Erectile dysfunction may stem from a number of different conditions. The most common cause, according to studies, is an abnormality in the arteries and veins that supply the penis with blood flow. The arteries and veins may have sustained injury, or they may be blocked with arterial plaque. This is why ED is sometimes considered a warning sign of atherosclerosis, hardening of the arteries. Atrophy of the smooth muscle of the penis is another abnormality that could cause erectile dysfunction.
Additional causes of ED include:
Diabetes.
Neurologic conditions such as nerve injury, spinal cord injury, multiple sclerosis, and other problems.
Depression or anxiety.
Low testosterone levels.
Too much or too little thyroid hormone.