The way we talk about testosterone, you’d think it was man juice in a bottle. After all, it’s in the balls and the boner. It’s in the beard, and it’s in the balding. It’s in the rage, and it’s in the aggression. And it’s in the life force itself: Men who undergo testosterone replacement therapy espouse its magical powers in providing an indisputable rush of “energy, strength, clarity, ambition, drive, impatience, and above all, horniness.” It’s what makes men men, and women not-men. We’re not from Mars and Venus; we’re from Planets Testosterone and Estrogen. Right?
Not exactly. Recent studies and closer scrutiny of old research has begun to find more and more proof that while testosterone works some of the ways we thought, it doesn’t function all the ways we thought. For example, a new study has found that one theory explaining autism — that it’s the result of “extreme male brain” more into building and machines and less into empathizing, due to overexposure of the hormone prenatally — has no legs to stand on. Meanwhile, other studies similarly contradict many implications pegged to T: that it makes men more violent, more hairy and more muscular, period.
“All you have to think of [to see it doesn’t work this way] is the people you know. Like men who are really big in the shoulders but can’t build up their legs,” explains Rebecca Jordan-Young, co-author of Testosterone: An Unauthorized Biography. “Some of that is just where the receptors are located in the body. In a lot of people, there’s a different density in the receptors in the lower and upper body. Think about someone with a whole lot of facial and arm hair, the guy who has to shave a ring around his neck to tell his chest hair from his beard. That guy is just as likely to be scrawny. You can’t predict testosterone based on one feature that somebody has, because how much the body will use testosterone for other things is also testosterone dependent. It’s confusing, because it’s not linear.”
“Sex is a really interesting arena,” she continues. “Testosterone is important for sexual function, but at the same time, you don’t need very much at all. There is a very, very low threshold effect that, above that, more testosterone doesn’t do anything more for sexual function. You can have low testosterone below clinical thresholds and still have perfectly good sexual function, making sperm, having erections and all the tissue function can be fine. That’s been clear for a long time — more T doesn’t make you a better lover or more libidinous. It’s not a linear effect, there’s just a little bit that’s necessary.”
That exaggeration of the relationship between testosterone and male sexuality is complicated by our desire for testosterone and estrogen to explain male and female, end stop. “This whole idea of sex hormones is this binary,” Jordan-Young explains. “When the so-called sex hormones were discovered, it wasn’t that they were discovered and experiments were done and observations to see what they actually do, and it turned out that testosterone controlled masculinity and estrogen controlled femininity. It was the opposite; scientists were looking to find what substance in the body cause masculinity and femininity to develop, and approached it with a very binary ideal that when they found them, they’d be sex specific — only the male in male bodies, only the female in female bodies — and that they would cancel each other out, and be antagonistic.”
Only, they don’t. “In many cases, it turns out, they’re synergistic, both are found in everyone, and they’re not just singular things — there isn’t one set called androgens and one estrogens. Even though we’ve known those easy ideas were wrong since the late 1920s, early 1930s, the idea of one-sex, one-hormone is so appealing that we haven’t been able to get past it.”
One clear place we haven’t been able to get past it is sports, particularly the idea that testosterone directly explains male superiority in sports performance over women, and is the key to athletic performance, which Jordan-Young and her co-author Katrina Karkazis recently addressed in a New York Times op-ed about the Court for Arbitration for Sport’s recent ruling that women with naturally high testosterone couldn’t compete as women.
“The idea that the reason men outperform women is testosterone is an article of faith rather than being something that’s been rigorously demonstrated,” Jordan-Young tells me. “It’s definitely the case that elite male athletes outperform elite female athletes in the easily quantifiable sports like weightlifting and track and field. But the data on how testosterone affects athletes within the two sexes is unconvincing.”
The rule blocking women with naturally high T, she says, is based on studies that are not independent and that a number of scientists have called to be retracted. “Even if you take them at face value, you see very small relationships — and in some cases negative relationships — between testosterone and performance,” Jordan-Young explains. “How do you explain the fact that in three out of 11 running groups, for instance, it’s the lowest testosterone group that does better? Even when comparing the highest with the lowest, in the events that they say matter the most, it’s only making a 2.9 percent performance gap, which is quite small overall. It doesn’t explain much of the variance.”
“Testosterone is one of the ingredients that’s implicated in long bone growth and muscle development, but so is estrogen,” she continues. “In studies, people look at testosterone all the time because it’s associated with masculinity, but the more scientists look at other hormones they’re finding surprise actors. Estrogen is as important for some of the functions, and that shouldn’t surprise people, because they’re not sex specific. Yet somehow all the functions viewed as manly are presumed to be covered by testosterone and off limits to estrogen.”
Jordan-Young’s view is that it’s easy to fall prey to broad strokes’ statements. Things like, “Men have more testosterone. Men are faster. Testosterone builds muscle. Testosterone is more important for oxygen uptake.” As she explains, “All of those things, on average, are true, but when it comes down to the nitty gritty of trying to trace the specific role of testosterone, you can easily step away from fact, because it’s much too individual and too dynamic to make broad statements about.”
So what, then, does T do for sure?
“Testosterone definitely affects skin texture and oiliness of sebum production,” Jordan-Young says. “It affects hair: the distribution and the thickness. It’s definitely related to balding. Along with exercise, it affects muscles and bone. It affects our daily energy rhythms and diurnal rhythms, and our wakefulness and sleeping. But it isn’t an on-off switch or even a volume button. It’s one ingredient in a complex feedback system of multiple hormones and multiple receptors and other things.”
A few examples of what she means: Some people who have very high testosterone don’t go bald. Others go bald with lower levels. Taking T for bodybuilding, she continues, “isn’t going to bulk you up. You still have to exercise. Guys were thinking for a long time it was a way around exercises, but it’s not at all. Without exercise, it can create more paunch.”
Paul Turek, a urologist and leading expert on male sexual health, adds, “I’d say the biggest myth is that testosterone helps you live longer. Testosterone will keep your muscles strong, and keep you more vital. But as for longevity, it’s complicated and your genetics are a bigger determinant than testosterone. I think [the myth] comes from the fact that when men get older, their testosterone levels fall and everyone associates the age-related changes in health to testosterone, but that just may be the car wearing out.”
Part of it is that we haven’t understood how we’re measuring it, either. Jordan-Young notes that in some people with low testosterone, we’ve come to understand that low levels can be a result of someone using it very efficiently, not necessarily having a deficit. Conversely, having too much can be about the body making more because it’s not using it efficiently enough. “What you’re measuring isn’t the cars that are running, but the cars in the parking lot,” Turek continues. “Total testosterone is all the cars in the lot, free testosterone are the cars in the lot that do the work of the day. They’re not the same. And free testosterone is only a small percentage of the total.”
Turek is keenly interested in the effects of testosterone because he runs a fertility clinic specializing in sexual function, and routinely sees patients driven by marketing efforts who think low testosterone is the cause of all their issues. Like the 32-year-old tow-truck operator who came to see him because his sex drive was in the tank and was ready for a T prescription.
Turek took his vitals and found out his hormones weren’t off, and through discussing other aspects of his life, Turek learned the man rarely got more than three hours a night of sleep due to taking towing calls throughout the evening. Once the man corrected his sleep deficit by hiring an assistant to cover the night shift, he altered his circadian rhythms and stress responses, and in three months, his sexual function recovered.
This isn’t to say that low testosterone isn’t real or doesn’t have sexual side effects; again, it’s just not at the level we’ve been led to believe. “The best data shows us that when testosterone is low by any standard, you might have problems with erections and sex drive,” Turek tells me. “Because when you replace it into the normal range, those problems can resolve. But only about 2 to 3 percent of erection problems are solely due to low testosterone. It’s a very rare event. It’s mostly due to many other things — cardiovascular health, hormonal health, sleep and stress, what you eat, what you take for recreational drugs, etc.”
Correcting those things, however, isn’t exactly the easy fix testosterone therapy offers. “The prescription for longevity, for better sex and for better erections is better health,” Turek tells his patients. “And that’s the hardest prescription or pill for them to swallow — to stay healthy.”