Laboratory testing: Laboratory testing is necessary for most men, although no laboratory work may be needed.
If laboratory tests are performed, they would normally start with an evaluation of your hormone status (testosterone or male hormone), particularly if one of your symptoms is low sexual desire (low libido). Blood tests for testosterone should ideally be taken early in the morning because that's when levels are usually at their highest. Other blood tests, such a luteinizing hormone and prolactin, can help determine if there is a problem with the pituitary gland.
Your blood may be checked for glucose, cholesterol, thyroid function, triglycerides, and prostate-specific antigen (PSA).
A urinalysis looking for blood cells, protein, and glucose (sugar) may also be done.
Imaging: An ultrasound may be performed. This test may be done on the lower abdomen, pelvis, and testicles, or restricted to just the penis.
A duplex ultrasound is a diagnostic technique that uses painless, high frequency sound waves to visualize structures beneath the skin's surface. The principle is similar to the sonar used on submarines. Sound waves are reflected back when they contact relatively dense structures such as fibrous tissue or blood vessel walls. These reflected sound waves can be converted into pictures of the internal structures being studied.
This procedure is usually performed before and after injection of a smooth muscle relaxing medication into the penis, which normally should significantly increase the diameter of the penile arteries. The procedure itself is painless. Duplex ultrasonography is most useful in evaluating possible penile arterial disorders, but further studies of the venous drainage system as well as arterial x-rays are usually recommended if vascular reconstructive surgery is anticipated.
Further testing: Following completion of this phase, the doctor should be able to determine the general type of dysfunction and the need for additional testing such as penile or pelvic blood flow studies, nocturnal penile tumescence testing, penile biothesiometry (nerve testing), or additional blood tests. Your doctor will discuss your results with you (including your partner when possible), summarize the risk factors such as smoking and medications that may be involved, review the various treatment options that can be considered, and work with you to develop a strategy and program to help you and your partner achieve a satisfactory result.
One of the most common tests used to evaluate penile function is the direct injection of PGE1 into the penis. (PGE1 is a medication that increases blood flow into the penis and normally produces erections.) If the penile structure is normal or at least adequate, an erection should develop within several minutes. You and your doctor can judge the quality of the erection. If successful, this test also establishes penile injections as one possible therapy.
Nocturnal penile tumescence testing (NPT) may be useful in distinguishing mental from physical impotence. This test involves the placement of a band around the penis that you would wear during 2 or 3 successive nights. If an erection occurs, which is expected during rapid eye movement (REM) sleep, the force and duration are measured on a graph. Inadequate or no erections during sleep suggests an organic or physical problem, while a normal result may indicate a high likelihood of emotional, psychological, or mental causes.
Formal neurological testing is not needed for most men. But anyone with a history of nervous system problems such as loss of sensation in the arms or legs and those with a history of diabetes may be asked to undergo testing.
The sensitivity of the skin of the penis to detect vibrations (biothesiometry) can be used as a simple office nerve function screening test. This involves the use of a small vibrating test probe placed on the right and left side of the penile shaft as well as on the head of the penis. The strength of the vibrations is increased until you can feel the probe vibrating clearly. Although this test does not directly measure the erectile nerves, it serves as a reasonable screening for possible sensory loss and is simple to perform. More formal nerve conduction studies are only performed in selected cases.