Hypothyroidism in Dogs: Symptoms, Diagnosis & Treatment

May 14, 2022

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Hypothyroidism in Dogs: Symptoms, Diagnosis & Treatment

Dr. Chandrakala, Pet Consultant, Patna

What is hypothyroidism in dogs?

Hypothyroidism is a condition that occurs when your pup’s thyroid isn’t producing enough essential thyroid hormones to properly regulate their metabolism, causing the metabolism to slow.

What is the thyroid gland and what does it do?

The thyroid gland is one of the most important glands in the body. It is located in the neck near the trachea or windpipe and has two lobes, one on each side of the trachea. The thyroid gland is controlled by the pituitary gland, which is located at the base of the brain.

“If the thyroid is overactive (hyperthyroidism), the body’s metabolism is elevated. If it is underactive (hypothyroidism), the metabolism slows down.”

The thyroid gland regulates the body’s metabolic rate. If the thyroid is overactive (hyperthyroidism), the body’s metabolism is elevated. If it is underactive (hypothyroidism), the metabolism slows down.

What causes hypothyroidism?

In dogs, hypothyroidism is usually caused by one of two diseases: lymphocytic thyroiditis or idiopathic thyroid gland atrophy. The former disease is the most common cause of hypothyroidism and is thought to be an immune-mediated disease. This means that the immune system decides that the thyroid is abnormal or foreign and attacks it. It is unclear why this occurs; however, it is a heritable trait meaning that genetics plays a role in this condition. In idiopathic thyroid gland atrophy, normal thyroid tissue is replaced by fat tissue. This condition is also poorly understood.

These two causes of hypothyroidism account for more than 95% of the cases in dogs. The other five percent are due to rare diseases, including cancer of the thyroid gland.

How is it diagnosed?

The most common screening test is a total thyroxin (TT4) level. This is a measurement of the main thyroid hormone in a blood sample. A low level of total thyroxin, along with the presence of clinical signs is suggestive of hypothyroidism. Definitive diagnosis is then made by performing a free T4 by equilibrium dialysis (free T4 by ED) or a thyroid panel that assesses the levels of multiple forms of thyroxin. If this test is low, then your dog has hypothyroidism. Some pets will have a low TT4 and normal free T4 by ED. These dogs do not have hypothyroidism. Additional tests may be necessary based on your pet’s condition. See handout “Thyroid Hormone Testing in Dogs” for more information.

https://www.pashudhanpraharee.com/hypothyroidism-in-dogs-diagnosis-and-treatment/

Thyroid Disease

Hypothyroidism is the natural deficiency of thyroid hormone that regulates your dog’s metabolism. This deficiency is produced by immune-mediated destruction of the thyroid gland by natural atrophy of the gland, by dietary deficiencies, or as a congenital problem. Low thyroid levels can affect all of your dog’s organ systems and if left unattended to, may develop into something really serious. The symptoms of hypothyroidism can vary greatly from dog to dog. There are different forms and reasons for thyroid disease but ultimately it manifests in a slowing of metabolism.

Conversely, hyperthyroidism, commonly found in cats, is metabolism in overdrive, due to the over production of hormones.

The main forms of thyroid disease such as Autoimmune Thyroiditis (Hashimotos), Hypothyroidism (non autoimmune), and Hyperthyroidism (Graves Disease).

Autoimmune Thyroiditis (Hashimotos) is the most common cause of primary hypothyroidism in dogs. The body’s immune system develops antibodies against its own thyroid gland because of an over reactive immune response. Cells as they become attacked and destroyed, leave remaining cells having to work harder, trying to over compensate. Around 95% of hypothyroidism is caused by Autoimmune Thyroiditis and not nutritional deficiency. A blood marker called Canine Thyroglobulin Autoantibody (TgAA), highlights the nature of this thyroiditis. Other, rarer causes of hypothyroidism include cancer and congenital defects.

Hypothyroidism (non-autoimmune), when not caused by autoimmunity, hypothyroidism is due to the under production of the two main hormones, T3 (triiodothyronine) and T4 (thyroxine). This is often caused by nutritional deficiency or genetics and accounts for about 5% of hypothyroid cases. It happens most often in female dogs over 5 years of age, but can affect dogs of any age and sex. This chronic condition typically comes on gradually and can go undetected for a long time.

In both hypothyroidism (non autoimmunity and autoimmunity) there are multi-factorial factors influencing thyroid health.

Hyperthyroidism (Graves Disease) occurs when your dog’s body produces too much of the thyroid hormone, increasing your dog’s metabolic rate to potentially dangerous levels. This disease is rare in dogs and is more commonly seen in cats. When it does affect dogs it tends to be incredibly serious.

Goitre can be a symptom of thyroid function and is the enlargement of this gland. Often caused by possible iodine deficiencies, eating a lot of goitrogenic foods, too much iodine in a diet, and inherited genetic polymorphisms, can affect the synthesis of thyroid hormones. Cancer of the thyroid is very rare but not unheard of.

Certain breeds certainly, genetically fall prey to such issues but not restricted to. Breeds most likely to develop the hypothyroidism are Cocker Spaniels, Miniature Schnauzers, Dachshunds, Golden Retrievers, Doberman Pinschers, Airedale Terriers, and Irish Setters.

There are number of signs and symptoms in Thyroid disease. If any of these arise consistently, you should go to the vets and get it checked out.

Possible signs and symptoms in Hypothyroidism

Aggression
Depression
Constipation/Diarrhoea
Dull and dry coat
Weight gain
Lethargy
Feeing the cold/signs such as dithering
Thickening of the skin
Thinning coat
Itching
Hair loss in patches
Various skin disorders
Anaemia
Muscle weakness
Possible stiffness
Dry cough
Slow heart rate
Development of furrowed head wrinkles

Some dogs also have other abnormalities such as:

thickening of the facial skin so they have a ‘tragic facial expression’
abnormal function of nerves causing non-painful lameness, dragging of feet, lack of coordination, and a head tilt
loss of libido and infertility in intact males
lack of heat periods, infertility, and abortion (miscarriage) in females
fat deposits in the corneas of the eyes
keratoconjunctivitis sicca (KCS) or dry eye due to lack of proper tear production

Unfortunately, the majority of these aren’t necessarily specific to thyroid disease as signs and symptoms can vary from case to case. A visit to the vets as soon as any symptoms arise, is always the best option.

Thyroid function

The thyroid gland is part of the endocrine system, a small butterfly-shaped gland in the neck, just in front of the windpipe (trachea). One of its main functions is to produce hormones that help to regulate the body’s metabolism (the process that turns food into energy). These hormones are called triiodothyronine (T3), thyroxine (T4).

What may cause Thyroid Disease:

Poor Diet; ultra processed food can trigger inflammation and an imbalanced immune system. Diet may not solely be to play in the etiology of this disease, but it certainly plays a huge role. Dry food contains a high amount of starch, imbalanced Omega 6:3 ratios and often inappropriate ingredients that create inflammation and in turn can lead to autoimmunity.

Nutritional Deficiencies; although only 5% of hypothyroidism boils down to nutritional deficiency, it is always advised to have testing done to cover all bases. Common nutrients are B2, B9, B12, Iodine, Zinc, Magnesium and Selenium.

Poor Methylation; leads us on from nutritional deficiencies. Very much like humans, dog’s have to convert folate into methyl folate to allow DNA methylation and synthesis to occur. Poor methylation due to diet and genetics may mean poor bodily function and B9 nutritional deficiency. A good B9 status is highly correlated to a healthy thyroid function.

Food sensitivities and allergies; the intestinal lining can become inflamed after immunological reactions, caused by sensitivities and allergies. This can lead to poor stomach acid, poor gut microbiota, possible SIBO (small intestinal bacterial overgrowth) and leaky gut.

Poor Stomach Acid: the most common instigator of poor absorption among thyroid patients is reduced levels of stomach acid. Stomach acid is necessary for the absorption of both macro and micro-nutrients, digesting protein and killing bad bacteria and yeasts.

Poor Gut Microbiota; the microbiota influences the uptake of iodine, selenium, and iron, and the microbiota may alter the availability of L-thyroxine.

Leaky Gut Syndrome; caused by poor diet, stress, toxins and so much more, an immune response within the gut can cause inflammation and damage to the ‘one cell epithelial’. Human findings have correlated celiac disease/leaky gut with Hypothyroidism

Stress; should never be underestimated in the pathogenisis of thyroid dysfunction. Trying to modulate the stress response is always helpful in any disease state. Stress is an inflammatory process that affects the immune system and can trigger autoimmunity.

Endocrine Disease; the endocrine system is just that, it is a system that works in close synergy for the body to operate effectively. Diabetes mellitus, hyperadrenocorticism (Cushing’s disease) and Liver disease can all be linked to hypothyroidism and hyperthyroidism. I often like to check glucose fasting, liver, kidney and pancreatic enzymes when looking at thyroid issues.

Kidney Disease; in older cats with hyperthyroidism there may also be kidney disease. Chronic kidney disease affects thyroid health by preventing the enzyme deiodinase in converting T4 into active T3.

Liver Disease; the liver metabolises thyroid hormones and regulates their systemic endocrine effects so if function is poor and disease arises, this can impact thyroid function.

Pharmaceuticals; certain pharmaceuticals can down regulate thyroid function such as steroids, certain behaviour medications, NSAIDS,and certain antibiotics.

Vaccinosis; I am so keen on safe vaccinations and adhere and recommend the WSAVA vaccination guidelines (world small animal veterinary association). I promote titer testing as vaccinations yearly and every 3 years, can elicit a deranged immune response, leading to inflammatory conditions such as arthritis, pancreatitis, colitis, addison’s disease, bone marrow failure, encephalitis, and any number of immune diseases like cancer, lymphoma, leukemia, and autoimmunity, in which the body attacks its own cells causing diseases of the pancreas (diabetes) and thyroid (Hashimoto’s type disease).

Veterinary Approach to Thyroid Disease

A variety of blood tests can be used in detecting and diagnosing thyroid disease. The most comprehensive blood tests check the T4, free T4, T3, free T3, TSH, TgAA (autoimmune antibodies) to obtain a clear picture of what is going on.

A low fat or restricted prescription diet is often prescribed to your beloved pet and a few different types of thyroid pharmaceutical drugs such as levothyroxin to help regulate hormone production and control weight gain.

Glucocorticoids and some beta blockers at high doses can also inhibit T4 to T3 production and so may interfere with thyroid function.

Increased hepatic enzymes from certain anti-epileptic medications such as phenobarbital and the antibiotic, rifampicin, may reduce the half-lives of T4 and T3 so may interfere with thyroid function.

Diet for Thyroid disease

The use of an appropriately formulated FRESH diet is the foundation shown to improve quality of life in pets with Thyroid Disease in my experience. I have seen the best results with freshly fed pets on a home cooked or raw food diet. Testing for vitamin and mineral deficiencies is an important part of treatment also.

Dry food is a big ‘no no’ in Thyroid Disease, as it puts extra pressure on the digestive system, pancreas and liver. Fresher and more bioavailable proteins are more effective as the protein is essential for TSH production and expression. Quality and digestibility of food is one of the most important factors in managing Thyroid Disease.

Many dry foods contain anywhere between 35-60% carbohydrate that can lead to gut inflammation and imbalance the immune response. Dog’s don’t have a high requirement for carbohydrates in their diet so feeding fresh food with minimal carbohydrates, in my experience has shown great benefit in these instances.

Some whole foods believed to support thyroid function are those high in omega-3 fats such as sardines, salmon, eggs, summer squash, and sweet red peppers.

Omega-3, Omega-6, Omega-9 fatty acid; dietary fat composition influences TSH secretion, thyroid peroxidase activity, hepatic deiodinase activities and T3 binding to nuclear receptors. Stimulating effects of n-3 PUFA have been observed for transthyretin expression in brain and thyrocyte proliferation. However, other results also suggest involvement of PUFA n-6 in stimulation of thyroid activity.

Goitrogenic foods such as broccoli, cauliflower and soy may affect thyroid function. Generally if fed with caution and in moderation, goitrogenic foods tend to outweigh the risks of feeding such foods due to containing vitamin K and antioxidants. The goitrogenic properties in leafy green vegetables are very small and should not cause great concern. Always lightly cook to air on the side of caution.

Incorporating natural fibrous vegetables such as asparagus, celery, cooked broccoli, bok choy and cabbage in small amounts, cucumber, lettuce, cooked spinach, mushrooms and greens beans are helpful in thyroid function. Lightly steaming and adding to any bowl can be helpful.

Blueberries, avocados (flesh only), pumpkin seeds and flaxseed oil (in small amounts) can be beneficial in the early diagnosis of hypothyroidism.

Treats

Treats and tidbits are fine for cats and dogs with Thyroid Disease as long as they are fresh and nutritious and not unnecessarily calorific.

Water

Always filter or provide fresh bottled water for your pet. Tap water contains flouride, pesticides, fungicides and many more toxins that the body must process during detoxification. Reducing fluoride exposure has shown to be helpful in hypothyroidism.

Supplements to consider

When supplementing we need to consider adrenal, liver, digestive, immune and thyroid support,

Ashwaganda; is the ultimate in supporting adrenal, liver and thyroid function by supporting cortisol levels (stress hormones). Intense levels of stress can affect thyroid function. I find most dogs experience some form of stress living in our 21st century homes under our rules. Ashwaganda is one of the most important herbs in Ayurveda, a form of alternative medicine based on Indian principles of natural healing that has been used for over 3,000 years. It’s a beautiful adaptogenic herb that supports the stress response and immunity in your pet. It’s classically known as a nervine tonic but this beauty has many strings to its bow. The clinical studies and research so far is very promising. This herb can have an indirect impact on liver function and thyroid function in a very positive way.

B vitamins; such as thiamine (B1), methylated forms of methyl folate (B9) and cobalamin (B12) are essential in hypothyroidism.

Slippery elm and Deglycerised Licorice; address the gut integrity and immune response. Slippery elm and deglycerised licorice have both shown to have healing properties to the gut mucosa and are wonderful in leaky gut, a syndrome linked to thyroid function and autoimmunity.

Probiotics; we know the thyroid and efficacy of the digestion are closely correlated so a healthy bowel can reduce the stress and impact of a healthy or unhealthy thyroid ultimately. The thyroid gland is responsible for releasing hormones that affect the way cells work throughout your body. As these hormones are involved in metabolism and digestion, a problem with the thyroid can result in gastrointestinal (GI) symptoms. Microbes influence thyroid hormone levels by regulating iodine uptake, degradation, and enterohepatic cycling. In addition, there is a pronounced influence of minerals on interactions between host and microbiota, particularly selenium, iron, and zinc. In manifest thyroid disorders, the microbiota may affect L-thyroxine uptake and influence the action of propylthiouracil (PTU).

Iodine; thyroid hormones are the only iodinated organic com-pounds in the body and a deficiency may indicate hypothyroidism. However a lot of emphasis is put onto Iodine and many owners tend to over supplement as there are no given upper limits. Care should be taken when supplementing.

Zinc; is needed to convert T4 into T3, so this mineral is a must. When hair loss is associated with hypothyroidism, zinc is often indicated.

Selenium; T3 is the active form of thyroid hormone and is converted from T4, if there isn’t an adequate level of selenium, this process cannot be completed.

Inositols: are essential for the signaling of hormones such as insulin, gonadotropins (follicle stimulating hormone [FSH] and luteinizing hormone [LH]), and TSH. Longterm use has shown to reduce TSH and regulate healthy thyroid hormones.

Reduced Glutathione; thyroxine and tri‐iodothyronine are essential for healthy organ growth, development and function. These hormones regulate the basal metabolic rate of all cells, including hepatocytes, and therefore help maintain hepatic function. The liver in turn metabolises the thyroid hormones and regulates their systemic endocrine effects. Supporting liver function is essential in supporting thyroid function in disease. Studies link low glutathione with autoimmune hypothyroidism and supports the liver in detoxification reactions and in regulating the thiol-disulfide status of the cell.

The nutrients mentioned in this blog and known to support thyroid function, are interestingly all critical for increasing glutathione synthesis. This is where I believe focus should be placed in new research for thyroid function.

Treatment for Hypothyroidism in Dogs

If your dog is diagnosed with hypothyroidism, don’t worry! Even though you can’t cure hypothyroidism in dogs, it’s usually easy and relatively inexpensive to manage with an oral thyroid supplement. The supplement mimics the effect of thyroid hormone on the body. If it’s successful, your dog will regain their energy, lose weight, have a brighter attitude and stop shedding hair.

The key thing to remember when treating thyroid problems in dogs is the importance of balance. If your dog takes too much thyroid supplement, they can develop signs of an overactive thyroid, which is the opposite of what you want. If the vet prescribes your dog a thyroid supplement, it’s important to follow all dosing instructions — don’t change the dosage without talking to the vet.

After starting your dog on a thyroid supplement, the vet will likely ask you to return in a couple of weeks to get a follow-up blood test to make sure your dog’s thyroid hormone levels are appropriate. Once their hormone levels are stabilized, the vet will probably want to check them once or twice a year.

Nutrition for Dogs With Hypothyroidism

Providing proper nutrition to a dog with hypothyroidism is an important part of supporting overall thyroid health. Dogs with hypothyroidism need to be supported by food that contains balanced levels of amino acids, iodine, probiotics for gut health, antioxidants and the right amount of calories that contribute to a healthy weight. Ask your vet for nutritional recommendations for your dog.

Low thyroid problems in dogs are common and can be easily managed. Even with a diagnosis of hypothyroidism, your dog can live a long, healthy and happy life.

Hypothyroidism is a common condition in dogs that can lead to unexplained weight gain, skin and coat issues, as well as behavioral changes and reduced energy. Today our Charlotte vets explain more about this condition including the best diet for dogs with hypothyroidism.

Hyperthyroidism occurs when your dog’s body produces too much of the thyroid hormone, increasing your dog’s metabolic rate to dangerous levels. This disease is rare in dogs and is much more common in cats, but when it does affect dogs, it is usually serious.

A type of cancer, called thyroid carcinoma, is the primary cause of hyperthyroidism in dogs. Once diagnosed, your veterinarian will discuss the treatment options and prognosis for your dog. These options will depend on the stage of the cancer, the size of the tumor, and the extent of nearby tissue involvement.

There are several treatment options available for thyroid carcinoma. Your veterinarian may recommend surgery, chemotherapy, or radiation treatments, depending on your dog’s condition. In the meantime, there are medications available to counteract the excess hormone levels to keep your dog comfortable.

The symptoms of hyperthyroidism in dogs include:

Weight loss
Hyper-excitability
Increased appetite
Increased thirst
Increased urination
Enlargement of thyroid gland
Vomiting
Diarrhea
Increased amount of stool
Congestive heart failure
Tachycardia (fast heart rate)
Heart murmurs
Cardiomegaly (enlarged heart)
Dyspnea (shortness of breath)

Unfortunately, the long-term prognosis for dogs with hyperthyroidism and thyroid carcinoma is poor to grave. Talk with your veterinarian about your dog’s condition for the most accurate prognosis.

Can it be treated?

Hypothyroidism is treatable but not curable. It is treated with oral administration of thyroid replacement hormone. This drug must be given for the rest of the dog’s life. The most commonly recommended treatment is oral synthetic thyroid hormone replacement called levothyroxine (brand names Thyro-Tabs® Canine, Synthroid®).

How is the proper dose determined?

All dogs are started on a standard dose of thyroid replacement hormone, based on the dog’s weight. After one month of treatment, a blood sample is taken to verify that the thyroid hormone levels are normal. The blood sample is usually taken just before or 4-6 hours after medication administration as hormone levels can fluctuate.

“Since the dog’s tolerance of the thyroid replacement hormone may change over time, the dose may need to periodically adjusted.”

Since the dog’s tolerance of the thyroid replacement hormone may change over time, the dose may need to be periodically adjusted. It is usually necessary to retest thyroid hormone levels every six months. Close communication with your veterinarian is necessary in order to ensure that your dog is neither over- nor under-dosed. It is also important to monitor your dog’s condition. If signs of hypothyroidism recur or if you feel your dog has signs of hyperthyroidism discussed below, let your veterinarian know right away.

Reference-on request

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