| SExUAL DySFUNCTioN | opinion
seem to agree that it increases with age. Furthermore, the incidence seems to
be increasing over time, although this may reflect the increasing availability of effective treatment and greater openness in dealing with the problem. The US National Ambulatory Medical Care Survey found that in 1985, 7.7 physician office visits were made for ED for every 1000 men. By 1999, that figure had almost tripled to 22.31
. With the availability of
effective drug treatments, that figure is bound to have risen.
Causes ED may be caused by a number of factors. it may be psychogenic in origin, or may have a physical cause. Among the latter, the most common are diabetes, complications of treatment for prostate cancer, and various types of trauma. it can also occur as a side-effect of drugs, such as certain antihypertensives, antidepressants, or drugs given for prostate cancer. Abuse of recreational drugs including alcohol may also lead to ED. in the case of diabetes, it is reported that
up to 75% of men with the disease experience some form of erectile difficulty over the course of their lifetime2
. Prostate
cancer treatments that can cause ED include surgery, radiation therapy, cryosurgery, and hormone therapy.
Further possible causes include multiple sclerosis, Parkinson’s disease and spinal cord injury. The primary objective when assessing
men who present with ED is to determine whether the cause is psychological or organic, although ED of sudden onset in otherwise healthy young men is almost certain to be of psychogenic origin. The presence of any normal erections (such as during sleep) indicates a psychological cause because organic causes prevent all erections. Consequently, men presenting with ED will normally be subjected to a battery of tests to try to identify the cause. one of the standard techniques is to monitor nocturnal penile tumescence using an appropriate device, such as the osbon Medical Systems RigiScan. Another way of assessing whether the
ED is of psychogenic origin is by observing the ability of intracavernosal injection of either papaverine or prostaglandin E1
to
elicit an erection. other tests carried out may include the determination of cavernosal artery blood flow via penile duplex ultrasound examination, which can also identify any venous leak present, while a penile angiogram can also be used to investigate penile haemodynamics. if an organic cause is indicated, further laboratory tests, such as measurement of blood testosterone levels, may be used.
At the molecular level, penile erection
occurs when the neurotransmitter nitric oxide is released from the so-called non-adrenergic non-cholinergic nerves and endothelial cells. Nitric oxide stimulates the enzyme guanylate cyclase in penile vascular smooth muscle, which leads to an increase in the concentration of cyclic guanosine monophosphate (cGMP), which in turn produces smooth muscle relaxation. At the physiological level, the result is increased blood flow into the penis and reduced venous outflow, leading to tumescence. Drugs such as Viagra, Cialis and Levitra
act by inhibiting an enzyme called phosphodiesterase type 5 (PDE5), responsible for breaking down cGMP. By inhibiting the enzyme, these drugs extend the time that cGMP is present in the penile vascular smooth muscle, thereby extending the vascular effects that lead to an erection. Viagra has been found to be effective in
most types of organic ED, including that caused by diabetes, following treatment of prostate disease, in patients with spinal cord injury, and even in patients with depression as a precipitating factor. Clinically, the other PDE5 inhibitors are
similar to Viagra, but there are some important differences. For example, Levitra is more selective for the enzyme
prime-journal.com | July 2011 ❚ 67
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