IS THE KEY TO VITALITY?

THIS MIGHTY HORMONE IS BEING PEDDLED AS A WAY TO GET EVERYTHING YOU WANT-STRENGTH, ENERGY, AND A HEALTHIER AND LONGER LIFE. BUT HOW MUCH TESTOSTERONE DO YOU REALLY NEED?

- CASSIE SHORTSLEEVE

FOR A LONG TIME, we accepted certain changes as the price (and privilege) of getting older. Your hair turns gray. Your hearing starts to... wait, what was that you said? And, of course, your testosterone level drops. But with a boom in testosterone-replacement clinics-by this point, who hasn't gotten an ad for a service offering to test your T for under $100?-and podcasts and influencers preaching the powers of hormone optimization, should guys over 40 think about winding back their T clocks? And by how much? Here's what to know.

T CAN HELP YOU LIVE LONGER

A SHORTAGE of testosterone is associated with a shorter life. "We now have several decades of high-quality research showing remarkable longevity and health benefits in men with normal testosterone levels compared with men with low levels," says Abraham Morgentaler, M.D., at Harvard Medical School and the author of Testosterone for Life. That's true whether guys have healthy levels naturally or underwent testosterone-replacement therapy to bring their levels out of the low range.

TCAN MAKE YOU FEEL BETTER, TOO

FEELING YOUNG and alive often boils down to a few things, says Dr. Morgentaler: being strong, staying active, and having the energy to do the activities you enjoy. "Men with low T often lose many of those things; people say they feel old," he adds. "Not only do men feel better with normal testosterone levels, but for a whole variety of general medical and health issues, they actually are better." That means improvements in sexual function, physical function, and mood, according to a major study in The New England Journal of Medicine in 2016.

BUT TESTOSTERONE LEVELS DECLINE WITH AGE