Mace Dekker: Feline hyperthyroidism |

Mace Dekker: Feline hyperthyroidism

Q: My 12-year-old cat is suddenly acting young again! What’s going on?

A: It may be that your cat has feline hyperthyroidism, a disease of older cats whose cause is poorly understood.

It is not uncommon for clients to say that their cat with hyperthyroidism has ‘a second lease on life’ – the disease causes the cat to initially have greater energy and lose weight, which may look like improved health.

Feline hyperthyroidism is the most common endocrine disorder in middle-aged and older cats. It occurs in about 10 percent of feline patients over 10 years of age.

Hyperthyroidism is a disease caused by an overactive thyroid gland that secretes excess thyroid hormone. Cats typically have two thyroid glands, one gland on each side of the neck. One or both glands may be affected.

The excess thyroid hormone causes an overactive metabolism that stresses the heart, digestive tract and many other organ systems.

The most common signs of hyperthyroidism are:

• weight loss despite a normal or even increased appetite

• increased urination, more urine in the litter box (and with that, increased drinking or thirst)

• defecation outside of the litter box

• increased vocalization

• restlessness, increased activity

• vomiting

• diarrhea

• poor hair coat, unkempt fur

• rarely, lethargy and a lack of appetite

Fortunately, it is a disease that can be treated relatively easily. The options include medication, sometimes diet changes which reduce the amount of iodine in the body, and in some cases surgical or radiation treatments on the thyroid gland.

There are many cats under treatment for this disease and most do quite well.

However, if left untreated it can lead to serious long-term consequences for multiple organ systems.

Grass Valley Veterinary Hospital’s Mace Dekker, D.V.M. will consider your questions each month in Vet Tips. Have a question? Submit it to

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