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Hyperthyroidism in Cats - Symptoms, Diagnosis & Treatment Options
Explore treatment options for feline hyperthyroidism including medications and radioactive iodine.
Mar 10, 2026
What is Feline Hyperthyroidism?
Feline hyperthyroidism occurs when the thyroid overproduces hormone. Common in older cats (8-10+ years). Proper treatment extends lifespan.
Hyperthyroidism
Symptoms
- Weight loss despite increased appetite
- Hyperactivity, anxiety
- Rapid heart rate (heart murmur)
- Frequent urination, increased thirst
Diagnosis
Blood tests measure T4 levels. Ultrasound checks thyroid size.
Treatment Options
- Medication (methimazole): Lifelong treatment
- Radioactive iodine: Possible cure (expensive)
- Surgery (thyroidectomy): Alternative option
- Special diet (iodine-restricted food)
Medication Management
Methimazole has side effects (low blood counts, liver damage). Regular blood tests are essential.
| Treatment | Advantages | Disadvantages |
|---|---|---|
| Medication (methimazole) | Low cost, start immediately | Daily dosing required, side effects possible |
| Radioactive iodine (I-131) | >95% cure rate, one-time treatment | High cost, isolation required |
| Surgery (thyroidectomy) | Rapid resolution | Anesthesia risk, parathyroid damage possible |
| Prescription diet (iodine-restricted) | No medication needed | No other food allowed, limited efficacy |
Sources & References
- Cornell Feline Health Center - Hyperthyroidism
Early diagnosis and treatment greatly improve quality of life.