By Dr. Michael Averill, Veterinarian and Practice owner

Hyperthyroidism is a relatively common hormonal disorder in cats. Most cases (up to 99%) result from a benign (non-malignant) nodular enlargement of the thyroid gland(s) located in the neck. In approximately 70 to 75% of cats with hyperthyroidism, both thyroid glands are affected.

The incidence of this disease has increased steadily since the early 1980’s but the reason for this is still unknown. Multiple factors such as dietary, environmental, genetic and immunological causes may be involved.

Hyperthyroidism occurs most commonly in middle-aged to older cats, with an average age of onset of 13 years. The thyroid gland produces thyroid hormones which regulate the body’s rate of metabolism and in hyperthyroid cats there is an excessive production of thyroid hormones which causes an increased metabolic rate.

The most common signs seen in hyperthyroid cats are weight loss, increased appetite, vomiting, increased thirst and urination, restlessness, unkempt hair coat and diarrhea. Some cats may present with loss of appetite and weakness. Cats with hyperthyroidism commonly develop rapid heart rates, heart murmurs and high blood pressure. Left untreated these can lead to heart failure, kidney failure, liver failure or blindness.

Change of diet - In recent years, a prescription diet has been developed to help manage hyperthyroid disease in cats by providing limited availability of iodine, reducing thyroid hormone production.  In many cats this is very effective as the sole treatment for hyperthyroidism. 

In conclusion, if your elderly cat is losing weight, remember to get it checked by your veterinarian, as it may be due to hyperthyroidism, not just old age. With appropriate treatment these cats will regain weight and can lead a normal, healthy life.

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