Erectile dysfunction

Erectile dysfunction (ED, "male impotence ") is a sexual dysfunction characterized by the inability to develop or maintain an erection of the penis sufficient for satisfactory sexual performance.^[1]

An erection occurs as a hydraulic effect due to blood entering and being retained in sponge-like bodies within the penis. The process is most often initiated as a result of sexual arousal, when signals are transmitted from the brain to nerves in the penis. Erectile dysfunction is indicated when an erection is difficult to produce. There are various circulatory causes, including alteration of the voltage-gated potassium channel as in the case of arsenic poisoning from drinking water.^[2] The most important organic causes are cardiovascular disease and diabetes, neurological problems (for example, trauma from prostatectomy surgery), hormonal insufficiencies (hypogonadism) and drug side effects. It is important to realize that erectile dysfunction can signal underlying risk for cardiovascular disease.

Psychological impotence is where erection or penetration fails due to thoughts or feelings (psychological reasons) rather than physical impossibility; this is somewhat less frequent but often can be helped. Notably in psychological impotence, there is a strong response to placebo treatment. Erection, tied closely as it is about ideas of physical well being, can have severe psychological consequences. There is a strong culture of silence and inability to discuss the matter. In reality, it has been estimated that around 1 in 10 men will experience recurring impotence problems at some point in their lives.^[3]

Besides treating the underlying causes such as potassium deficiency or arsenic contamination of drinking water, the first line treatment of erectile dysfunction consists of a trial of PDE5 inhibitor drugs (the first of which was sildenafil or Viagra). In some cases, treatment can involve prostaglandin tablets in the urethra, intracavernous injections with a fine needle into the penis that cause swelling, a penile prosthesis, a penis pump or vascular reconstructive surgery.^[4]

The Latin term impotentia coeundi describes simple inability to insert the penis into the vagina. It is now mostly replaced by more precise terms. The study of erectile dysfunction within medicine is covered by andrology, a sub-field within urology.

Signs and symptoms

Erectile dysfunction is characterized by the regular or repeated inability to obtain or maintain an erection. There are several ways that erectile dysfunction is analyzed:

• Obtaining full erections at some times, such as when asleep (when the mind and psychological issues, if any, are less present), tends to suggest the physical structures are functionally working.

• Obtaining erections which are neither rigid nor full (lazy erection), or are lost more rapidly than would be expected (often before or during penetration), can be a sign of a failure of the mechanism which keeps blood held in the penis, and may signify an underlying clinical condition, often cardiovascular in origin.

• Other factors leading to erectile dysfunction are diabetes mellitus (causing neuropathy) or hypogonadism (decreased testosterone levels due to disease affecting the testicles or the pituitary gland).

Erection problems are very common. The Sexual Dysfunction Association estimates that 1 in 10 men in the UK have recurring problems with their erections at some point in their life.^[3]

Causes

• Drugs (anti-depressants (SSRIs) and nicotine are most common. A study entitled “Drug-induced male sexual dysfunction” concluded that of the 12 most commonly prescribed medications on the market today, 8 of those medications list impotence as a side effect of the drug. Other drugs such as alcohol, cocaine, and heroin negatively impact male sexual libido.)
• Neurogenic Disorders (spinal cord and brain injuries, nerve disorders such as Parkinson's disease, Alzheimer's disease, multiple sclerosis, and stroke.^[5])
• Hormonal Disorders (pituitary gland tumor; low or abnormally high levels of the hormone testosterone).

• Arterial Disorders (peripheral vascular disease, hypertension; reduced blood flow to the penis).
• Venous leak
• Cavernosal Disorders (Peyronie's disease.^[6])
• Psychological causes: performance anxiety, stress, mental disorders (clinical depression, schizophrenia, substance abuse, panic disorder, generalized anxiety disorder, personality disorders or traits.^[7]), psychological problems, negative feelings.^[8]
• Surgery (radiation therapy, surgery of the colon, prostate, bladder, or rectum may damage the nerves and blood vessels involved in erection. Prostate and bladder cancer surgery often require removing tissue and nerves surrounding a tumor, which increases the risk for impotence.^[9])
• Aging. It is four times higher in men in their 60s than in men in their 40s.^[10]
• Kidney failure
• Lifestyle: alcohol and drugs, obesity, cigarette smoking (Incidence of impotence is approximately 85 percent higher in male smokers compared to non-smokers^[11]., Smoking is a key cause of erectile dysfunction.^[12][13] Smoking causes impotence because it promotes arterial narrowing.^[14] See also Tobacco and health. )
• Other disorders.

A few causes of impotence may be iatrogenic (medically caused). Various antihypertensives (medications intended to control high blood pressure) and some drugs that modify central nervous system response may inhibit erection by denying blood supply or by altering nerve activity.

Surgical intervention for a number of different conditions may remove anatomical structures necessary to erection, damage nerves, or impair blood supply. Complete removal of the prostate gland or external beam radiotherapy of the gland are common causes of impotence; both are treatments for prostate cancer. Some studies have shown that male circumcision may result in an increased risk of impotence,^[15][16] while others have found no such effect,^[17][18][19] and another found the opposite.^[20]

Excessive alcohol use has long been recognised as one cause of impotence, leading to the euphemism "brewer's droop," or "whiskey dick;" Shakespeare made light of this phenomenon in Macbeth.

A study in 2002 found that ED can also be associated with bicycling. The number of hours on a bike and/or the pressure on the penis from the saddle of an upright bicycle is directly related to erectile dysfunction.^[21]

Pathophysiology

Penile erection is managed by two different mechanisms. The first one is the reflex erection, which is achieved by directly touching the penile shaft. The second is the psychogenic erection, which is achieved by erotic or emotional stimuli. The former uses the peripheral nerves and the lower parts of the spinal cord, whereas the latter uses the limbic system of the brain. In both conditions, an intact neural system is required for a successful and complete erection. Stimulation of penile shaft by the nervous system leads to the secretion of nitric oxide (NO), which causes the relaxation of smooth muscles of corpora cavernosa (the main erectile tissue of penis), and subsequently penile erection. Additionally, adequate levels of testosterone (produced by the testes) and an intact pituitary gland are required for the development of a healthy erectile system. As can be understood from the mechanisms of a normal erection, impotence may develop due to hormonal deficiency, disorders of the neural system, lack of adequate penile blood supply or psychological problems. Restriction of blood flow can arise from impaired endothelial function due to the usual causes associated with coronary artery disease, but can also be caused by prolonged exposure to bright light.

Diagnosis

There are no formal tests to diagnose erectile dysfunction. Some blood tests are generally done to exclude underlying disease, such as hypogonadism and prolactinoma. Diabetes is considered a disorder, but is also a risk. Impotence is also related to generally poor physical health, poor dietary habits, obesity, and most specifically cardiovascular disease such as coronary artery disease and peripheral vascular disease.

A useful and simple way to distinguish between physiological and psychological impotence is to determine whether the patient ever has an erection. If never, the problem is likely to be physiological; if sometimes (however rarely), it could be physiological or psychological. The current diagnostic and statistical manual of mental diseases (DSM-IV) has included a listing for impotence.

Duplex ultrasound

Duplex ultrasound is used to evaluate blood flow, venous leak, signs of atherosclerosis, and scarring or calcification of erectile tissue. Injecting prostaglandin, a hormone-like stimulator produced in the body, induces erection. Ultrasound is then used to see vascular dilation and measure penile blood pressure. Measurements are compared to those taken when the penis is flaccid.

Penile nerves function

Tests such as the bulbocavernosus reflex test are used to determine if there is sufficient nerve sensation in the penis. The physician squeezes the glans (head) of the penis, which immediately causes the anus to contract if nerve function is normal. A physician measures the latency between squeeze and contraction by observing the anal sphincter or by feeling it with a gloved finger inserted past the anus. Specific nerve tests are used in patients with suspected nerve damage as a result of diabetes or nerve disease.

Nocturnal penile tumescence (NPT)

It is normal for a man to have five to six erections during sleep, especially during rapid eye movement (REM). Their absence may indicate a problem with nerve function or blood supply in the penis. There are two methods for measuring changes in penile rigidity and circumference during nocturnal erection: snap gauge and strain gauge. A significant proportion of men who have no sexual dysfunction nonetheless do not have regular nocturnal erections. Thus presence of NPT tends to signify physically functional systems, but absence of NPT may be ambiguous and not rule out either cause.

Penile biothesiometry

This test uses electromagnetic vibration to evaluate sensitivity and nerve function in the glans and shaft of the penis. A decreased perception of vibration may indicate nerve damage in the pelvic area, which can lead to impotence.

Penile Angiogram

Invasive test - allows visualization of the circulation in the penis and is used during the repair of a priapism.

Dynamic Infusion Cavernosometry

(Abbreviated DICC) technique in which fluid is pumped into the penis at a known rate and pressure. It gives a measurement of the vascular pressure in the corpus cavernosum during an erection. To do this test, a vasodilator like prostaglandin E-1 is injected to measure the rate of infusion required to get a rigid erection and to help find how severe the venous leak is.

Corpus Cavernosometry

Cavernosography measurement of the vascular pressure in the corpus cavernosum. Saline is infused under pressure into the corpus cavernosum with a butterfly needle, and the flow rate needed to maintain an erection indicates the degree of venous leakage. The leaking veins responsible may be visualised by infusing a mixture of saline and x ray contrast medium and performing a cavernosogram.^[22]

Digital Subtraction Angiography

In DSA, the images are acquired digitally. The computer creates a mask from lower-contrast x-rays of the same area and digitally isolates the blood vessels (this is done manually through darkroom masking with traditional angiography).

Magnetic resonance angiography (MRA)

This is similar to magnetic resonance imaging. Magnetic resonance angiography uses magnetic fields and radio waves to provide detailed images of the blood vessels. Doctors may inject a "contrast agent" into the patient's bloodstream that causes vascular tissues to stand out against other tissues. The contrast agent provides for enhanced information regarding blood supply and vascular anomalies. Aside from the IV used to introduce the contrast material into the bloodstream, magnetic resonance angiography is noninvasive and painless.

Treatment

Treatment depends on the cause. Testosterone supplements may be used for cases due to hormonal deficiency. However, the cause is more usually lack of adequate penile blood supply as a result of damage to inner walls of blood vessels. This damage is more frequent in older men, and often associated with disease, in particular diabetes.

Treatments (with the exception of testosterone supplementation, where effective) work on a temporary basis: they enable an erection to be attained and maintained long enough for intercourse, but do not permanently improve the underlying condition.

ED can in many cases be treated by drugs taken orally, injected, or as penile suppositories. These drugs increase the efficacy of nitric oxide, which dilates the blood vessels of corpora cavernosa. When oral drugs or suppositories fail, injections into the erectile tissue of the penile shaft are extremely effective but occasionally cause priapism.

Exercise, particularly aerobic exercise is an effective cheap treatment for erectile dysfunction.^[23]

When pharmacological methods fail, a purpose-designed external vacuum pump can be used to attain erection, with a separate compression ring fitted to the penis to maintain it. These pumps should be distinguished from other penis pumps (supplied without compression rings) which, rather than being used for temporary treatment of impotence, are claimed to increase penis length if used frequently, or vibrate as an aid to masturbation. More drastically, inflatable or rigid penile implants may be fitted surgically. Implants are irreversible and costly.

All these mechanical methods are based on simple principles of hydraulics and mechanics and are quite reliable, but have their disadvantages. In a few cases there is a vascular problem which can be treated surgically.

Counselling is often a consideration, both where a psychological cause is suspected or must be ruled out, or to assist in management of any distress.

Medications

The cyclic nucleotide phosphodiesterases constitute a group of enzymes that catalyse the hydrolysis of the cyclic nucleotides cyclic AMP and cyclic GMP. They exist in different molecular forms and are unevenly distributed throughout the body.

One of the forms of phosphodiesterase is termed PDE5. The prescription PDE5 inhibitors sildenafil (Viagra), vardenafil (Levitra) and tadalafil (Cialis) are prescription drugs which are taken orally. They work by blocking the action of PDE5, which causes cGMP to degrade. CGMP specific phosphodiesterase type 5 causes the smooth muscle of the arteries in the penis to relax, allowing the corpus cavernosum to fill with blood.

These medications work when there is sexual stimulation. Depending on the treatment, it will need to be taken 20 minutes to 1 hour before sex and the period of time over which it works can vary between 3 hours and up to 36 hours.

Alprostadil

Alprostadil can be injected into the penis or inserted using a special applicator - usually just before sexual intercourse.

Alprostadil has also become available in some countries as a topical cream (under the brand name Befar),^[24] and preliminary studies have shown a clinical efficacy of up to 83%.^[25]

Androskat

Androskat is a mixture of papaverine and phentolamine injected into the penis before sexual intercourse. It does not require refrigeration.

Surgery

Often, as a last resort if other treatments have failed, the most common procedure is prosthetic implants which involves the insertion of artificial rods into the penis.^[26]

Devices

Vacuum Therapy

These work by placing the penis in a vacuum cylinder device.^[27] The device helps draw blood into the penis by applying negative pressure. A tension ring is applied at the base of the penis to help maintain the erection.^[27] This type of device is sometimes referred to as penis pump and may be used just prior to sexual intercourse. Several types of FDA approved vacuum therapy devices are available with a doctor's prescription.

Alternative medicine

Numerous alternative therapies are used to improve sexual function. Some include: niacin, zinc, ginseng root, ginkgo. None of these however have been recognized as effective by the FDA.^[28] While zinc deficiency may be a cause of lower testosterone levels in hemodialysis patients, which may benefit from zinc supplementation,^[29] such supplements have no effect on the testosterone levels of healthy males who consume a zinc-sufficient diet.^[30]

Research

A new research was conducted at the Ramban Medical Center in Haifa, Israel by Dr. Yoram Vardi, head of the Neuro-Urology Department and its results were presented to the European Society of Sexual Medicine in Lyon, France in November, 2009.

The study involved 20 middle – aged volunteers who had suffered erectile dysfunction for more than three years. The participants were administered a shockwave therapy in two 20-minute sessions each week, during a three week treatment. Patients rested for three weeks and then received the treatment for three weeks more.^[31]

The treatment involved the use of a mild form of lithotripsy, which is a technique that uses sound waves that can smash up kidney stones. Several studies showed in recent years that this therapy triggers the release of Vascular Endothelial Growth Factor (VEGF), in charge of sending out a signal for new blood vessels to start growing.^[32] In the case of erectile dysfunction, this therapy appears to stimulate the growth of new blood cells in the genital region. This treatment uses a device that looks like a computer mouse to beam the wave sounds through the skin

Vardi reported that 15 of the 20 men had consistent results and that all men noted a return of erectile functioning by the seventh week. These men were followed up for six months and 13 of them showed long lasting effective effects and the other two men had to take additional treatments. Furthermore, they did not report pain or side effects. However, Vardi reported that the treatment would not work on men with muscle or nerve problems and stressed that this therapy is intended for those men whose erectile problem arises from reduced blood flow.^[31] Erectile Dysfunction treatments depend on the underlying cause that triggers them which may be psychogenic or physiological, therefore, these causes must previously identified in order to use the appropriate treatment.

The study is still experimental and according to Dr. Andrew McCullough, director of Male Sexual Health, Fertility and Microsurgery in the Department of Urology at NYU Langone Medical Center, more study is necessary before this treatment could be available in the United States.^[33]

History

The earliest attempts at treating erectile dysfunction date back to Muslim physicians and pharmacists in the Islamic Golden Age. They were the first to prescribe medication for the treatment of this problem, and they developed several methods of therapy for this issue, including a single-drug therapy method where a drug was prescribed and a "combination method of either a drug or food." Most of these drugs were oral medication, though a few patients were also treated through topical and transurethral means. Erectile dysfunctions were being treated with tested drugs in the Islamic world since the 9th century until the 16th century by a number of Muslim physicians and pharmacists, including Muhammad ibn Zakarīya Rāzi, Thabit bin Qurra, Ibn Al-Jazzar, Avicenna (The Canon of Medicine), Averroes, Ibn al-Baitar, and Ibn al-Nafis (The Comprehensive Book on Medicine).^[34]

Dr. John R. Brinkley initiated a boom in male impotence cures in the US in the 1920s and 1930s. His radio programs recommended expensive goat gland implants and "mercurochrome" injections as the path to restored male virility, including operations by surgeon Serge Voronoff. After the Kansas State Medical Board revoked his medical license and the Federal Radio Commission refused to renew his radio license (both in 1930), Brinkley moved his operations just over the Texas border to Mexico where he opened a medical clinic and broadcast advertisements into the US from a border blaster radio station.

Surgeons began providing patients with inflatable penile implants in the 1970s.

Modern drug therapy for ED made a significant advance in 1983, when British physiologist Giles Brindley, Ph.D. dropped his trousers and demonstrated to a shocked American Urological Association audience his phentolamine-induced erection. The drug Brindley injected into his penis was a non-specific vasodilator, an alpha-blocking agent, and the mechanism of action was clearly corporal smooth muscle relaxation. The effect that Brindley discovered established the fundamentals for the later development of specific, safe, orally-effective drug therapies.^[35][36]

See also

• Erectometer
• Sex and drugs

References

External links

• Erectile dysfunction at the Open Directory Project