Feline hyperthyroidism is one of the most common diseases affecting middle aged to older cats. Affected cats have over-active thyroid glands that produce too much thyroid hormone. This is usually caused by the over-functioning nodules within the thyroid gland. Occasionally, in a small percentage of cases, it can be secondary to a cancer of the thyroid. Since the thyroid hormone affects multiple organs and helps to control an animal’s metabolic rate, there can be many different presenting symptoms.
Hyperthyroid cats usually display the following symptoms:
- Have an increased appetite and thirst. However, despite eating more, they lose weight and condition.
- They often exhibit changes in behaviour and may become cranky/agitated. Cats may seem to vocalise loudly!
- Some cats may suffer from intermittent vomiting and diarrhoea.
- As the thyroid hormone also affects the heart, an increase in thyroid hormone levels will increase the heart rate and blood pressure. Left unchecked, hyperthyroidism can eventually result in heart and/or kidney failure.
Hyperthyroidism is diagnosed by a simple blood test, in conjunction with the patient history and physical examination of the patient. There are several treatment options that the veterinarian will discuss with you.
- Most affected animals may be managed on daily oral medication.
- Some cats are great candidates for surgical removal of the thyroid.
- Others may undergo radioiodine therapy, which involves the injection of radioactive iodine, which destroys the abnormal thyroid tissue, while leaving the normal thyroid tissue unharmed. Although this is the gold standard for treatment of feline hyperthyroidism, it is only available at specially licensed facilities.
Ongoing monitoring of thyroid levels, regular blood test monitoring of organ function and physical examination of these patients is essential.