Max was a 14-year-old moggie whose owner brought him in because he was losing weight - despite consuming five tins of cat food a day.
Yes ... five.
She reported that Max was waking her in the middle of the night, demanding food with an urgency she had not seen before.
One night she woke up to find that he had chewed a hole in his bag of dry food and was helping himself.
When I examined Max, he had lost approximately 700 grams since I vaccinated him six months earlier.
His heart was beating rapidly.
I could feel that Max had an enlarged thyroid gland.
Blood tests confirmed that his thyroid gland was producing high levels of hormones.
Thyroid hormones help control the body's metabolic rate. Having an overactive thyroid gland, also known as hyperthyroidism, was accelerating Max's metabolism.
Hyperthyroidism most commonly occurs in cats over the age of 10 years.
In 98 per cent of cases, hyperthryoidism is caused by a benign tumour of the thyroid glands - similar to a goitre in people.
Clinical signs of hyperthyroidism include weight loss, increased appetite, vomiting, diarrhoea, increased thirst, restlessness, irritability and an unkempt looking coat.
Some cats buck the trend, showing a decreased appetite.
Cats with thyroid disease are at much higher risk of developing heart failure, high blood pressure (hypertension) and blood clots.
There are other conditions that may cause some of these signs in cats, including diabetes and kidney disease. It is not uncommon for cats to suffer from both kidney disease and hyperthyroidism.
Along with physical examination findings, diagnosis requires blood tests including thyroxine or T4 concentration, and urine tests to check kidney function. Other tests may include chest x-rays, blood pressure measurement, or echocardiogram to assess heart function. In some cases, imaging of the thyroid glands via scintigraphy may be needed.
As suspected, Max had increased T4 levels, but didn't have any signs of kidney disease.
His owner elected referral for radioactive iodine therapy. In most cases this involves giving a one-off dose of radioactive iodine, which is taken up by the overactive thyroid tissue.
This targeted treatment destroys the abnormal tissue without damaging other tissues including the surrounding parathyroid glands.
To prevent exposure of people to radiation, Max was boarded in a specialist cat facility for around a week.
Six months after treatment, Max has regained his weight.
His coat is shiny, and his appetite has normalised. He now eats two cans a day, with a bit of kibble.
Other treatment options are available. They include medical management, involving administration of tablets or in some cases topical application of cream, to suppress the production and release of thyroid hormones. Medical management requires ongoing monitoring, including blood tests, and may require dose adjustments.
Surgical removal of the thyroid glands can be curative if abnormal thyroid tissue is removed.
The key risk of this procedure is damage to the nearby parathyroid glands, which maintain vital blood calcium levels.
Dietary treatment is now available, but this requires a cat to eat a therapeutic diet that has regulated levels of iodine (used by the thyroid gland to produce thyroid hormones). In order for this to work, the cat should only consume this diet.
This can be hard to manage in cats with outdoor access, or in multi-cat households.
If your cat is losing weight, shows a change in appetite or is going to great lengths to convince you to feed them, check in with your veterinarian.
Dr Anne Quain, BVSc (Hons), MANZCVS (Animal Welfare), Dip ECAWBM (AWSEL),is a lecturer at the Sydney School of Veterinary Science and a practising veterinarian.
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