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Hypothyroidism in Dogs

Hypothyroidism in Dogs: Effects, Causes, Treatment

Hypothyroidism in dogs is an endocrine condition in which the thyroid gland fails to produce sufficient thyroid hormones. The two thyroid hormones are triiodothyronine (T3) and thyroxine (T4). 

Canine thyroid issues in dogs are common, and hypothyroidism is the reported endocrine condition. Primary hypothyroidism is caused by lymphocytic thyroiditis or idiopathic thyroid atrophy. Secondary hypothyroidism or thyroid issues in dogs are due to thyroid tumors, medications, radiation, or constant pressure. 

Thyroid hormones play an essential role in many body functions, and hypothyroidism triggers a constellation of clinical signs and symptoms. 

The main hypothyroidism in dogs symptoms are weight gain, lethargy, feeling cold, chronic ear infections, skin problems, hair loss, and behavioral changes. Atypical symptoms include tragic faces, neurological deficits, reproductive challenges, arrhythmias, and megaesophagus. 

The condition is diagnosed by measuring thyroid hormone levels and considering the dog’s history and clinical signs. A hypothyroidism dog treatment plan is based on lifelong supplementation with levothyroxine, a synthetic thyroid hormone replacement. Hypothyroidism in dogs is not curable but is treatable. Hypothyroidism lowers the dog’s life quality and expectancy if left untreated. 

What is Hypothyroidism in Dogs?

Hypothyroidism in dogs is an endocrine condition marked by underactive thyroid glands. Canine thyroid issues such as hypothyroidism are widespread in canines. 

Hypothyroidism is the most common endocrine disorder in dogs, says a study “Hypothyroidism in Dogs: Pathophysiology, Causes and Clinical Presentation,” issued in Companion Animal in 2013. 

The dogs thyroid gland is located in the neck and has two different lobes, one on each side of the windpipe. 

The thyroid gland produces two hormones, triiodothyronine (T3) and thyroxine (T4). The thyroid hormones participate in many vital body functions and regulate metabolism. 

Hypothyroidism occurs when the thyroid gland fails to produce enough T3 and T4. Low thyroid hormone levels trigger various clinical signs and symptoms of thyroid issues in dogs

What are the effects of thyroid disease in dogs?

The effects of thyroid disease in dogs are listed below. 

  • Sensitive Skin: Sensitive skin is a common effect in dogs with hypothyroidism. Telltale signs include flakes, excess dryness, sores, and scabs. 
  • Skin Infections: Repeated superficial skin infections that are difficult to clear up result from hypothyroidism in dogs. 
  • Ear Infections: Chronic or recurrent infections of the outer ear or otitis externa manifest with red, inflamed ears with waxy and pungent-smelling discharge. 
  • Hair Loss: Hypothyroidism leads to hair loss in certain canines. Dogs lose hair on the neck, the sides of the body, and the tip of the tail (known as a rat tail). 

1. Sensitive skin

Sensitive skin is a condition in which the skin is prone to adverse reactions, such as redness, irritation, and lesions. 

Dogs with hypothyroidism develop sensitive skin. The skin is flaky, dry, and covered with dandruff and skin lesions, such as scabs and sores. 

Oatmeal baths paired with chamomile or green tea relieve the dog’s sensitive skin. Home remedies include apple cider vinegar, coconut oil, and omega supplements. 

2. Skin infections

Skin infections, or dermatitis, in dogs with hypothyroidism, are superficial but stubborn and hard to heal. The diseases are chronic and recurring. 

The initial skin changes in hyperthyroid dogs are not itchy but become pruritic as skin infections develop. The disease causes the dog pain and discomfort. 

Skin supplements, soothing oatmeal baths, aloe vera, coconut oil, and CBD products are safe and beneficial home remedies for skin infections

3. Ear infections

Outer ear infections, or otitis externa, is inflammation of the outer portion of the ear or ear lobe. Dogs with hypothyroidism develop bilateral otitis (on both ears). 

Otitis externa manifests with redness, itchiness, and discharge. The discharge has a wax-like consistency and an unpleasant odor. 

Cleaning the ears with apple cider vinegar is an excellent home remedy for ear infections. Mix one part of apple cider vinegar with one part water to prepare the cleaning solution. 

4. Hair Loss

Hair loss, or alopecia, is a condition in which the hair production cycle is interrupted. Dogs with hypothyroidism experience excessive shedding, coat thinning, and stunted hair growth. 

Hair loss occurs everywhere on the dog’s body but is intense on the neck, body sides, and tail tip. The hair loss on the tip of the tail gives the dog’s tail a rat-like appearance. 

Regular brushing, omega-rich oral supplements, and topical use of CBD and coconut oil are among the best home remedies for dog hair loss

What causes hypothyroidism in dogs?

The causes of hypothyroidism in dogs are listed below. 

  • Lymphocytic Thyroiditis: Lymphocytic thyroiditis is an autoimmune condition in which the dog’s immune system misidentifies the thyroid as a threat and triggers an attack. The damaged thyroid tissue is less productive, causing hypothyroidism. Lymphocytic thyroiditis is the most common cause of hypothyroidism in dogs.  
  • Idiopathic Thyroid Atrophy: Idiopathic thyroid atrophy is a condition of unknown origin in which the thyroid tissue gets damaged and is replaced by fat tissue. Fat tissue is unable to produce thyroid hormones, resulting in hypothyroidism.  
  • Thyroid Gland Tumors: A severe cause of hypothyroidism in dogs is tumors in the thyroid gland. Thyroid tumors are rare but impair the gland’s hormone production ability when they develop. 
  • Medication Side Effects: Certain medications, like non-steroid anti-inflammatory drugs (NSAIDs), steroids, diuretics, antibiotics, and antiepileptics, interfere with the thyroid gland’s function, causing thyroid problems in dogs
  • Physical or Chemical Damage: Tight collars put pressure on the neck and thyroid gland, causing inflammation and impaired gland function. Dogs subjected to radiation therapy in the neck region experience thyroid gland damage. 
  • Hypothalamus/Pituitary Issues: The thyroid gland’s hormone production is controlled by the hypothalamus and pituitary gland. Problems with these glands result in secondary hypothyroidism. 

What are hypothyroidism in dogs symptoms?

The hypothyroidism in dogs symptoms are listed below. 

  • Weight Gain: Unexplained weight gain is a textbook sign of hypothyroidism. Dogs with underactive thyroid glands gain weight regardless of food intake due to their delayed metabolism. 
  • Lethargy: Dogs with hypothyroidism exhibit reduced energy levels. The dog becomes lethargic and prefers to sleep, lacking the stamina to exercise. 
  • Dull Mental State: A dull mental state, known as depression or apathy, is disinterest in otherwise fun activities. Apathy negatively affects the dog’s quality of life. 
  • Feeling Cold: Hypothyroidism slows down metabolism, making the dog feel cold. Shaking and seeking heat sources are signs the dog is chilly. 
  • Skin and Ear Infections: Chronic or recurrent skin and ear infections are frequent in dogs with hypothyroidism. The dog’s coat becomes brittle and unkempt, and the ears are inflamed and malodorous. 
  • Hair Loss:  The skin infections progress and result in hair loss or alopecia. Typical hair loss regions in dogs with hypothyroidism are the neck, the sides, and the tail. A rat tail-like appearance indicates thyroid gland problems. 
  • Behavioral Changes: “Canine hypothyroidism may be associated with aggression,” reports a study “Canine Behaviors Associated with Hypothyroidism,” published in the Journal of the American Animal Hospital Association in 2003. 
  • Tragic Face: Tragic face is a rare, telltale sign of hypothyroidism in dogs. Low thyroid hormone levels trigger an accumulation of polysaccharides in the deep skin tissues, causing thickening or mixedema. Mixedema on the face drops the eyelids, resulting in a mournful facial expression. 
  • Reproductive Issues: “Hypothyroidism in dogs may cause reproductive difficulties,” states an observational study titled “Hypothyroidism in Canine Reproduction published in Clinical Theriogenology in 2023. 
  • Neurological Disorders: Dogs with hypothyroidism develop secondary neurologic deficits. The most common neurologic issue is facial paralysis. Other signs of the disorder include loss of palpebral reflexes, eye drops, lip drops, and reduced tear secretion.  
  • Cardiac Arrhythmias: Hypothyroidism affects the heart function, causing an irregular heartbeat. Cardiac arrhythmia is a rare and atypical sign of hypothyroidism in dogs. 
  • Megaesophagus: Megaesophagus is a rare symptom of hypothyroidism in dogs. Dogs with megaesophagus have enlarged esophagi or food pipes that lose motility and are unable to transport food from the mouth to the stomach. 

How Does Hypothyroidism Cause Dog Allergies?

The reason for how hypothyroidism causes dog allergies is unknown. Evidence suggests that there is a connection between autoimmune thyroid disease and allergic rhinitis in humans. 

Hypothyroidism can be a hidden predisposing factor of rhinitis, reports a study “Association of Allergic Rhinitis with Hypothyroidism, Asthma, and Chronic Sinusitis: Clinical and Radiological Features” published in the World Journal of Otorhinolaryngology in 2022. 

Hypothyroidism’s connection to dogs’ allergies is indefinite based on current research. “Canine hypothyroidism can cause skin, metabolic, and neurological issues, but its relationship to other conditions remains unclear,” says a study “Conditions Associated with Canine Hypothyroidism” published in The Veterinary Clinics of North America in 2001. 

How to Diagnose Hypothyroidism in Dogs?

To diagnose hypothyroidism in dogs, veterinarians conduct a detailed history of the dog’s health, consider the clinical signs, perform physical examinations, and order lab tests. 

The golden standard for diagnosing hypothyroidism in dogs is the TSH-stimulation test, according to a study “Clinical, Hematological, Biochemical and Endocrinological Aspects of 32 Dogs with Hypothyroidism” published in Schweizer Archiv fur Tierheilkunde in 2003.

High thyroid-stimulating hormone (TSH) suggests hypothyroidism. Low total thyroxin concentration (T4) and free T4 (fT4) confirm the diagnosis

Veterinarians suspect hypothyroidism based on blood analysis alone. A study, “Epidemiological, Clinical, Haematological and Biochemical Characteristics of Canine Hypothyroidism,” published in the Veterinary Record in 1999, explains that approximately 75% of hypothyroid dogs have high cholesterol levels.

What are hypothyroidism dog treatments?

The hypothyroidism dog treatments are listed below. 

  • Give Levothyroxine: Levothyroxine (brand names: Thyro-Tabs® Canine and Synthroid®) is a synthetic thyroid hormone replacement available in an oral pill form. Hypothyroid dogs need lifelong use of levothyroxine. Levothyroxine achieves good efficacy when given once a day, according to a study, “Treatment and Therapeutic Monitoring of Canine Hypothyroidism,” published in the Journal of Small Animal Practice in 2002. Vets recommend twice-daily levothyroxine administration in the initial phases.
  • Regular Monitoring: Hypothyroid dogs require regular monitoring of their thyroid levels through blood tests and evaluation of clinical signs. The first blood checkup is performed four weeks after starting the levothyroxine. The vet decides if the dose needs modification based on the results. The clinical signs of hypothyroidism in dogs improve within four to six weeks, with skin issues requiring up to several months to resolve. 
  • Healthy Diet: A balanced and nutritious diet supports overall health and thyroid function. Consult the veterinarian regarding the best dog food formula and consider thyroid supplements containing minerals like iodine, selenium, and zinc. 
  • Daily Exercise: Exercise is vital for dogs with thyroid issues. Hypothyroid dogs are susceptible to weight gain and obesity, which complicates the clinical manifestation of the endocrine imbalance. Create an exercise regimen and stick to it to keep the dog’s body weight within the breed’s standard limit. 

What would happen to a Dog with Untreated Hypothyroidism?

A dog with untreated hypothyroidism has a lower quality of life and reduced lifespan. 

Thyroid hormones in dogs influence almost all body organs and control metabolism. Untreated hypothyroidism causes reduced immunity, high cholesterol, slow heart rate, and neuromuscular deficits. 

The dog's weakened immunity leaves it susceptible to common infectious diseases. Reported neuromuscular disorders include head tilts, unsteady gait, and seizures. 

Can Hypothyroidism Lower the Dog's Immune System?

Yes, hypothyroidism can lower the dog’s immune system. The exact cause of low levels of thyroid hormones compromising immunity levels is unknown. 

“The interdependence between thyroid hormones (THs) and the immune system is nowadays well-recognized, although not yet fully explored,” reports a human study, “Thyroid Hormones Interaction With Immune Response, Inflammation and Non-thyroidal Illness Syndrome,” published in Frontiers in Cell and Developmental Biology in 2021. 

Thyroid hormones regulate many body functions and organs, and scientists suspect immunity is one of the targeted processes. Vigorous dog immunity is necessary for fighting off common infections. 

Is Hypothyroidism in Dogs Curable?

No, hypothyroidism in dogs is not curable. Hypothyroidism is treatable. Dogs with underactive thyroid glands require lifelong administration of thyroid replacement hormones. 

Levothyroxine is the most frequently used synthetic thyroid hormone replacement. The drug is sold under several brands, including Thyro-Tabs® Canine and Synthroid®. 

Successful management of hypothyroidism in dogs requires regular exercise and a strict dieting regimen for weight control purposes.  

What are the Side Effects of Too Much Thyroid Medication in Dogs?

The side effects of too much thyroid medication in dogs are listed below. 

  • Hyperactivity: Excess thyroid hormone levels cause hyperactivity. Dogs exhibit sudden outbursts of energy and get the so-called zoomies. 
  • Insomnia: Insomnia or inability to sleep is a sign of too many thyroid hormones. The dog paces around restlessly, unable to sleep properly at regular hours. 
  • Weight Loss: High levels of thyroid hormones increase the dog’s metabolism, resulting in fast weight loss despite the food intake rate. 
  • Increased Thirst: Thyroid medications increase the dog’s thirst when administered excessively, increasing water intake and urination frequency.

Are there Specific Breeds of Dogs Susceptible to Hypothyroidism?

Yes, there are specific breeds of dogs susceptible to hypothyroidism. Mid- to large-sized breeds are more prone to underactive thyroid glands than toy and small-breed dogs. 

High-risk breeds include Doberman Pinschers, Golden Retrievers, Tibetan Terriers, Miniature Schnauzers, Irish Setters, Airedale Terriers, Cocker Spaniels, Alaskan Malamutes, Dachshunds, and Boxers. 

The Cavachon and Cavapoo are the only two dog breeds without recorded hypothyroidism diagnosis, according to a study “Frequency, Breed Predispositions and Other Demographic Risk Factors for Diagnosis of Hypothyroidism in Dogs Under Primary Veterinary Care in the UK,” published in Canine Medicine and Genetics, in 2022. 

How can CBD Oil Help Hypothyroidism in Dogs?

CBD oil helps hypothyroidism in dogs by providing symptom relief. CBD promotes healthy energy levels, prevents behavioral changes, and has a soothing effect on irritated skin. 

CBD has potent anti-inflammatory and antioxidant properties, protecting thyroid tissue against damage. 

Promising new research says that CBD has the potential to assist in treating hypothyroidism. “CBD can be considered for use in hypothyroidism conditions,” reports a study, “Cannabidiol Improves Thyroid Function via Modulating Vitamin D3 Receptor in Vitamin D3 Deficiency Diet-Induced Rat Model” published in the Journal of Food Science and Technology in 2022.  

CBD works naturally through the endocannabinoid system. CBD oil for dogs is safe to combine with mainstream hypothyroidism medications and is fit for dogs of all ages.