This book provides extensive information regarding the thyroid hormone. Thyroid hormone is necessary for controlling metabolism and several other body functions. Alterations in thyroid hormone physiology, its regulation and diseases pose a significant challenge for the humankind. Comprehension of thyroid hormones has continuously undergone updates and revisions. Authors from distinct specialties have contributed in this book. Its aim is to serve as a useful reference for furthering the knowledge on thyroid and help in establishing novel vistas of research.