Testosterone is synonymous with strong muscles, Viking-esque beards, and an intense sex drive. But T—a primary hormone produced in your testicles that regulates your reproductive system—affects a lot more than you may think. In addition to its muscle-building and sex-drive functions, it also plays a role in the clarity of your skin, the speed of your metabolism, and even your brain function. Go figure. “It’s a hormone that travels around the body and is metabolized into different hormones—dihydrotestosterone and estradiol,” says Robert Tan, M.D., professor of medicine and family medicine at the University of Texas Health Science Center and research director of the Low T Center. “So it isn’t just about sexuality or strength—it’s a very generalized hormone.” 

Dihydrotestosterone, for example, initiates the development of male characteristics, while estradiol induces sperm production. These days, more and more men are turning to testosterone replacement therapy (TRT) for better gains in the gym, more energy, and a healthy sex life. Think you’re a candidate? Read on to learn more about TRT.