Erectile Dysfunction: Epidemiology, Physiology, and Etiologies

ED is defined as the consistent inability to achieve or maintain an erection adequate for sexual activity. It is a widely prevalent disease, affecting approximately 20 million men in the United States alone. ED rates increase as men get older; however, ED is not necessarily a normal part of aging. Early-onset ED has been a predictor of underlying cardiovascular diseases, and most clinicians now advocate for a cardiology evaluation in men with new-onset organic ED. The most common etiology of ED is a vascular disease; however, ED can be caused by diabetes, endocrinopathies, medications, chronic illness, and trauma. Psychogenic causes of ED are also common. Physiology of the penile erection is complicated; however, its comprehensive understanding is imperative to enable a proper etiologic diagnosis of ED. Blood supply to the penis originates from the hypogastric arterial system, and nitric oxide is the primary neurotransmitter involved in penile erections. The epidemiology, physiology, and etiologies of erectile dysfunction are discussed in detail in this chapter. This review contains 1 figure, 2 tables, and 50 references. Key Words: causes of erectile dysfunction, epidemiology of erectile dysfunction, erectile dysfunction, nitric oxide, phosphodiesterase-5 inhibitors, physiology of the penile erection, psychogenic erectile dysfunction, sexual dysfunction, cyclic guanosine monophosphate, detumescence.