Feline Hyperthyroidism

Eating endlessly but still losing weight, that would sounds like a dream come true to many of us. However, for the feline population, this phenomenon is a sign of a serious, yet quite common metabolic disorder called Hyperthyroidism.

The thyroid glands are organs situated in the neck and secrete hormones that are responsible for the pace of all of the processes in the body (also known as metabolism).

Hyperthyroidism is a condition in which the thyroid gland produces excess of its hormones and every function of the body tends to speed up resulting in multi-systemic disease.

Hyperthyroidism is probably the most common endocrine (hormonal) disorder in cats. It occurs in middle age-older cats, with no breed or sex predilection.

In the vast majority of cases the increased thyroid hormone production is due to a benign (non-cancerous) change but a malignant (cancerous) tumor known as a thyroid adenocarcinoma can also be an underlying cause of some cases of hyperthyroidism.

Cats affected with hyperthyroidism usually develop a variety of clinical signs, which are usually quite subtle at first, but then become more severe as the disease progresses.

The most common symptom is weight loss despite an increased appetite. Many cats also show signs of restlessness, increased drinking and urination, intermittent vomiting and diarrhea.

The multi-systemic effects of hyperthyroidism lead to a variety of symptoms depending on the affected organ. Also, as this disease occurs mostly in older cats, some affected cats will have other diseases that can complicate and even mask some of the clinical signs.

The most common secondary complications of hyperthyroidism are high blood pressure, cardiac failure and renal failure.

In my experience, many cats are unfortunately diagnosed much too late when they have one of the most devastating outcomes of the cardiac dysfunction, associated with hyperthyroidism - back legs paralysis - resulting from a blood clot lodge in the main blood vessel supplying the back legs. This condition has a very poor prognosis for recovery.

On physical examination, your veterinarian can assess the cat’s body condition. One or two enlarged thyroid glands can often be felt as a small, firm mass in the neck.

Hyperthyroidism is easily confirmed by a blood test, measuring the level of the hormones associated with the thyroid gland. A general blood and urine test are also recommended in order to assess the secondary effects on the body organs.

Due to the toxic effect of the thyroid gland hyperfunction on the heart, it is important to assess the heart function. The first and easiest test is measuring the cat’s blood pressure. If secondary heart disease is suspected then an electrocardiogram (ECG), and a chest X-ray or ultrasound may be indicated.

Despite the possibility of horrific outcome of hyperthyroidism, if caught on time, it is actually fairly easy to manage.  The most common treatment for hyperthyroidism is life long anti-thyroid drug administration. Radioactive iodine therapy also exists but it is not readily available in most of the veterinary practices. Surgical removal of the glands is also an option.

Clinical signs associated with hyperthyroidism can be quite dramatic and cats can become seriously ill with this condition. However, I find that because this condition progress over time, many cat owners have a hard time noticing the weight changes in their pet. I was witness to a few cases where the owners only noticed the change in their pet after spending a few days away, on a vacation for example. This is where an annual health check at your vet comes in handy. Your veterinarian can notice abnormalities that you as the owner may overlook. If diagnosed on time, most cases of hyperthyroidism are controllable and prolongation of life, while maintaining a good quality of life is very possible.

This article is written by or on behalf of an outsourced columnist and does not necessarily reflect the views of Castanet.