Hyperthyroidism is the most common endocrine disease in cats over 10 years. Multiple effective treatment options exist, but the welfare impact of untreated disease makes early detection critical.
Untreated hyperthyroidism causes profound suffering through the metabolic consequences of excessive thyroid hormone: constant hunger that cannot be satisfied, anxiety and hyperactivity that prevents rest, muscle wasting despite high caloric intake, cardiovascular complications including hypertension and heart disease. The disease progresses to cardiac failure and death if untreated. The treatable nature of the condition makes each untreated hyperthyroid cat a preventable welfare failure. Treatment with radioactive iodine or medication typically produces dramatic clinical improvement within weeks. The welfare transformation from uncontrolled hyperthyroidism to well-managed euthyroid status represents one of veterinary medicine's most rewarding interventions.