The nerves are the control mechanism which coordinate the increase in pressure in the penis as well as the closing down of the veins. A man needs sufficient levels of testosterone in order to have the desire, feel aroused, and to get an erection. Any physical or emotional factor that affects a man's arteries, veins, nerves, or hormones can impact his erections. A man must allow himself to relax in order for the blood vessels of the penis to also relax so that he can get and maintain an erection. A discussion of the problem followed by a physical examination is the first step toward diagnosing the cause of the problem.
Blood flow is measured by assessing pulse and penile blood pressure.
Hormone status is assessed by evaluating testicle size and inspection of the prostate through a prostate exam. Preliminary screening includes blood tests to audit male hormone level, thyroid function, presence of diabetes and a man's cholesterol level. A stress audit involves a questionnaire to be completed at home. A man may also apply a simple snap gauge that can reveal if the penis is becoming erect during the night. The normal male has about two or three erections a night.