Is Hypothyroidism Behind Your Dog's Bad Behavior?

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Your dog started out cute, fluffy, loving, and adorable, and now he is anxious, whines constantly, does not behave, and has become intolerant of other dogs and people despite your best efforts to socialize him. Some vets might just tell you that he needs a good trainer or that it is canine puberty and it won’t last, but despite your best efforts, your formerly compliant puppy is out of control. Before you make the decision to find your dog another home, thinking his behavior is your fault or just his breed, have your vet check him for thyroid problems.

Hypothyroidism is often missed in dogs, because many dogs do not display the traditional signs of hypothyroidism and only present with behavioral problems, making it easy to miss. Just as humans can have changes in behavior with hypothyroidism, so too can dogs, and this is often the first and sometimes the only indication of thyroid problems. A study was conducted on 1,500 dogs with behavioral problems and it was found that out of those 1,500, 60% of them had a thyroid problem. Fortunately, like people, dogs can be treated with thyroid hormones and achieve marked changes in their behavior.

Dogs with Behavioral Problems Should Be Assessed for Thyroid Problems

Traditionally, dogs have only been tested for hypothyroidism when they present lethargy or other classic thyroid symptoms such as dry, brittle coat, allergies, or flaky skin. While a couple of authors noted links between behavior and thyroid function early on, aggression was not recognized as a symptom. Because the symptoms of thyroid dysfunction are so varied and widespread across multiple systems, a single system is often not connected to the thyroid but rather seen as an isolated problem. Also, because thyroid problems often start so young in dogs, between 6 months and 1.5 years, the symptoms are often not connected to a potential physiological problem but rather the temperament of the individual dog.

Many experts believe now that when a dog has changes in behavior they should be assessed and tested for thyroid problems. While it would stand to reason that your vet would test for thyroid problems if there were other symptoms involved, according to at least one study not all dogs with thyroid dysfunction and behavioral problems had other symptoms.

One of the primary disruptions that occurs with thyroid dysfunction is with norepinephrine and serotonin, which both affect behavior. For those dogs that have subclinical or moderate disruption in their thyroid function, behavior changes are likely to be the first and possibly only symptom you will see. For this reason, given the high rate of thyroid problems in dogs with behavioral problems, it may be up to you to advocate for your dog and insist your vet does a thyroid test.

Other Symptoms of Hypothyroidism in Dogs

Your vet will also look for the following symptoms as he assesses your dog for thyroid problems:

  • Allergies

  • Dry itchy skin

  • Hair grows back slowly after being shaved

  • Dull, brittle coat

  • Constant shedding

  • Seizures

  • Sad or worried facial expression

  • Difficulty in learning

  • Anxiety or hyperactivity

Diagnosing and Treating Hyperthyroidism

There are blood tests your vet can do to check for thyroid problems, including T4, TSH, and CBC. If your dog tests for low thyroid or even subclinical hypothyroidism, a twice a day synthetic thyroid hormone replacement can help your dog return back to his normal self. Dosages may be adjusted as needed, as changes in behavior improve, or regular test can be done to keep an eye thyroid levels.

Final Thoughts

Many experts are now recommending that all dogs with behavioral problems should have a full thyroid panel done, so if you suspect this might be your problem, your first step will be to talk to your vet. It is important to keep in mind that, even in humans, thyroid testing was not routinely done until a few years ago, and without obvious symptoms, you may need to do your homework to find a vet that will help you assess the cause of your dog’s behavioral symptoms.