Hyperthyroidism is a condition commonly seen in middle aged to older cats. The symptoms of hyperthyroidism are caused by over production of thyroid hormone from the enlarged thyroid gland in the neck. The thyroid gland would normally function to regulate metabolic processes in the body. However, when there is too much thyroid hormone being produced we can see a number of “classic” symptoms which are usually readily identifiable in these patients.

Some of the most common symptoms associated with hyperthyroidism are highlighted below:

(Important to note that not every patient will get every symptom!)

Spotting some of these symptoms either at home or through regular veterinary examinations is the first step in the diagnostic pathway to identifying and subsequently controlling hyperthyroidism. In Cassie’s case, our vet was suspicious of hyperthyroidism and advised that the easiest way to confirm Cassie’s diagnosis would be to perform a blood test which measures the thyroid hormone levels in the patient’s blood stream. Cassie’s blood test was performed on the day of her initial presentation and a diagnosis of hyperthyroidism was confirmed, allowing treatment to be started immediately.

It is always worrying to receive the diagnosis of a new medical condition for your pet. However the good news for Cassie and her owner, and other cats diagnosed with this condition, is that hyperthyroidism has several good and often very successful treatment options, ranging from oral medication through to thyroid surgery. Every type of thyroid treatment will have pros and cons but it is generally accepted that if treated correctly many of these patients will go on to live as long as they would have had they never developed the condition in the first place.

Feline hyperthyroidism treatment options:

  • Oral medication is the most commonly used treatment for hyperthyroid patients. These types of medications act on the thyroid gland in order to reduce the abnormal production of thyroid hormone. The drugs come in both tablet and liquid form, and need to be given daily to maintain control of thyroid hormone levels in the body. It is important to note that oral medications are not a cure therefore lifelong treatment is usually required. Oral medications can often be used to stabilise feline patients in preparation for further treatment such as surgery.
  • Surgical removal of the thyroid gland (thyroidectomy) would be the second most common treatment option here at Aurora. We will often perform what is called staged unilateral thyroidectomy which means that we remove one half of the thyroid gland at an initial surgery followed by the second half of the thyroid being removed at a later date. This is done to minimise the risk of blood calcium issues caused by damage to the parathyroid glands which are anatomically very close to the thyroid glands. However, the surgery itself is usually a relatively simple procedure and if performed successfully most cats make an extremely good recovery and can essentially be cured of their condition. As mentioned earlier, most cats will receive medical management before surgery to stabilise their thyroid hormone levels.
  • Radioactive Iodine therapy (I-131) is another well-established treatment for hyperthyroidism. It is a safe and very effective method of treatment, with 95% of cases cured by their first treatment. The radioactive iodine is given by injection and although it has very few side effects, the patient requires to be hospitalised for up to a few weeks after treatment due to the radioactive nature of the drug used. The length of time the cat has to stay in isolation depends on a number of factors such as the presence of growing children or immunocompromised individuals in the home in which the patient will be returning to. In this corner of the world the closest feline radioactive iodine units are at Glasgow and Edinburgh University.
  • Dietary treatment is the final option for management. This requires cats to be strictly fed on a prescription diet which contains no iodine. Iodine is required for the production of thyroid hormone therefore if dietary sources of iodine are eliminated this limits the cats ability to produce thyroid hormone. This treatment is not a cure and it requires that the cat has no access to any other food sources therefore is more suited to indoor cats that can have their food intake closely monitored. If adherence to the diet can be achieved then this method of control can also be very successful however sticking to a single food source can be challenging for many cats and owners.

Each of these treatment options were discussed in detail with Cassie’s owner and the decision was made that medical management with the liquid formulation of the thyroid medication was the most viable option for Cassie and her owners.

Throughout the hyperthyroid treatment period these patients need to be closely monitored to ensure they are responding positively to their management. This is generally done by monitoring thyroid hormone levels through blood testing along with regular clinical assessment to look for improvement in the initial symptoms; for example an increase in body weight, a reduction in drinking or an improvement in demeanour.

Cassie has initially responded very well to her treatment but we will continue to keep a close eye on her. If you have any questions or concerns regarding your own cat and hyperthyroidism then please contact your vet who will be happy to discuss this condition with you.