The medical condition that affects the function of the thyroid gland is referred to as thyroid disease. The thyroid gland produces thyroid hormones. These hormones help in regulating energy use, infant development and childhood development. Thyroid diseases are classified into five groups. These are hypothyroidism, hyperthyroidism, structural abnormalities, tumors and abnormal thyroid. The symptoms of hypothyroidism are tiredness, slow movement, muscle cramps, etc. Common symptoms of hyperthyroidism are insomnia, anxiety, palpitations, etc. The diagnosis of this disease is based on these symptoms. Its further diagnosis can be done through ultrasound, biopsy and radioiodine scanning. The treatment of thyroid involves the intake of medications like thioamide drugs, or through surgery such as thyroidectomy, and radioiodine therapy. Different approaches, evaluations and advanced studies on thyroid disease have been included in this book. It will also provide interesting topics for research which interested readers can take up. The extensive content of this book offer the readers new insights into this field.