Hyperthyroidism is a common disease in cats that usually starts when they are middle-aged or older. In most cases it occurs when the thyroid gland develops a benign tumour called an adenoma, causing it to overproduce thyroid hormones. Thyroid hormones are responsible for regulating many body processes, so when too much hormone is produced nearly all organs in the body are affected and cats can become very ill. The cause of hyperthyroidism is currently unknown, though there are many theories about possible contributing factors such as deficiencies or excesses of certain compounds in the diet, or chronic exposure to thyroid-disrupting chemicals in the environment.
Clinical signs of hyperthyroidism include weight loss despite an increase in thirst and appetite, which can often be quite dramatic. Restlessness, irritability, increased activity, an increased heart rate, a poor and unkempt coat, and an increased breathing rate are also common signs. Uncontrolled hyperthyroidism causes high blood pressure (hypertension) and puts a lot of strain on the heart, which can cause heart failure if left untreated.
Hyperthyroidism is diagnosed via a simple blood test that can be performed in our hospital in as little as 20 minutes. The ideal treatment for hyperthyroidism is radioactive iodine therapy to safely destroy the abnormal thyroid tissue. Lifelong medication, diet modification, and surgery are also possible treatment options; our vets weigh up the benefits of each mode of treatment to create a tailored treatment plan for each cat and their humans.