Australian Shepherd Health & Genetics Institute

Australian Shepherd Health & Genetics Institute

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Autoimmune Thyroiditis


What is autoimmune thyroiditis?

Autoimmune thyroiditis causes the immune system to attack the thyroid gland.  This leads to reduced production of thyroid hormones and ultimately the elimination of the gland altogether.

 How do I know if my dog has autoimmune thyroiditis?

Weight gain, skin problems, and a tendency to seek heat are some of the more common signs of thyroiditis. Definitive diagnosis must be made with blood tests.  Tests specifically aimed at detecting thyroid hormone antibodies are required to definitively diagnose the autoimmune form of the disease.

 What does having autoimmune thyroiditis mean for my dog?

Once diagnosed, thyroiditis can be effectively treated with medication.  The medication must be given for life and may require periodic adjustment.  Thyroid medications are inexpensive and have minimal side effects.

 How common is autoimmune thyroiditis in Aussies?

It is by far the most common autoimmune disease in the breed and a very common disease in dogs overall.  It is important to keep in mind that breeders should approach all chronic autoimmune disease as a single health concern; different types of autoimmune disease frequently occur in affected families.

 Is autoimmune thyroiditis inherited?

Yes, though it is important to establish that the disease is autoimmune through proper testing.   All autoimmune diseases are genetically predisposed:  The dog must have the genes to get the disease, but not every dog with the genes will become ill.

 Is there a screening or DNA test for autoimmune thyroiditis?

Yes.  Ask for the panel approved by OFA.  It contains T4, TGAA (the antibody test), TSH and maybe one or two others but these three are most important.  The T4 and TSH will give you current levels.  TGAA tells you if there is an active autoimmune action against the thyroid.  In late stage disease TGAA will be absent because the thyroid will have been destroyed, but dogs at this stage of disease should have clinical signs.  The test should be given annually from 1-4 years, at 6 and fially at 8 years of age.  Test results can be swayed one way or the other by other illness, medication, or female hormone levels.  Thyroid screening should be done only when the dog is sound, healthy and has not received thyroid medication within the previous three months.  Female dogs should not be in or close to their heat cycles, pregnant, or lactating.

 What does autoimmune thyroiditis mean for my breeding program?

Breeders should approach each autoimmune disease as part of an overall health and breeding issue because different autoimmune diseases frequently occur in an affected family.  See Autoimmune Disease & Breeding.

Is it true that normal thyroid values for Aussie are different from average for other breeds because they are active working dogs?

It is true in some sighthounds but has not been demonstrated to be so in Aussies.  Thyroid values can fluctuate in response to a variety of things:  Disease, stress level, recent trauma, and, n females, hormone fluctuations.

Does the use of flea and tick products cause thyroid disease?


Could a dog fail thyroid screening because it has a thyroid tumor?

Any fluctuation from normal thyroid levels caused by a tumor will not be the same as is seen in autoimmune thyroiditis, especially the signature sign of autoimmune disease – the autoantibodies.

Is fighting with other dogs caused by thyroid disease?

In most cases fights between dogs have strictly behavioral causes (though some of those may be influenced by genetics).  However, autoimmune thyroiditis occasionally causes affected dogs to exhibit aggressive behavior.    But if the cause is thyroiditis or any other non-behavioral issue  you should be seeing other signs that indicate something else is wrong in addition to the aggressive behavior.