Hyperthyroidism in Dogs - Signs & Symptoms

Hyperthyroidism is a serious condition in dogs that occurs when the thyroid produces an excess of hormones. In this post, our Brooklyn veterinarians will explain the causes of hyperthyroidism in dogs and the available treatments.

What does the thyroid do?

The thyroid gland in your dog is in charge of producing thyroxine (T4) and a variety of other important hormones. Thyroid hormones play an important role in regulating your pup's metabolism and can cause serious health problems if their levels are too high or too low. 

What is the difference between hypothyroidism and hyperthyroidism in dogs?

Hyperthyroidism and hypothyroidism are similar in that they are both related to the thyroid's function, but they are two entirely different conditions. Hyperthyroidism occurs when the body's metabolism is elevated due to increased thyroid hormone levels. Hypothyroidism occurs when the levels are decreased and the metabolism slows down.

What is the cause of hyperthyroidism in dogs?

While becoming increasingly common in cats, hyperthyroidism is still relatively rare in dogs. When dogs develop this condition, it becomes 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 & Symptoms of Hyperthyroidism in Dogs

The high levels of thyroid hormones caused by your pet's overactive thyroid leads 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. The hyperthyroid symptoms in dogs can include:

How is hyperthyroidism diagnosed?

The primary way this condition is diagnosed in dogs is through diagnostic bloodwork that analyzes thyroid hormone levels; however, your vet may feel a thyroid mass or notice an increased heart rate by performing a simple physical examination on your pup.

What is the treatment for hyperthyroidism in dogs?

Depending on the stage of the thyroid cancer, tumor size, and the extent to which nearby tissue is affected, treatment for hyperthyroidism in dogs may include surgery, chemotherapy, radiation therapy, or iodine therapy. If the mass is freely movable, less than 4cm in size, and has not spread to other parts of your pet's body, surgery to remove the thyroid tumor is usually the best option.

What happens if hyperthyroidism is left untreated in dogs?

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.

Can hyperthyroidism in dogs cause aggression?

While some dogs may exhibit increased aggression with hyperthyroidism, this behavior most commonly occurs with hypothyroidism (decreased thyroid function).

What is the prognosis for dogs with hyperthyroidism?

Thyroid carcinoma in dogs has a good prognosis when detected and treated early. With proper treatment, many dogs can enjoy a good quality of life and a 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.

If you suspect hyperthyroidism in your dog and the symptoms listed above are present, contact the Brooklyn veterinarians at one of our two convenient locations to schedule an exam.