Factors that mediate contraction in the penis include noradrenaline, endothelin-1, neuropeptide Y, prostanoids, angiotensin II, and others not yet identified. Factors that mediate relaxation include acetylcholine, nitric oxide (NO), vasoactive intestinal polypeptide, pituitary adenylyl cyclase–activating peptide, calcitonin gene–related peptide, adrenomedullin, adenosine triphosphate, and adenosine prostanoids.

The role of the endothelium in erectile function became clearer with the observation that the phosphodiesterase type 5 (PDE5) inhibitor, sildenafil, enhanced erectile function. Erection occurs with the release of nitric oxide (NO) from the vascular endothelial cells.17 The reduction in endothelial cell production of NO results in the negative impact on the smooth muscles in the corporal bodies and results in less relaxation of the smooth muscle cells with decrease in blood supply and resulting ED. A similar phenomenon is well known to impact the coronary arterial system resulting in CVD.
Neurogenic erectile dysfunction (NED) is a traditional classification of erectile dysfunction (ED) encompassing disorders impairing erections via neurologic compromise or dysfunction. The disorders compromising erections may act centrally, peripherally or both. The prevalence of neurogenic ED has been suspected to be between 10% and 19% of all causes of ED (1,2). However, several classically defined neurogenic processes may affect several components of the normal pathway to achieve erection e.g., multiple sclerosis (MS), diabetes mellitus, iatrogenic surgical and spinal cord injury. Each disease state has its own unique characteristics that require acknowledgement to fully understand their effect on ED.
Commercials for drugs to improve “low T,” or testosterone, the male hormone, are now vying for airtime, but they address desire, not performance. "Male hormone is not an approved treatment for erectile dysfunction," notes Bennett. "It may be used to increase desire in men who have low testosterone, but it doesn’t improve blood flow to an erection." A doctor can do a blood test to check you for low testosterone, but it is a rare cause of ED. Hormone therapy with injections, patches, or gels applied to the skin may improve mood and sex drive, but it likely won’t fix any mechanical issues. Also, testosterone drugs should not be used by men with prostate cancer. Side effects include acne, breast enlargement, prostate enlargement, and fluid retention.
Watts and coworkers, in their review article, make several points about this ED/CAD nexus. Endothelial dysfunction is present in both CVD and ED, and is linked through the NO mechanism. The authors note that PDE5 inhibitors improve endothelial function and have a salutary effect on both CVD and ED. Both ED and cardiac disease respond to modifications in lifestyle as well as pharmacologic manipulation. These authors also report that the presence of ED gives the clinician an opportunity to assess CVD and prevention as well.20
One of the first steps is to distinguish between physiological and psychological ED. Determining whether involuntary erections are present is important in eliminating the possibility of psychogenic causes for ED.[2] Obtaining full erections occasionally, such as nocturnal penile tumescence when asleep (that is, when the mind and psychological issues, if any, are less present), tends to suggest that the physical structures are functionally working.[19][20] Similarly, performance with manual stimulation, as well as any performance anxiety or acute situational ED, may indicate a psychogenic component to ED.[2]
There are many effective treatments for impotence. The most popular is a class of drugs called phosphodiesterase type 5 (PDE5) inhibitors. These include sildenafil (Viagra), vardenafil (Levitra), tadalafil (Cialis) and avanafil (STENDRA). These drugs are taken in pill form. They work in most men. But they are less effective in men with neurological causes of impotence.
As recently as two decades ago, doctors tended to blame erectile dysfunction on psychological problems or, with older men, on the normal aging process. Today, the pendulum of medical opinion has swung away from both notions. While arousal takes longer as a man ages, chronic erectile dysfunction warrants medical attention. Moreover, the difficulty is often not psychological in origin. Today, urologists believe that physical factors underlie the majority of cases of persistent erectile dysfunction in men over age 50.
Treatments include psychotherapy, adopting a healthy lifestyle, oral phosphodiesterase type V (PDE5) inhibitors (Viagra, Levitra, Cialis, Stendra, and Staxyn), intraurethral prostaglandin E1 (MUSE), intracavernosal injections (prostaglandin E1 [Caverject, Edex], Bimix and Trimix), vacuum devices, penile prosthesis and vascular surgery, and (in some cases) changes in medications when appropriate.
Yes, the vacuum device is effective. In fact, with use of the vacuum device, 88% of men will have an erection that is satisfactory for completion of sexual activity. The vacuum device may be the only therapy that is effective after the removal of a penile prosthesis. Patients also use vacuum devices as part of penile rehabilitation after radical prostatectomy to help preserve the tissue of the penis and prevent scarring within the penis and loss of penile length. Its use, however, is limited by the mechanical nature of it and the time taken to pump the device and apply the band. Sex partners may complain of the penis being cool to touch.

In a prospective study from the Prostate Cancer Prevention Trial database, Thompson et al reported that men presenting with ED had a significantly higher chance of developing a cardiovascular event over a 7-year follow-up period. [55] The hazard ratio was 1.45, which is in the range of risk associated with current smoking or a family history of MI.
As blood flows into the penis, the corpora cavernosa swell, and this swelling compresses the veins (blood vessels that drain the blood out of the penis) against the tunica albuginea. Compression of the veins prevents blood from leaving the penis. This creates a hard erection. When the amount of cGMP decreases by the action of a chemical called phosphodiesterase type 5 (PDE5), the muscles in the penis tighten, and the blood flow into the penis decreases. With less blood coming into the penis, the veins are not compressed, allowing blood to drain out of the penis, and the erection goes down.
You may find that using a vacuum device requires some practice or adjustment. Using the device may make your penis feel cold or numb and have a purple color. You also may have bruising on your penis. However, the bruises are most often painless and disappear in a few days. Vacuum devices may weaken ejaculation but, in most cases, the devices do not affect the pleasure of climax, or orgasm.

Lifestyle choices that impair blood circulation can contribute to ED. Smoking, excessive drinking, and drug abuse may damage the blood vessels and reduce blood flow to the penis. Smoking makes men with atherosclerosis particularly vulnerable to ED. Being overweight and getting too little exercise also contribute to ED.  Studies indicate that men who exercise regularly have a lower risk of ED.
A vacuum erection device is a plastic tube that slips over the penis, making a seal with the skin of the body. A pump at the other end of the tube makes a low-pressure vacuum around the erectile tissue, which results in an erection. An elastic ring is then slipped onto the base of the penis. This holds the blood in the penis (and keeps it hard) for up to 30 minutes. With proper training, 75 out of 100 men can get a working erection using a vacuum erection device.
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