Diagnosis of canine hypothyroidism - Perspectives from a testing laboratory

The most common sample received by our endocrine testing laboratory is subm itted for the diagnosis of hypothyroidism in a dog. The current tests most frequently employed in our laboratory for thyroid evaluation in dogs are to tal T4, free T4 by dialysis, and canine TSH measurement. Each test has stre ngths and weaknesses and suffers from the possibility of both false positiv e and false negative results. This article provides a working description o f each test and an approach to interpretation of results. Other tests that are less commonly used are also discussed. Examples of interpretation of te st results in individual hypothyroid-suspect dogs are presented for illustr ation.