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Hormonal disease · Updated 2026-09-21

Feline hyperthyroidism

Excess thyroid hormone in older cats can accelerate metabolism and strain the heart, kidneys and other organs.

Prompt veterinary attentionCats
Veterinary examination relevant to feline hyperthyroidism
Visual guide to warning signs including breathing difficulty, appetite loss, vomiting, mobility change, abnormal droppings and collapse
Changes in breathing, appetite, movement, digestion or alertness can need veterinary assessment. Collapse and breathing difficulty are emergencies.

Signs to watch for

  • Weight loss despite appetite
  • Restlessness
  • Vomiting or diarrhoea
  • Drinking more
  • Fast heartbeat
  • Poor coat

Causes and risk factors

Most cases result from benign overactive thyroid tissue; malignant thyroid tumours are uncommon.

How veterinarians diagnose it

Examination, blood pressure and thyroid hormone testing are combined with kidney, liver and heart assessment.

Treatment and management

Options include radioactive iodine, medication, surgery or a strictly controlled iodine-restricted diet; suitability varies by cat.

Prevention

There is no proven prevention. Routine senior examinations and weight tracking support early detection.

Outlook

Often excellent with definitive treatment or careful lifelong control, though concurrent disease influences outcome.