Vitamin T for Sex (cont.)
Here is the critical point: Give Sullivan replacement testosterone so that his circulating levels return to 15% of normal, 100% of normal, or 150% of normal, and you will have roughly the same effect in all cases. The best single review on this subject is "Behavioral effects on androgens in humans," published in the August 1996 issue of the American Journal of Psychiatry. Over a very wide range, testosterone has pretty much the same effect on behavior. Push levels below that range (due to castration or any of a number of diseases), and physiology and behavior change. Push levels above that range, by abusing anabolic steroids, and you'll typically boost aggression, perhaps libido as well. But within that broad range -- from 15% to 150% of normal -- behavior and libido remain roughly the same.
Increases Body Mass, Not Sex Drive
So what CAN extra testosterone do? A few studies, including one in the October 1992 issue of the Journal of Clinical Endocrinological Metabolism, have shown that boosting testosterone levels in aged males increases body mass and decreases cholesterol levels. Sullivan, who experienced a 20-pound weight gain, can now squat more than 400 pounds and feels a surge of energy "less edgy than a double espresso but just as powerful."
However, there have been no double-blind studies showing that supplemental testosterone reinstates "youthful" sexual performance or libido, alertness, or energy.
And the testosterone experts agree. Consider the following summary from a recent review published in the July 2000 issue of the journal Geriatrics: "Hormones such as DHEA, human growth hormone, and testosterone tend to decline with aging, but the therapeutic value of [restoring] them to 'normal' physiologic levels has not been substantiated by controlled clinical trials." Furthermore, Williams' Textbook of Endocrinology (1998, 9th edition), essentially the "bible" of the field, states that "The decline in male sexual function with age does not appear to be endocrine-mediated."
So a 50% decline in some guy's testosterone level as he ages from a 20-something to a 50-something is unlikely to have much impact on his physiology and behavior. And therefore using something like AndroGel to boost his levels from 50% to 100% won't likely have much of an impact, either.
Stress Inhibits Testosterone, But Does It Matter? Similarly, low testosterone secretion induced by stress is no reason to take supplemental testosterone, either. All sorts of stressors, whether physical or psychological, can inhibit the secretion of all the hormones involved in the complex release of testosterone. Anesthetize someone for surgery, slice into his belly with a scalpel, and testosterone levels begin to decline. The same thing will happen for a male primate who has just been toppled from a high rank in the group hierarchy. Ditto for a man going through a stressful cognitive task like a final exam. Or -- an example that I get an odd pleasure out of citing -- a study in the May 1972 Archives of General Psychiatry found that men in the early, highly stressful period of officer's training in the military have suppressed testosterone levels, too.
So this decline under stress appears to be a well-established phenomenon. But the bottom line is, what are the consequences of this decline in testosterone levels during stress? A loss of sexual drive or performance? Decreased aggressiveness? Decreased muscle metabolism?
None of the above, almost certainly. The declines in testosterone levels during stress, even with severe, chronic stress, just aren't dramatic enough to produce such adverse consequences.
So, men shouldn't worry much about the consequences of yet another traffic jam or deadline on their testosterone. The problem isn't that testosterone levels go down during stress. It's that erect penises do. But that's another subject . . . for another story.
Robert Sapolsky is professor of biological sciences at Stanford University, and of neurology at Stanford University School of Medicine. He is the author of Why Zebras Don't Get Ulcers: A Guide to Stress, Stress-Related Diseases,.
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