Modern Veterinary Practice, 1985. 13(6): p.309-312.
Hyperthyroidism should be considered in cats that eat well yet lose weight. Excessive concentrations of circulating thyroid hormones are usually due to functional thyroid adenomas (adenomatous hyperplasia). However, thyroid carcinomas also occur in cats. Hyperthyroidism is usually diagnosed by elevated basal serum thyroxine (T4) concentrations. Pleural effusion is uncommon in cats with hyperthyroidism, and such effusions have not been well characterized.