Abraham Morgentaler, a pioneer of testosterone therapy for men from Harvard Medical School, explains why testosterone has long fallen out of favor in medicine.In men over the age of 45-50, low testosterone is present in at least 20-30 percent, an estimated 2 to 4 million men in the U.S.[1][2].[1][1] Many physicians have long believed that testosterone decline is a natural part of aging and does not need to be treated.1 Morgentaler reports that testosterone replacement therapy (TRT) improves energy, sex drive, and quality of life in men with hormone deficiency.[Studies show that TRT does not increase the risk of prostate cancer, including placebo-controlled studies and longitudinal data.1 Today, TRT is also given to men with advanced prostate cancer or high-risk prostate cancer, which was previously thought to be unsafe.[1][2][3] Morgentaler predicts that in 5-10 years, physicians will routinely check testosterone levels like cholesterol or PSA.[1] His research, published in prestigious journals like the New England Journal of Medicine, has changed decades-old views about the risks of the therapy.[2]