The thyroid is the largest of the endocrine glands.   It is shield shaped and located in the neck near the larynx or voice box.  The thyroid’s job is to secrete the hormones which regulate growth and metabolism.  It also acts as a storehouse for iodine.  So when there is a problem with the thyroid gland we will often see significant changes throughout the body systems.

Hypothyroidism is caused by a decrease in the hormones produced by the thyroid gland.  Hypothyroidism is seen in middle aged dogs, generally 7 years of age or older. It is very rare in cats.  It is occurs most often in larger breeds but we see hypothyroid problems in all sizes and breeds of dogs. Thyroid dysfunction in dogs is generally caused by damage or atrophy of the gland itself. It is rare to see hypothyroidism caused by cancer.


Our typical thyroid patient is overweight, with thinning hair, dark pigmented, dry skin and a brittle hair coat. Hair loss on the trunk of the pet’s body is frequently seen.   Owner’s may mention that their pet has become less active  and lost muscle tone There may also be an increase in ear infections or the sudden onset of seizures.

Diagnosis and Tests:

Hypothyroidism is trickier to diagnose because other problems can look very similar.  Cushing’s disease, Diabetes and other endocrine related dysfunction can present with many similar symptoms. That is why laboratory tests are crucial when diagnosing and treating thyroid dysfunction.  Complete blood count and serum chemistries help us to rule out other causes and point us in the right direction if the thyroid is involved. Specific tests, such as Free T4 and TSH stimulation tests, target the thyroid hormone levels and provide a definitive diagnosis.  Periodic monitoring of blood thyroid levels will be needed over the lifetime of the pet to make certain therapeutic levels are maintained.


Once it occurs, Hypothyroidism requires lifelong supplementation to keep hormone levels normal.  The good news is that supplementation is easy, relatively inexpensive and quite successful in managing the disease.  Most of signs will lessen or disappear over time once treatment begins. Some medications such as steroids, sulfonamides and Phenobarbital can interfere with thyroid levels so it is important to always make certain that everyone involved with the treatment of your pet knows what medications they are taking.

We hope this will help you recognize the signs of thyroid dysfunction in your dog. At Animal Family, we try to help by including a screen for Thyroid disease in our Senior Wellness Blood test.  It is our hope that through early detection and treatment we can help to improve the quality of life for your pet.