What causes some men to have trouble getting and keeping an erection?

Many factors. An erection is a vascular, neurologic and hormonal event. Therefore, problems with blood vessels, nerves and hormones can all cause erection difficulties. A doctor's visit can help figure out where the problem is and provide appropriate treatment. The most concerning thing is that men under 50 with erectile difficulties have a 2 times higher risk of developing heart disease in the next 10 years.