Companion Animals

Companion Cat Hyperthyroidism and Cardiac Health

Untreated hyperthyroidism in cats causes severe cardiac complications that cause significant suffering and shorten lifespan dramatically.

Key Facts

Hyperthyroidism increases cardiac workload causing hypertrophic cardiomyopathy
Up to 70 percent of hyperthyroid cats have cardiac changes on echocardiography
Treating hyperthyroidism may unmask concurrent kidney disease
Sudden cardiac death is a risk in severely affected untreated cats

Welfare Considerations

The cardiac complications of hyperthyroidism cause heart failure symptoms including labored breathing, exercise intolerance, and fluid accumulation in the chest. Cats with severe cardiac disease experience chronic respiratory discomfort and fear from breathlessness. Paradoxically, treating thyroid disease may reveal kidney disease that was masked by the high blood flow from the overactive thyroid. Careful monitoring of kidney function after treatment is essential.

What You Can Do

Screen all older cats annually for hyperthyroidism
Begin treatment promptly if hyperthyroidism is diagnosed
Monitor kidney function carefully after starting thyroid treatment
Report any exercise intolerance or breathing changes in older cats