Find out about the variety of laboratory tests involved in diagnosing the cause of erectile dysfunction.
After a careful and thorough history and physical examination, I generally tailor the use of laboratory investigation to the individual patient. I try to avoid doing every lab to every patient as it is typically a waste of money.
The initial lab procedure, the urinalysis, is an inexpensive test that is done by the treating physician in the office. It provides a wealth of information. The urinalysis provides the most medical information in the most cost-efficient way. This test will provide information regarding the presence or absence of infection, as well as the possibility of diabetes.
I frequently make the initial diagnosis of diabetes when evaluating men for sexual dysfunction. Diabetes is one of the major causes of erectile dysfunction in the United States. I am also able to screen for urologic problems such as blood in the urine, which can be a prognostic sign of cancer, and make a positive impact on the patient’s life by finding a cancer that would otherwise not be discovered until it had spread. We also frequently find urinary tract infections by examining the urine during this phase of the investigation. Following a careful urinalysis, the remainder of the tests should be at the discretion of the physician, based on suspicious findings in the history or physical examination.
The next test I consider is the testosterone level. Low serum testosterone can be a cause of erectile dysfunction. Truly low serum testosterone level is indicated by the history and physical examination, including decreased sex drive, poor erections, dry skin, small testicles, a decreased need to shave, and a decreased amount of muscle mass.
The single best test for testosterone level is the free serum testosterone. Free and total testosterone means the amount of testosterone that is active in the body. By measuring the free testosterone, you are measuring the type of testosterone that is the most active in the patient. Remember that the testosterone is transported through the body bound to a substance that helps carry it through the various organs requiring it for growth.
The vast majority of men who have their testosterone checked only have a total testosterone level. This can be adequate in most cases, but if there is any question as to whether the testosterone is truly low, I do a free serum testosterone test. Men with lower levels of binding globulin, which can artificially lower the testosterone, include older men and men on low-fat diets or those with liver damage or who are taking other hormones that compete for these binding sites.
Men who have very high levels of the binding globulin include obese men and men on high-fat diets. A truly low free testosterone level finding should always be repeated to be certain of the diagnosis prior to placing a patient on what may be lifelong therapy.
The treatment for low serum testosterone is androgen replacement therapy, which is not without side effects.
Serum Prolactin Level
The next test I generally obtain in certain clinical situations is a serum prolactin level. A normal testosterone level rarely accompanies an elevated prolactin level in men. Common causes of a mildly elevated prolactin level include diabetes, kidney failure, and certain medications such as alphamethyldopa, female hormones, and the antipsychotic drugs, phenothiazines.
The instance of elevated prolactin is extremely rare, although it is one of the most common forms of pituitary hormone excesses.
Clinically, cases of truly elevated prolactin levels can be predicted from the clinical history. The key question in the clinical history is to ask about a lack of interest versus an inability to get an erection. These men will typically say that they are able to get a good erection, but they have no interest in having sexual relations.
When a prolactin-secreting tumor, which is a benign tumor, enlarges, it can put pressure on the optic nerves causing visual changes. It is also not uncommon to see headaches and breast swelling in these men. When an elevated prolactin level is found, it is extremely important for the physician to rule out other tumors as a cause. This is a fairly straightforward workup and merely requires a CAT scan or MRI of the pituitary area.
A CAT scan is an X ray that looks at the area of the pituitary gland where prolactin-secreting tumors can grow. Interestingly, as the prolactin level gets higher, the chances of finding an abnormal pituitary on an X ray increase dramatically. This is an extremely easy problem to treat with simple oral medications.
Other laboratory tests in the evaluation of erectile dysfunction include the gonadotropins. Gonadotropins are substances produced by the pituitary gland that are useful when trying to discover the reasons for low testosterone levels.
The first clinically useful test is called the luteinizing hormone, the hormone that stimulates the production of testosterone. A man with low testosterone and a low luteinizing hormone (LH) is diagnosed as hypogonadotrophic. The condition called hypogonadism is low testosterone and a high LH, which indicates testicular failure.
A thyroid function test may be done in situations where the man may have a low thyroid level. This can generally be associated with a decrease in sexual drive and weight gain.
More frequently, I will check the lipid profile, which is a measure of the cholesterol level as well as the components of cholesterol, known as high-density lipoproteins and low-density lipoproteins.
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.
In certain situations, a complete blood count and chemistry profile is necessary, especially among men who indicate other, more unusual causes.
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.
Some physicians may want to order every test on every patient. Remember, this is unnecessary and costly, and generally does not improve the patient in any way.