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The Sex Hormone Secrets

Testosterone and estrogen drive touchdowns and boost brainpower, but they work their magic with a selectivity that science is only beginning to understand.

Playing in front of a wildly cheering hometown crowd, the Canadian ice hockey team whizzed around the ice with more speed and sizzle than usual, scoring goal after goal and winning the game. And it wasn't just that night, either. The high-energy performance of the all-star team, hailing from northern Ontario, always peaked during home games, suggesting a home-field advantage.

Hoping to learn their secret, psychologists Cameron Muir and Justin Carre of Brock University in Ontario studied the team over a season, measuring testosterone levels in saliva before and after each game. As they expected, the increase in status following a win always resulted in a rise. But the surprise came in measurements prior to the games: Whenever the competition was on home turf, testosterone increased ahead of time, suggesting the hormone provided impetus for defending one's territory. "Just as a dog defends its yard, these players are encouraged to defend home ice," Carre said.

The Brock scientists found that testosterone ebb and flow tracked emotional states: Self-confidence increased for home games, and, according to player reports, slid back down when players were away. The bottom line: Testosterone changes are directly related to personality, mood, and aggression—and not just in sports.

For men and women alike, sex hormones (including testosterone, produced by the testes, and estrogen, from the ovaries) are power players in myriad human abilities and behaviors. Language, cognition, libido, and health all fluctuate as hormone levels change. Yet the impact is nuanced and often counterintuitive. Testosterone revs aggression in status-hungry men, but has little effect in more laid-back souls. Estrogen has long been thought to keep memory sharp before menopause—but for women who start taking estrogen supplements years after going through menopause, the result may be memory problems instead. Finally, just as sex hormones influence behavior, changing situations often modulate the hormones. "The causal arrow between hormones and behavior points in both directions," says University of Nevada anthropologist Peter Gray. The subject is complex and often confusing. But given the common manipulation of sex hormones through prescription drugs and supplements, unraveling their hidden forces has never been more critical.

Testosterone Warriors: Why one man's triumph is another man's torment

A humble priest renowned for his wisdom, Peter Morrone wanted nothing more than to live out his days in the hermetic monastery near his home in Italy. But his dream came crashing down when he was tapped to succeed Pope Nicholas IV in 1294. As the new Pope Celestine V, Morrone lacked the assertiveness of his predecessor and soon became a pawn of King Charles II. Unsuited for the job, he abdicated the papacy after four short months. But the next pope, Boniface VIII, so feared Celestine's popularity that he hunted him down and threw him in jail where, 10 months later, he died.

According to Robert Josephs, a social endocrinologist at the University of Texas, Celestine's reaction to the lofty status of pope can be seen through the lens of testosterone: Naturally low levels of testosterone could explain his shrinking-violet personality and his failure to rise to the challenge when his status demanded it most. High levels of testosterone, meanwhile, might explain why Boniface went to such extremes to put Celestine in his place.

When Josephs arrived on the endocrine scene in the late 1990s, the research connecting sex hormones and human behavior was contradictory. A strong connection had been shown in many animal species. But human experiments found no consistent connection and experts theorized that our developed prefrontal cortex simply overrode messages the sex hormones sent to the midbrain.

Josephs soon demonstrated that humans are hardly exempt from the passions of other animals—those passions are just more complex. As with Celestine and Boniface, testosterone plays out differently depending upon whether an individual is driven by status or prefers a more modest leadership role. Men motivated by the quest for power have higher baseline levels of testosterone—and the more they feel threatened, the higher their testosterone (and their aggression).

One study, for instance, tracks testosterone after loss of a game. Baseline testosterone drops, it turns out, only in those who don't much care about dominance or whether they win or lose. These less-competitive players start out with modest testosterone levels and after a loss, their levels fall. But in those with high-baseline testosterone—typically of competitive mindset—the levels soar. "High-T men react to a loss as if in the throes of testosterone addiction—the more testosterone climbs, the more testosterone they crave, and they can get more only by challenging the winner and playing again," Josephs explains.

He found the rule applied not just to competition in sports or games, but also to competition for mates. In one study, Josephs paired male college students and sent them into a room with an attractive female confederate. Each was to try to woo her, doing whatever it took. Students with high testosterone routinely slammed the other man, making fun, putting him down, refusing to laugh at his jokes.

Josephs also found that high-testosterone men communicate stress to their dogs. In a study of pet owners who had entered their dogs in a contest of agility, high-T men experienced surging testosterone after a loss. They yelled at or shoved their dogs. Josephs compares the phenomenon to injecting steroids. "If you put testosterone in muscle fibers they will fire more frequently," he says. "The more they fire the more you'll be able to punch, and the more you punch the more testosterone you need." Women and low-T men (who had still had lower testosterone following a loss) were sympathetic to pets that lost, petting and hugging them. All pet owners, men and women alike, responded with no change in testosterone when their dogs won—and usually treated the victorious dogs in the same, positive way. But no matter how much testosterone a woman had at baseline or how badly her dog lost, all females reacted like low-T men, soothing the losing pets.

Baseline testosterone even impacts cognition, Josephs found. In experiments, when status-striving, high-testosterone men are stripped of their status, they become angry, excited, and cognitively impaired. But more surprising, men with low resting-testosterone, without much impetus for status, become angry and impaired when placed in high-status positions they simply do not want.

The studies point to innate human hierarchies every bit as immutable as those seen in primates or dogs. At first blush, says Joseph, "striving for status seems sensible because with it come resources and goodies that ensure survival." Yet from an adaptive perspective, the differences appear to make evolutionary sense. "If you look across the landscape of our species you'll see a high variation in resting testosterone, with each person seeking his particular place in the hierarchy and few people wanting to be out of their zone. If everyone were an alpha we'd have fights all the time. The group is more stable and life is more harmonious when hormone level and social niche correspond."

Brain-Building Hormones: Prenatal testosterone steers Spatial reasoning, but only to a point

The ability to read a map or engineer a bridge isn't due to gender per se, but rather to the way sex hormones influence the structure and function of the brain. Before we're even born, testosterone in the womb influences development of brain regions handling spatial tasks. And as adults, optimum levels of testosterone and estrogen hone these skills yet again. In animals, there is a direct relationship between testosterone and spatial ability—for humans, that's not the case.

In fact, it was hard for scientists to study testosterone's impact in humans at all until researchers discovered that a high "2D4D" digit ratio—a ring finger longer than the index finger—is linked to high exposure to prenatal testosterone. In women, who as a rule don't receive as much exposure, ring and index fingers are often equal in length, while in males the ring finger tends to be longer.

Scientists at the University of Giessen in Germany used the association to correlate mathematical and spatial skill with pre-birth testosterone levels. It was already known that men outscore women on spatial and numerical tests overall. But last year in the journal Intelligence, the German scientists reported that women with a "male-like" finger ratio (and therefore higher levels of prenatal testosterone) scored better than those whose wedding finger was shorter—and they also outperformed the men on the numerical tests.

While prenatal testosterone enhances performance of spatial tasks, the relationship is complex and varies from skill to skill. Using finger ratios to estimate, University of Cambridge psychologists graphed prenatal testosterone against three spatial tasks: mental rotation (recognizing two-dimensional representations of three-dimensional shapes), targeting (literally hitting a target on a computer screen), and figure-disembedding (finding a smaller simple form that is part of a larger, complex picture).

Their findings, published last year in the Journal of Biological Psychology, show that the exclusive predictor for mental rotation ability is gender, with men beating women. Because testosterone level played no role whatsoever, the researchers theorize that the advantage comes from more exposure to the task, and thus, more practice.

Finger ratio alone, on the other (ahem) hand, predicted targeting and figure-disembedding performance. For figure disembedding, the more prenatal testosterone, the better the performance. But for targeting, the level of prenatal testosterone helped only to a degree. In fact, the relationship was what researchers called "curvilinear"—the best performance required a highly favorable level of prenatal testosterone. Too much or too little, and the skill fell off. This could explain why men excel overall in targeting but also why some women may make better sharp-shooters or pilots than many men.

The picture is also complex for free-flowing testosterone in adulthood. Instead of equating high-T with spatial skills, the relationship is reversed. It turns out that lower testosterone signals greater skill, University of Cincinnati psychologist Julie Yonker reported in the journal Cortex in 2006.

The results show just how complex the interactions are. In both men and women, excess testosterone is converted to estradiol, a form of estrogen. Studies of women in their childbearing years have found that visual-spatial performance declines during ovulation, when estrogen levels are highest, and is enhanced during menstruation, when estrogen is low. "We infer that estradiol binds to the brain receptors directing visuospatial tasks, hindering performance," Yonker states.

Bottom line: We've got to get away from the idea of "female" brains and "male" brains and start thinking in terms of high- and low-testosterone and estrogen brains to understand how spatial skills develop.

Supercharging Memory with Estrogen: Why timing is key in Hormone therapy

For years the debate over estrogen loss and hormone replacement therapy has raged: As women enter and then pass through menopause, does the loss of estrogen cause not only hot flashes and mood swings but also memory impairment? And can hormone replacement therapy (HRT) protect cognitive sharpness that might otherwise be lost? Many experts have long insisted that memory problems emerge at midlife not because estrogen tanks but because of psychological factors—stressed-out and sleep-deprived women are naturally going to feel less mentally sharp. Therefore, when it comes to protecting memory, HRT would do little good and might even hurt.

Yet the naysayers based their conclusions on studies of older women—in one pivotal study, the average age was 72. Should we really extend the reaction of elderly women to younger women, whose hormones were just starting to decline? To find out, McGill sex-hormone researcher Barbara Sherwin studied working memory in a group of young women whose menopause had been temporarily induced during treatment for tumors. Sherwin's research, published in the journal Psychoneuroendocrinology in 2006, showed that memory scores in the young women given the estrogen-lowering drug Lupron plummeted but, when estrogen was added back, working memory deficits were restored. The clear conclusion was that estrogen supplements, timed correctly, kept working memory sharp.

Sherwin cautions that more research is needed because not all estrogen is identical and different forms of the hormone might affect cognition in different ways. She also notes that the route of administration, via patch instead of a pill, might affect what estrogen does to memory, the brain, and the rest of the body. In fact, a 2006 study from the San Francisco VA Medical Center found that extremely low doses of estradiol delivered through a patch had no ill effects on the cognitive abilities or general health of older women. If estrogen can be taken safely and if it does, in fact, preserve memory in women entering menopause, when is the best time to take it? "Probably in the late perimenopause, just around the time of menopause, around age 49," Sherwin says.

The Daddy Profile: The "Low-T," Long-term Commitment Guy

High testosterone males might be less emotionally connected, sure, but that doesn't mean they're violent, sexually craven cave men. That, at least, is the conclusion of a recent study on testosterone and language. To do the research, James Pennebaker of the University of Texas followed two people receiving testosterone therapy—a man for improvement of upper body strength, and an individual who was female-to-male transgendered. For both, he found that the higher the levels went, the less likely they were to use emotional, socially connecting words in written notes. The level of anger and sexual content, however, remained unchanged. Testosterone steers written language—and presumably, the writer—away from social connections but not necessarily toward anger or preoccupation with sex.

The findings are in line with a host of other studies showing Low-T guys and gals provide us with social glue. Testosterone tends to be low in family men raising children and high in single men playing the field. "Lower levels of testosterone may increase the likelihood men will stay home and care for their wives and kids and decrease the likelihood they will go out drinking with the guys and chasing other women," says Harvard anthropologist Peter T. Ellison, who has studied the phenomenon for years.

The allure of the Low-T man was illuminated in the journal Psychoneuroendocrinology in 2006. Heterosexual men and lesbian and bisexual women with partners all had lower testosterone than their footloose counterparts. But gay and bisexual men with partners had similar levels of testosterone whether or not they had partners.

"The findings suggest that lower testosterone individuals might be more attractive for long-term relationships," says Sari M. van Anders of Simon Fraser University, the neuroendocrinologist who led the work. Van Anders notes that heterosexual men and lesbian women are both interested in women. "So one fascinating possibility is that females prefer long-term partners—whether male or female—with lower T." Another obvious way to interpret van Ander's data is that lower-T people, male or female, are just more interested in long-term relationships.

Because the "chicken or egg" conundrum of hormones and behavior is still unresolved, the effect of artificial hormones on marriage, parenting, or friendship is also a gray area. "Taking testosterone may improve relationships for some people; as testosterone is raised, improved mood, libido, and self-worth could be the result," speculates Nevada's Peter Gray. "For others, the supplements could do harm." The fact is that studies showing the precise connections between our hormones and our minds and personality have yet to be done. Even when we understand specific mechanisms, the low-T and high-T among us may be loathe to change. Would a satisfied family man or woman really relinquish social comfort and connectivity to battle on the corporate front? Perhaps even more absurd: the idea that a Lothario would agree to suppress his testosterone just to appease a spouse.

The emotional and cognitive pull of sex hormones is undeniable, but with so many twists and turns that the idea of gender-specific traits has given way to the reality of hormone-associated tendencies. Forget the concept of the "male brain" and "female brain." High-T and Low-T personalities and estrogen-driven smarts are the real buzzwords.

Hormone Fixes

Adjusting your hormones may rev everything from your mental faculties to your libido. But get the full facts before any do-it-yourself hormone shift.

Hormone Replacement Therapy: Prescription hormone replacement therapy, consisting of estrogen and progesterone or estrogen-only replacement, for women without a uterus, may help mood.

Testosterone for men: Supplements may give low-testosterone men a mood boost and increase their libido. Side effects range from thickened blood to enlarged prostate, but may be averted with monitoring.

Testosterone for women: May help a tanking libido recover after menopause. Testosterone and estrogen therapy given together may be especially effective.

"Bioidentical" hormones: An alternative to traditional HRT, these nonpharmaceutical plant-derived estrogens supposedly mimic the optimum female hormonal environment. But "bioidenticals" may be created without much regard to the way natural hormones are metabolized.

DHEA : This steroid precursor to testosterone and estrogen declines rapidly after age 25. DHEA supplements are a popular, nonprescription way to supposedly rejuvenate hormones. But recent research concludes it has no anti-aging, nor mind- and strength-sparking benefits.

Phytoestrogens: Studies have found black cohosh relieves depression and anxiety better in menopausal women than Valium or Premarin. The plant contains phytoestrogens that bind to the estrogen receptors and work much like natural estrogen.