Pathogenesis refers to the origin, development, and progression of a disease or disorder. Understanding these factors is essential for determining the appropriate treatment approach. Therapeutic options for canine thyroid cancer typically include surgical removal (thyroidectomy), radiotherapy - eventually involving radioactive iodine -and chemotherapy. Thyroid cancer in dogs is one of the most common endocrine cancers. Endocrine cancers originate in hormone-producing organs or tissues, such as the thyroid gland, pancreas, or neuroendocrine cells of the gastrointestinal tract. The clinical presentation of the disease is variable and often depends on the size of the tumor and specific signs of thyroid hormone imbalance. Most dogs are euthyroid, while 30 to 40% may exhibit hypothyroidism, which is rarely symptomatic. A small percentage develops hyperthyroidism, showing typical signs such as hyperactivity, weight loss, excessive thirst, frequent urination, and cardiac arrhythmias.