Hyperthyroidism in Dogs: Signs Your Dog‘s Thyroid May Be Overactive
Hi there, dog lovers! As a veterinarian, I know how much you care about keeping your furry friend healthy and happy. That‘s why I want to talk to you today about an important topic – hyperthyroidism in dogs.
What exactly is hyperthyroidism? In simple terms, it means your dog‘s thyroid gland is producing too much thyroid hormone. This tiny gland in the neck usually regulates your pup‘s metabolism. But when it becomes overactive, it can speed up many of your dog‘s body functions to an unhealthy degree.
Now, you may have heard about hyperthyroidism being common in cats. And that‘s true – feline friends frequently develop this hormonal disorder, especially in their older years. But in dogs? It‘s actually quite rare. Only about 1-2% of dogs will ever be diagnosed with an overactive thyroid.
However, that doesn‘t mean you can ignore the possibility entirely. While uncommon, canine hyperthyroidism is a serious medical issue that requires prompt treatment. Left untreated, excess thyroid hormones can wreak havoc on your dog‘s body, potentially leading to heart problems, high blood pressure, and other complications.
So how can you tell if your pup‘s thyroid is in overdrive? Let‘s dive into some of the telltale signs and symptoms to watch for.
5 Signs Your Dog May Have an Overactive Thyroid
- Unexplained weight loss despite a normal or increased appetite
One of the hallmark signs of hyperthyroidism is sudden, unexplained weight loss. You may notice your once plump pup is looking a little slimmer lately, even though their appetite hasn‘t changed – or has even increased.
That‘s because the excess thyroid hormones are basically sending your dog‘s metabolism into hyperdrive. They‘re burning calories at an abnormally high rate, so no matter how much they eat, the number on the scale keeps dropping.
If you can easily feel your dog‘s ribs or see their hip bones jutting out, it‘s time to schedule a check-up. While there are other potential causes of weight loss to rule out, hyperthyroidism should be on the list of suspects, especially in a middle-aged to older dog.
- Increased thirst and urination (polydipsia and polyuria)
Another common clue that points to an overactive thyroid is changes in your dog‘s drinking and bathroom habits. Hyperthyroid dogs tend to drink excessively because their body is working overtime and needs more water to fuel those revved-up systems. Veterinarians call this polydipsia.
More water intake naturally means more potty trips too. If your usually housetrained pup starts having accidents or asking to go out constantly, overproduction of thyroid hormones may be to blame. We refer to this increased urination as polyuria.
Of course, excessive thirst and urination can also be signs of other health problems like kidney disease or diabetes. So don‘t delay in getting your dog checked out if you notice these changes. Your vet can run tests to get to the bottom of what‘s causing your dog‘s unquenchable thirst.
- Restlessness, nervousness, and hyperactivity
Imagine feeling jittery, on-edge, and unable to relax. That‘s how a dog with hyperthyroidism might experience the world, thanks to their turbocharged metabolism.
You may notice your normally calm pup seems restless, pacing and having trouble settling down. They might startle more easily at noises or seem nervous in situations that didn‘t bother them before. Some dogs even become uncharacteristically hyperactive, racing around as if they‘re powered by an invisible battery pack.
These behavioral changes can be distressing for both dogs and their humans. If your dog‘s energy level and demeanor seems "off," it‘s worth a discussion with your vet. Getting those overactive thyroid hormones under control can help your dog feel more like their old self again.
- Rapid heartbeat and other cardiovascular signs
Thyroid hormones don‘t just influence metabolism – they also have significant effects on the cardiovascular system. When the thyroid gland is working overtime, it can send the heart into overdrive too.
One sign of this is an abnormally fast resting heart rate, called tachycardia. You might feel your dog‘s heart racing or pounding when they‘re lounging on the couch. Some hyperthyroid dogs also develop a heart murmur – an abnormal whooshing or humming sound a vet can detect with their stethoscope.
In more advanced cases, the heart muscle can thicken and enlarge from being overworked. This puts a dog at risk for developing congestive heart failure. That‘s why it‘s so important to have any heart-related symptoms checked out promptly.
- Poor skin and coat condition
Healthy thyroid function is key for maintaining your dog‘s lustrous coat and supple skin. But when thyroid hormones are out of whack, it can show up as lackluster fur, itchy or flaky skin, and other dermatological woes.
In hyperthyroid dogs, the coat may become dull, dry, and brittle. Some dogs shed excessively or develop bald patches. The skin itself can be red, greasy, and prone to infections. Ears may be especially inflamed and prone to waxy buildup.
While skin and coat issues can have many potential culprits, it‘s important to rule out thyroid disease, especially if you notice other telltale signs too. Getting those hormones balanced can help restore your dog‘s coat to its full glory.
Other signs to watch for
The above represents some of the most common signs of an overactive thyroid in dogs. But there are a few other symptoms that may appear, including:
- Vomiting and/or diarrhea
- Increased panting
- Enlarged thyroid gland (may be felt as a lump on the neck)
- Weakness in rear legs
- Vision changes or eye abnormalities
Of course, many of these signs can also occur with other health conditions. That‘s why it‘s so important to see your vet right away if you notice anything amiss with your dog. They‘ll likely recommend some diagnostic tests to check for hyperthyroidism and other potential problems.
Diagnosing hyperthyroidism in dogs
If your vet suspects your pup‘s thyroid is in overdrive, there are a few key tests they‘ll want to run. The first step is usually a physical exam. Your vet will feel your dog‘s neck area for any signs of an enlarged thyroid gland. They‘ll also listen to the heart and lungs, check for signs of muscle wastage, and look for any skin or eye abnormalities.
From there, blood tests provide the key information needed to diagnose hyperthyroidism. Your vet will order a complete thyroid panel, which measures the levels of several different thyroid hormones circulating in the bloodstream. In a hyperthyroid dog, these levels will be abnormally high.
Your vet may recommend some other tests too, such as:
- A complete blood count to check for anemia or other abnormalities
- Blood chemistry tests to evaluate organ function
- A urinalysis to assess kidney health and check for urinary tract infection
- Chest x-rays to look for heart enlargement or signs of lung disease
- An ultrasound of the thyroid gland to check for tumors
- A special thyroid scan using radioactive iodine to see if the gland is overactive
Determining the underlying cause
Once hyperthyroidism is confirmed, the next step is figuring out why those thyroid hormones are elevated. Unlike in cats, where a benign growth of the thyroid gland is the most common culprit, dogs usually develop hyperthyroidism due to thyroid cancer.
In fact, thyroid carcinoma accounts for about 90% of hyperthyroidism cases in dogs. These tumors are typically aggressive and can spread quickly to other parts of the body, especially the lungs and lymph nodes.
Less commonly, a benign tumor called an adenoma can also cause the thyroid to produce excess hormones. And in rare cases, hyperthyroidism develops if a dog is given too high a dose of synthetic thyroid hormone as treatment for an underactive thyroid (hypothyroidism). Finally, diets unnaturally high in iodine, such as those containing kelp, can sometimes trigger thyroid problems.
Your vet may need to do some additional diagnostic tests, like a biopsy of the thyroid mass, to determine the underlying cause. This information is important for developing an appropriate treatment plan.
Treatment options for canine hyperthyroidism
Speaking of treatment, what can be done to help a hyperthyroid dog? The approach depends on the specific case, including the size and spread of a thyroid tumor, as well as the dog‘s overall health.
Here are some of the main treatment options veterinarians consider:
-
Surgical removal of the thyroid tumor. If the tumor is relatively small and localized to the thyroid gland, surgical excision may be curative. The surgeon will remove as much abnormal thyroid tissue as possible while trying to preserve the parathyroid glands (which sit behind the thyroid and help regulate calcium).
-
Radioactive iodine therapy. For dogs who aren‘t good candidates for surgery, this treatment can be an effective alternative. The dog receives an injection of radioactive iodine, which is taken up by the overactive thyroid tissue and destroys it. This is the most common treatment for hyperthyroidism in cats but is less frequently used in dogs.
-
Anti-thyroid medication. Oral drugs like methimazole can help lower thyroid hormone production. They don‘t treat the underlying tumor but can be a good option for dogs who can‘t undergo other therapies. Lifelong medication is typically required.
-
Chemotherapy and radiation. If a thyroid tumor has spread to other parts of the body, chemotherapy drugs may help slow the progression. Radiation directed at the tumor site can sometimes shrink it and alleviate symptoms as well.
-
Dietary changes. If the hyperthyroidism is determined to be caused by too much iodine in the diet, switching to a food with controlled mineral levels is important. Your vet can recommend an appropriate dog food.
-
Supportive care. Depending on how the excess thyroid hormones have affected your dog‘s body, additional treatments may be needed. For example, dogs with heart abnormalities may require cardiac medications. Skin problems may improve with medicated shampoos or supplements. Your vet can tailor a treatment plan to your dog‘s specific needs.
Prognosis for dogs with hyperthyroidism
I know learning your dog has an overactive thyroid can feel overwhelming and scary. And it‘s true that the prognosis for these pups is often guarded, especially if a cancerous tumor is to blame.
The median survival time for dogs with a malignant thyroid carcinoma is reported to be 1-3 years with appropriate treatment. But there are many individual factors that influence a dog‘s outcome. The size and invasiveness of the tumor, as well as whether it has spread to other parts of the body, play a big role. Dogs who are able to have surgical removal of a localized tumor tend to fare better than those with metastatic disease.
It‘s also important to remember that these survival statistics are just averages. I‘ve known some dogs who have defied the odds and thrived for many happy years after a hyperthyroidism diagnosis. Early detection and prompt treatment can make a big difference in a dog‘s quality and quantity of life.
If your dog‘s hyperthyroidism is caused by something reversible, like an iodine-heavy diet or an overshot of thyroid medication, the prognosis is usually excellent. Once the underlying issue is corrected, thyroid function should return to normal.
No matter the cause, dogs with hyperthyroidism require regular check-ups and lab work to monitor their condition. Your vet will likely recommend blood tests every few months to check thyroid hormone levels and make sure the treatment plan is working. Over time, medication doses may need to be adjusted or other therapies added to keep your pup feeling their best.
The bottom line
Hyperthyroidism may not be as common in dogs as it is in cats, but it‘s still a condition every dog owner should be aware of. Knowing the signs, like unexplained weight loss, increased thirst, restlessness, and heart abnormalities, can help you detect a potential thyroid problem early. And when it comes to any health issue, prompt diagnosis and treatment is always the goal.
If you notice any of the symptoms we‘ve discussed, don‘t hesitate to reach out to your veterinarian. They can run the necessary tests to check your dog‘s thyroid function and develop a tailored treatment plan. With the right veterinary care and a little luck, many dogs with hyperthyroidism can go on to enjoy a good quality of life.
Wishing you and your furry friend all the best,
Dr. [Name]
