Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. Erectile dysfunction (ED, or "male impotence") is a sexual dysfunction characterized by the inability to develop or maintain an erection of the penis sufficient for satisfactory sexual performance.An erection occurs as a hydraulic effect due to blood entering and being retained in sponge-like bodies within the penis. The process is most often initiated as a result of sexual arousal, when signals are transmitted from the brain to nerves in the pelvis. Erectile dysfunction is indicated when an erection is consistently difficult or impossible to nerves in the pelvis. Erectile dysfunction is indicated when an erection is consistently difficult or impossible to produce, despite arousal. There are various and often multiple underlying causes, some of which are treatable medical conditions. The most important organic causes are cardiovascular disease and diabetes, neurological problems (for example, trauma from prostatectomy surgery), hormonal insufficiencies (hypogonadism) and drug side effects. It is important to realize that erectile dysfunction can signal underlying risk for cardiovascular disease.