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Erectile Dysfunction

Erectile dysfunction (ED) is the inability to sustain an erection sufficient for satisfying sexual activity. The Massachusetts Male Aging Study (MMAS) reported that 52% of participants, aged 40-70 years, had some degree of erectile difficulty. Other studies indicate that between 18 and 30 million American men are affected by ED.

Erectile dysfunction may result from any of the following etiologies:

Psychogenic
Vasculogenic
Neurogenic
Endocrine
End-organ failure
Iatrogenic and drug induced

Psychogenic ED is now thought to account for less than 30% of cases. Psychogenic pathology can result in inhibition of the spinal erection center and/or excessive sympathetic stimulation. When sympathetic stimulation predominates, the smooth muscle of the corpora cavernosa can not fully relax.

Anxiety/discord/insecurity can elevate sympathetic stimulation.
Cultural/religious taboos can suppress or sublimate sexual response.
Psychological disorders - depression, personality disorders, psychosis can decrease sexual performance.

Vasculogenic ED: may result from conditions which affect blood flow within the penis. Atherosclerosis, diabetic vasculopathy, hypertension, smoking, hyperlipidemia and trauma can diminish blood flow and erectile function. Conditions that reduce endothelial nitric oxide production and release inhibit the relaxation of vascular smooth muscle.

Neurogenic ED: can result from lesions in the peripheral, spinal or cerebral nerves that serve the perineum and genitals. Diabetes, multiple sclerosis, tumors, disc herniation, Parkinson's, stroke, Huntington's chorea and electroshock therapy have all been associated with erectile dysfunction.

Endocrine & metabolic disorder ED: diabetes is the leading cause of ED in the US. Between 30 and 50% of all diabetic American men over 50 are impotent. Hypogonadism is the primary endocrinopathy causing ED. Hypogonadism can result from testicular failure to produce androgens or a failure of the anterior pituitary to produce luteinizing hormone. ED is also associated with: hyperprolactemia, thyroid disorders, uremia and dialysis (often reversible following kidney transplant).

End-organ failure: congenital defects, Peyronie's disease, priapism, prostatitis and seminal vasculitis have all been associated with ED.

Iatrogenic and drug induced ED: GU trauma related to surgery or irradiation and certain procedures performed on the spinal and brain can cause ED. Alcohol, sympathomimetics, antihypertensives, psychotropics and recreational drugs have all been associated with ED.

Until the discovery of sildenafil citrate, treatment options for ED included:

penile prosthesis
vacuum pump and occlusive bands
transurethral alprostadil
intracavernosal injections of vasoactive agents, such as alprostadil
CNS acting oral agents like yohimbe

These options are often unsatisfactory, awkward, occasionally painful and sometimes traumatic.

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Diabetes is the leading cause of ED in America.