Hypothyroidism is common in middle-aged dogs and causes multiple welfare-relevant clinical signs. Diagnosis and appropriate medication restores quality of life effectively.
Hypothyroidism causes progressive deterioration in quality of life through multiple mechanisms including lethargy that limits normal activity and engagement, weight gain increasing joint loading, skin thickening causing facial changes, and the subjective experience of feeling chronically unwell that we can infer from the dramatic improvement seen after treatment. Many dogs with hypothyroidism have been symptomatic for months or years before diagnosis as the gradual onset is normalized as aging. The response to levothyroxine treatment is often described by owners as transformative, revealing the degree to which the condition was affecting daily welfare.