High Dog Thyroid Levels and Hoarse Bark

Our 14 yr old Australian Healer/Lab started to lose a lot of weight (had always been the chunky one)& is ravenous. He looks like he is overheated, panting alot. He developed a hoarse bark. Several months ago, his seizures increased in frequency (monthly that we know of) & severity. They had been once a year or so. He has become ataxic off and on as well.

Took him to the vet and his thyroid level was very high. Thyroid gland was palpated and felt normal. He said sometimes it is paradoxyl in dogs...high levels present, but it's really hypothyroid. It's related to an immune response, with the body attacking his thyroid. I don't understand this relating to our dog since all his symptoms are hyperthyroid like.

We followed up with more specific dog thyroid blood tests and we are waiting for results (said they can take up to 3 wks). One is a culture. Could it be an infection?

What are the chances this is hypothyroidism; or could be purely hyperthyroidism and not cancer? What are other causes of high blood thyroid levels? Brain Tumor?


Suggestions from our Veterinarian regarding High Dog Thyroid Levels


I’m afraid the most likely cause of high canine thyroid levels along with symptoms consistent with hyperthyroidism in an older dog is a cancerous tumor of the thyroid gland. This also fits with your dog developing a hoarse bark in that the thyroid gland is located in the throat where its enlargement could be affecting the quality of his voice.

The fact that your veterinarian palpated your dog’s thyroid gland and thought that it didn’t feel abnormally large does not rule out a tumor, unfortunately. In some dogs, the mass lies within the thoracic inlet (where the lower neck meets the upper chest) where it cannot be felt.

If your veterinarian is still unsure of what’s going on after the results of the blood tests are in, you could ask to be referred to a specialty center where a thyroid scan could be performed.

This would pick up abnormal thyroid tissue wherever it was located.

Best of luck,

Jennifer Coates, DVM

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