By Madeleine Castellanos, M.D.
Most people know that a man's testosterone level peaks around age 20, and begins a steady decline from about 40 years old on, so that it is about 50% less by the time he is 80 years old. What I don't hear people talking about is the fact that, except in extreme cases, knowing what a man's testosterone level is not really that helpful. First, there is a huge range in what is considered "normal" for testosterone. For example, in men 20-30 years old, a normal testosterone level is anywhere between 270-1030 (almost a four-fold difference). That level refers to total testosterone level, most of which travels through the body attached to a protein that keeps it from having any effect in the body. Only free testosterone is what is important. Furthermore, testosterone levels fluctuate greatly throughout the day. Since testosterone levels are highest in the morning, that is usually when a sample is taken.
The other thing to consider is that since there is such a large range of normal, different men will feel differently with exactly the same testosterone level. It is probably more helpful to know if there has been a significant change from your baseline testosterone level. In order to know this, a man would have to have his testosterone level checked when he was in his early 20s and feeling good. Then he could know if there was a dramatic change from his baseline. How many of you have done that? Everybody's baseline testosterone level is different and is determined mainly by your genetics, but there are many factors that can influence the increase or decrease in a man's testosterone. I think it is important to talk about these factors, because testosterone replacement is not without negative side effects, and I believe that working in cooperation with your body is the best way to achieve health and balance.
So what people aren't saying about testosterone levels is that a man's testosterone level is very sensitive and varies greatly in response to what is happening around him. This serves to regulate his activity and helps him adapt to many different situations. For example, when a man meets a woman he finds very attractive and believes there is potential to have her as a partner, his testosterone level spikes up. After he "gets the girl," it goes back down again. In fact, men in stable long-term relationships tend to have lower testosterone levels than single men their age, and even less if they are parents. If there is arguing, or if the marriage is on the rocks, however, testosterone levels rise again. It would be interesting to study how testosterone levels respond to novelty and variety that one may experience with their long-term partner, and therefore investigate if this would result in periodic increases of testosterone while strengthening (instead of threatening) the relationship.
Testosterone is also influenced by activity level. If a man engages in moderate resistance training, he will naturally increase his testosterone. Too much strenuous activity, however, causes testosterone to fall precipitously. This helps explain why new recruits going through boot camp circulate the rumor that the Army puts salt peter in their food to decrease their sex drive. It's actually due to the rigors of their training schedule (but who better than Army recruits to subscribe to conspiracy theories?). Zinc deficiency also results in decreased production of testosterone, which is easily remedied with supplementation or zinc-rich foods in the diet (oysters are by far the highest with almost ten times the amount of zinc found in beef). Getting proper sleep is important too, since REM sleep increases the release of testosterone.
Perhaps the most interesting response that a man's testosterone level can have is that in response to competition. It has been shown that before a fight or a match, such as tennis or wrestling, the competitors' testosterone levels spike. After the match is the biggest change, with the winner's testosterone increasing about 20%, and the loser's dropping a whopping 90%! But it wasn't only physical competitions that saw this response. A study done with chess players reproduced similar results. In fact, another study showed that even watching a sports competition, such as football or baseball, resulted in increased testosterone levels for people who sided with the winning team, and dropping testosterone levels for those siding with the losing team. Imagine the implications that this has for testosterone levels and one's career choice or work environment? If a man has a steady stream of challenges (within reason) that he accomplishes, this may increase his testosterone, while men who frequently feel defeated or helpless may have decreased testosterone. This gives new meaning to a psychologist's use of the word "castrated" and invites men to consider their lifestyle as a major contributing factor to their mental and physical health.
Keep in mind that the body, directed by the brain, always tries to find a balance with it's environment. Testosterone levels are monitored by the brain, which will decrease the production of testosterone if the circulating level in the body is too high. This is why testosterone replacement is not without its side effects. Long-term testosterone replacement can result in decreased sperm production and shrinkage of the testicles. Also, it can be downright dangerous for men with prostate disease. Even studies that hypothesized that testosterone was important for bone density have been refuted by research suggesting that it is the conversion of testosterone to estrogen which is responsible for maintaining strong bones in elderly men. The truth is that testosterone replacement is not needed for most men. Lifestyle changes are well worth a try, since their side effects are usually healthier and enhance your life, rather than take from it. Tennis anyone? (You'll probably win.)