Testosterone has an important influence on major organ systems and tissues, including brain, metabolism, cardiovascular as well as musculoskeletal and immune systems. Covering many clinical areas, this book pays particular attention to the diagnosis and management of hypogonadism, discussing current guidelines, biochemical assessment, new options in testosterone replacement therapy and long-term monitoring of treated men. Furthermore the role of testosterone deficiency in aging, obesity, muscle function and frailty and erectile dysfunction is covered. Recent evidence for the role of testosterone in the pathogenesis of chronic diseases such as diabetes, cardiovascular disease and osteoporosis is reported. New developments in the potential treatment of these clinical conditions are also presented. Primarily of interest to endocrinologists, urologists, andrologists and sexologists, the range of topics covered is also relevant to primary care physicians, gerontologists, diabetologists and cardiologists.