The thyroid gland is a commonly diseased endocrine organ of human body. The disorders affecting the thyroid gland are varied but are very much amenable to treatment. The enlargement of the thyroid is termed goiter. It can affect the whole gland or only part of it. The disease is perplexing but in-depth knowledge of the pathophysiology helps in elucidating causes and thereby treating the disease. In this book, the diffuse and nodular goiter has been addressed as well as the functional abnormalities of the gland and its implications on the body are discussed in various chapters. The relevant updated information is included. To address a few of these current issues and recent updated information, authors have put in a lot of effort to organize the book.