The thyroid glands rest on each side of the neck. These small glands secrete thyroid hormone to regulate the body’s metabolism. An excess of this hormone increases the metabolic rate (hyperthyroidism), while a deficiency slows down the metabolic rate (hypothyroidism). Hyperthyroidism is much more common in cats; hypothyroidism is rare. Cats with hyperthyroidism tend to be middle aged and older cats. The increase in metabolic rate causes cats to develop a voracious appetite with weight loss, excessive thirst and urinations, vomiting, diarrhea, and behavioral changes. Multiple therapies exist for hyperthyroidism. Your veterinarian will discuss with you the safest treatment for your cat.