What is Hyperthyroidism?
Hyperthyroidism, or overactive thyroid glands, is a fairly common condition in cats over 10 years old. The thyroid glands, which are situated on the underside of the neck, produce an excessive amount of thyroid hormone. Thyroid hormone regulates the metabolism, and an excess of it causes them to burn up more energy.
An excess of thyroid hormone also has effects on many of the organs in the body. It makes the heart work much harder, and can cause the heart muscle to thicken which can ultimately lead to heart failure. High blood pressure (hypertension) can occur as a result of hyperthyroidism, which in turn can damage the kidneys, eyes and brain.
What causes the condition to develop is poorly understood.
What are the signs of Hyperthyroidism in Cats?
The signs you may notice are:
- Weight loss
- Appetite and thirst are normally increased. Some cats will however have a reduced appetite, especially if they are suffering from one of the complications of the disease
- Restlessness and irritability are common, and they sometimes appear a little twitchy. Some cats will become quite depressed.
- Some cats will become more vocal, yowling loudly
- Vomiting and diarrhoea are sometimes seen
These signs are often subtle at first, but become more pronounced over time. The sooner it is diagnosed and treatment started, the less chance there is of developing complications, and the better the long term outlook.
A diagnosis of hyperthyroidism will often be suspected by a vet after a thorough clinical examination, but a blood test is required to confirm. The blood sample can normally be collected and results back on the same day.
Hyperthyroidism can normally be treated very successfully. Treatment options include:
- medication – this is administered once or twice a day, and tablet and liquid forms are available. Treatment is lifelong, and regular blood tests and check ups are required to ensure the dose is correct and that no other problems are developing.
- surgery to remove the affected glands – there are some risks associated with this surgery, but if successful it can mean that ongoing medication is not needed.
- radioactive iodine treatment – this needs to be done at a specialist centre. Cats are injected with a radioactive agent which destroys the overactive thyroid tissue. As they are radioactive following this treatment, they need to be hospitalised in a special facility for 9-14 days. As with surgery, this can mean that ongoing medication is not needed.
- special diet – there is a prescription diet which has extremely low levels of the mineral iodine, which is needed to produce thyroid hormone. This can be successful in managing thyroid disease, but only if they eat the diet, and absolutely nothing else!