Low testosterone levels are linked to obesity, diabetes, kidney disease, heart attack, stroke, and lung disease. A 16-year-long study by researchers from the Johns Hopkins Bloomberg School of Public Health found that low levels of biologically-available testosterone increased the risk of premature death from all causes and from cardiovascular disease by 52 percent. Low levels of total and free estrogen (estradiol) were also linked to premature death.
Testosterone levels were not related to the incidence of cancer. Last year, physicians wrote more than 3.3 million prescriptions for testosterone in the United States. We have no evidence that supplemental testosterone will increase longevity or reduce the risk of cardiovascular disease.
Source: American Journal Epidemiology, 171:583-592