Hyperthyroidism in cats causes progressive heart disease that affects quality of life and longevity, making early diagnosis and treatment critical for welfare outcomes.
Cats with untreated hyperthyroidism experience chronic physiological distress. The racing heart, high blood pressure, and anxiety-like effects of excess thyroid hormone cause what can be understood as a constant state of physical agitation. Weight loss despite hunger is physically weakening. The secondary heart disease progresses silently until congestive heart failure or aortic thromboembolism - a catastrophically painful condition where blood clots cut off circulation to the hindlimbs. Early treatment prevents this suffering effectively.