The Latin term impotentia coeundi describes simple inability to insert the penis into the vagina. It is now mostly replaced by more precise terms.
Erectile dysfunction is characterized by the inability to maintain an erection. Normal erections during sleep and in the early morning suggest a psychogenic cause, while loss of these erections may signify underlying disease, often cardiovascular in origin. Other factors leading to erectile dysfunction are diabetes mellitus (causing neuropathy) or hypogonadism (decreased testosterone levels due to disease affecting the testicles or the pituitary gland).
There are no formal tests to diagnose erectile dysfunction. Some blood tests are generally done to exclude underlying disease, such as diabetes, hypogonadism and prolactinoma. Impotence is also related to generally poor physical health, poor dietary habits, obesity, and most specifically cardiovascular disease such as coronary artery disease and peripheral vascular disease.
A useful and simple way to distinguish between physiological and psychological impotence is to determine whether the patient ever has an erection. If never, the problem is likely to be physiological; if sometimes (however rarely), it is more likely to be psychological. The current diagnostic and statistical manual of mental diseases (DSM-IV) has included a listing for impotence.