Not Just for Men
Testosterone—just for men? Hardly! Often referred to as the "hormone of desire," testosterone is involved in maintaining muscle mass, mood, sex drive, 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). More than two decades later, American women still do not have a testosterone product to treat sexual dysfunction or arousal problems, despite the fact that after the age of thirty their testosterone levels start to decrease (just like they do in men). 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 men.
Although women producehave only about one-tenth the testosterone of men, a woman's levels drop by about half by the age of forty-five (compared to the amount she produced at age twenty). In a scientific review by the North American Menopause Society, nine out of ten studies on testosterone in women showed increasing testosterone levels to be effective in improving sexual desire, energy levels, and overall emotional outlook. Unfortunately, despite the results of these research studies, there is no female-specific testosterone treatment available to American women, so either they have to try preparations made for men (which may not be appropriate in terms of dosage) or they have to "deal with" feeling lousy. Luckily, there exist a variety of natural options for improving the body's release of endogenous testosterone (testosterone that is present naturally). Both men and women can benefit from freeing up the testosterone that is already circulating in the blood but that may be locked up by transporters called "binding hormones."
Most testosterone production in women comes from the ovaries and in men 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), our natural production of testosterone falls. Considering that women produce only about one-tenth the amount of testosterone found in men, any stress-induced drop in testosterone would be expected to affect women as much as or more than most men. The effects of stress in older women are even worse because female testosterone levels peak in the mid-twenties—just as they do in young men—and fall every year thereafter. So the average person is less able to "bounce back" from a stressful event at age forty compared to age twenty. 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 ages thirty-one to fifty-six yields the very same benefits in sexual function, mood, energy, and overall sense of well-being as those found in studies of men.
Maintaining Balance: The Cortisol-to-Testosterone Ratio
Think you're tough enough to fight stress? Think again. Scientists from the United States Army Research Institute have found that even the most elite combat soldiers are not immune to the detrimental effects of stress. In one training exercise, elite Army officers (the most highly motivated and well-trained troops), when exposed to moderate levels of sleep deprivation, experienced elevated cortisol and reduced testosterone, leading to significant changes in mood such as reduced vigor and increased fatigue, confusion, and depression. This study, and others like it, show us that "being tough" in the face of stress is ridiculous, because your body reacts with a predictable stress response: cortisol up and testosterone down (unless you do something to modulate it).
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, you want to have a relatively low cortisol level and a relatively high testosterone level, a hormonal profile that we would refer to as "anabolic" to suggest fat loss and muscle gain. This is what athletes strive for, but it is also your target for optimal weight loss and long-term health. Iranian medical researchers have shown that the psychological stress of exams 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 British study, which followed men ages forty-five to fifty-nine for more than sixteen 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 (prediabetes). Researchers in 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 (prediabetes), 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 athletes represent an ideal "high-stress" situation that can 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 overtrained athletes have elevated levels of sex hormone–binding globulin (SHBG, which binds testosterone, making it unavailable to the body) and reduced testosterone levels—both of which could be prevented by dietary supplementation.