Erectile dysfunction (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 due to hydraulic effects due to blood entering and being retained in sponge-like bodies inside the penis. 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, hormonal insufficiencies (hypogonadism) and drug side effects. It is important to realise that erectile dysfunction can signal underlying risk for cardiovascular disease.