All of these deleterious effects have prompted the FDA to approve testosterone for the treatment of hypogonadism. The next important question is, What testosterone level constitutes hypogonadism? On the face of it this seems to be a very straight forward question. After all, it is just a number for which one is looking, right? Not exactly.
Testosterone, depending on the laboratory, is measured in nanograms per deciliter (ng/dl)—the number of billionths of a gram found in 100 milliliters of blood serum. The “normal range” usually reported on a laboratory report runs from about 290 to 900 ng/dl. The problem with this “normal range” is that it is determined by using a standard Gaussian distribution (bell-shaped curve) of all of the patients who, at one time or another, for various reasons have had their blood tested for testosterone. The lower number is equal to two standard deviations below the average and the higher number two above it. Two standard deviations means that if you are below the 290, then your testosterone level is in the bottom 2.5 percent of all male testosterone levels. Unfortunately, most doctors think that if the test value falls in the “normal” range, then there is no problem. What they don’t understand is that the groups of men that form the basis of this normal range at most laboratories are not homogeneous. They can be 80 years old, or 20 years old; they can be chronically ill, or very healthy; they can be obese or thin; and they can be under a great deal of stress or stress free. All of these conditions can profoundly alter a man’s testosterone level.
The medical definition of hypogonadism generally uses a level below 300 ng/dl because virtually all men below this range exhibit the signs and symptoms discussed above. But what about a level of 350 or 450 ng/dl? The difference between a man with this level and a man who meets the cut off for “hypogonadism” is less than between him and a man with a level of 800 ng/dl. And what about the average level of about 600; is it adequate or does a man with a level of 900 feel better, have denser bones, stronger muscles, and greater sexual potency? A clue to the answer is thinking back to how you felt when you were 18 years old, a time when testosterone levels run between about 800 and 1500. A more scientific clue is the number of studies that have shown improvements in strength, muscle, and libido when middle aged men with “normal” testosterone levels have those levels boosted with TRT to the high end of normal or even above that. Why then should a man be denied treatment if his testosterone level is 500 ng/dl and has only a mild degree of decreased libido and only slightly reduced musculature? This gets us to the heart of the issue when debating the use of testosterone as an anti-aging therapy. Before we begin this debate, however, let’s discuss what happens—on average—to a man’s testosterone level as he ages.
NEXT: Testosterone and Aging