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Do testosterone levels decline with age?


The latest fashion in the lay press (abetted by many anti-aging practitioners) is to rephrase this question in a more catchy way and capitalize on familiarity with menopause. Thus, the question is posed on the cover of men’s health publications: Is there an Andropause?  Strictly speaking, the answer is ‘No.’  There is no point in a normal, healthy man’s life cycle when testosterone levels universally abruptly drop to less than 20 percent of youthful levels as occurs with a woman’s estradiol level at about age 51.  Unfortunately, many physicians seize on this difference to bolster their argument that because the decline is not abrupt, treatment isn’t as necessary as for menopause. We think this is fallacious reasoning.  Let’s look a little more closely at what is now a robust body of data on the effect of aging on testosterone levels.


One of the largest studies to look at testosterone levels in aging men was the Massachusetts Male Aging Study. It found that total testosterone levels declined by about five percent per decade from the thirties to the seventies and more precipitously in ill or obese men.  Some men didn’t have much of a decline at all.  This set back general acceptance of TRT in aging for many decades, because many physicians didn’t think this was enough of a decline to warrant treatment.  What wasn’t appreciated enough, however, was that the free testosterone level—the most biologically important fraction—declined twice as fast, about 10 percent per decade, so that approximately 50 percent of men over 55 years old have ‘hypogonadism,’ defined as levels below the lowest normal range for young men.  Subsequently, many well-designed studies have corroborated these numbers, and it is widely agreed in the endocrine literature that over time testosterone levels decline in men, often to a point equivalent to menopause in women.  (The reason that the total testosterone does not decline as steeply with age is that there is an increase in SHBG with age which offsets the decline in testosterone production.)


To see if the decline in bioavailable testosterone correlates with some of the signs and symptoms of aging, Dr. John Morley looked at 54 men between the ages of 20 and 84 years old to see if the bioavailable testosterone level could predict which men had declining cognitive and physical functioning.  He found a strong correlation as have many subsequent studies.


In summary, we can now say with assurance that testosterone levels decline with age and that this decline is, at least in part, responsible for some of the important manifestations of aging.  Other factors, such as obesity, chronic illness, and stress can be very important determinants as well, but if one controls for these elements, age is still associated with a very significant drop in testosterone.


NEXT: Timing and Risks