originally written for Advance for Healthy Aging Journal by Shawn M. Talbott, PhD
What is Testosterone?
In both men and women, testosterone is needed to build muscle and other proteins, such as immune system components, and control many aspects of physiology, including blood cell production and metabolism of protein, carbohydrates, and fat from food. A drop in testosterone in men leads to fatigue, a loss of sex drive, and weight gain in the belly – the old potbelly that nobody wants. This same drop in testosterone causes the same fatigue and loss of sex drive in women, but it also induces women’s bodies to lose their “hourglass” shape of youth and grow into an apple (or “shot glass”) shape with the same kind of “male” pattern of abdominal weight gain.
Because of the media reports of athletes abusing anabolic steroids (synthetic versions of testosterone), testosterone has suffered a negative public image that is not deserved. Many people view testosterone as the hormone that causes bulging muscles and aggressiveness, but it is important to understand that these effects of testosterone are caused by a gross overuse of synthetic testosterone used at extreme mega-dose levels. When bodybuilders inject testosterone and other anabolic steroids to promote freakish muscle growth, they are artificially increasing their testosterone levels to 10, 20, or 100-times normal values. The result of this unnatural testosterone exposure is the clearly unnatural changes in body shape, mood, and metabolism characteristic of professional bodybuilders.
Some of the most common effects of low testosterone (in both men and women) include:
•Emotional changes (increased anxiety and depression)
- •Low sex drive
- •Decreased muscle mass
- •Reduced metabolic rate
- •Increased abdominal fat
- •Weak bones
- •Back pain
- •Elevated cholesterol
Testosterone – just for men? Hardly! Often referred to as the “hormone of desire,” testosterone is involved in maintaining muscles mass, mood, and energy levels in BOTH men and women. We have known since the mid-1980s, that testosterone is not just a “male” hormone, because it was in 1985 that researchers published the first major study showing that testosterone was vitally important in boosting and maintaining a woman’s libido, sexual arousal and desire. After the age of 30 (just like in men) testosterone levels start to drop in women. What follows is the very predictable drop in sex drive, loss of muscle mass, reduction in metabolic rate, and decrease in energy levels and mood. What goes up? You guessed it – body weight – and we see the same thing happening in both men and women.
Although women have only about one-tenth the testosterone of men, her levels drop by about half by the age of 45 (compared to the amount she produced at age 20). In a scientific review by the North American Menopause Society, 9 out of 10 studies on testosterone in women showed that restoring testosterone levels back to normal to be effective in improving sexual desire, energy levels, and overall emotional outlook.
Testosterone production in women comes from the ovaries and in men it comes from the testes – but in both genders, a substantial amount of testosterone also comes from the adrenal glands – the same gland responsible for cortisol production. During periods of high cortisol production (stress, dieting, and sleep loss), natural production of testosterone falls. Considering that women produce only about one-tenth the amount of testosterone found in men, any stressed-induced drop in testosterone would be expected to affect women as much or more than most men. The effects of stress in older women is even worse because female testosterone levels peak in the mid-twenties just as in young men – and fall every year thereafter – so you are less able to “bounce back” from a stressful event at age 40 compared to age 20.
For women who want to stay lean, strong, healthy, fit, and sexually active, maintaining a youthful testosterone level is just as important as it is for men. In fact, studies published in the New England Journal of Medicine have shown that testosterone maintenance in women (aged 31-56 years) yields the very same benefits in sexual function, mood, energy, and overall sense of well being as found in studies of men.
Maintaining Balance – the Cortisol-to-Testosterone Ratio
The balance between cortisol and testosterone is probably even more important than the absolute level of either hormone. From the perspective of achieving peak physical and mental performance, we want to have a relatively low cortisol levels and a relatively high testosterone level – a hormonal profile that we would refer to as “anabolic” to suggest fat loss and muscle gain. This anabolic hormonal profile is what athletes strive for, but it is also your target for optimal weight loss and for long-term health.
Iranian medical researchers have shown that the stress of exams (psychological stress) increases cortisol and reduces testosterone levels in both male and female students – and British researchers from the University of Bristol, have found that elevated cortisol and reduced testosterone (which we refer to as an elevated C:T ratio) increases the risk of heart disease. The study, which followed men aged 45-59 years for more than 16 years, and was published in the scientific journal of the American Heart Association, also found that the C:T ratio was strongly related to insulin resistance (pre-diabetes). Researchers from Denmark have confirmed the heart-damaging effects of stress by showing that increased cortisol and reduced testosterone are independently related to an increase in blood vessel thickening (a significant risk factor for heart disease) in both men and women. Italian researchers have shown that low testosterone is associated not only with weight gain, but also with increased levels of “bad” cholesterol, lower levels of “good” cholesterol, insulin resistance (pre-diabetes), and an overall higher risk of heart disease.
The C:T ratio is studied quite often in athletes, not only because of the performance aspects of cortisol and testosterone, but also because they represent an ideal “high stress” situation to help answer important questions about how humans adapt to chronic stress. For example, physiology researchers from the University of North Carolina have shown a clear negative relationship between cortisol levels and testosterone levels in athletes – meaning that as stress gets higher, cortisol goes up and testosterone drops. Researchers from the University of Connecticut have shown that over-trained athletes have elevated levels of sex hormone-binding globulin (SHBG – which binds testosterone and makes it unavailable to the body) and reduced testosterone levels – both of which could be prevented by dietary supplementation.
Testosterone and Aging – Menopause & Andropause
Athlete studies aside, by the time most of us reach our forties (men and women), our testosterone levels are about 20% lower compared to the levels we had as robust twenty-year-olds (no wonder we’re fatter and more exhausted). In most people, testosterone levels start to fall by about 10% per decade (1% per year) after age 20 or 30. At the same time, our bodies start to produce more of a binding protein called sex-hormone binding globulin (SHBG) – which traps most of the testosterone that is still remaining in circulation. This is bad because SHBG binds and “traps” testosterone in a way that makes it unavailable to the rest of the body – effectively reducing your “bioavailable” levels of testosterone even further.
Around age 50, women are likely to hit menopause, and experience dramatic drops in both estrogen and testosterone. While men obviously don’t experience menopause, they do have a much larger drop in testosterone levels – a change that is referred to as andropause. During this time of life, when hormone production is falling in both men and women, as many as 30% of people in their 50s will have testosterone levels low enough to cause noticeable symptoms. Some of the clearest signs of a testosterone imbalance are changes in attitude and mood, as well as a loss of energy and sex drive.
Researchers from the Mayo Clinic have documented the fall in testosterone levels to be in the range of 35-50% by age 60 in healthy men, while aging researchers from Saint Louis University have shown that testosterone levels fall 47% in men from age 20 to 89.
It is well described in the scientific and medical literature that men who have low level of testosterone are more likely to be depressed than men with normal testosterone levels. When testosterone levels are brought back to normal levels, mood also returns back to normal levels.
Dozens of studies show that maintaining testosterone levels at more “youthful” levels (that is, keeping them from dropping with age) is associated with numerous health benefits in BOTH men and women. For example, men and women with low testosterone develop abdominal obesity (belly fat), a loss in sex drive (interest and ability), and become depressed (or at least moody). Preventive medicine specialists from the University of California at San Diego have shown that high levels of stress lead to lower testosterone levels (reduced by 17%) and increase rates of depression in men over 50 years of age. Bringing testosterone levels back to normal levels reduces depression. If you look at testosterone on an overall scale – it is not a “more is better” story, but rather one of “maintaining is good” and “falling levels are bad” – it’s one of overall balance.
Testosterone and Weight Gain
Perhaps the most noticeable side effect of a falling testosterone level for many people will be their expanding waistline. Just as increasing cortisol levels can lead to excess belly fat – so can falling testosterone – and when you have both occurring simultaneously (cortisol rising and testosterone falling) it is virtually inevitable that weight gain will follow.
One study, published more than 10 years ago in the Journal of Clinical Endocrinology and Metabolism (1996) showed that obese women who boosted their testosterone levels lost significantly more abdominal fat and gained more muscle mass compared to women given a placebo and whose testosterone levels remained suppressed. This was ten long years ago – and still most doctors and health professionals view testosterone strictly as a “male” hormone – when the reality is that while women certainly don’t want “male levels” of testosterone, they certainly want to maintain what they have.
The scientific literature in support of maintaining normal youthful testosterone levels (versus allowing them to fall in the face of stress and aging) is at least as strong as the research in support of maintaining normal youthful cortisol levels (which rise in response to stress and aging).
Researchers from Penn State University have shown that weight loss induced by diet alone leads to a significant drop in testosterone and fat-free mass (muscle) – an effect that can reduce metabolic rate and make weight regain easier. Scientists from Northwestern University in Chicago have shown that weight gain in young men (ages 24-31) was significantly related to low testosterone levels – with a graded relationship between the lowest testosterone levels and the greatest degree of weight gain. In a related series of studies, researchers at Cornell Medical College in New York found that the age-related decrease in testosterone is significantly exacerbated in overweight men with the Metabolic Syndrome. As testosterone drops, body weight goes up – and the drop in testosterone and the rise in weight are more pronounced in men who have Metabolic Syndrome, compared to men without (but who also gain weight as testosterone drops, but to a less severe degree). In a very important study from aging researchers at the University of Florida, the incidence of low testosterone in a general population of men (over age 45) as estimated to be 38.7% - and those with low testosterone were about twice more likely to also be overweight and have hypertension, high cholesterol, and diabetes.
These studies represent only a small fraction of the research on the relationship between testosterone, stress, cortisol, and weight gain, but it should be clear to you by now that the failure to maintain a normal C:T balance is an important reason why weight gain (and regain) is so easy for so many people. As we lose weight, cortisol levels rise, testosterone levels drop, muscle mass and metabolic rate fall, fat cells lose the “fat breakdown” signal (testosterone) and receive the “fat storage” signal (cortisol) – and weight appears (or easily comes back).
Maintaining Testosterone Levels Naturally
Like other hormones, including cortisol, we know quite clearly that maintaining normal levels, not too high and not too low, is the approach associated with the most dramatic long-term health benefits. It is important to keep in mind that one of the most central concepts in the study of endocrinology is that hormones tend to work in concert with one another to control metabolism. This means that changing two hormones – each by a little bit – is likely to have a better overall effect on a given outcome (such as weight loss) than changing a single hormone by a large amount.
In terms of exercise, we know that virtually all forms of exercise help to elevate testosterone levels in both men and women – and endurance exercise works almost as well as lifting weights for maintaining testosterone in most moderate exercisers. Researchers at the University of Texas have shown that not only does inactivity lead to a rapid loss of muscle mass, but when accompanied by high levels of stress and cortisol, muscle loss is accelerated. The good news about exercise is that while it is boosting testosterone, it is also reducing cortisol (the “de-stressing” effect of a workout) – but the best news of all is that your patients will be pleasantly surprised by how little exercise is needed to have these positive hormonal effects.
Avoiding dehydration is another way to keep hormones balanced. Researchers from the University of Connecticut’s Human Performance Laboratory have shown that cortisol levels are increased by dehydration – and C:T ratio was significantly higher (elevated C and reduced T) – a biochemical state that interferes with the balance between anabolism and catabolism (shifting the body toward fat gain and muscle loss).
Finally, stress researchers from around the world have shown that how we perceive and cope with a given stressor can determine our hormonal response to that stressor. More important than winning or losing, is the coping pattern that you display – thus determining the hormonal changes. Psychologists at the University of Miami use CBSM – cognitive behavioral stress management – to reduce perceived stress in stressful or competitive situations. Participating in CBSM activities cause cortisol levels to drop and anabolic hormones (like testosterone and DHEA) to rise – effects which typically translate into an improvement in both mood and in immune function.
It is probably quite apparent by this point that it is the balance between anabolic and catabolic hormones that represents the “metabolic sweet spot” that your patients should be shooting for. In a perfect world, we would easily maintain our relatively high cortisol and low testosterone levels of youth. Alas, the very process of living and aging (gracefully or not) leads us inexorably toward elevated cortisol and suppressed testosterone (among many other changes) – all of which combine to make us rounder and softer and tired and less happy – unless we take proactive steps to maintain those levels.
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