According to the Sexual Function Health Council of the American Foundation for Urologic Disease, 30 million men are estimated to have some form of erectile dysfunction in the U.S. Erectile dysfunction (ED) is defined as the inability to obtain and/or maintain penile erection sufficient for satisfactory sexual performance, lasting at least 3 months. The definition of erectile dysfunction distinguishes itself from other disorders, e.g., inability to achieve orgasm, low libido, and premature ejaculation. ED has a significant impact on the quality of life and it is a common problem. Its prevalence is directly proportional to aging. Its prevalence varies from 30%–40% at age 40, to up to 70% at 70 years and older. One must comprehend the intricate mechanisms of erection in order to understand the underlying cause of dysfunction. Normal aging, as well as psychogenic, vascular, neurogenic, and endocrinologic causes and/or those due to structural abnormalities of the penis should be considered when attempting to determine its cause. Low libido has either a psychogenic or endocrinologic component.
Erection is a complex, involuntary, neuropsychological, hormonemediated vascular event. Alpha-Adrenergically mediated contraction of cavernosal and vascular smooth muscle limits blood flow to the penis and maintain the usual flaccid state. An erection occurs when erotic stimuli, received via any of the five senses and processed in the hypothalamus, results in inhibition of sympathetic tone and release of nitric oxide (NO) from nonadrenergic, noncholinergic nerves and endothelial cells of the arterioles in the penis.
NO activates guanyl cyclase, thereby generating cyclic guanosine monophosphate (cGMP). cGMP decreases calcium uptake into vascular and cavernosal smooth muscle and induces relaxation. Smooth muscle relaxation permits engorgement of cavernosal sinusoids with blood and the development of an erection. In addition to NO, other neurotransmitters postulated to play a role in the erectile mechanism include prostaglandins, vasoactive intestinal peptide, serotonin, and dopamine.
Ejaculation is reflex sympathetic discharge from the nerves of the penis to the seminal pathway, the muscle coats of the epididymis, ductus deferens, the seminal vesicles, and the prostate gland, causing the release of sperm and seminal fluid.
Any derangement in this sequence of neurovascular events can result in ED. For example, compromise of neural pathways either centrally (stroke) or peripherally (diabetic autonomic neuropathy) may lead to ED. Alternatively, veno-occlusive failure may occur from intrapenile lesions (Peyronie’s disease).
Libido is the conscious feeling of the sexual urge, mediated by dopamine and sex hormones, which originates in the cerebral cortex. In the event of aroused libido, the brain center sends impulses to the spinal center, which in turn passes them to the nerves of the penis.
Recent findings suggest that ED has an organic cause 75% of the time. This finding contrasts with the previous view that more than three quarters of erectile dysfunctions are of psychogenic origin. Organic causes include vascular disease, neurotransmitter imbalances, neurologic disease, hypogonadism, drug use, structural problems (Peyronie's disease etc.) and systemic diseases such as chronic renal failure and cancer.
Prescription drugs, narcotics and alcohol are common causes and should always be ruled out first before referral to an Urologist.