Testosterone Therapy for Functional Hypogonadism provides an evidence-based examination of the role of testosterone treatment in men with functional hypogonadism. Written for healthcare professionals, medical researchers, and readers seeking a deeper understanding of testosterone deficiency, the book explores the complex interplay among testosterone, aging, lifestyle, metabolic health, and chronic disease. It offers a clinically focused overview of the pathophysiology, clinical presentation, diagnosis, and management of the condition, while critically evaluating the evidence for treatment. Drawing on recent randomized clinical trials, systematic reviews, and meta-analyses, it examines efficacy and safety, patient selection, monitoring, and long-term outcomes. Particular attention is given to metabolic and cardiometabolic health, body composition, sexual function, physical performance, and quality of life, as well as to key areas of ongoing scientific debate. By integrating research findings with practical clinical considerations, the book provides a framework for informed, individualized patient care and highlights priorities for future research.