Erectile dysfunction can result from the following mechanisms:
- failure to initiate, with a psychologic, endocrinologic, or neurogenic origin
- failure to fill with a vascular origin
- failure to store adequate blood volume due to venoocclusive dysfunction
The most frequent organic cause of erectile dysfunction is a disturbance of blood flow to and from the penis.
Disorders that affect the sacral spinal cord or the autonomic fibers to the penis preclude nervous system relaxation of penile smooth muscle. Multiple sclerosis, peripheral neuropathy, diabetes and alcohol abuse can also cause erectile dysfunction.
There can be an endocrinologic origin in case of hypogonadism, although the exact role of androgens in erectile function remains unclear.
The following classes of drugs are known to cause erectile dysfunction by their mechanism of action:
A patient with a heterosexual relationship is not able to initiate or maintain his erections. His condition has developed over several weeks. He has DM and uses captopril (ACE-inhibitor) and metformin. He has erections early in the morning and during sleep. Which is the most probable cause of his erectile dysfunction?
Extra info: The fact that he has erections in the morning and during sleep suggests that he is able to get erections and that the cause is not vascular or neurogenic. His medications do not induce erectile dysfunction. Therefore the cause must be psychological and the doctor should ask about such factors.