Weight loss is always something we like to look out for in our older feline patients – and sometimes it doesn’t make a lot of sense for a particular cat to be losing weight. It’s not uncommon for us to see older cats with good appetites – even ravenous appetites – that are losing weight. This odd combination of symptoms can be a sign of hyperthyroidism.
The thyroid is a gland that sits in the neck not far from the larynx (voice box). The thyroid has a few different functions but its main purpose is to produce hormones that affect metabolism. If the thyroid is producing too much of these hormones it can cause a big increase in appetite, but also cause the body to burn more calories than usual.
Middle-aged to older cats sometimes develop tumours in this gland. Usually they’re benign tumours called adenomas that don’t spread to other organ, but they can produce uncontrolled amounts of thyroid hormones. Usually the body controls the amount of thyroid hormone produced very closely but thyroid tumours don’t respond properly to the chemical signals the body sends.
Weight loss and ravenous appetite aren’t the only signs of thyroid disease in cats, but they’re the most common. We might see:
- Increased thirst and urination
- A greasy, unkempt coat
- Increased vocalisation (meowing)
- Vomiting and diarrhoea
At a checkup with the vet, we might also notice:
- Increased heart rate
- High blood pressure
There are a couple of other conditions in older cats that can have similar signs, so if we’re suspicious of hyperthyroidism we’ll usually recommend a blood test. We can directly test the amount of thyroid hormone (also called T4) in your cat’s blood.
There are many ways to treat hyperthyroidism in cats.
- Medication: there are various forms of medication that counteract the thyroid gland directly, and can be used in cats. If your cat is on medications we need to monitor their thyroid levels from time to time to make sure we don’t accidentally make their levels too low. Cats can become resistant to the medication over time so it’s also important to make sure their dose is still working.
- Diet: there are various anti-thyroid diets available for cats such as Hill’s Y/D. These diets work my minimising the amount of iodine in the food; the body needs iodine to build thyroid hormones. These will not be recommended if your cat spends time outdoors as they cannot have any other kind of food at all, or the diet won’t work.
- Radioactive iodine therapy: this is the only kind of therapy that can offer a complete cure for hyperthyroidism, but isn’t offered by every clinic as it does involve using radioactive material. It involves a hospital stay of a few days while kitty has and recovers from a radioactive injection that targets and destroys overactive thyroid tissue. Occasionally this can cause the thyroid to become underactive and will need to be remedied with oral thyroid hormone supplements.
- Surgery: this is usually not recommended as hyperthyroid cats can have heart and kidney problems that make anaesthesia risky, but the thyroid glands can be removed surgically. With newer treatments like diet and radioactive iodine available, thyroid surgeries are rare now. Cats that have their thyroids removed will need thyroid hormone supplements.
The good news is that hyperthyroidism is highly manageable. Though complications such as kidney and heart disease can occur, most cats with hyperthyroidism can live normal lives with appropriate medications and monitoring by your vet.