This book uniquely presents conceptual understanding as well as advancements in the field of endocrinology. It emphasizes the harmonization between the function and the structure of different endocrine glands in the body. The book's initial chapters introduce hormones' biological synthesis, structure, function, and signaling pathways. The subsequent chapters examine the functional relationship between hypothalamus and pituitary gland and its leading and regulating roles on other endocrine and non- endocrine organs. A separate chapter discusses the synergistic functions of adrenal glands and pineal gland in the circadian rhythm and analyze the role of corticoids in carbohydrate and mineral metabolism. Furthermore, the book addresses the role of growth hormones, prolactin, gonads regulating hormones, adrenocorticotropin, thyroid hormones, parathormone, gluco- and mineral corticoids, insulin and glucagon, Physiology of bone remodeling is presented with the role of parathyroid glands, C cells and vitamin D explaining the bone as an endocrine organ. The regulation of male and female reproductive functions is represented well. Lastly, the book reviews the novel endocrine role and metabolic aspects of adipose tissue as an endocrine tissue and its relationship to inflammatory diseases, insulin resistance and many metabolic disorders. The book introduces key parts for endocrine's stem cell in each gland is discussed in term of its survival, proliferation, migration, homing, differentiation and its regeneration and remodeling roles.