Hypothyroidism in Dogs

Post by Dr. Jamie Senthirajah


Has your pup recently become (or has always been) a lazy bum that seems to be packing on the pounds? We’ll it may not be just because he is a couch potato, but he could have a condition called hypothyroidism.

Hypothyroidism is an endocrine disorder that is caused by decreased production of thyroid hormone. The thyroid glands, although tiny in size, pack a punch as the hormone they produce affect most cells throughout the body. The two most common causes for this condition in dogs are lymphocytic thyroiditis (fancy name for an auto-immune attack against the thyroid gland) or due to a congenital defect (they were born with it (no, it’s not Maybelline)).

Any breed of dog can be affected by this disorder, but it affects Golden Retrievers, Dobermans, Beagles, and Spaniels more commonly. The mean (average) age that dogs are diagnosed is about 7 years-of-age, but dogs 6 months to 15 years have been diagnosed with this disease. Spayed and neutered dogs appear to be at a higher risk of developing this disease.


Some of the common signs you may see in your pooch include weight gain (despite them not eating too much), weakness, lethargy, heat seeking (and we mean more than searching for your warm lap), and dullness. Skin problems including alopecia (especially if symmetrical), skin infections, dry and brittle hair, ear infections, and hyperpigmentation (darker skin), among others… can be noted. Some dogs even have a “tragic look” (see below) to their face. Less common, but still possible complications of hypothyroidism, (which include neurologic, cardiac, ocular, and reproductive abnormalities) have been reported.



If we suspect your pet has hypothyroidism (or any other metabolic condition), we will recommend your pet receive bloodwork. This screening test will look at the total thyroid levels in the blood. If this is low, your pet could have hypothyroidism, but some dogs have low thyroid levels because of breed, time, ambient temperature, age, other illnesses, or drug interactions (please let us know if your pet is receiving any other medications such as steroids, Phenobarbital, sulfonamides, and aspirin). To confirm hypothyroidism, we measure the amount of thyroid hormone that is not bound to proteins, as this is a more accurate (but still not perfect) assessment of thyroid function.


If your pet has been diagnosed with hypothyroidism, we have medications that will make your dog jump for joy, literally. An oral pill is given to your pet once every 12-24 hours for the remainder of his life. It is ideal to give this medication on an empty stomach as food can hinder the absorption.


Once we start your dog on medications we will need to see them back four weeks later to reassess thyroid levels to make sure it is within the appropriate range. If we need to adjust the dose, repeat checks of the thyroid hormone may be done again four weeks later. An important aspect to note is that we need to recheck the levels 4-6 hours after you give the medication as this is the timeframe where we would see the peak (highest level of) thyroid hormone in the blood. So, please please please schedule your appointment within this time window so your time and money are well spent. Once we have your dog’s thyroid levels at an appropriate level, we need to recheck their bloodwork every 6 months or sooner if anything is concerning or if clinical signs return.


So when can you expect to see improvement?! Well, you will likely see an increase in activity level within the first two weeks of starting treatment. Weight gain and improvement in skin and hair growth take at least a minimum of one month. Rest assured, we will get your pet on the right path!

As always, if you have any questions about your pet, please do not hesitate to contact us!

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