Ed | Health Knowledgebase

Erectile Dysfunction

15th December, 2008 - Posted by Andy - No Comments

INTRODUCTION

Erectile dysfunction (impotence) is the inability to achieve or maintain an erection sufficiently rigid for sexual intercourse, ejaculation, or both. Sexual drive and the ability to have an orgasm are not necessarily affected. Because all men experience erection problems from time to time, doctors consider impotence to be present if attempts at intercourse fail on at least 25% of attempts.

Erectile dysfunction is not new in medicine or human experience, but it is not easily or openly discussed. Cultural expectations of male sexuality inhibit many men from seeking help for a disorder that can, in most cases, benefit from medical treatment. The term “impotence” comes from Latin and means loss of power; a more accurate term is “erectile dysfunction.”

STRUCTURE OF THE PENIS
The penis is composed of the following structures:

Two parallel columns of spongy tissue called the corpus cavernosa, or erectile bodies. A central spongy chamber called the corpus spongiosum, which contains the urethra, the tube that carries urine from the bladder through the penis. These structures are made up of erectile tissue. Erectile tissue is rich in tiny pools of blood vessels called cavernous sinuses. Each of these vessels are surrounded by smooth muscles and supported by elastic fibrous tissue composed of a protein called collagen.

Erectile Function and Nitric Oxide
The penis is either flaccid or erect depending on the state of arousal. In the flaccid, or un-erect, penis, the following normally occurs:

Small arteries leading to the cavernous sinuses contract, reducing the inflow of blood. The smooth muscles regulating the many tiny blood vessels also stay contracted, limiting the amount of blood that can collect in the penis. During arousal the following occurs:

The man’s central nervous system stimulates the release of a number of chemicals, including nitric oxide, which is now considered the main contributor for eliciting and maintaining erection. Nitric oxide stimulates production of cyclic GMP, a chemical that relaxes the smooth muscles in the penis. This allows blood to flow into the tiny pool-like cavernous sinuses, flooding the penis. This increased blood flow nearly doubles the diameter of the spongy chambers.

The veins surrounding the chambers are squeezed almost completely shut by this pressure. The veins are unable to drain blood out of the penis and so the penis becomes rigid and erect. After ejaculation or arousal, cyclic GMP is broken down by an enzyme called phosphodiesterase-5 (PDE5), and other compounds are released that cause the penis to become flaccid (un-erect) again.

DRUG RISKS
In 2005, the US Federal Drug Agency (FDA) added warnings of partial vision loss to the labels of sidenafil (Viagra), tadalafil (Cialis), and vardenafil (Levitra). It is not certain if the risk for vision loss (a condition called non-arteric anterior ischemic optic neuropathy or NAION) is related to the medications or the vascular disease conditions that cause erectile dysfunction (ED). Patients who use these drugs and experience vision loss should immediately stop the medication and contact their doctor.

Risk Factors
Older age is the main risk factor for ED. Nearly 80% of men ages 75 and older experience ED. However, according to a 2006 study, other physical and lifestyle factors greatly increase the risk for ED:

• Diabetes (by 169%)
• Current smoking (by 74%)
• Obesity (by 60%)
• High blood pressure (by 56%)

ED and Heart Disease
Recent research strongly suggests that ED may be an important warning sign of heart disease:

In a 2006 study in the Archives of Internal Medicine, ED was a stronger predictor of coronary artery disease (CAD) than smoking, family history, cholesterol levels, or blood pressure. Men with ED are at increased risk for angina, heart attack, and stroke, according to a 2005 study in the Journal of the American Medical Association.
ED may indicate that CAD is developing, even in men without typical heart disease risk factors, suggests a study in the Journal of the American College of Cardiology. Men with ED have a 46% greater risk of heart disease than men without erectile problems, according to research presented at the 2006 American Urological Association annual meeting. Researchers recommend that doctors ask men about their ED status to determine who may be at risk for heart disease. Patients with ED should receive a complete heart disease evaluation.

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[Sources: NHS Direct, Google, NIH (USA)]
[Compiled 12.09.08]

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