Erectile dysfunction (ED) may be defined as the consistent inability to achieve or maintain an erection sufficient to permit satisfactory sexual intercourse. The word “consistent” is included in the definition because most men experience transient episodes of ED that are temporary and usually associated with fatigue , anger, depression , or other stressful emotions. The use of the formerly used term “impotence” has been virtually abandoned because of its inherent stigma of weakness and lack of power.
Erectile dysfunction can occur as part of several mental disorders recognized by the mental health professional’s manual, the Diagnostic and Statistical Manual of Mental Disorders , often shortened to the DSM. ED is the main symptom in the disorder the manual calls “male erectile disorder.” ED can also be a symptom of other disorders, such as sexual dysfunction due to a general medical condition or substance-induced sexual dysfunction. In this entry, however, ED is examined and discussed as its own medical entity, and not within the strict guidelines of the DSM.
Penile erection occurs essentially when the penis becomes engorged with blood. The anatomical compartments (two corpora cavernosa and one corpus spongiosum) are capable of being distended with seven times their normal amount of blood. When this occurs in association with relaxation of the penile muscles, erection results.
The sequence of events resulting in penile erection is complex. It is usually initiated by sexual arousal stimuli arising in the brain as a result of visual, auditory, or olfactory sensations or erotic thoughts. Tactile (touch) sensations of the penis acting through the spinal cord play a similar role. Sexual arousal results in the release of a chemical (nitric oxide) from specialized cells. Nitric oxide causes the formation of a substance (cyclic glutamine monophosphate [cGMP]), which is responsible for dilating the blood vessels of the penis and relaxing its muscles, thus allowing for an increase in blood flow and resultant penile erection. Compression of the dilated blood vessels against the firm outer lining of the penis prevents the blood from escaping and perpetuates the erection. A specialized substance (phosphodiesterase 5 [PDE-5]), causes the breakdown of cGMP and, with the help of nerves from the sympathetic nervous system, allows the penis to return to its flaccid relaxed state.
Any defect in this complex cascade of events can result in erectile dysfunction.
Different men experience varying patterns of ED. Men with ED may report the inability to experience any erection from the beginning of a sexual experience, while others experience an erection that is not maintained at penetration. Other men may lose the erection during sexual intercourse, and others can only experience erection upon awakening or during self-masturbation.
Impact of ED
It is well recognized that adults of all ages view sex as an important quality-of-life issue, and that the imposition of ED usually results in a reduced quality of life. In spite of this and for a number of reasons—most of them unfounded—the victims often suffer in silence. Included among the reasons for their silence are the following:
- ignorance of the availability of safe and effective therapy for ED
- inadequate information provided by the physician concerning timing of medication, need for preliminary sexual arousal, etc.
- undue concern about the irreversibility of marital discord and lack of partner support
- concerns about administration of invasive therapies, adverse effects of therapy, discomfort, inconvenience, and cost of therapy
- high rates of discontinuation of therapy due to inadequacy of therapeutic response and associated adverse effects
Studies indicate that in the United States, between 15 million and 30 million men have some degree of erectile dysfunction (ED). Of these, 10 to 20 million have a severe degree of ED resulting in the complete inability to attain or maintain a penile erection. The number of men with ED in the United States is projected to increase by nearly 10 million by the year 2025. With the advancement of men’s median age in western industrial countries and the general population growth in developing nations, the worldwide incidence is projected to increase to greater than 320 million by 2025. ED accounts for more than 500,000 annual visits to health care professionals.
As with other chronic disorders and the conditions that are commonly associated with ED (diabetes, hypertension, cardiovascular disease), the prevalence of ED increases with advancing age, with an estimated occurrence of 26% in men who are in their 50s, 40% in men who are in their 60s, and 77% in men 75 years and older. These figures may actually underestimate the true dimensions of the problem since ED is notoriously under-reported, undiagnosed and under-treated because of the perceived stigma associated with the diagnosis of ED. It is reported that 70% of ED remains undiagnosed and in a survey of general medical practice less than 12% of men with ED reported having received treatment for it.
A precise determination of the cause of any individual case of ED is often difficult and may be impossible because ED is often due to multiple factors. This is a consequence of the complicated nature of the human sexual response and the complex physiology of penile erection and relaxation. Normal erectile function requires the coordination of vascular, neurologic, hormonal, and psychological factors and any condition that interferes with one or more of these processes may result in ED.
Attitudes concerning age and psychological factors, commonly associated with ED in the past, have changed in the last two decades. Although the prevalence of ED increases with advancing age, ED is no longer regarded as an inevitable consequence of aging. Whereas most cases of ED were once considered primarily psychological and/or psychiatric in origin, it is now well recognized that organic, non-psychological causes of ED play a much more significant role in the development of ED. Most researchers agree that pure psychological (emotional) mechanisms are causative in 10-20% of cases with medical causes responsible for at least 80% of ED cases. In a number of cases, the situation is mixed, with significant secondary psychological and social components such as guilt, depression, anxiety , tension, ormarital discord being present in addition to one or more underlying organic components.
Causes of ED may be grouped into those factors that arise within the individual (endogenous) and those factors arising from sources outside the body (exogenous). Endogenous factors include endocrine imbalances, cardiovascular and other medical conditions, and emotional causes. Included among exogenous factors are medications, surgery, trauma and irradiation, smoking, and alcohol and substance abuse. These endogenous and exogenous factors may include:
- diabetes mellitus. This is the single most common cause of ED by virtue of its combined nerve and blood vessel damage. As many as 50% of male diabetics have ED.
- circulation abnormalities. Vascular (circulation-related) causes include diseases of the aorta or the arteries supplying the pelvis and penis. Hardening of the arteries (arteriosclerosis) is the most common vascular cause, but damage to the arteries may result from trauma, surgery, or irradiation. Surgery involving the prostate gland may involve both the arteries and nerves in that region.
- neurological causes, including diseases of the brain (such as Alzheimer’s disease) and spinal cord (e.g., multiple sclerosis).
- hormonal or endocrine causes. These are uncommon causes for ED, however. ED may occur in males with deficient testicular function and low circulating levels of the male sex hormone, testosterone. These cases are referred to as hypogonadism and may be due to congenital abnormalities or testicular disease such as that accompanying mumps.
- penile diseases. Organic causes of ED may be related to diseases of the penis. Many factors influence penile circulation. For instance, Peyronie’s disease, a condition characterized by fibrous tissue and a downward bowing of the penis, limits the expandability of the penile tissues, thus preventing venous compression and allowing blood to leave the penis. Similarly, arteriosclerotic plaque, injury to blood vessels’ inner lining due to trauma, surgery, or irradiation, or even aortic occlusion (blockage in a main artery leading out of the heart) can be the cause of compromised penile blood flow and prevent penile erection.
- medications. A number of classes of medications can cause ED. Not all agents within each drug class produce the same effects. For example, some antidepressants are associated with ED, whereas an anti-depressant called trazodone hydrochloride (Desyrel) has been used in institutional studies for the treatment of ED because of its tendency to produce priapism (prolonged penile erection). Some medication classes that can cause ED include (but are not limited to) medications that reduce high blood pressure, medications taken for central nervous system diseases like Parkinson’s disease (methyldopa), antidepressants, sedatives or tranquilizers like barbiturates, anti-anxiety medications like diazepam (Valium), non-prescribed drugs such as tobacco and alcohol, and illicit drugs including heroin.
- psychological factors. Psychological factors that can precipitate ED include stress, fatigue, depression, guilt, low self-esteem, and negative feelings for or by a sexual partner. Depressive symptoms and/or difficulty coping with anger may be particularly influential.
- lifestyle. Obesity, physical inactivity, cigarette smoking, and excessive intake of alcohol are risk factors for the development of ED. These suggest that changes in lifestyle may constitute an important aspect of both the therapy and prevention of ED.
The identification of risk factors for ED has an important impact not only on the treatment, but on the prevention of ED as well. For example, if a doctor is treating a patient for high blood pressure who is also at risk for ED, the doctor may make an informed decision to prescribe an effective medication that is not associated with ED instead of one that is.
ED AS A MARKER FOR OTHER DISEASES
The frequent association between ED and a number of important vascular conditions such as hypertension and coronary artery heart disease has raised the possibility that ED may serve as an important marker for the detection of these vascular disorders. Additionally, an increased incidence of depression has been noted in men with ED that is believed to be distinct from reactive depression that might occur because of ED. This has led to the recognition of a possible syndrome linking depression and ED. Thus, the presence of depression should be investigated in men presenting with ED.
The main symptom is the inability to attain or maintain adequate erection to complete sexual activity.
As a result of this symptom, affected men may also experience depression and distress, and this symptom can cause interpersonal problems.
An essential first step in the diagnosis of ED is taking a thorough sexual, medical, and psychosocial (both psychological and social) history. The sexual history should include information such as the frequency of sexual intercourse, its duration, the quality and degree of penile erection, the presence or absence of nocturnal erections, and the success or failure of penetration. Any sexual dysfunction on the part of the partner, such as painful intercourse (dyspareunia ) or vaginal dryness, should be ascertained. The use of one of several available self-directed patient questionnaires may be a useful adjunct to the sexual history. The sexual history helps in distinguishing ED from other abnormalities in sexual function such as ejaculatory and orgasmic disturbances and loss of sexual desire.
The general medical history may disclose one or more distinct causes of ED including the presence of associated conditions (such as high blood pressure, diabetes, or arteriosclerosis), the use of medications that can cause the disorder, and/or a history of substance abuse.
A psychosocial history, preferably with the participation of the patient’s sexual partner, should include current sexual practices, the presence or absence of stress and performance anxiety, and any special circumstances under which ED occurs.
For a patient with ED, the physical examination should not differ substantially from that performed routinely by a primary care physician. The doctor looks for evidence of hypogonadism or congenital conditions in which there is defective testicular function. The examination of the genitourinary, circulatory and neurologic systems might be especially emphasized. The patient’s genitalia are carefully examined for testicular size and consistency and penile deformities. A rectal examination is needed to evaluate the size and consistency of the prostate gland and for the performance of certain muscular reflexes. Vital signs such as blood pressure and pulse would be recorded. Because the presence of ED may serve as a marker for high blood cholesterol, hypertension, coronary artery heart disease, and depression, the physician may also request blood work and/or may perform other assessments to check for these conditions.
Other diagnostic methods that may be performed
Laboratory tests may be performed to evaluate levels of hormones including testosterone and prolactin.
Nocturnal studies present a true picture of erectile dysfunction due to organic causes. The most complete evaluation of nocturnal erectile function is obtained in a sleep laboratory, where patients are monitored for nocturnal erections during sleep.
Duplex Doppler ultrasonography has been used extensively in the evaluation of erectile function. It provides information about both arterial and venous blood flow.
Pharmacological testing involves intracavernosal injection of a small amount of an active agent (e.g., 10 micrograms of alprostadil [prostaglandin E1]) that would produce a normal or priapic erection in a patient with normal erectile function but a poor response in a patient with erectile dysfunction.
There are several self-administered questionnaires available to assist in the evaluation of sexual function in men with erectile dysfunction. The best known and most widely used is the International Index of Erectile Function (IIEF). The IIEF addresses the five relevant domains of male sexual function: erectile function, orgasmic function, sexual desire, intercourse satisfaction, and overall satisfaction.
The first step in the treatment of ED includes the elimination or alteration of modifiable risk factors or causes, such as lifestyle or psychosocial factors including smoking, obesity, substance and alcohol abuse, and the adjustment of prescription and over-the-counter medications if necessary.
Recommended treatment options for ED include the following medications:
- PDE5 inhibitors. This class of drugs, which includes sildenafil (Viagra), vardenafil hydrochloride (Levitra), and tadalafil (Cialis), work by relaxing the muscles in the penis to increase penile blood flow and produce an erection. These drugs should not be used by men who take nitroglycerin for heart problems, because they can cause a sudden drop in blood pressure. Also, PDE5 inhibitors have been associated with an increased risk of a rare condition called nonarteritic ischemic optic neuropathy, which can lead to sudden sight loss.
- Apomorphine. This morphine derivative targets dopamine receptors to facilitate erections.
- Alpha adrenergic blockers. These drugs target adrenergic receptors in smooth muscles, causing the blood vessels to dilate more easily.
If those therapies are unsuccessful, the following treatment options may be recommended:
- vacuum constriction device therapy. Vacuum constriction device therapy involves a mechanical device to increase penile blood flow and erection may also be recommended. Psychosexual therapy is also recommended so that any psychological causes for ED can be detected and therapy can be instituted. Individual psychotherapy or couples therapy may be helpful. These various treatment methods can be used alone or in combination.
- intracavernous therapy (ICIT). This therapy involves injection of the penile structures with the drugs alprostadil (Caverject), papaverine (Pavabid), or phentolamine, which promote blood flow and produce erection.
Diabetes mellitus —A chronic disease affecting the metabolism of carbohydrates that is caused by insufficient production of insulin in the body.
Hypertension —High blood pressure, often brought on by smoking, obesity, or other causes; one of the major causes of strokes.
Hypogonadism —Abnormally decreased gonad function with retardation of sexual development.
Priapism —Persistent abnormal erection of the penis, usually without sexual desire, and accompanied by pain and tenderness.
Prostate gland —The gland at the base of a male’s urethra that produces a component of semen.
- intraurethral therapy. The medication alprostadil is inserted into the urethra and acts to increase blood flow and muscle relaxation, allowing for erection.
- penile prostheses. These are various devices inserted surgically into the penis to produce the erect state.
- surgery. In rare cases, surgery may be used to correct a defect that interferes with penile erection.
Regardless of the therapy chosen, follow-up at regular intervals and good communication between the patient and the doctor is essential. Patients need to keep their doctors informed about adverse reactions, and patients need to be informed about drug interactions. The doctor may adjust the dosage of medication, or may substitute or add a therapeutic agent into the treatment, as necessary.
The patient and his sexual partner can work with their treatment team so that they are both well informed about various treatment options and can maximize treatment results.
The combination of the increased understanding of ED, an improved approach to the problem and the development of newer and more effective therapies has resulted in a marked improvement in the prognosis of ED. It is estimated that at least 65% of all cases of ED currently have a satisfactory therapeutic outcome. However, several factors affect individual prognostic forecasts. Risk factors that cannot be changed and that have a negative effect on individual prognoses include increasing age, the presence of comorbid (cooccurring) conditions such as diabetes, and pelvic surgery in which the nerves were not spared. In contrast, potentially modifiable risk factors such as physical inactivity, smoking, excessive alcoholic intake, certain medications, and obesity improve prognosis when treated effectively.
Carson, Culley. Erectile Dysfunction, An Issue of Urologic Clinics. New York: Saunders, 2005.
Dorey, Grace. Pelvic Dysfunction in Men: Diagnosis and Treatment of Male Incontinence and Erectile Dysfunction. 1st ed. Hoboken, NJ: John Wiley and Sons, 2006.
Lue, Kirby, Roger S. An Atlas of Erectile Dysfunction. 2nd ed. New York: Taylor and Francis, 2003.
American Urological Association. 1000 Corporate Boulevard, Linthicum, MD 21090. Telephone: (866) 746-4282. <http://www.auanet.org/>.
National Kidney and Urologic Diseases Information Clearinghouse. 3 Information Way, Bethesda, MD 20892-3580. Telephone: (800) 891-5390. <http://kidney.niddk.nih.gov>.
Ralph Myerson, MD