functional anatomy of the penis (for example, the tunica albuginea, the tissue surround the corpora). In determining a physical (or organic) cause, your health care provider will first rule out certain medical conditions, such as high blood pressure, high cholesterol, heart and vascular disease, low male hormone level, prostate cancer, and diabetes, which are associated with erectile dysfunction. Medical/surgical treatment of these conditions may also cause ED. In addition to these health conditions, certain systemic digestive (gastrointestinal) and respiratory diseases are known to result in erectile dysfunction:

• Scleroderma (stiffening or hardening of the skin)
• Kidney failure
• Liver cirrhosis
• Hemachromatosis (too much iron in the blood)
• Chronic obstructive pulmonary disease

Fully restoring sexual health with treatment of a medical condition (such as high blood pressure with diet and/or exercise or by controlling diabetes or other chronic diseases) may not be possible. Identification and treatment of these conditions may prevent the progression of ED and affect the success of various ED therapies. Nutritional states, including malnutrition, obesity, and zinc deficiency, may be associated with erectile dysfunction, and dietary changes may prove a sufficient treatment. Masturbation and excessive masturbation are not felt to cause ED, however, if one notes weak erections with masturbation, this may be a sign of ED. Some men who masturbate frequently may have troubles with achieving the same degree of stimulation from their partner, but this is not ED.

Almost any disease or condition can affect erectile function by altering the nervous, vascular, or hormonal systems.

• Diseases that affect the nervous system (brain, spinal cord, nerves in the pelvis and penis) that may be associated with erectile dysfunction include the following:
  • Epilepsy
  • Stroke
  • Multiple sclerosis
  • Guillain-Barré syndrome
  • Alzheimer disease
  • Parkinson's disease
  • Pelvic trauma
  • Spinal cord injury
  • Diabetes mellitus
  • Metabolic syndrome
  • Dementia
  • Brain tumors
• Cardiovascular diseases account for nearly half of all cases of erectile dysfunction in men older than 50 years. Cardiovascular causes include those that affect arteries and veins. Damage to arteries that bring blood flow into the penis may occur from hardening of the arteries (atherosclerosis) or trauma to the pelvis/perineum (for example, pelvic fracture, long-distance bicycle riding).
  • Vascular disease includes atherosclerosis (fatty deposits on the walls of the arteries, also called hardening of the arteries), a history of heart attacks, peripheral vascular disease (problems with blood circulation), and high blood pressure.
  • Prolonged tobacco use (smoking) is considered a common health risk factor for erectile dysfunction because it is associated with poor circulation and its impact on cavernosal function.
  • Blood diseases, such as sickle cell anemia and leukemias, are also associated with erectile dysfunction. Individuals with sickle cell disease are at increased risk for priapism (an erection lasting six hours or longer that is associated with penile pain and can cause penile damage leading to ED).
  • Diabetes mellitus may affect blood vessels and lead to ED.
  • Radiation therapy to the pelvis for cancers such as prostate cancer can affect the blood vessels to the penis.
  • Traumatic arterial injury

Problems with the veins that drain the penis can also contribute to erectile dysfunction. If the veins are not adequately compressed, blood can drain out of the penis while blood is coming into the penis and this prevents a fully rigid erection and maintaining an erection. Venous problems can occur as a result of conditions that affect the tissue that the veins are compressed against, the tunica albuginea. Such conditions include Peyronie's disease (a condition of the penis associated with scarring [plaques] in the tunica albuginea that may be associated with penile curvature, pain with erections, and ED), older age, diabetes mellitus, and penile trauma (penile fracture).

• An imbalance in your hormones, such as testosterone, prolactin, or thyroid, can cause erectile dysfunction. The following hormonal (or endocrine) conditions are commonly associated with erectile dysfunction:
  • Hyperthyroidism (overactive thyroid gland)
  • Hypothyroidism (underactive thyroid gland)
  • Hypogonadism (leads to lower testosterone levels)

Medications used in the treatment of other medical disorders may cause erectile dysfunction. If you think erectile dysfunction is caused by a medication, talk with your doctor about drugs that might not cause this side effect. Do not just stop taking a prescribed medication before talking with your health care provider. Common medications associated with erectile dysfunction are:

• Antidepressants (medication for depression) can cause ED. You should discuss with your doctor the different antidepressant choices, your response to them, and their risk of causing ED.
• Antipsychotics (for psychological illness)
• Medications used to treat high blood pressure (hypertension), including diuretics and beta-blockers, may cause ED. Not all blood pressure medications are associated with ED; alpha-blockers, ACE inhibitors, calcium channel blockers, and angiotensin II receptor blockers don't appear to cause ED. If you are on a blood pressure medication, have an ED talk with your doctor about whether or not your medication may be contributing to your ED and if there is an alternative blood pressure medication that is safe for you to try.
• Antiulcer drugs, such as cimetidine (Tagamet)
• Medications to treat prostate cancer, such as goserelin (Zoladex) and leuprolide (Lupron), and medications to treat benign enlargement of the prostate, such as finasteride (Proscar) and dutasteride (Avodart)
• Drugs that lower cholesterol, such as statins (for example, atorvastatin [Lipitor]), may lower testosterone levels. Whether or not this effect can cause ED requires further evaluation.
• Alcohol abuse: Alcohol in large amounts can cause sedation, decreased sex drive (libido), and transient ED. Chronic abuse of alcohol can lead to liver damage, low testosterone levels, high estrogen levels, and nerve damage that can affect the penile nerves.
• Recreational drugs such as marijuana and cocaine

Surgery in the pelvic area may injure the nerves and the arteries near the penis, resulting in ED. Also, surgical procedures on the brain and the spinal cord may cause erectile dysfunction. Those procedures often associated with ED include:

• Aortoiliac or aortofemoral bypass
• Abdominal perineal resection, low anterior resection
• Proctocolectomy
• Radical prostatectomy
• Radiation therapy for prostate cancer as well as for other cancers, such as bladder cancer, colon cancer, or rectal cancer
• Brachytherapy (seed implants) for prostate cancer
• Cryosurgery of the prostate
• Cystectomy (removal of the urinary bladder)

Trauma or injury to the penis and/or the pelvic blood vessels and nerves is another potential factor in the development of ED.

• Peyronie's disease is a condition associated with ED. Peyronie's disease is thought to result from minor repetitive trauma to the penis that leads to scarring of the tunica albuginea. It is often associated with a palpable scar in the penis, plaque. The scarring can cause the penis to curve in the direction of the scar, along with painful erections and erectile dysfunction. Some treatments for Peyronie's disease (excision of the plaque and placement of new tissue in its place, grafting) may cause ED also.
• Bicycle riding for long periods has also been implicated as a cause of ED. Some of the newer bicycle seats have been designed to soften pressure on the perineum (the soft area between the anus and the scrotum).
• Pelvic trauma (for example, pelvic fracture) can cause injuries to the nerves and blood vessels responsible for normal erectile function. Penile fracture can result in damage to the blood vessels and tunica albuginea affecting erectile function.

ED is common and has a significant impact on men and their partners. The first step is acknowledging that ED is affecting you and that it bothers you. If so, then it is time to get help. Often your primary care health provider can start the evaluation of your ED to determine if there are any potential reversible causes. It is important to be evaluated if you have ED as ED is often caused by medical conditions, which if not recognized and treated, could cause you harm. Did you know that the ED is a strong predictor of underlying cardiovascular disease? If you have underlying cardiovascular disease, your primary health care provider or a specialist (if needed) needs to make sure it is safe for you to participate in sexual activity.

Once evaluated, there are a number of treatments for erectile dysfunction, varying from oral therapies that can be taken on demand (for example, sildenafil [Viagra, Revatio], vardenafil [Levitra, Staxyn], avanafil [Stendra], and tadalafil [Cialis, Adcirca]) or once daily (tadalafil), intraurethral therapies (alprostadil [Muse]), injection therapies (alprostadil, combination therapies), the vacuum device, and penile prostheses. Less commonly, arterial revascularization procedures can be performed. It is important to discuss the indications and risks of each of these therapies to determine which is best for you.