Normal Erectile Function

For something that appears so natural, an erection is a rather complicated process involving the coordination of the psychological, neurological and cardiovascular systems. The penis becomes erect following a series of events. First, the nerves are stimulated, a sensation known as arousal. No matter what the nature of the stimulus, visual, mental or physical the brain coordinates the following series of events:Nerve impulses transverse the length of the spinal cord to the pudendal nerve and on to the penis. Smooth muscle within the walls of the penile arteries respond by relaxing. Subsequently, the penile arteries dilate allowing up to eight times more blood to flow into the corpora cavernosum, (two parallel cylinders that transverse the length of the penis).

• Nerve impulses transverse the length of the spinal cord to the pudendal nerve and on to the penis. Smooth muscle within the walls of the penile arteries respond by relaxing. Subsequently, the penile arteries dilate allowing up to eight times more blood to flow into the corpora cavernosum, (two parallel cylinders that transverse the length of the penis).
  
• The cavernosum become engorged with blood expanding and lengthening the penis. The expanding tissue then exerts a positive pressure compressing the veins that normally empty the blood from the penis, maintaining the blood in the penile tissue. When ejaculation occurs or when arousal is discontinued the penis returns to its non-erect state.

Causes of Erectile Dysfunction

Historically, when an individual consulted his physician concerning Erectile Dysfunction he was usually informed there were no known physiological answers concerning his condition. Today, a generation of research has resulted in significant advances in both the diagnosis and treatment of Erectile Dysfunction . Physicians now understand that approximately 85% of Erectile Dysfunction is attributable to physical/organic conditions while only 15% is due to psychological or mixed origin (both psychological and organic). Some important causes of physiological Erectile Dysfunction are as follows:

Vascular Disease

Vascular Disease is the leading cause of Erectile Dysfunction. Vascular disorders include arteriosclerosis (hardening of the arteries), hypertension, hyper-cholestremia and other conditions which interfere with the blood flow to the penis. Additionally, "venous leakage", a condition occurring when the penile veins are unable to constrict efficiently during an erection, also contributes to poor erections. When these veins "leak", blood escapes to the periphery resulting in a poor erection.

Diabetes is another common cause of Erectile Dysfunction. Approximately 50% of men with insulin dependent diabetes experience some degree of ED after 55 years old. Diabetes results in poor circulation and/or peripheral neuropathy. When the nerves are involved, sexual stimuli are not transmitted appropriately to or from the brain and Erectile Dysfunction develops.

Neurological diseases such as multiple sclerosis, Parkinson's disease, spinal cord injuries and long term effects of diabetes can also result in the disruption of the normal sequence of events necessary for an erection to occur.

Endocrine System

Deficiencies in the Endocrine System are another source of Erectile Dysfunction. Low levels of testosterone or thyroid hormone can interfere with the stimulation process necessary in the erection sequence. Excessive production of prolactin by the pituitary gland may contribute to decreased levels of testosterone resulting in a lack of desire. Diabetes once again enters the scenario as it is classified as an endocrine disorder.

Prescription medications often cause Erectile Dysfunction as a side effect. Some two hundred known medications fall into this category including:

Antihypertensives medications specifically:

1. Beta-blockers e.g. Atenolol, Propanolol and Tenorium.
   
2. Diuretics medications e.g. HydroDiuril and Lasix.
   
3. Ace Inhibitors/Calcium Channel Blockers medications e.g. Vasotec®, Lotension®, Cardizem® and Norvasc® periodically cause Erectile Dysfunction , however, they are generally represent an excellent alternative medication for individuals with drug induced Erectile Dysfunction.
   
   Antidepressant/Antipsychotic medications -of almost any label can also result in Erectile Dysfunction e.g. Prozac®, Elavil®, Zoloft®, Thorazine® and Haldol®. Note: Many other medications in a variety of classes can periodically cause ED. If you take a prescription medication or an over-the-counter medication, regularly, please consult with your physician. However, never alter a dosage or discontinue a medication without the advice of your physician.

Smoking

Smoking as been linked to Erectile Dysfunction in numerous clinical studies.

The most common causes of the organic component in erectile dysfunction or impotence are vascular abnormalities associated with atherosclerosis and diabetes mellitus. Atherosclerosis causes 40% of cases of erectile dysfunction, and in cases of diabetes mellitus the prevalence of erectile dysfunction is 50%. Smoking is significantly associated with the development of both atherosclerosis and diabetes mellitus.

The Epidemiology and Pathophysiology of Erectile Dysfunction.
The Journal of Urology 1999 Jan; 161(1):5-11

After smoking two cigarettes, the diameter of the internal pudendal artery narrows and the penile arteries almost completely close. This evidence suggests that smoking can cause an acute vasospastic constriction of the arteries in the penis. These observations are supported by physiological evidence that nicotine causes acute peripheral vasoconstriction. Acute Vasospasm of Penile Arteries in Response to Cigarette Smoking. Urology 1990; 36(1):99-100

Researchers at Wake Forest University in Winston Salem, North Carolina concluded that male smokers who suffer from long standing hypertension are 26 times more likely to be impotent than those individuals who do not smoke. January 2000, The Journal of Family Practice.

Aside from impotence, smoking as also been linked to the following negative effect concerning male sexual health:

• Reduced volume of ejaculation
• Lowered sperm count
• Abnormal sperm shape
• Impaired sperm motility

LH-RH Analogs/Antiandrogen medications e.g. Lupron Depot®, Eulexin®, Nilandron®, Casodex®, etc. are medications are used in the treatment of prostate cancer. They function by decreasing the production of testosterone in the testes and adrennal glands, which decrease in testosterone often results in Erectile Dysfunction.

Chemotherapy/Radiation therapy is also a significant contributors to Erectile Dysfunction. These drugs/treatments are used in the treatment of cancer.

Substance Abuse can also negatively effect male potency. The chronic use of cocaine, marijuana, alcohol, steroids etc. often results in Erectile Dysfunction, as well as a decrease in desire. Excessive tobacco use can also attribute to Erectile Dysfunction by accentuating the effects of other risk factor such as vascular disease or hypertension.

Radical Pelvic Surgery also result in Erectile Dysfunction. Surgical procedures involving the prostate gland, bladder or colon may interfere with the nerves involved in the erectile response. Radiation therapy for cancer may also effect the erectile process.

Psychological ED is usually diagnosed when no physical causes can be defined. Pure psychological Erectile Dysfunction usually occurs suddenly without warning as opposed to physical ED that may gradually develop over the years.

Some common causes of psychological Erectile Dysfunction are as follows:

• Performance anxiety is one of the most common causes of psychological Erectile Dysfunction. When a man feels pressured to achieve or maintain an erection, he will commonly become anxious and nervous when in a sexually demanding situation. Stress increases the body's production of catecholamines such as adrenaline and nor- adrenaline, which act as erection inhibitors. The release of these inhibitors further contributes to failure resulting in more anxiety. Therefore, the cycle begins, increased stress resulting in increased catecholomines that further inhibits the erectile process.
  
• Depression is another cause of psychogenic Erectile Dysfunction. Unfortunately, many of the popular antidepressant medications (for a list see prescription medications in the next section) have side effects which include erectile failure.

Anatomical Deviation of the Penis

Anatomical Deviation of the Penis, known as Peyronie's Disease, may also cause Erectile Dysfunction. This condition usually develops from an inflammatory process and results in fibrous scaring of the penis. The cause of this process is not yet understood; however, when an erection does occur, there is a bending of the penis secondary to the scar tissue. This curvature may interfere with erectile capacity and/or ejaculation.

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