Testosterone is a vital hormone in men, responsible for masculine traits like muscle mass, a deeper voice, facial hair, and the development of genitals during adolescence. It also supports sperm production, sex drive, healthy erections, red blood cell production, mood, and cognitive function.

Low testosterone, or “low T,” occurs when levels drop below the optimal range. While age-related decline typically begins in the late 20s and continues at about 1% per year, other factors—such as stress, alcohol or drug use, chronic illness, obesity, and certain medications—can also contribute.

By their 40s and 50s, many men start noticing symptoms like decreased libido, reduced energy, diminished muscle mass and bone density, erectile dysfunction, and even anemia. These symptoms are often linked to hypogonadism, or impaired testicular function.An estimated 3 to 7 million men in the U.S. suffer from low testosterone, yet only 5–10% receive treatment. Testosterone replacement therapy (TRT) has been shown to improve mood, vitality, libido, bone density, cognition, muscle mass, and red blood cell production in men with hypogonadism.