Laboratory investigation of the patient with erectile dysfunction is directed at identifying treatable conditions or previously undetected medical illnesses that may be contributing to impotence. Metabolic disturbances such as renal insufficiency, diabetes, and endocrine abnormalities (eg, hypogonadism, hyperprolactinemia) may play a role in the development of the dysfunction.
If not previously done, some basic studies should be considered to identify unrecognized systemic conditions that may predispose to erectile dysfunction. These include a complete blood count, urinalysis, renal function, lipid profile, fasting blood sugar, and thyroid function.
A man who has evidence of liver disease or alcoholism should have a liver function test, as this can directly affect the ability to achieve an erection. Renal function tests should be done in men who also indicate renal failure. A blood count, which measures the amount of red blood cells in the bloodstream, can be useful in determining anemia as the cause of erectile dysfunction. Some men are so anemic that they are extremely fatigued, which is apparent in a physical examination.
One of the startling facts revealed by the Massachusetts Male Aging Study is that men with erectile dysfunction frequently have low levels of high-density lipoproteins, the good form of cholesterol. Men with high levels of cholesterol and triglycerides, which are a form of fat in the bloodstream, frequently have erectile dysfunction directly related to this condition.