Feline thyroid disease is most commonly known as an overactive thyroid or hyperthyroidism. In general, dogs get underactive thyroids (low/hypo) and cats get overactive thyroids (high/hyper). Hyperthyroidism is usually seen in cats over 7 years old.
Cats have two thyroid glands situated in the neck and their job is to produce thyroid hormones. These hormones are responsible for regulating many body processes, including metabolism. When a cat has an overactive thyroid, or hyperthyroidism, this essentially means that their metabolism is going too fast – they are burning too much energy.
The signs that you will have probably seen in your cat include weight loss but also being ravenously hungry – so they can eat a lot while continuing to lose weight. They can also become very hyperactive and restless, almost to the point of manic (sometimes yowling), especially around food. Other signs can include poor coat condition, drinking more and urinating more, vomiting and diarrhoea.
So, what is happening in the thyroid glands to cause this? The vast majority of cases are caused by a non-cancerous change which cause the glands to become bigger and then produce more thyroid hormone. The underlying cause of this change is unknown. Very rarely, a cancerous tumour (thyroid adenocarcinoma) can be the cause of the disease.
Although most hyperthyroid cats show an increased appetite and restlessness, in some cases they may show the opposite signs and be weak and have a loss of appetite.
If untreated, hyperthyroidism can cause an increase in heart rate as well as changes in the muscular wall of the heart that will eventually cause heart failure. They may also have high blood pressure which can cause damage to other organs including the kidneys. Along the way, your cat will have a stressful time of feeling constantly hyperactive and hungry, no matter how much they are fed.
There is no known prevention for hyperthyroidism but early diagnosis and treatment can dramatically reduce the secondary effects such as kidney disease, high blood pressure and heart damage.
The great news is that there are a number of treatment options available for hyperthyroidism and your cat can return to their normal selves and continue to have a long and happy life. Once diagnosed, treatment of hyperthyroidism should continue for the remainder of your cat’s life.