Causes of erectile dysfunction.

Erectile dysfunction (ED) arises as a result of a collision of circumstances among any of a number of factors (e.g., risk factors, causes, probable associations), each with its own primary power to affect the outcome. Furthermore, each of the components has its own timing as part of a complex effort of compensation and adjustment that often obscures the individual details. In the end, ED results from a failure of local tissues or systemic supply and control structures. The power of any individual "cause" to degrade erectile function is an important but as-yet unquantified property. The power of a small abnormality over a long or critical period (e.g., organogenesis), or many small contributions, or multiple risk factors will certainly be greater than the sum of the individual elements. Without a full quantitation of pathways and their potential influence, one can compare the importance of causative factors only in limited ways. Not surprisingly, it is the presence of a multiplicity of unidentified or poorly understood causative factors that accounts in large measure for the current inability to cure and prevent ED. There are two other important properties of a putatively causative factor for ED--reversibility and preventability--and these are strongly influenced by the time of onset and the duration of impact. Thus, a critical understanding that comes from recognizing the importance of the temporal associations of component factors is that the causes of ED in an individual may be guessed at but cannot be fully disclosed by an analysis of a "snapshot" of the disease taken at the time of diagnosis.