The Testosterone Dilemma
Credit: Photograph by Travis Rathbone

If you've ever wondered why modern American life seems bent on making you less of a man, a new study from Northwestern University may have your answer. Raising children decreases men's testosterone, reports the study. Its authors, anthropologists at Northwestern, suggest that this decline in testosterone helps facilitate men's "role as fathers and caregivers, as a key component of reproductive success."

Researchers have long known that testosterone, the hormone that confers masculinity, declines naturally with age – about 1 percent per year after you hit your mid-30s, – taking your muscle mass and libido with it. But emerging evidence suggests that men have less testosterone today than their fathers did, most likely owing to increasing rates of obesity and possible exposure to environmental toxins. Add this to the results of the Northwestern study, and they add up to a grim prognosis for middle-aged men helping their wives raise children in a polluted world. It also adds up to a vast target market for the obvious cure: testosterone replacement therapy, or TRT.

The sales pitch for TRT reads like a wish list for every man on Earth: build muscle, trim fat, improve mood, recharge energy, crank up sex drive. No wonder prescriptions for the therapy have jumped 500 percent over the past 18 years. But while more men are trying TRT, a fierce debate rages among doctors about the safety and ethics of prescribing it to anyone without a defined deficiency. The therapy has serious side effects, and the long-term risks aren't known – and may not be for decades.

Approximately 30 percent of men ages 40 to 79 are affected by hypogonadism, also called androgen deficiency, a condition marked by testosterone levels below 300 ng/dL (nanograms per deciliter), with symptoms that include muscle atrophy, weight gain, exhaustion, depression, bad sleep, disinterest in sex, and/or erectile dysfunction. Before prescribing TRT for hypogonadism, a responsible doctor will recommend lifestyle changes to raise testosterone levels, including weight loss, exercise, and better sleep, says Dr. Harry Fisch, a professor of urology at Manhattan's Weill Cornell Medical College. Only when these modifications fail to cure a patient do TRT's benefits outweigh its risks, he adds.

The controversy surrounding TRT starts with doctors like Harvard Medical School's Dr. Abraham Morgentaler, who believes that more men suffer from hypogonadism than meet the condition's standards, and in 'Testosterone for Life,' he writes that fading testosterone should be considered a treatable part of the aging process. "'Normal, healthy aging' is associated with bad eyes, bad hearing, bad teeth, bad joints, bad blood vessels, bad hearts, and cancer. We treat all of these to improve the quality of life or to increase longevity. Should we withhold offering prescription glasses to older men and women because poor vision is common with advancing years?"

Other doctors take this argument even further, advocating that TRT should be used to make men as vigorous as possible, regardless of age. Dr. Jeffry Life, the buff 72-year-old star of many shirtless ads, became the poster boy for the Las Vegas–based Cenegenics Medical Institute precisely because his tremendous physique demonstrates how synthetic testosterone can help men defy expectations of frailty and physical decline. Dr. Elizabeth Yurth, catering to Colorado's sports-enthusiast crowd at the Boulder Longevity Institute, says testosterone is "high-performance medicine" for people who don't want to grow old: "They want to be riding their bikes at 80." Her typical patient is a guy in his 40s or 50s who "can't keep up with his bike-riding buddies" – or with his wife in the bedroom. Testosterone can help change all that.

But it could also be argued that Yurth and Life are simply bringing men back up to the testosterone levels enjoyed by their forefathers. Population-wide, testosterone levels have dropped markedly in the past 20 years – 16 percent in 65- to 69-year-old men, for example. Obesity plays a role, since body fat helps turn testosterone into estrogen. But even when the research is corrected for weight and smoking, it suggests that other factors may be at play – environmental toxins, perhaps. A study from the University of California, for example, found that atrazine, a common pesticide, is so high in estrogen that it can transform an adult male frog into a fully reproducing female.

Some doctors, like Life, believe that medicine's current standard of "low" – defined as anything under 300 ng/dL, with 500 to 700 considered healthy for men under age 40 – is too low and that men should aim for a higher optimal target. Life likes to boost patients' testosterone to 800 to 1,000 ng/dL, pointing to studies that show that men with testosterone levels in the upper 25 percent of normal have a lower risk of chronic disease. "The typical story," Life explains, "is that you go first to a traditional MD and say, 'You know, I'm losing my edge. I'm going to the gym, but I dread it, and I'm losing muscle mass and strength, even though I'm working out, and I'm getting belly fat.' So they give you a blood test, and your hormone levels come back at 300. You're told you're normal, so you walk out thinking, 'I got normal testosterone. What's up?' What they won't tell you is that you're really a D student." And even if a doctor will treat you, Life adds, "he'll shoot for a new target of 350 to 400, making you a C student."

But others warn that there could be a downside to having high testosterone, and that our bodies lower production for good reasons. For one, evidence suggests that high testosterone may accelerate prostate cancer. And the Northwestern study makes the point that lower testosterone levels in fathers may be an evolutionary occurrence, helping men become more sensitive and nurturing and, thereby, better dads. Yet Fisch and others counter that fathers' declining testosterone levels aren't evolutionary but a result of the demands of child raising. "The lack of sleep, the lack of exercise, the belly starts showing up – it's that sedentary lifestyle," says Fisch.

While few doctors doubt that the more testosterone you take, the more muscle you build, some urologists, like Dr. Natan Bar-Chama of New York City's Mount Sinai Medical Center, question if more testosterone can also help other symptoms like depression, fatigue, and libido. "Are there physicians saying your numbers are low, testosterone could help?" asks Bar-Chama. "Yes. But are there also wellness centers giving people sesame oil and telling them it'll cure all diseases? Yes."

Studies on the relationship between testosterone and heart health have also been mixed. While large studies have shown lower mortality at higher testosterone levels, more recent research has found just the opposite, or that higher testosterone correlates with higher cardiac risk. One TRT study even had to be halted last year because of an uptick in cardiac events among subjects.

TRT has other side effects, too, including shrunken testicles, hair loss, acne, breast enlargement, and sterility. The therapy can also raise hematocrit levels (red blood cell concentration), which in turn can help improve athletic performance. But if your hematocrit level gets too high, the blood can become so viscous that it increases the risk of stroke and heart attack. And what many patients don't realize, says Bar-Chama, is that testosterone is a "lifelong therapy: Once you're on, your body stops making its own. Your brain sees the level is normal and shuts down."

While regular tests can monitor increased cancer risk and unhealthy hematocrit levels, only an individual can decide if TRT's potential benefits outweigh its possible side effects. Of course, there could also be dangers to TRT that doctors don't entirely understand yet. "Medicine is at the same stage with testosterone replacement therapy in men as it was with hormone replacement therapy [HRT] for women 20 years ago," Fisch writes in 'The Male Biological Clock.' "That should be a big red flag for everyone involved in the current debates over TRT. When hormone replacement therapy was first used with women, it was considered to be very safe...But it became clear that HRT not only increases the risk of certain cancers, it is not beneficial to the heart."

For guys without hypogonadism, a wait-and-see approach may make the most sense. "We just don't have the data to prove that raising testosterone in men who already have normal levels confers any real benefit," says Dr. Robert Mordkin, a urologist in Arlington, Virginia. Furthermore, Mordkin adds, "Natural waxes and wanes of testosterone as we age may have some not yet entirely understood protective effects." In addition to making us better fathers, as the Northwestern study infers, declining testosterone "may lower our vulnerability to prostate cancer at a time in our lives when we're at the greatest risk for it." That said, if you have classic symptoms of hypogonadism – low libido, fatigue, erectile dysfunction – "it's probably reasonable to check your testosterone. And for those guys whose blood levels come under definitions of low testosterone, it's probably reasonable to try the therapy for a while. But that's very different from saying testosterone is the fountain of youth."