Thyroid Health in Dogs — The Overlooked Wellness Factor
When it comes to your dog's health, you probably think first about diet, exercise, or keeping up with vaccines. But there's another piece of the puzzle that often goes overlooked — the thyroid gland.
Reviewed by Dr. Arielle Walton
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STORY AT-A-GLANCE
- The thyroid gland may be small, but it controls metabolism, energy, growth, skin, heart, and nervous system function — when it falters, your dog's whole body feels the effects
- Hypothyroidism is the most common thyroid disorder in dogs, yet signs like weight gain, lethargy, or coat problems are often mistaken for aging or other illnesses
- A veterinary study found that up to half of dogs treated for hypothyroidism may not truly have it, highlighting the risks of misdiagnosis and unnecessary lifelong medication
- Proper diagnosis requires more than a single T4 test — ask for a full thyroid panel, antibody tests, and careful review of symptoms before starting treatment
- Beyond medication, you can support thyroid health naturally with balanced nutrition, reduced toxin exposure, stress management, and by using harnesses instead of collars to protect the neck
Despite being small, the thyroid has a massive influence on your dog's overall well-being. This tiny, butterfly-shaped lobe in the neck produces hormones that affect metabolism, growth, energy levels, and even how your dog's skin, heart, and nervous system function.1,2 When the thyroid doesn't work properly, your dog's entire body feels the consequences.
Unfortunately, thyroid problems in dogs are both common and often missed. Studies show that veterinarians frequently misdiagnose dogs, sometimes treating them for hypothyroidism (low thyroid function) when they don’t actually have it,3 or living with the disease undetected for years. Because symptoms can mimic normal aging or other illnesses, thyroid health is often left out of the conversation until problems become severe.
The Small but Mighty Thyroid Gland
The thyroid gland is part of your dog's endocrine system, which is a network of glands that produce hormones to control body processes. Located in the neck near the voice box, the thyroid absorbs iodine from food and turns it into two key hormones, which are:
- Thyroxine (T4) which is mostly inactive until the body converts it into T3.
- Triiodothyronine (T3) is the active hormone that fuels the body's metabolism.
These hormones regulate how your dog burns energy, keeps warm, grows hair, repairs skin, and keeps the brain and heart functioning smoothly. But when thyroid hormone levels drop, nearly every system slows down. Your dog might put on weight without eating more, become sluggish, or develop skin and coat issues that don't improve with grooming or diet changes.4
Understanding Hypothyroidism
Hypothyroidism is a condition wherein the thyroid doesn't produce enough hormones, and is the most common thyroid disorder in dogs. It usually develops slowly, and symptoms creep in so gradually that owners may mistake them for "normal aging." There are different types of hypothyroidism, namely:5
- Primary hypothyroidism — This form occurs most often, usually because the immune system attacks the thyroid (autoimmune thyroiditis) or because the thyroid tissue shrinks and fat replaces it (idiopathic atrophy). Dogs typically don't show clinical signs until they have lost about 75% of their thyroid tissue.
- Secondary hypothyroidism — A much less common disorder, this is caused by problems in the pituitary gland, which is the "master gland" in the brain that tells the thyroid when to work.
- Congenital hypothyroidism — It's a rare, inherited condition seen in puppies. It results from genetic defects or iodine deficiency at birth.
Signs and Symptoms You Shouldn't Ignore
Because thyroid hormones affect nearly every organ system, symptoms of hypothyroidism vary widely. Many are subtle at first. If your dog has more than one of the following issues, it's worth asking your veterinarian about thyroid testing:
- Low energy and exercise intolerance (especially noticeable in once-active dogs)
- Weight gain
- Skin and coat problems (Dull coat, thinning hair, bald spots on the tail or trunk, dry or flaky skin, or frequent skin infections)
- Sensitivity to cold
- Behavioral changes (Depression, anxiety, or irritability)
- Neurological issues like seizures, facial paralysis, or loss of coordination
- Heart-related conditions
- Vomiting, constipation, or diarrhea
- A "tragic face" appearance — A puffy skin on the face leading to drooping eyelids or a sad expression
Why Misdiagnosis Happens So Often
A major study of 102 dogs treated for hypothyroidism in everyday veterinary practices found something alarming — Up to half of them may not have been truly hypothyroid. The study, published in the Journal of Veterinary Medicine, pointed to a few possible reasons:6
- Nonspecific symptoms — Dozens of other illnesses can cause signs like lethargy, skin issues, or weight gain.
- Routine blood panels — Some labs automatically include thyroid tests in general wellness panels. This means dogs without actual symptoms may still be labeled as having 'low thyroid,' even when their thyroid is normal.
- Other illnesses — Dogs with chronic disease may show low thyroid hormone levels as part of the "euthyroid sick syndrome,"7 a temporary state where the body lowers metabolism to cope with illness.
- Medication interference — Drugs like steroids, anti-seizure medications, and even some painkillers can throw off thyroid test results.
- Testing limits — Basic thyroid tests (like total T4 alone) aren't always reliable. A complete thyroid panel is much more accurate.
According to the study, the risk of misdiagnosis is twofold. Dogs who don't need thyroid medication end up on lifelong drugs unnecessarily, while dogs who truly have hypothyroidism may go untreated if signs are dismissed or masked by other conditions.
The Risks of Overtreatment (and Why Getting an Accurate Diagnosis Is Necessary)
Levothyroxine, the standard medication for hypothyroidism, is often considered "safe." But overprescribing or unnecessary treatment can have consequences:8
- Overmedication can mimic hyperthyroidism, leading to restlessness, weight loss, or heart strain.
- Long-term unnecessary supplementation may cause thyroid atrophy.
- Dogs on treatment need to undergo lifelong blood monitoring, which is stressful for them and costly for you.
Experts stress the importance of testing only when there's a strong suspicion of thyroid disease and using a complete diagnostic approach before prescribing medication. If you suspect hypothyroidism, don't settle for a single T4 test. Ask your vet about:9
- Full thyroid panel, which includes Total T4, Free T4, T3, Free T3, and TSH.
- Thyroid antibody tests (TgAA) — These help detect autoimmune thyroiditis before hormone levels drop.
- Imaging (ultrasound or scintigraphy) — This will help assess the thyroid's size and structure to see if there are any abnormalities. Rarely used, but helpful in confusing cases.
- Therapeutic trial of hormone supplementation — Sometimes vets prescribe thyroid medication and monitor for improvement to confirm the diagnosis.
Pro tip — Never test thyroid function while your dog is sick with another condition. Illness alone can cause temporarily low thyroid hormone levels (euthyroid sick syndrome), which can look like hypothyroidism but isn't.
Supporting Your Dog's Thyroid Health Naturally
While medication is necessary for dogs with diagnosed hypothyroidism, there are ways you can support your dog's thyroid health and possibly reduce risks. One of the first strategies is to optimize your dog's nutrition with foods and supplements.10,11
- Iodine sources like seaweed, kelp, and fish provide the raw materials for thyroid hormone production.
- Selenium-rich foods like eggs and fish help convert T4 into active T3.
- Omega-3 fatty acids reduce inflammation and support overall health.
- Herbs like ashwagandha may help regulate stress and support thyroid balance.
- Probiotics promote a healthy gut microbiome to support immune balance and hormone regulation.
However, remember that too much iodine can suppress thyroid function rather than support it. Always work with your vet before supplementing and get assistance to help put together a thyroid health-supportive diet. In addition, follow these strategies:
- Reduce environmental toxins — Limit exposure to pesticides, lawn chemicals, and household cleaners. The toxins act as endocrine disruptors, interfering with thyroid hormone production. Avoid unnecessary flea/tick chemicals unless absolutely needed, and store pet food in safe containers to reduce contamination.
- Protect your dog's neck — Repeated trauma to the thyroid area can damage the gland. Use a harness instead of a neck collar to prevent pressure or injury to this sensitive area.
- Avoid overvaccination — It may contribute to autoimmune thyroiditis in genetically susceptible dogs. Talk to your vet about tailored vaccine schedules and titer testing.
- Manage stress — Stress hormones affect the endocrine system. Creating a calm environment and giving your dog regular exercise helps maintain thyroid balance.
Being Proactive Helps Protect Against Thyroid Problems
Even if your dog shows no signs of thyroid issues, proactive care can make a difference. Make sure to bring your dog for annual wellness exams, which include a thyroid check, especially if your dog is middle-aged or older.
Breed awareness is also helpful. If you have a Doberman, Golden Retriever, Irish Setter, Dachshund, Boxer, or Great Dane, keep in mind that these breeds are more prone to hypothyroidism.12
Putting It All Together
Your dog's thyroid is a small gland with a big job. When it falters, your dog's whole body suffers. The good news is that hypothyroidism is treatable and manageable with the proper care. The key is awareness — learn the signs, ask for proper testing, and be cautious about overdiagnosis and unnecessary treatment. Support your dog's thyroid naturally with good nutrition, toxin reduction, and stress management.
By being proactive, you can catch thyroid issues early — or even help prevent them altogether. In doing so, you're not just treating a condition — you're giving your dog the chance at a longer, healthier, and more vibrant life.
