While rare compared to cats, hyperthyroidism does occur in older dogs, typically associated with thyroid carcinoma, and causes significant metabolic disturbance, weight loss, and cardiovascular stress if untreated.
Senior dogs with hyperthyroidism from thyroid carcinoma experience chronic metabolic distress: their hearts race, muscles waste, and organ systems are pushed to their limits by excessive thyroid hormone. Weight loss despite ravenous appetite, combined with heat intolerance and restlessness, substantially impairs quality of life. Early diagnosis through neck palpation during routine senior wellness examinations, combined with prompt specialist referral, gives the best chance of meaningful treatment. Owners should be aware that unlike in cats, canine hyperthyroidism usually signals malignancy, making thorough staging — including thoracic radiographs and abdominal ultrasound — essential before planning treatment.