Hypothyroidism In Dogs Caused by
Autoimmune Thyroiditis

The canine thyroid is one of many amazing glands in the body. 

A malfunctioning thyroid can take a while to discover because the varying signs and symptoms, usually slow onset, and advanced age can prevent diagnosis. By that time an owner notices the symptoms, the damage has already been done.

Signs And Symptoms Of Hypothyroidism In Dogs

Generally, a change in skin where it is dry and flakey or loss of coat is a common sign that there is hypothyroidism in dogs.

Lack of energy (less desire to go out and play) is another sign.

Weight gain, while it could be due to simply overfeeding (and that is pretty common, in my experience) or lack of exercise, (have you played with your pup today?) can also be caused by hypothyroidism.

Change in temperament is also a good sign that the canine thyroid needs to be evaluated. (Something many people are not aware of).

The Disease

Hypothyroidism in dogs is certainly an easily treatable illness whether it is the genetic type or due to some other underlying cause. The pup can live a long and healthy life with medication.

Supporting the function of this important gland with seaweed supplements such as kelp is also another way to reduce symptoms. (Just don’t overdo it. More is not necessarily better.)

When a body attacks its own thyroid it is called “autoimmune thyroiditis”. This is the type of illness that is genetic and inheritable. However, other things can cause hypothyroidism that are not hereditary, including reactions to vaccines, environmental toxins and other situations.

Responsible breeders use this information to cross fault in breeding with these dogs to reduce the possibility of passing it on to pups if it does happen to be genetic for a particular dog.


testing hypothyroidism in dogs

Because sometimes it can be hard to diagnose simply from how a Sheltie looks and acts, testing is done long before any symptoms are evident.  Checking for hypothyroidism in dogs is performed at 2, 4 and 7 years of age.

Testing isn’t done BEFORE 2 years old because 99.9% of tests will not show abnormal results until after that age.

The lab test involves not just the T4 level but a complete panel that shows thyroxine, triiodothyronine and antibodies:

  • TT4(total thyroxine)
  • TT3 (total triiodothyronine)
  • FT42S (free thyroxine determined by the 2 step method… don’t ask, I don’t have a clue, it’s just the method used to get the free T4 level)
  • FT3 (free triiodothyronine)
  • T4AA (thyroxine 4 auto-antibodies)
  • T3AA (triiodothyronine auto-antibodies)
  • TSH (thyroid stimulating hormone)
  • TgAA (thyroglobulin auto-antibodies)

Orthopedic Foundation of Animals, the registry for hip evaluations, also registers lab results. They have a list of labs from which they will accept results. I use Michigan State University. There is also Jean Dodd, DVM’s lab, Hemopet that is expert in interpreting lab results for hypothyroidism  in dogs.

Not all labs are created equal when it comes to this particular type of testing.

Depending on the cost to have your vet draw blood, pack it in ice, ship it overnight plus the lab test itself, it can run about $180. 

When To Test

Testing of bitches must be done during anestrus (12 -16 weeks after her heat) as lab results are affected by estrogen and progresterone. Vaccines such as Rabies will increase the Thyroglobulin antibodies significantly for at least 45 days after administration. (But vaccinations are totally harmless, r-i-i-g-h-t!! NOT!!)

Steroids, overfeeding seaweed / kelp (see, I told you not to overdo it!) phenobarbital and sulfa drugs can decrease function as well. 

Generally speaking if you have an elevated TgAA or persistently elevated T4AA or T3AA you have a problem. 

High TSH means your Sheltie’s body is trying to get the gland to put out more hormones. Sometimes it can and sometimes it can’t. That’s when you look at the T3,T4 levels.

The End Result

While it can be a disappointment to a pup for breeding and showing only to have it develop canine thyroid disease at 4 years old or more, I think it’s better to know the facts with medical clearances than stick one’s head in the sand. 

For those of you with Shelties as pets/companions. Please understand that the Shetland Sheepdog as a breed generally needs a thyroid result on the high side of normal to function well.

So when your vet says, "the thyroid is fine." Ask for the actual numbers. A low normal on a Sheltie can still cause symptoms that can be relieved by supplementation with thyroid medication.

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