Dogs have Thyroid Glands Too

While dogs have thyroid glands just like cats, and the hormone has similar functions in both animals, the diseases that these two species are generally the opposite.  Cats get functional thyroid adenomas, that is benign tumors of the thyroid gland that secrete active thyroid hormone, and hence cause hyperthyroidism.  Dogs get tumors of the thyroid gland, but these are usually thyroid adenocarcinomas.  Non functional, malignant tumors of the thyroid gland that can metastasize to other parts of the body.

Fortunately, thyroid cancer is not the most common disease of this gland in dogs.  Rather, decreased secretion of hormone, or hypothyroidism, is the condition that we see most often.

Hypothyroid dogs present just as one would expect if you think about thyroid hormone as the regulator of metabolism.  Dogs have low energy, poor hair coat, bad appetites, and often weight gain. If caught early, there may not be time for any symptoms to have become apparent.  

We include thyroid screening in our recommended blood work for all middle age and older dogs. It is important, because if caught early, simple supplementation with thyroid hormone on a regular basis will prevent clinical signs from ever starting.  I do want to emphasize that while many hypothyroid dogs are overweight, not all overweight dogs are hypothyroid.  So, just as with their owners, dogs with a weight problem often do not have a hormonal issue, it's an eating issue.