Erectile Dysfunction: A Comprehensive Guide for Men

Published August 16th, 2021 by Leann Poston, M.D., MBA, M.Ed.
Fact Checked by
Chris Riley
Medically Reviewed:
Dr. Angel Rivera

What is ED? | Physiology Behind an Erection | Risk Factors | Psychological Causes of ED | Medications that cause ED | Diagnosing ED | Tests for ED Treatment Options | Prevention of ED

Erectile dysfunction (ED) can be a sensitive topic. For this reason, many men avoid seeing their doctor. However, as with any health issue, it is critical to understand what is causing your symptoms as well as learn about the full range of treatment options.

ED affects at least 18 million men in the United States or approximately 18.4% of men twenty years or older. The incidence rises with age, affecting 1-10% of men under the age of 40, 2-9% of men 40 to 49 years, 20-40% of men 60-69 years, and 50-100% of men over the age of 70. Up to a third of men will experience ED at some point in their lives. However, aging does not cause ED, so it is important to identify the underlying cause.

Physical causes, such as blood vessel and nerve disease, cause 90% of cases of ED. Having type 2 diabetes mellitus triples the risk of ED when compared to the general population. Stress and anxiety can play a role in sporadic or situational ED. However, when ED persists, there is usually an underlying physical cause.   

What Is Erectile Dysfunction?

Erectile dysfunction is the inability to get and maintain an erection firm enough to engage in sexual intercourse. An erection involves a coordinated effort from the brain, blood vessels, nerves, hormones, and muscles. Problems in any of these areas can lead to ED.

The specific criteria for the diagnosis of ED in DSM-5, a reference manual used by healthcare professionals, include:

Experiencing one of these symptoms

  • Recurrent difficulty in attaining an erection after sexual stimulation
  • Difficulty maintaining an erection until the end of sexual activity
  • A marked decrease in erectile rigidity during sexual activity

The symptoms must have been present for at least six months, be causing significant distress, and not be better explained by another condition.

According to a study conducted by the Sexual Dysfunction Association, 62% of men surveyed felt that ED reduced their self-esteem, 29% said it affected their relationships, and 21% reported that ED was the direct cause of a relationship ending.

The Physiology Behind an Erection

The Structure of the Penis

The urethra, a tube that transports both urine and sperm, is located in the center of the penis. The penis is part of both the reproductive and urinary systems. The penis is flaccid during nonsexual activities such as urination and rigid during sexual activities.

The shaft of the penis surrounds the urethra and is made up of three column-like structures. Two of these columns are called the corpora cavernosa. The columns are made of spongy tissue that fills with blood during an erection. The third column is the corpus spongiosum. It contains the urethra.

How an Erection Occurs

An erection can occur during both sexual arousal and rapid eye movement (REM) sleep. Blood must flow into the penis and be trapped in the corpora cavernosa to get and maintain an erection.

An erection ends with an orgasm when blood vessels leaving the penis dilate and blood from the corpora cavernosa drains into the venous circulation.

Blood Vessels

Smooth muscle lining the small blood vessels that enter and exit the penis contract and relax to regulate blood flow through the blood vessels. When blood enters the penis and fills the corpora cavernosa, the swollen tissue presses against the small blood vessels that drain the penis. This process results in vasocongestion or the retention of blood in the penis. As a result, the pressure within the penis rises, and it stiffens.

Nervous System

The penis is densely packed with nerves from all three major systems: the sympathetic, parasympathetic, and somatic nervous systems. The parasympathetic nervous system stimulates blood vessels in the penis to dilate, resulting in an erection. The sympathetic nervous system appears to have the opposite effect. The somatic nervous system innervates the bulbospongiosus and ischiocavernosus muscles. When these muscles contract, the penis stiffens. When they contract rhythmically, they aid in the expulsion of ejaculate.

The Importance of Nitric Oxide

Nitric oxide is a small molecule found throughout the body that plays an important role in maintaining blood flow into the penis. Following sexual stimulation, nitric oxide is released from nerve endings near the small blood vessels in the corpora cavernosa of the penis. Nitric oxide initiates a chemical cascade that dilates blood vessels and increases blood flow into the penis. Increasing pressure in the penis usually results in an erection.

To maintain an erection, cyclic guanosine monophosphate (cGMP, another chemical in the cascade) levels must stay high. Phosphodiesterase (PDE5) inactivates cGMP. When cGMP is deactivated, the smooth muscle contracts, and blood flow into the penis decreases. Veins drain blood from the penis, and it softens.

Oral ED medications such as sildenafil and tadalafil inhibit phosphodiesterase and maintain nitric oxide levels. The discovery of the link between nitric oxide, cGMP, and phosphodiesterase resulted in the development of oral medications to treat ED.

Risk Factors for Erectile Dysfunction

Medical conditions, emotional issues, psychological conditions, and drug side effects can all lead to ED.

Physical Causes of ED

Physical causes of ED have a more gradual onset, are progressive, and may not respond as well to treatment. Physical causes of ED occur when there is not enough blood entering the penis, blood is not trapped in the corpora cavernosa, or there is small blood vessel or nerve damage in the pelvis.  

Physical causes of ED:

  • Aging, being over age 50
  • Cardiovascular disease
  • Diabetes mellitus
  • Endocrine disorders
  • Hyperlipidemia
  • High cholesterol
  • High blood pressure
  • Neurologic disorders such as Parkinson's disease or multiple sclerosis
  • Obesity
  • Peyronie's disease
  • Prostate cancer treatment
  • Trauma
  • Low testosterone levels
  • Kidney disease
  • Spinal cord injury
  • Benign prostatic hyperplasia (a non-cancerous enlargement of the prostate gland)

ED and Cardiovascular Disease

Because erections are dependent on blood flow into and out of the penis, cardiovascular disease, particularly when it affects the blood vessels, is a significant risk factor for ED.

Almost half of men with damage to the lining of the blood vessels in their heart also have ED. ED is frequently present prior to the onset of symptoms of cardiovascular disease, often appearing two to five years before coronary artery disease. Therefore, early identification and treatment of ED can result in a better outcome because cardiovascular disease is treated earlier.

Younger men with ED should be aware that they are at a higher risk of developing cardiovascular disease. Men who have ED are at increased risk for angina, heart attacks, strokes, congestive heart failure, and abnormal heart rhythms. Furthermore, after controlling for age, smoking, obesity, and medication use, men with ED have a 75% higher risk of developing peripheral vascular disease.

High cholesterol, high blood pressure, cigarette smoking, physical inactivity, obesity, and diabetes mellitus are all risk factors for cardiovascular disease. Having ED can serve as a wake-up call that it is time to address these risk factors. Seeking treatment now can help to keep cardiovascular disease from worsening.

ED and Diabetes

Undiagnosed diabetes affects 11.5% of men with ED and 2.8% of men without. In one study, diabetes was found in 19.1% of men with ED versus 3.3 percent of men without ED in men aged 40 to 59 years. Similarly, men over the age of 50 who have diabetes are roughly twice as likely (46%) to have ED as men who do not have diabetes (24%).

In another study, men with diabetes were three times more likely to develop ED than men who do not have diabetes. This is because uncontrolled blood sugar levels damage the inner lining of blood vessels. Over time, damage to blood vessels reduces blood flow into the penis, resulting in ED. Having high blood pressure, high cholesterol, or smoking also increases the risk of developing ED.

Low Testosterone Levels

After the age of 30, testosterone levels begin to decline at a rate of about 1% per year. In one study, low testosterone levels, defined as less than 300 ng/dl in men aged 45 and younger, were found in 38.7% of men.

Testosterone plays a key role in sexual function, affecting libido, ejaculation, and spontaneous erections. In men with low testosterone levels, testosterone replacement may improve mild ED symptoms but does not improve moderate or severe ED.

Psychological Causes of ED

Psychological causes of ED manifest themselves more abruptly and intermittently. When psychological or emotional issues underlie the causes of ED, erections with sexual stimulation are usually affected, whereas those during REM sleep are not.

Psychological causes of ED:

  • Anxiety, including performance anxiety
  • Depression
  • Stress
  • Fatigue
  • Past sexual trauma
  • Exposure to negative sexual messaging

Medications That May Cause Erectile Dysfunction

Medications can interrupt nerve impulses or blood flow to the penis. One of the most common reasons men stop taking medications for conditions such as high blood pressure and diabetes is developing ED as a side effect.

Medications with ED as a known potential side effect:

  • Alcohol
  • Nicotine
  • Anti-seizure medications
  • Anti-depressants
  • Antihistamines
  • Anti-hypertensives (blood pressure medications)
  • Hormones
  • Drugs of abuse

Symptoms of ED

Other symptoms that may co-occur with ED include:

  • Reduced interest in sex
  • Low self-esteem

Diagnosing Erectile Dysfunction

Your doctor may ask questions about the following subjects. Although some of these questions may feel intrusive or even embarrassing, answering them completely and fully is important. The more information you provide your doctor, the more likely it is that your diagnosis will be accurate and that your treatment will be effective.  

  • Family history of cardiovascular disease, high blood pressure, or diabetes
  • Drug, alcohol, or tobacco use
  • History of surgery or radiation to the pelvic area
  • History of urinary problems or symptoms
  • Current medical or psychological diagnoses
  • Current or recent medications, the prescribed dosage, and any recent changes
  • Sexual history, including frequency, number of partners, past sexually transmitted diseases
  • Length and frequency of erections, ability to penetrate and retain an erection
  • First onset of ED symptoms and any trends
  • Whether ED affects nocturnal erections
  • Problems with ejaculating or climaxing
  • Any pain or other symptoms with sexual activity
  • Personal history of stress or depression
  • Level of satisfaction with personal relationships

After taking a history, your doctor may conduct a physical exam. 

Tests for Diagnosing Erectile Dysfunction

Screening Tests for ED

Several validated screening tests exist for ED, including a five-question version of the International Index of Erectile Function Questionnaire.

Users are asked to consider the following questions and respond with a rating of very low, low, moderate, high, or very high.

Over the last six months:

  • How do you rate your confidence that you could get and keep an erection?
  • When you had erections with sexual stimulation, how often were your erections hard enough for penetration?
  • During sexual intercourse, how often were you able to maintain your erection after penetrating your partner?
  • During sexual intercourse, how difficult was it to maintain your erection to completion of intercourse?
  • When you attempted sexual intercourse, how often was it satisfactory for you?

Blood Tests

Hormone levels: The American College of Physicians does not recommend routine hormone levels as part of the testing for ED. Hormone levels may be ordered if the physical exam suggests low levels are a possibility. 

Hemoglobin A1c: Hemoglobin A1c is used to screen for diabetes

Serum chemistry panel: Checks for abnormal electrolyte levels

Lipid Profile: Checks for elevated triglyceride and cholesterol levels

Prostate-Specific Antigen (PSA): Is a screen for prostate cancer.

Urinalysis: Is a screen for genitourinary disorders, including infections.

Thyroid test: May be checked in men with symptoms of low thyroid (hypothyroidism).

Testosterone levels: An early morning testosterone level may be checked if low testosterone levels might be a contributing factor to ED symptoms.

Prostaglandin E1 Response

Prostaglandin E1 is a vasodilator. For this test, prostaglandin E1 is injected into the corpus cavernosa. A strong erection should develop within about five minutes. If it does not, blood vessel damage is a high possibility as the cause of ED.

Ultrasonography

An ultrasound uses sound waves to check blood flow into and through the penis. An ultrasound may be done before and after an injection of prostaglandin E1 or Trimix.

Nocturnal Penile Tumescence Testing

A nocturnal penile tumescence test uses a device such as a Rigiscan monitor to measure whether an erection occurs at night during REM sleep and, if it does, its force and duration. Data is stored in the device for your doctor to review.

What Is Priapism?

Priapism is a prolonged erection that becomes painful and is not associated with sexual activity. It is a medical emergency that requires immediate attention. Priapism is a potential side effect of any treatment for ED. Using ED medications more frequently or in higher doses than prescribed can increase the risk of priapism.

Sexual stimulation increases blood flow into the penis, where it becomes temporarily trapped in the corpora cavernosa. Filling these cavities puts pressure on the veins that drain the penis. This process is required to maintain an erection. Otherwise, the corpora cavernosa would drain as quickly as they fill. If an erection lasts more than four hours, even intermittently, the tissues in the penis become deprived of oxygen and nutrients due to the lack of fresh blood flowing into the penis. If priapism is not treated, damage to penile tissue may result.

Treatment Options for Erectile Dysfunction

The first-line treatment for ED is modifying any lifestyle or medication choices that may be contributing to ED. Taking care of your cardiovascular health is a great first step to treating ED. The causes of cardiovascular disease are the same ones that cause ED. Treating or preventing one naturally treats the other.

Oral ED Medications

After lifestyle changes, PDE5 inhibitors are the first-line treatment for ED. PDE5 is an enzyme that breaks down cyclic guanosine monophosphate (cGMP). When cGMP levels remain high, blood flows into the penis, resulting in an erection. Therefore, oral ED medications can improve the quality of erections for men who have ED due to decreased blood flow into the penis.

Oral ED medications do not result in an erection unless preceded by sexual stimulation. They also have no impact on sexual desire.

Eating a fatty meal before taking PDE5 inhibitors may delay or reduce their effects. Oral ED medications should be taken exactly as directed and no more than once every 24 hours.

Side effects from PDE5 inhibitors are typically mild and may include headaches, flushing, indigestion, nasal congestion, and vision changes. Headache is the most common reported side effect, affecting approximately one in ten users. In rare cases, men may experience vision or hearing loss after taking a PDE5 inhibitor. If this should happen, seek immediate medical attention.

PDE5 inhibitors should not be taken with nitrates because they can cause life-threatening drops in blood pressure, as can taking a PDE5 inhibitor within four hours of an alpha-blocker. Finally, PDE5 inhibitors should not be taken with guanylate cyclase stimulators, such as riociguat or other PDE5 inhibitors.

Testosterone replacement therapy may be combined with oral PDE5 inhibitors if testosterone levels are low.

Sildenafil

Sildenafil citrate is the generic form of Viagra. It is an oral medication that is used to treat ED. It usually starts working within 30 minutes to two hours of taking a dose and lasts three to five hours. Sildenafil can cause a blue-green tint to your vision. This shading is a rare and temporary side effect. People with diabetes do not seem to respond as well to sildenafil.

Vardenafil

Vardenafil (Levitra) is taken up to one hour before sexual activity and lasts four to five hours. Grapefruit has the potential to interact with Levitra and cause side effects. Drinking alcohol while taking Levitra can also worsen the side effects.

Tadalafil

Tadalafil (Cialis) is a medication used to treat ED and symptoms of benign prostatic hypertrophy. It starts to work within 30 minutes to two hours of taking a dose and can be effective for 36 hours. Because of tadalafil's longer half-life, men have two dosing options: taking it up to 12 hours before sex or as a low-dose once-a-day medication. After taking Cialis, some men experience increased or new-onset lower back pain. Grapefruit has the potential to interact with Cialis and cause side effects.

Avanafil

Avanafil (Stendra) is taken up to 15 minutes before sexual activity. It lasts for five to ten hours. Stendra can be taken with or without food and should not be taken with excessive alcohol as it may cause headaches and dizziness.

Penile Injections

Approximately 70% of men report that oral ED medications work well for them. The remaining 30% have contraindications to using them, or they do not work well. For these men, penile injections may be an option. Injectable ED medications trigger immediate blood flow into the penis and do not require sexual stimulation to work.

Alprostadil

Alprostadil (Caverject, Edex) is injected into one of the corpora cavernosa on the side of the penis. Men are taught how to self-inject by their healthcare providers. The needle used for injection is very fine, so any pain is usually minimal. The lowest effective dose should be used. Side effects include penile pain and dizziness. Very rarely, fibrous tissue can develop at the injection site. Using good injection techniques and injecting on opposite sides with each injection can minimize this effect.

Alprostadil (MUSE) is also available as a dissolvable pellet that can be inserted into the urethra. A tiny applicator is used to insert the suppository into the urethra. An erection usually starts within 10 minutes and lasts between 30 minutes and an hour. Urethral bleeding, formation of scar tissue, pain with urination, and aching in the penis, testicles, and perineum (area between the penis and the testicles) are all reported side effects.

Trimix

The most common form of penile injection is a combination of three medications: alprostadil, phentolamine, and papaverine (Trimix). Only alprostadil is currently approved by the Food and Drug Administration (FDA) for treating ED.    

As many as 95% of men who took part in erectile dysfunction studies using oral ED pills, then subsequently switched to Trimix injections when oral ED pills failed, saw effective results from Trimix.

Vacuum Devices

Vacuum devices work by placing a tube over the penis and sealing it at the base of the penis with a lubricant. The vacuum pump pulls blood into the penis by sucking the air out of the tube. Once an erection has been achieved, a constricting ring is slid off the base of the tube, where it remains on the penis to maintain the erection. Because the constricting ring holds blood in the penis by restricting blood flow, it should not be left in place for more than 30 minutes. Bruising and restricted ejaculation are potential side effects. Decreased blood flow can also make the penis feel cold to the touch.

Vacuum devices are commonly recommended for men with ED and severe diabetes, high blood pressure, or coronary artery disease, or for men in whom PDE5 medications are ineffective or contraindicated. They are also used in men who have had prostate surgery to prevent side effects that may lead to ED.

Vacuum devices can be hard to use at first, but three out of four men get a suitable erection after proper use.

Surgery

If other treatment options have been exhausted, surgically implanted penile prosthetics are another option. Semimalleable prosthetics can be surgically implanted into the corpora cavernosa. The penis can be straightened for an erection and bent to conceal an erection or to urinate.  

Another option is to use inflatable prostheses. Like semimalleable prostheses, inflatable prostheses are placed in the corpora cavernosa. A pump is surgically implanted in the scrotum, and a reservoir is placed in the abdomen. Risks include scarring of the penis, mechanical failure, penile shortening, and infection.

Blood vessel surgery may be recommended for younger men with ED who have had a history of injury or trauma to the pelvic region.

Psychotherapy

Psychogenic ED is more common in men under the age of 40. Performance anxiety and relationship issues can be contributing factors. Problems with premature ejaculation, genital pain, or pain with sex can be contributing factors as well. Men can also have a combination of physical and psychological factors causing ED.

Psychogenic ED is more likely when men report normal nocturnal erections but experience ED when having sex with a partner.

Prevention of Erectile Dysfunction

There are several steps you can take to reduce your risk of developing ED. Many of these steps improve overall health.

  • Avoid or limit alcohol use
  • Engage in physical activity
  • Stop smoking, if relevant
  • Monitor your blood pressure, cholesterol, and blood sugar levels
  • Maintain a healthy weight
  • Reduce stress
  • Seek help for anxiety, depression, and unmanageable stress
  • Seek treatment for drug or alcohol problems
  • Consider therapy or counseling if recommended

ED can be a source of stress, exacerbating other physical or psychological conditions. However, for most men, ED is treatable. Although most ED is caused by physical rather than psychological factors, therapy or counseling may still be helpful to ease anxiety or treat depressive symptoms.

Involve your partner as you seek to understand ED better. Talking can help decrease anxiety and prevent misunderstandings. For example, your partner may perceive ED as a lack of interest in sex or a failure on their part. Open and honest communication with your partner and your doctor can reduce stress and speed up the process of regaining full erectile function.

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