Hyperthyroidism affects cats of all ages but is another common disease in senior cats. Cats have a pair of thyroid glands located in the neck area either side of their windpipe and these can commonly become overactive in older cats. In humans and dogs, we mostly see an underactive gland which leads to lethargy and weight gain but this is rarely seen in cats.
The thyroid gland is responsible for controlling metabolism so when it becomes overactive, it speeds up the cat’s metabolism by producing too much hormone.
Muscles, heart, stomach and intestines, urinary and nervous system are all affected. The disease will also change the cat's behaviour. Signs shown by hyperthyroidsim can vary. They often start with the cat seeming to be irritable and unable to settle. The most common sign is a voracious appetite although weight loss will also be evident. Sometimes owners will notice their cat being quite sick and this can be due to the cat being so hungry it scoffs its food too quickly so that it comes back up. Other signs include a rapid heart rate and an unkempt coat.
On examination the vet will usually be suspicious if the cat has a very fast heart rate, often up to 240 beats a minute. They will then check to see if they can feel an enlarged thyroid gland in the neck. However, the disease is confirmed by a blood test to measure the amount of thyroid hormone being made.
If hyperthyroidism is confirmed by a blood test, there are two treatment options.
The first is to medicate your cat with tablets. In most cases, these need to be given twice daily and work by stopping the thyroid gland from producing too much hormone. They work well provided the cat is good at taking tablets! Luckily the tablets are very small but they do need to be continued for the cat’s life as without them the gland will become overactive again.
The other option is to have the enlarged gland surgically removed. The vet will assess each individual case and decide on the best treatment option. Sometimes you can start with tablets and progress to surgery. It is important not to leave the condition untreated because the fast metabolism puts a lot of pressure on the heart and can lead to failure.