Cats & thyroid problems

Updated November 21, 2016

Cats are prone to dysfunction of the thyroid glands, just as humans are. The thyroid glands are located in the cat's neck. Their job is to regulate the body's metabolism. Hyperthyroidism---an overproduction of thyroid hormone by the thyroid glands---is the more common condition that affects cats, although some cats do develop hypothyroidism, which is the underproduction of the thyroid hormone. Thyroid problems can put you cat's life in danger if not addressed. Fortunately, dysfunction of the thyroid glands is fairly easy to treat in most cases.

Symptoms of Hyperthyroidism

Symptoms of hyperthyroidism can include weight loss, increased appetite, increased water consumption and urination, increased activity, restlessness, aggressive behaviour, a poor quality coat, a fast heart rate, vomiting and diarrhoea. Occasional difficulty breathing, weakness and depression can also be present. The weight loss can be quite dramatic, although the cat's appetite increases to the point of never seeming satisfied.

Symptoms of Hypothyroidism

Symptoms of hypothyroidism include lethargy, weight gain, hair loss, constipation, a dull and flaky coat, aggressive behaviour, increased urination, weakness and vomiting. The weight gain will be significant, despite no change in the cat's consumption of food.


Take you cat to a veterinarian for a diagnosis. The veterinarian will examine your cat, including palpitating your cat's throat to check for possible enlargement of the thyroid glands. He or she will also perform blood tests to determine the level of thyroid hormones in the blood. In some cases, a nuclear medicine scan of the thyroid glands may be performed. A blood panel and urinalysis will be done to screen for abnormalities that may be present in other organs.


There are three forms of treatment available for dysfunction of the thyroid gland in cats. The first option is to put the cat on an oral thyroid medication, such as methimazole (Tapazole), which is used to treat hyperthyroidism. The medication will need to be continued life long. Surgical removal of the thyroid glands in another option, in which part or all of the affected thyroid glands will be removed. Treatment with radioactive iodine is also available. Although this was initially a very expensive form of treatment, it is less costly in recent years. You will need to discuss these options with the veterinarian to determine which may be the best solution for your cat. Financial considerations, other diseases the cat may have and the age of the cat are all issues that will factor into the decision.

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