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Hyperthyroidism in Dogs: Causes, Symptoms, & Treatment

Hyperthyroidism is a serious condition in dogs that develops when your pet's thyroid produces too much hormone. Today, our San Diego vets discuss the causes, signs, and treatment of hyperthyroidism in dogs.

Canine Hyperthyroidism

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.

Causes of 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.

Signs 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 symptoms are evident they can include:

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

Hyperthyroidism Diagnosis

Diagnostic bloodwork that analyzes thyroid hormone levels is the primary way that 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.

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.

The Prognosis for Dogs With Hyperthyroidism

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

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.

Is your dog showing signs of hyperthyroidism? Contact our San Diego vets to have your pup diagnosed and treated.

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