Erectile dysfunction Health Article

Definition

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 stigmaof 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.

Description

First, it may be useful to understand the mechanisms of normal penile erection. 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 brainas 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 or cGMP) that 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 or 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 conceptions:

• 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.

Causes

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 15% to 20% of cases with organic 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 or marital 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. Many of these causes are discussed in more detail in the following list of causes:

• Diabetes mellitus. This is the single most common cause of ED by virtue of its combined nerve and blood vessel damage. At least 40% 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 (multiple sclerosis, for example).
• 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 antidepressant called trazodonehydrochloride (Desyrel) has been used in institutional studies for the treatment of ED because of its tendency to produce priapism. 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), common, non-prescribed drugs such as tobacco and alcohol, and drugs of abuse including heroin.
• 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, and ED may be related to a "submissive personality."
• 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 the reactive type of 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.