Men and women are asking the same question.

It’s the Essence of Macho, the juice of choice for rogue major league baseball players who want to hone their muscles and sharpen their skill set. It’s also the magic elixir that creates horndogs of both genders.  When the level of testosterone plummets in middle age (in both sexes, although in women it’s in concert with the decline in menopause of estrogen, DHEA and other hormones), it can bring big changes in prowess, from athletics to sex.  But what about the mental drive to succeed itself?  Will ambition go down with the hormonal ship, literally leaving us with no fire in the belly?

There isn’t much research addressing ambition, per se.  “If excitement and enthusiasm for life in general falls with testosterone levels, one would imagine that ambition would, too” says Paresh Dandona, chief of endocrinology at the State University of New York at Buffalo’s School of Medicine and Biomedical Sciences.  “It makes sense that drive is drive,” agrees Tareneh Shirazian, assistant professor of obstetrics, gynecology and reproductive science at the Icahn School of Medicine at Mount Sinai in New York City.  

The research that does exist measures traits that may correlate with ambition, but aren’t quite the same thing – like aggression and risk-taking.  And there’s no doubt that testosterone is linked to winning. Neuroscientist John Coates sampled the testosterone of 17 high-powered Wall Street traders over a two-week period.  In his book, The Hour Between Dog and Wolf: Risk Taking, Gut Feelings and the Biology of Boom and Bust, Coates reported that high testosterone levels in the morning were predictive of how much money a particular trader would make that afternoon.  In fact, the difference between an individual’s higher and lower testosterone days “if annualized could amount for some of the traders to over $1 million in pay.” 

Coates also notes that there’s a “winner effect” that’s been observed in animals. When two rams or lions compete for turf or a female, both experience a spike of testosterone, but the loser’s testosterone goes down and the winner’s goes up--literally girding his loins for the next fight. (Coates suspects the phenomenon, which has not been replicated in human subjects, may account for winning and losing streaks in sports.)

Transgender people who are transitioning from female to male also give anecdotal evidence that testosterone is, at the very least, a source of vigor that could translate into ambition. “They’re ramping up their testosterone ten- to thirty-fold,” says Louann Brizendine, professor of clinical psychiatry at the UCSF, neurobiologist, psychiatrist and the author of The Male Brain and The Female Brain. Her transgender clients “say that their energy and ambition and personality have changed. They have an active, can-do attitude and a feeling of wanting to get on with it.”

But if testosterone is indeed the fuel in the tank of ambition, then where does that leave men who are at an age where the gas gauge is going southwest fast?  Where does that leave women of any age who have less of it to begin with? 

“The one female study I know of--that measured testosterone levels in women in an unnamed corporation and found that the highest ranked women had the highest levels and the secretaries had the lowest--was never replicated,” says Brizendine.  There probably won’t be too many future studies because of “political correctness,” she adds. “Anything that could be used against women getting equal pay for equal work is going to be swept under the rug and put in a locked box.”

But that being said, Brizendine says that things aren’t so simple where women are concerned.  For starters “estrogen [in a woman] can work a lot like testosterone in the male.”  Many post-menopausal women would say this is true in regard to libido, which can decrease along with estrogen. There’s also the matter of how we perceive and define ambition, and which gender has traditionally been encouraged or discouraged to express it.  “Look at all the little girls who feel confident enough to feel like they should have a say and some power over people...and who are called ‘bossy.’”

There are also paths to success that don’t depend on raw drive. Coates found that by many measures, female traders do better than men – but they succeed by taking time to study the market, not by ramping up risk. (He thinks that companies who bring a range of hormonal profiles to the table--hot-headed young studs, women, more careful and experienced older men--are going to have the best shot at success.)  

Testosterone therapy for women has fallen out of favor, mostly because treatment tends to grow facial hair and deepen voices. But it’s still a big business for men, and those who want to boost their juice will find themselves in the midst of a medical controversy.  Last winter the American Urological Association put out a position statement expressing concern for “the potential for misuse of testosterone for non-medical indications, such as body building or performance enhancement” (although the organization stands behind its use in treating hypogonadism, defined as “a cluster of symptoms which may include reduced sexual desire (libido) and activity, decreased spontaneous erections, decreased energy and depressed mood.”  The FDA is meanwhile looking into evidence that testosterone therapy interferes with cardiovascular function, and its own advisory committee recommended stricter controls on the hormone in September.

“Do these levels decline in a way that really makes a difference in terms of drive and sexuality? They probably do,” says Shirazian. However, one shouldn’t jump to the conclusion that all the life passages of middle age are due to marks on the hormone dipstick. Since each person’s chemical balance is so individual, there’s no hard and fast rule. And of course, there’s always the possibility that less drive in the workplace might be a result of wisdom.  As you get more experience, you re-envision endless ambition as a treadmill you're ready to get off of rather than a race to be won.