Download FELINE HYPERTHYROIDISM The thyroid glands (paired glands on

FELINE HYPERTHYROIDISM The thyroid glands (paired glands on either side of the windpipe) produce a hormone called T4 which is converted by the body tissues to the active form, called T3. This hormone regulates your cat’s metabolism. In older cats, the thyroid glands can become overactive (hyperthyroid) and produce too much of this hormone. Hyperthyroidism is usually due to a benign growth of the glands, with only 3 to 5% of cases due to cancer. The affected cat’s metabolism greatly increases, and the hallmark sign is weight loss despite an excellent, often greatly increased, appetite. They also usually drink and urinate more (polydipsia/polyuria); sometimes the enlarged glands can be palpated (this is known as goitre). One unusual aspect is that the increased metabolism can mask underlying kidney disease, which becomes apparent when the hyperthyroidism is treated. Diagnosis of hyperthyroidism is usually straightforward by measuring the cats T4 blood levels, with an elevated level confirming the diagnosis. Hypertrophic cardiomyopathy (a form of heart disease involving the heart muscle) is often found is cats with hyperthyroidism, and your vet may want to check for this. There are three main treatment options. Radiotherapy, using radioactive iodine to selectively destroy the abnormal thyroid tissue is very effective, but also very expensive and not widely available. Surgical treatment, by removal of the affected glands, can also be performed, and one or both glands may need to be performed. This has its’ own risks, as a general anesthetic needs to be given to what is usually a geriatric patient. Medical treatment, with drugs to suppress the production of thyroid hormone, is also very effective, but requires lifelong daily, or twice daily, medication. Medical treatment is the least expensive and carries the least risks for the cat. It has also the advantage of being reversible, in case kidney disease becomes apparent when treatment is initiated. Most hyperthyroid cats respond well to treatment and survive with a good quality of life for years after diagnosis.