Hyperthyroidism In Dogs - Causes, Symptoms, and Treatments for Hyperthyroidism

Hyperthyroidism is a fairly uncommon health condition that many pet owners are unaware of. This is because the symptoms often go undetected until the disease is in its later stages.

Hyperthyroidism in dogs is a relatively rare condition but increasingly common in cats. It is related to thyroid glands and can be life-threatening if not treated properly and in time.

This article will explore what Hyperthyroidism is, the symptoms to look out for and how it is treated.

What Is Hyperthyroidism In Dogs?

A collar around a dog's neck in a post about Hyperthyroidism In Dogs

Hyperthyroidism in dogs is a disease that occurs when your pet's thyroid releases excessive hormones.

Your pet's thyroid gland is located in the neck and produces a hormone called thyroxine. The thyroxine hormone is in charge of regulating the body's metabolism. When there is an overproduction of thyroxine, it results in an accelerated metabolism which can lead to a number of health problems.

Hyperthyroidism is rare in dogs but can be life-threatening if left untreated. It is most often seen in middle-aged to older pets and is common in medium to large breed dogs, as the FDA states in Hypothyroidism in Dogs—There are FDA-Approved Drugs to Treat It.

Note that Hypothyroidism and Hyperthyroidism are two different medical conditions, but they are both related, which we will explain below.

What Causes Hyperthyroidism In A Dog?

There are only a few causes of Hyperthyroidism in dogs, but the most common is a benign tumor on the thyroid gland. This type of tumor, called a thyroid carcinoma, or thyroid tumor is, often become cancerous and malignant when left untreated.

Another common cause of Hyperthyroidism is medication taken for Hypothyroidism. Hypothyroidism is a condition where the thyroid gland doesn't produce enough thyroxine. A synthetic form of thyroxine is given in pill form To compensate for this, which can sometimes lead to Hyperthyroidism.

Another possible cause of Hyperthyroidism is a raw food diet. Certain raw foods are naturally higher in thyroid hormones which can cause an overproduction of thyroxine in thyroid glands if not fed in moderation. As explained in Pubmed, this condition is known as Dietary Hyperthyroidism in dogs and is curable.

While Hypothyroidism and raw meat diet can cause Hyperthyroidism, the main cause is still an underlying tumor in the thyroid gland. This tumor often becomes thyroid cancer and can spread to other organs in the body, which then can be life-threatening.

What Dog Breeds Are Prone To Hyperthyroidism?

A happy Labrador in post about Hyperthyroidism In Dogs

According to an article in the American Kennel Club about Thyroid Disease in Dogs, medium-to-large breeds are more likely to develop canine Hyperthyroidism than toy and miniature breeds.

Some common dog breeds that are prone to Hyperthyroidism include;

  • Airedale Terrier
  • Cocker Spaniel
  • Dachshund
  • Doberman Pinscher
  • Miniature Schnauzer
  • Golden Retriever
  • Irish Setter

Hyperthyroidism In Dogs Symptoms

common signs and symptoms of Hyperthyroidism In Dogs

Hyperthyroidism is often left unchecked since the symptoms are not always apparent in the early stages.

Furthermore, the symptoms of Hyperthyroidism are often mistaken for other health conditions such as; allergies, heart disease, or even old age.

However, a few common symptoms to look out for may indicate your pet has this condition. These symptoms include;

  • Weight loss (even with no change of diet or appetite)
  • Constant hunger (increased appetite)
  • Increased thirst
  • Increased urination
  • Enlargement of the thyroid gland
  • Panting (rapid breathing)
  • Restlessness
  • Hyperactivity
  • Diarrhea (or increased amount of stools)
  • Vomiting
  • Muscle weakness
  • Shortness of breath (Dyspnea)

Some clinical signs include;

  • Congestive heart failure
  • Tachycardia (fast heart rate)
  • Cardiomegaly (enlarged heart)
  • Heart murmurs

If your pet is displaying any of these signs and symptoms, it's important to take them to the veterinary hospital today for a checkup as soon as possible. The sooner the condition is diagnosed, the better the chances are for a successful treatment.

How is Hyperthyroidism Diagnosed?

To diagnose Hyperthyroidism, your vet will likely perform a physical examination and take a complete medical history. They will also run some tests, including;

  • A complete blood count (CBC) can help rule out other conditions with similar symptoms.
  • A biochemical profile to evaluate your pet's organ function.
  • Urinalysis to check for dehydration or other health conditions.
  • Thyroid hormone levels – The most important test to diagnose Hyperthyroidism is a thyroid hormone level test, also called a T4 test. This measures the amount of thyroxine (the active form of thyroid hormone) in the blood.

If your pet tests positive for Hyperthyroidism, your vet will likely recommend a course of treatment.

Is Hyperthyroidism In Dogs Curable?

If your pet has thyroid issues because of medication or its diet, the condition is curable by simply discontinuing the medication or switching to a more balanced diet.

However, if your pet has an underlying tumor in the thyroid gland, the condition is often not curable. However, you can manage the symptoms and extend your pet's life with proper treatment.

Hyperthyroidism Dog Treatment

thyroid tumor treatment

Treatment options can vary depending on the underlying cause of the condition.

Dietary Hyperthyroidism Treatment

If your pet has dietary Hyperthyroidism, the treatment is simply to switch to a more balanced diet. Your vet may recommend a healthy diet that is lower in thyroid hormones.

In dietary Hyperthyroidism, as a study about Dietary Hyperthyroidism in dogs in Pubmed suggests,

nutritional management is all that is needed to keep the condition under control and your pet healthy.

Medication-Induced Hyperthyroidism Treatment

If your pet has medication-induced Hyperthyroidism, the treatment is simply to discontinue the medication causing the problem. In most cases, the thyroid levels will return to normal within a few weeks after stopping the medication.

However, if your pet has been taking the medication for an extended period of time, it may take several months for the thyroid levels to return to normal.

Thyroid Carcinoma Hyperthyroidism Treatment

If your pet has an underlying tumor, the appropriate treatment options will depend on the size and location of the tumor.

If the tumor is small and localized, your vet may recommend thyroid surgery to remove the tumor. However, if the tumor is large or has spread to other parts of the body, surgery may not be an option.

In these cases, your vet may recommend one of the following treatment options;

Radioactive iodine therapy – This treatment involves giving your pet a small amount of radioactive iodine. Iodine enters the thyroid cells and kills them. This treatment is often the most effective option, but it can be expensive and may not be available in all areas.

Radiation therapy – This treatment involves exposing the tumor to high-energy waves that destroy the cancer cells. This treatment is often less effective than iodine therapy, but it is less expensive and may be more available.

Chemotherapy – This treatment uses oral medication to kill the cancer cells. This treatment is often less effective than iodine therapy or radiation therapy, but it is less expensive and may be more available.

Prednisone – This is a steroid medication that can help to reduce the symptoms of Hyperthyroidism. It is not a cure, but it can help to make your pet more comfortable. Alternatively, you can supplement your pet's diet with The Best Reviewed Nutramax Dasuquin to help with the treatments.

According to a review about Canine thyroid carcinoma in Pubmed, thyroidectomy (thyroid surgery) is advised in the case of unilateral, movable thyroid carcinomas. Dogs with invasive or bilateral thyroid carcinomas should receive radiation therapy or radioactive iodine therapy. However, to decide on the most effective treatment, your vet will need to run some tests and get an accurate diagnosis of the condition.

Tip: Often, dogs with Hyperthyroidism suffer greatly in the late stages. If you have such a pet, we recommend buying one of The Best Reviewed Pet Strollers so that you can carry him anywhere safely.

What Is The Prognosis For Dogs With Hyperthyroidism?

The prognosis for dogs with Hyperthyroidism depends on the condition's underlying cause.

If your pet has dietary Hyperthyroidism, the prognosis is excellent, and the condition is easily controlled with a balanced diet.

If your pet has medication-induced Hyperthyroidism, the prognosis is also excellent, and you can control the condition by discontinuing the medication.

If your pet has thyroid carcinoma, the prognosis depends on the size and location of the tumor.

If the tumor is small and localized, the prognosis is good. However, the prognosis is poor if the tumor is large or has spread to other parts of the body.

With proper treatment, most dogs with Hyperthyroidism can live a normal life for at least 1 to 3 years. However, keeping a close eye on your pet and taking them to the vet for regular checkups is important.

Preventing Hyperthyroidism in dogs

There is no sure way to prevent Hyperthyroidism in dogs. However, you can help to reduce your dog's risk by feeding them a balanced diet and avoiding giving them any medication that a vet does not prescribe. You should also take your dog to the vet on a regular basis so that any potential concerns can be identified early.

It is hard and time-consuming to prepare healthy food for your dog. Therefore we recommend feeding your pet with prepared food like These Pet Food Express Nulo and Pet Food Express Non-Rawhide Products.


Hyperthyroidism is a serious condition that can be fatal if left untreated. If you think that your dog may have Hyperthyroidism, it is important to take them to the vet as soon as possible. With proper treatment, most dogs with Hyperthyroidism can live a normal life for at least 1 to 3 years.


How Much Does It Cost To Test A Dog's Thyroid?

The cost of testing a dog's thyroid depends on the type of test that is performed. A basic thyroid panel, which includes a T4 and TSH test, typically costs between $50 and $100. A more comprehensive thyroid panel, which may also include a T3 test, can cost between $100 and $200.

Can Thyroid Medicine Hurt A Dog?

Thyroid medicine can hurt a dog if it is not given at the correct dosage. Overdosing a dog on thyroid medication can lead to serious side effects, such as heart problems, muscle tremors, nervousness, panting, and aggression. If you think your dog has been given too much thyroid medication, it is necessary to take them to the vet as soon as possible.

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