Hyperthyroidism
Also called: Overactive thyroid
- Cats
- Hormonal (endocrine)
- Senior
Hyperthyroidism is caused by the thyroid glands in the neck producing too much thyroid hormone, which speeds up the cat's metabolism. It is the most common hormonal disease in cats and almost always affects middle-aged and older cats. The great majority of cases are caused by a benign enlargement of the gland; a small percentage involve thyroid cancer.
Signs to look for
- Weight loss despite a normal or increased appetite
- Increased thirst and urination
- Hyperactivity, restlessness, or irritability
- Vomiting or diarrhoea
- A poor, unkempt, or greasy coat
- Increased vocalisation
- Rapid heart rate
How a vet diagnoses it
Physical exam (feeling the neck for an enlarged thyroid) plus blood tests — most affected cats have elevated total T4. A small percentage need additional tests (free T4, repeat testing, or thyroid scan). Other bloodwork checks for concurrent disease such as kidney disease or heart changes.
Treatment
Options include daily anti-thyroid medication (methimazole, tablet or transdermal gel), radioactive iodine therapy (often curative), surgical removal of the gland, or a prescription iodine-restricted diet. Choice depends on the cat's age, other health issues, and circumstances.
Monitoring at home
Thyroid hormone (T4) levels and dose adjustment, kidney values (treatment can unmask kidney disease), blood pressure, heart status, and body weight.
Who tends to get it
Middle-aged to older cats; no strong sex or breed predilection.
This library is educational reference only. It is designed to help you learn about health conditions your pet may have been diagnosed with — it does not interpret your pet's symptoms, cannot diagnose, and is not a substitute for veterinary care. Cats and dogs often hide illness well, so signs can be subtle. Any new, persistent, or worsening sign warrants a vet visit.