Does Dog Hypothyroidism Cause Anxiety or Behavior Problems?

Hypothyroidism in dogs is relatively common and gets blamed for many symptoms that are caused by something else. My own dog has hypothyroidism and anxiety but the two may not be related. 

Dog hypothyroidism anxiety happens much less frequently than people on the internet tell you. Recent research has failed to find a correlation between hypothyroidism and anxiety or aggression in dogs. The main behavior change caused by canine hypothyroidism is lethargy.

Dog Thyroid Gland Anatomy and Function

A dog’s thyroid gland is located on the neck just below the “Adam’s apple” area. The gland produces hormones called thyroxine (T4) and triiodothyronine (T3) that affect many metabolic functions in the body including 

  • Metabolic rate
  • Rate of tissue turnover
  • Heart function
  • Cholesterol metabolism
  • Red blood cell production
  • Central nervous system development 

What Causes Hypothyroidism in Dogs?

Hypothyroidism is one of the most common endocrine diseases in dogs. Autoimmune thyroiditis and atrophy of unknown origin are the most common causes of hypothyroidism in dogs. The disease is hereditary and runs in breeds and families.

Some internet gurus warn about damage from neck collars causing hypothyroidism. There is no clinical evidence that neck trauma contributes significantly to the likelihood of a dog developing hypothyroidism.

Which Dogs Are Most Susceptible to Thyroid Problems?

Certain dogs are more likely to develop hypothyroidism than others. It does seem to run in families and is more prevalent in some breeds. The typical profile of a hypothyroid dog follows: 

  • Age: 2–9 years old
  • Breeds: Akita, Basenji, Beagle, Border Collie, Boxer, Chesapeake Bay Retriever, Cocker Spaniel, Dachshund, Dalmatian, English Setter, Golden Retriever, Great Dane, Maltese Dog, Miniature Schnauzer, Old English Sheepdog, Poodle, Rhodesian Ridgeback, Shetland Sheepdog, Siberian Husky (1)

Physical Symptoms of Low Thyroid Function

Symptoms are variable, but some are more common than others. Here’s a list ordered from most common to least common symptoms of low thyroid disease in dogs:

  • Weight gain without a change in diet
  • Lethargy
  • Poor coat quality–dull, thin/hair loss, bristly, “rat tail”
  • Skin problems–excessive dander, skin infection, bad odor, ear infections
  • High cholesterol
  • Anemia
  • Heart abnormalities–slow heart rate, abnormal rhythm
  • Eye abnormalities–corneal dystrophy (uncommon)
  • Neurologic problems–weakness (rare)

Can Hypothyroidism Cause Behavior Changes in Dogs?

Whether hypothyroidism causes aggression or anxiety in dogs is controversial. Many non-veterinary enthusiasts report behavioral problems are a major symptom of the disease while other researchers and veterinary specialists are less convinced. 

For example, LA Radosta, et. al found no significant differences in thyroid hormone levels of aggressive and non-aggressive dogs.(4) And another study found no difference in owner-directed aggression after hypothyroid dogs received hormone replacement therapy. (2)

And another study of 20 client-owned hypothyroid dogs did not find any improvement in aggression or anxiety after they were treated with thyroid hormone replacement therapy. (3) Lethargy/inactivity was the only behavior that did improve. 

While that doesn’t prove that aggression and anxiety are not caused by hypothyroidism, it seems logical that those behaviors should improve with treatment if the main cause is a lack of thyroid hormone. 

It’s possible that the same dogs who get hypothyroidism are genetically predisposed to aggressive and anxious behavior. This is a case to remember that correlation does not equal causation. In other words, just because two health problems occur in the same animal it does not mean one problem caused the other.

Diagnosis and Treatment

Diagnosis of this disease is not always straightforward. There are several thyroid hormone levels involved in the thyroid health of dogs. Testing only one hormone gives an incomplete picture of the situation.

Veterinary endocrinologists recommend running several different tests in order to make a diagnosis of hypothyroidism. 

Lab TestHypothyroid Expected Result
Total T4 (total thyroxine, the main hormone produced by the thyroid gland)Normal or Low
TSH (thyroid-stimulating hormone)Normal or High
Free T4 by equilibrium dialysis (the active portion of thyroxine in the body)Usually Low
Anti-thyroid antibodies (presence indicates active autoimmune disease)Normal or High

Anti-thyroid antibodies can show up before the hormones test low and may alert you to watch closely for developing hypothyroidism.

Even with all of these tests, the diagnosis may not be completely clear. Sometimes, the best you can do is a trial with treatment and then evaluate the response.

The standard treatment for dog hypothyroidism is synthetic thyroid hormone given orally once or twice a day for life. The most common medication used in dogs is levothyroxine sodium, one popular brand name is Thyro Tabs. 

Desiccated thyroid supplements like Armour Thyroid can also work for some dogs. These human thyroid supplements are often quite a bit more expensive than Thyro Tabs. And it may be difficult to determine the right dose for a dog.

Truly hypothyroid dogs will have a remarkable improvement in symptoms within four to eight weeks after starting thyroid hormone supplements.

Cost of Hypothyroid Testing & Treatment for Dogs

The cost to test a dog for hypothyroidism varies by region and clinic. Currently, in a large U.S. city, the cost is about $300-400. Periodic monitoring tests will cost less, around $100-150. Additional costs include exam fees and medication.

Medication costs will depend on your dog’s size plus the amount and frequency of medication required. In general, the cost of thyroid medication for dogs is inexpensive. You may spend around $15-20 per month on medication (Thyro Tabs is a common brand) for a 50-pound dog.

dog under a blanket - dog hypothyroidism anxiety
My dog before her diagnosis.

My Dog’s Low Thyroid Experience

I adopted two mixed-breed puppies from the same litter in 2008. They look like German Shepherd mixes and a genetic breed test reported the same thing. 

Both pups had extreme shyness and anxiety from the day I adopted them. They were shy at home but when it came to new people and places, their reactions were extreme. One would bark non-stop and the other became very sleepy and tried to hide. 

I worked with them as they grew up and some of the behaviors improved. I had them both taking anti-anxiety medication for a while and it helped them quite a bit. It allowed them to calm down enough to benefit from the desensitization and counter-conditioning training I was doing with them. 

Then when they were about four years old, one of the pups started having some new and unusual symptoms. At first, I thought these were an extension of her anxiety, but before long it was clear something else was going on. Here’s an outline of my dog’s case:

Physical Symptoms

  • Cold intolerance, cool ears, cool feet
  • Lethargy & reluctance to go for walks
  • Weight gain without diet change
  • Rough looking coat
  • Hair loss on lower chest and sides of the belly
  • Very dry, flakey skin and inflamed elbow calluses

Behavioral Symptoms

Although this dog had always been anxious, now her anxiety seemed much worse. She would stay behind the bed or in the bathroom most of the day. 

She had previously loved going for walks and now she planted herself down on the sidewalk outside our house, refusing to move and trying to get back to the house. She also stopped playing with her brother.

First Round of Blood Tests

I did not suspect hypothyroidism as a cause of my dog’s symptoms but ran a routine blood panel since she was acting so strangely. The first test showed a low T4 level, but that’s not uncommon in dogs suffering from any disease so I didn’t think much of it. 

Natural Treatment Trial

I decided to try giving my dog natural supplements for “thyroid support” first. Among the things I tried were a Chinese herbal combination for hypothyroidism, a nutritional thyroid supplement for dogs from Standard Process and various homeopathic remedies. 

Her physical and behavioral symptoms did not improve after several months of natural treatment. In fact, the symptoms got worse and she seemed to be having muscle or back pain in addition to everything else. 

black dog with hypothyroid skin problems
Skin problems and hair loss before hypothyroid diagnosis and treatment.

Second Round of Testing

I finally ran her blood tests again, this time with a full thyroid panel included. 

My dog had a classic picture of hypothyroidism on her blood panel:

  • Slightly low total T4
  • Low free T4
  • High thyroid stimulating hormone (TSH)
  • High anti-thyroid antibodies

Add to that the weight gain, lethargy, hair loss, dry skin and the fact that she is likely a breed that tends to have thyroid problems… I diagnosed her with hypothyroidism.

dog's coat with thyroid hormone medication
Shiny coat and more energy a couple months after starting levothyroxine.

Response to Thyroid Medication

I started my dog on a standard dose of l-thyroxine tablets twice a day. And although we tell pet owners improvement in symptoms happens within a few weeks, I could see a slight positive change after only four or five days on the medication. 

Her energy level improved first and she no longer hid all day. She started playing with her brother more and was willing to go on walks without a big fuss. 

After about a month, her rough hair coat fell out as new, shiny black hair grew in. And she effortlessly lost the ten pounds she had gained before treatment.

Thyroid Medication Effects on Anxious Behavior

My dog’s anxious behavior did not disappear with the treatment of her hypothyroidism. Her overall behavior improved, but that was mostly because her extreme lethargy went away. 

She continued to have noise phobias and fear of new people. As she got older and we continued training, those problems improved.


Hypothyroidism is a hereditary disease that is relatively common in dogs. Making a diagnosis requires testing for multiple thyroid hormone levels.

Synthetic thyroid hormone treatment causes a near-miraculous return to health in dogs with hypothyroidism. Behavioral problems like anxiety and aggression are unlikely to improve even when optimal thyroid levels are achieved and can be addressed as a separate issues.

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  1. Bell, J. S. (2003). Hereditary hypothyroidism: understanding the disease process. In Tufts’ Canine and Feline Breeding and Genetics Conference.
  2. Dodman, N. H., Aronson, L., Cottam, N., & Dodds, J. W. (2013). The effect of thyroid replacement in dogs with suboptimal thyroid function on owner-directed aggression: A randomized, double-blind, placebo-controlled clinical trial. Journal of Veterinary Behavior, 8(4), 225-230.
  3. Hrovat, A., De Keuster, T., Kooistra, H. S., Duchateau, L., Oyama, M. A., Peremans, K., & Daminet, S. (2019). Behavior in dogs with spontaneous hypothyroidism during treatment with levothyroxine. Journal of veterinary internal medicine, 33(1), 64-71.
  4. Radosta, L. A., Shofer, F. S., & Reisner, I. R. (2012). Comparison of thyroid analytes in dogs aggressive to familiar people and in non-aggressive dogs. The Veterinary Journal, 192(3), 472-475.