The world Health Organization estimates that by 2025, worldwide, the number of people aged over 65 years will rise from the current figure of 390 million to 800 million. In the Hypogonadism in Males (HIM) study of men treated in the primary care setting, 38.7% of men aged ≥45 years tested positive for hypogonadism (TT <300 ng/dL). Applied to U. S. census data, these findings suggest that 13.8 million American men aged ≥45 years may be testosterone- deficient. Furthermore, the prevalence of testosterone deficiency increases with age, reaching 50% for men aged ≥85 years. As the population ages, the burden of testosterone deficiency is expected to grow. The prevalence of low testosterone also increases in men with common co- morbidities, such as obesity, diabetes, and metabolic syndrome.