Hyperthyroidism Common in Older Cats

Feline hyperthyroidism affects more than 10 percent of cats older than 10 and is now the most common endocrine disease among cats.

Cats given canned food are two to five times more likely to develop hyperthyroidism than cats that eat dry food. Zhuravlev Andrey/Shutterstock

Q: Our senior cat has hyperthyroidism. How common is hyperthyroidism, and what causes it?

A: Hyperthyroidism is caused by benign tumors in the two thyroid glands located in the cat’s neck. The tumors produce excessive amounts of thyroid hormone, which affects all body systems.