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Hyperthyroidism in Dogs - Symptoms, Treatment & Prognosis

While more common in cats, hyperthyroidism can be a serious health problem for our canine family members too. Here, you will find information on how to spot the signs of hyperthyroidism in dogs, diagnosis and treatment options.

What is the thyroid's job?

Your dog's thyroid is responsible for producing a hormone called thyroxine (T4), as well as a host of other important hormones. Thyroid hormones play a key role in the regulation of your pup's metabolism and can cause serious health issues when the levels of these hormones are either too high or too low. If your pup's thyroid is producing too much hormone, they will be diagnosed with hyperthyroidism. 

What causes hyperthyroidism in dogs?

While becoming increasingly common in cats, hyperthyroidism is still relatively rare in dogs. When dogs do develop this condition it is a very serious health concern. Hyperthyroidism in dogs is typically caused by thyroid carcinoma (cancer). In the majority of cases, thyroid carcinoma in dogs is malignant and can grow rapidly.

What are the symptoms of hyperthyroidism in dogs?

The high levels of thyroid hormones caused by your pet's overactive thyroid lead to a dangerous increase in their body's metabolic rate. Many dogs will show no symptoms in the early stages of the disease, or perhaps just a lump on the underside of their neck. When they do appear, symptoms of hyperthyroidism in dogs can include:

  • Weight loss
  • Gagging
  • Increased appetite
  • Increased urination
  • Vomiting
  • Increased amount of stool
  • Rapid heart rate
  • Enlarged heart
  • Facial swelling
  • Poor sleep
  • Hyper-excitability
  • Difficulties swallowing
  • Increased thirst
  • Enlargement of thyroid gland
  • Diarrhea
  • Congestive heart failure
  • Heart murmurs
  • Shortness of breath
  • Change in bark
  • Short temper

How is hyperthyroidism diagnosed?

Diagnostic bloodwork analyzing thyroid hormone levels is the primary way this condition is diagnosed in dogs, however, your vet may be able to feel a thyroid mass or note an increased heart rate,  by conducting a simple physical examination of your pup.

What is the treatment for hyperthyroidism in dogs?

When it comes to hyperthyroidism in dogs, treatment may include surgery, chemotherapy, radiation therapy, and/or iodine therapy depending on the stage of the thyroid cancer, tumor size, and the extent to which nearby tissue is affected. Surgery to remove the thyroid tumor typically has the best outcome provided that the mass is freely movable, less than 4cm in size, and has not yet spread to other parts of your pet's body.

If your pup's thyroid carcinoma is left untreated the tumor is likely to grow very quickly and spread to other parts of your pet's body.

What will happen if my dog's hyperthyroidism is left untreated?

Because thyroid hormones play a key role in many functions throughout the body, leaving hyperthyroidism untreated could lead to heart and kidney problems, decreased immune function, neuromuscular issues and more. 

Can hyperthyroidism in dogs cause aggression? 

An excess of thyroid hormones in your dog's system can lead to edginess, anxiety, tension, poor sleep and mood swings. Subsequently, these issues could lead your otherwise friendly pooch to become easily irritated and aggressive towards people and other dogs. 

What is the prognosis for dogs with hyperthyroidism?

When detected and treated early, the prognosis for dogs with thyroid carcinoma is good. With appropriate treatment, many dogs can go on to enjoy a good quality of life and long survival time. 

Note: The advice provided in this post is intended for informational purposes and does not constitute medical advice regarding pets. For an accurate diagnosis of your pet's condition, please make an appointment with your vet.

Hyperthyroidism symptoms in dogs should be investigated as early as possible. If your dog is displaying any of the symptoms listed above, contact Stoney Creek Veterinary Hospital right away to book an examination for your cherished pup. 

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Stoney Creek Veterinary Hospital is accepting new patients! Our experienced vets are passionate about the health of companion animals in Morton and surrounding areas. Get in touch today to book your pet's first appointment.

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