|Dr. Sergey A. Dzugan|
Erectile dysfunction (ED) is defined as a consistent or recurrent inability to achieve or maintain penile erection sufficient for satisfactory sexual function. A common disorder for men of all ages and ethnic and cultural groups, ED affects an estimated 152 million men worldwide1 and 50% of men aged 40-70 in the United States.2
In aging men, tissue sensitivity to hormonal impulses usually decreases, secretory function from hormonal glands declines, and the endocrine system’s central controlling mechanism changes. With the world’s population growing rapidly and average male life expectancy increasing, we can expect to see erectile dysfunction become an important public health problem. Not only does ED adversely affect quality of life for millions of aging men, but this condition can also be the first warning sign of more serious underlying problems such as heart disease or diabetes. Your physician should consider erectile dysfunction as an important part of your larger health picture.
Physiology of Normal Erection
Penile erection occurs through the synchronized action of psychological, neuronal, hormonal, vascular, and cavernous smooth muscle systems. Normally, neurovascular response is modulated by psychological factors and hormonal status.3 Normal erection requires a dynamic balance of excitatory and inhibitory forces.4 There are inputs to penis function from the central and autonomic (both the sympathetic and parasympathetic) nervous systems. The sympathetic nervous system works in one direction, the parasympathetic works in the other.
Stimulation of parasympathetic activity can lead to a release of nitric oxide from the terminal end of axons, which are nerve fibers that conduct impulses away from the body of the nerve cell. Nitric oxide then diffuses into the smooth muscle of the penile arteries. These arteries relax or dilate, and blood flow into the organ increases. The spongy erectile tissue of the penis fills with blood, leading to compression of the veins that normally remove blood from the penis. In other words, erection is produced by the trapping of blood in the corpus cavernosum (corporal body) of the penis. During rapid eye movement (REM) sleep, the dominance of the parasympathetic system normally triggers nocturnal erection.2
Stimulation of the sympathetic system works in the opposite direction, maintaining the penis in a flaccid condition. The sympathetic nervous system can be stimulated by stress, exercise, and low temperature.
Causes of Erectile Dysfunction
Erectile dysfunction can have both psychological and organic (physical) causes. The latter may involve various bodily pathologies or the effects of medications or alcohol. In addition, ED can be a symptom of numerous conditions, including cardiovascular disease.1,5,6
In cases of psychological ED, most often the condition is related to depression, anxiety, psychiatric diseases, marital or relationship problems, or financial difficulties.7 Erectile dysfunction attributable to psychological factors most frequently occurs at a younger age.
Organic ED can have numerous causes. Age appears to be a strong risk factor, as organic erectile dysfunction becomes more prevalent as men grow older. Organic ED may be due to vascular causes when blood flow to and from the penis is disrupted. Medical conditions such as cardiovascular diseases (atherosclerosis, or hardening of the arteries, as well as hypertension and high cholesterol) and diabetes may lead to vascular dysfunction.5,8 Men with these conditions represent the largest group of ED patients. Penile injury and surgery in the pelvic and abdominal area can also cause reduced penile blood flow and erectile dysfunction. Smoking is an additional factor that can indirectly reduce genital blood flow by accentuating the effects of other risk factors such as cardiovascular disease and hypertension.9,10
Organic erectile dysfunction can also have neural causes. Disorders such as stroke, multiple sclerosis, Parkinson’s disease, spinal cord damage, and, again, diabetes can lead to nerve damage and affect normal response to sexual stimulation.11-15 ED is also common in men who have had surgical treatment for prostate enlargement or prostate cancer.
Hormonal deficiencies or imbalances are another major component of organic erectile dysfunction. In aging men, an impaired feedback mechanism of the pituitary-gonadal axis can lead to diminished production of gonadal and adrenal androgens, contributing to the development of ED.16 Low levels of hormones such as testosterone, dehydroepiandrosterone (DHEA), pregnenolone, and thyroid hormones likewise may contribute to ED.7,17-20
Finally, medications may contribute to organic erectile dysfunction. Prescription medications for treating high blood pressure (beta-blockers), depression (Prozac®, Zoloft®), insomnia (Ambien®), heart disease (statins), prostate enlargement (Proscar®) or cancer (Zoladex®), and other conditions have side effects that may include inducing ED.5-7,21 Excessive alcohol consumption can likewise negatively affect sexual function, especially with aging.1
A diagnosis of erectile dysfunction can be based on general medical history, sexual history, physical examination, and laboratory testing.
Medical history is important in detecting the presence of concomitant health conditions such as heart disease, diabetes mellitus, hypertension (high blood pressure), endocrine disorders, depression, and insomnia, as well as in assessing possible contributing factors such as smoking, alcohol consumption, and prescription drugs. Use of over-the-counter medications and nutritional and herbal remedies must also be evaluated.
The physical examination and laboratory assessment should include measurement of body weight, height, pulse rate, blood pressure, complete blood cell count, glucose, lipid profile, prostate-specific antigen (PSA), and urine analysis. While a physical examination may reveal signs of an androgen deficiency, it is crucial to test for levels of hormones such as pregnenolone, DHEA-sulfate, testosterone (total and free), estradiol, and progesterone. Additional testing may include Doppler ultrasound of the penile blood vessels and the nocturnal penile tumescence study for assessing erection during sleep. Physical examination and other testing should be performed before initiating therapy.
There are many options for treating erectile dysfunction. Managing ED may involve psychological, medical (oral, transdermal, or injected drugs), nutritional (supplements), and surgical therapies. To correct ED, it is essential to address any underlying chronic conditions and modify lifestyle factors such as obesity, smoking, alcohol consumption, and lack of exercise. Psychological therapy such as counseling and behavioral therapy can be effective if psychological factors are contributing to erectile dysfunction. Because ED can be a side effect of certain medications, it may be helpful to change drug regimens under a doctor’s care. Finally, it is important for men to remain physically and sexually active for as long as possible.
Today, aging men are exposed to information and advertisements touting a wide variety of drugs and supplements that may help restore sexual function. The most popular option is a class of drugs called phosphodiesterase type 5 inhibitors such as Viagra® and Levitra®. These drugs dilate blood vessels in the genital region, leading to an erection; unfortunately, however, they do very little to increase libido (sexual desire). While these medications are valuable tools in the symptomatic treatment of erectile dysfunction, they may produce multiple side effects such as headaches, changes in blood pressure, irregular heart rhythm, flushing, nasal congestion, and others, and their long-term risks are unknown.22
Men whose blood tests indicate hormonal deficiencies or imbalances can use bioidentical hormones to help manage ED. Replacement of androgens can be crucial in restoring normal sexual function. While testosterone is available by prescription only, over-the-counter hormones such as DHEA and pregnenolone may help boost testosterone levels and thus improve erectile dysfunction.
Owing to a lack of research in this area, the efficacy of some supplements in managing ED is considered moderate to uncertain. The benefits of most of the products available have been described through cultural experience and anecdotal reports. Many herbal “aphrodisiacs” have a positive influence on erectile dysfunction, and some have an effect on hormonal output as well.
Emerging evidence and case reports suggest that naturally occurring agents such as L-arginine,2,23 Korean red ginseng,24 zinc,25 DHEA,26-31 maca root,2,32 and Tribulus terrestris33 may help improve sexual function and thus ED. A naturally occurring alkaloid called yohimbine, derived from the African tree, Pausinystalia yohimbe, has been used for over 70 years as a pharmacological agent in treating ED.2,34,35 Other herbs that have been reported to improve ED include horny goat weed, oat straw (Avena sativa), damiana, muira puama, and ashwagandha. Studies of these herbal plants have often yielded inconsistent results, and clinical evidence to support herbal agents in managing ED is still minimal.
Those who do not benefit from drugs, supplements, or psychological treatment may see improvement with intracavernosal injection (such as prostaglandin and papaverine plus phentolamine),36 vacuum/constrictive devices, penile prostheses, or vascular surgery.