How to tell if your cat has hyperthyroidism

As cats become older, they can often develop hyperthyroidism. Find out everything you need to know about the causes, symptoms and treatment of this disease.

Hyperthyroidism commonly affects middle-aged or senior cats. Symptoms develop slowly, so it’s a good idea to keep a close eye on your cat as they age and speak to your vet if you’re concerned.

What is hyperthyroidism in cats?

Hyperthyroidism is when the two thyroid glands in a cat’s neck start to enlarge and produce excess amounts of thyroid hormones. These hormones help control metabolism, and when there’s too much of these in your cat’s bloodstream, their metabolic rate and bodily functions speed up.

What causes hyperthyroidism?

This disease is very common in senior cats. Usually, it’s caused by benign swelling, but in rare cases, it’s triggered by a cancerous growth.

Some cat breeds seem to have a lower incidence of hyperthyroidism, including the British Shorthair, Siamese, Persian and Burmese.

The top five symptoms of hyperthyroidism

In the early stages of this disease, the symptoms can be very subtle and easy to miss. But early intervention increases your cat’s chances of living with hyperthyroidism. Keep an eye out for the following five symptoms, and if you’re concerned about your cat, it’s always best to book a vet appointment as soon as possible.

1. Your cat is eating all the time, but still losing weight

Polyphagia – weight loss despite an increased appetite – is a classic sign of feline hyperthyroidism. If your cat is always hungry and asking for more food, yet never puts on weight, hyperthyroidism may be the cause. Checking your cat’s body condition score regularly can help you keep an eye on their weight. Speak to your vet practice for more advice on how to check your cat’s body condition score.

2. Your cat is drinking more than normal

Excessive thirst is typical of many health conditions that affect cats, including kidney disease. But when combined with polyphagia, your vet may want to check for hyperthyroidism and feline diabetes.

3. They have an increased heart rate

An overactive thyroid makes your cat’s heart work too fast. You may feel this when you pick them up and their heart races. This is the main reason for the urgent need to diagnose hyperthyroidism as early as possible, in order to reduce the chances of heart failure and hypertension developing.

4. They’re looking scruffy

Cats with hyperthyroidism develop an unkempt and scruffy coat, which may also look dull. Longhaired cats can develop mats. You might only realise this has happened when you look back at old photographs. This may not be a sign of simply ageing, but one of hyperthyroidism.

5. Diarrhoea and vomiting

Cats with hyperthyroidism may develop diarrhoea, vomiting or both. Some also urinate more frequently, sometimes outside their litter tray. If you don’t know where your cat toilets, keep an extra careful eye on their behaviour for any signs of diarrhoea.

How is hyperthyroidism in cats diagnosed?

If you’re concerned your cat may have hyperthyroidism, take them to the vet as soon as possible. They’ll probably run some blood tests to check your cat’s thyroid hormone levels.

Hyperthyroidism can also sometimes mask the early signs of kidney disease, so your vet may carry out further tests to check for this, too.

How is hyperthyroidism in cats treated?

If your cat is diagnosed with hyperthyroidism, your vet will likely recommend three possible treatment options: medication, surgery or iodine therapy, as well as discuss what you can do to support them at home.

Medication is the most common treatment option and involves giving your cat medication up to three times per day. This blocks excessive hormone production and is usually given as a tablet, liquid or gel. This option requires lifelong medication and regular vet check-ups. If you forget to give your cat their medication, the symptoms return.

Another option is surgery to remove any enlarged sections of your cat’s thyroid glands. Your vet will explain the procedure but usually, medication is needed for around three weeks before the operation. After your cat is recovered, they won’t need any ongoing treatment.

Sometimes, radioactive iodine therapy can be used to break down your cat’s thyroid glands without the need for invasive surgery. During this treatment, your cat will need to stay at the vet.

A low-iodine diet can also sometimes control the symptoms of hyperthyroidism, but you need to take care that your cat doesn’t eat any other types of food. If you have a multi-cat household, or your cat spends a lot of time outdoors, this may not be the best choice.

If you notice any symptoms of hyperthyroidism in your cat, it’s always best to speak to your vet straight away. Once their condition is diagnosed and treated, cats with hyperthyroidism can live happy and healthy lives.

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