Hyperthyroidism in Cats
What is the function of the Thyroid glands?
The thyroids are two glands in the ventral (underside) neck just to either side of the trachea (windpipe). The thyroids secrete a hormone known as Thyroxine that regulates metabolism. An overactive thyroid (Hyperthyroidism) is quite common in older cats.
The most common sign of hyperthyroidism in cats is weight loss despite an increased appetite.
Other common signs include vomiting, diarrhoea, hyperactivity and restlessness at night, drinking and urinating more than normal, and an unkempt, matted, and/or greasy coat. Because this disease develops gradually, signs are often easy to miss at first.
How is hyperthyroidism diagnosed?
If your vet suspects hyperthyroidism in your cat (generally based on the symptoms above) this diagnosis can be confirmed with a simple blood test.
This test checks the circulating levels of T4 – the hormone that increases in Hyperthyroidism.
We usually also recommend a complete blood panel to test other organs’ functions and ensure there are no other concurrent issues that need to be addressed. If your cat’s T4 level is above normal, we start treatment.
How is hyperthyroidism managed long term?
With medication, this disease can be managed, unfortunately not cured. The “gold standard” treatment is radioactive iodine treatment which is soon to be offered in WA. Previously this has involved flying the cats over East for 3 weeks of treatment. This option is quite expensive but generally curative.
Currently, in WA, the most accessible treatment is daily medication. This is usually administered twice daily, with tablets or in some cases we can have the drug compounded into a pump pack that is smeared onto the inner ear and absorbed through the skin. With medication, repeat T4 testing is required 6-8 weeks after starting treatment to ensure we have the correct dosing for your cat.
Best practice is to test at least every 6 months ongoing. In some cases, we can offer surgical removal of the thyroid – please speak to your vet about this option.
Do I need to change my cat’s diet?
A change of diet is not necessary for cats with this condition, although in some cases a low iodine diet may be of benefit.
What happens if hyperthyroidism is left untreated?
Untreated hyperthyroidism usually leads to several serious issues – it can result in heart failure, blindness and can exacerbate kidney disease. As with most illnesses, early treatment will result in the best outcomes.
Does this diagnosis shorten my cats’ life?
With good management, Hyperthyroid cats can lead long and healthy lives.