Hypothyroidism in Dogs

Is your dog more lethargic or tired than you would expect? Does he/she hate the cold and prefer somewhere warm to rest? Are they gaining weight despite eating an appropriate amount of calories per day? Maybe they are itchy, or their behaviour seems off? If any of this sounds familiar than your furry friend may be hypothyroid.

Hypothyroidism is one of the most common metabolic conditions in dogs. Hypo means “under” — therefore this condition is when the dog’s thyroid gland (located in the neck near the voice box) is not producing as much thyroid hormone as the dog needs.

Thyroid hormone is constantly circulating in the body and aids in numerous bodily functions not limited to metabolic, dermatologic, behavioural, reproductive, cardiovascular and neurological functions. Given the importance of the thyroid gland, clinical signs in your pet can be vague with ups and downs. Ultimately, the condition is caused when the dogs’ thyroid gland is compromised or destroyed in one way or another and subsequently no longer functions to produce thyroid hormone. The lack of thyroid is what then causes the associated clinical signs you may see at home or may be picked up at your annual exam.

The good news is that once we suspect a dog to be hypothyroid, testing is usually straight forward. Not always, unfortunately, but usually. We take a blood sample and traditionally check three important values. Two of these values are the actual hormone that the thyroid gland is producing and the third value is the canine thyroid stimulating hormone (cTSH). It is the hormone that is produced by the pituitary gland that then tells the thyroid gland to produce thyroid hormone. What a mouth full. Don’t worry, your veterinarian sees this condition often and will be able to explain it to you in more detail should the need arise. In the most traditional sense of the disease, both thyroid hormone values will be low (hence being hypothyroid), and the cTSH will be high. It is because the body is trying to squeeze every last bit of thyroid hormone out of the thyroid that it can.

Once the diagnosis has been obtained, the solution is also relatively easy. We have to give the body back the hormone it can’t produce for itself. We do this by supplementing thyroid hormone orally twice a day. Dogs often respond very positively and quickly to the medication and clinical signs associated with being hypothyroid often go away. Your veterinarian will work with you and your 4-legged friend to determine the best approach for follow up care. It generally includes some repeat bloodwork to make sure we are giving just the right amount of medications. The treatment is lifelong. Once your pet is hypothyroid, you are always hypothyroid.

Dogs diagnosed with hypothyroidism will live long, happy, healthy lives. They need a little boost twice a day and a bit more veterinary care.

If you think your dog may be hypothyroid, please talk with your veterinarian about possible bloodwork to screen for the condition.

Written by: Jeremy Mount, DVM