Hyperthyroidism is the most common endocrine disorder in older cats and causes significant suffering when undiagnosed, but responds well to a range of effective treatments.
Undiagnosed or undertreated hyperthyroidism causes significant suffering through weight loss, gastrointestinal distress, cardiovascular strain, and the profound discomfort of uncontrolled hypertension. Cats with uncontrolled disease experience constant hunger despite eating continuously, and the associated cardiovascular strain causes physical discomfort. Many owners attribute weight loss and increased energy in older cats to normal aging rather than recognizing disease, delaying treatment. Hypertensive blindness, when it occurs, is sudden and irreversible but entirely preventable through prompt treatment. With appropriate management, most hyperthyroid cats return to excellent quality of life and can live for years with well-controlled disease.