Why Your Dog’s Anti-Thyroid Antibody Test Is Positive

Ron Hines DVM PhD

To see what normal blood and urine values are for your pet, go here 

For an explanation of causes of most abnormal blood and urine tests go here 

To see how tests are often grouped, go here 

Anti-Thyroid Antibodies In Your Pet’s Blood

Your vet can identify most hypothyroid dogs (and even the much rarer hypothyroid cat) with a combination of FreeT4,  T3, and, when required, a TSH stimulation test.

However, a few cases that your veterinarian sees have all the common symptoms of hypothyroidism – but they can’t seem to be confirmed hypothyroid with those first three tests alone. Other dogs are checked for the presence of anti-thyroid antibodies because they haven’t responded to a standard veterinary dose of thyroid medication.

In some of those dogs – particularly golden retrievers, Shetland and Old English sheepdogs, and doberman pinschers – anti-thyroid antibodies that destroy the dog’s own thyroid hormones as well as thyroid supplements are to blame. The anti-thyroid antibody test can help identify those dogs. 

In another situation, potential breeding dogs can be screened for genetic susceptibility to this form of hypothyroidism. Elevated anti-thyroid antibody often appears in dogs before actual disease becomes evident and before T3 and T4 levels become subnormal. Hypothyroidism is extremely rare in cats so I can not tell you much about the test’s use in felines.

Complementary Tests:

Most likely, a complete thyroid panel would have been run before an anti-thyroid antibody test was suggested. An exception would be dogs being screened for a tendency toward hypothyroidism.


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