Hypothyroidism in Dogs


Bryan Huynh

- Updated February 22, 2024

Key Takeaways

  1. Hypothyroidism in dogs is a common endocrine disorder characterized by decreased thyroid hormone levels.
  2. Certain breeds, like Golden Retrievers, Dobermans, and Irish Setters, are more prone to this condition.
  3. Symptoms include weight gain, lethargy, coat issues, and skin infections. Diagnosis relies on blood tests.
  4. Treatment involves oral hormone replacement therapy, typically levothyroxine, adjusted to each dog's needs and monitored through blood tests.
  5. Prevention is challenging due to genetic factors, but responsible breeding and regular veterinary screenings can aid in early detection and management.
Hypothyroidism in Dogs

What is Hypothyroidism?

Hypothyroidism is a prevalent endocrine disorder where the thyroid hormone levels drop below the standard range. This reduction can stem from an autoimmune response leading to the gradual destruction of the thyroid gland, termed "lymphocytic thyroiditis", or from a congenital condition present since birth.

Among dogs, acquired hypothyroidism stands out as the most frequently diagnosed endocrine issue. This condition arises when an auto-immune reaction causes the thyroid gland to shrink. Initially, the symptoms of this treatable disease are mild and affect various organ systems, but over time, they can become more pronounced and covertly advance. Pet insurance can provide financial support for the diagnosis and treatment of hypothyroidism.

While it's widely believed that there's a genetic link to acquired hypothyroidism, the congenital form clearly has hereditary ties. However, it's worth noting that congenital hypothyroidism is exceptionally rare. The acquired form is more typically observed in middle-aged, medium to large-sized dogs.

Causes of Hypothyroidism in Dogs

Hypothyroidism, a prevalent endocrine disorder in our canine companions, arises primarily when the thyroid gland fails to produce sufficient amounts of critical hormones. This shortfall can have various origins. One of the leading causes is an autoimmune condition known as "lymphocytic thyroiditis," where the dog's immune system mistakenly targets and damages its own thyroid gland.

Another significant cause is "idiopathic thyroid gland atrophy," where the gland's tissue gradually deteriorates and is replaced by fat without a clear underlying reason. While these acquired forms dominate the landscape, there's also a congenital form of hypothyroidism, present from birth, which is relatively rare but has evident hereditary links. Breed predispositions further compound the complexity, with some breeds demonstrating a heightened vulnerability. Understanding these causes is paramount for early detection and effective management, ensuring our dogs lead healthy, vibrant lives.

Affected Breeds

Hypothyroidism does not discriminate widely among the canine population, but certain breeds show a more pronounced susceptibility to this endocrine disorder. Notably, the Golden Retriever, Doberman Pinscher, and Irish Setter have been identified with a higher predisposition to the ailment. Similarly, the Boxer, Dachshund, and Cocker Spaniel are other breeds that have been observed to have a greater incidence of hypothyroidism.

However, it's crucial to understand that while these breeds may be at an elevated risk, hypothyroidism can and does affect dogs across the breed spectrum. Such breed-specific tendencies emphasize the importance of regular veterinary check-ups, especially for those breeds with a known predisposition. By staying informed and vigilant, dog owners can ensure timely interventions and optimal care for their cherished companions.

Symptoms and Clinical Presentation

Hypothyroidism, while often subtle in its initial stages, can manifest through a diverse array of symptoms that dog owners should remain vigilant for. One of the most noticeable indicators is an unexplained weight gain despite no significant change in appetite. Affected dogs may also exhibit a lackluster coat, often accompanied by excessive shedding, hair thinning, and recurrent skin infections.

Lethargy, decreased activity levels, and a general sense of sluggishness are commonly observed behavioral changes. Cold intolerance may become apparent, with some dogs seeking warmth more frequently. Other signs can include a slowed heart rate, ear infections, and, in some cases, a darkening of the skin.

Given the broad symptomatology, regular veterinary assessments are indispensable. An early diagnosis based on these clinical presentations can pave the way for timely and effective treatments, ensuring our canine companions maintain their zest for life.


Detecting hypothyroidism in dogs is a meticulous process that hinges on a blend of clinical observation and diagnostic testing. While the symptoms can provide strong indications, definitive diagnosis demands more precise measures. A comprehensive veterinary examination lays the foundation, with particular attention to the dog's medical history and presenting symptoms. Blood tests serve as the cornerstone of diagnosis. A serum panel assessing the levels of Total T4, Free T4, TSH, and, in some cases, T3 provides invaluable insights into thyroid function.

However, interpreting these results requires nuance; factors like non-thyroidal illnesses or certain medications can influence thyroid hormone levels. In some situations, further specialized tests, like the TSH stimulation test, might be employed to confirm the diagnosis. With a judicious combination of clinical acumen and advanced diagnostic tools, veterinarians can accurately identify hypothyroidism, paving the way for targeted treatments and improved quality of life for our four-legged friends.

Treatment Options

Once a dog is diagnosed with hypothyroidism, the pathway to effective treatment is straightforward, aiming to restore the balance of the thyroid hormones. The cornerstone of treatment is oral hormonereplacement therapy, typically using a synthetic form of the hormone called levothyroxine. Administered daily, this medication compensates for the thyroid gland's decreased hormone production, helping to alleviate the symptoms.

The precise dosage is tailored to each dog's unique needs, determined through regular blood tests that monitor thyroid hormone levels and ensure optimal dosing. With diligent administration and periodic adjustments as required, most dogs respond exceptionally well to this treatment. Within a few weeks, noticeable improvements in energy levels, skin health, and overall well-being can be observed. It's crucial, however, for pet owners to understand that hypothyroidism is a lifelong condition. With consistent treatment and regular veterinary follow-ups, dogs diagnosed with hypothyroidism can lead full, active, and joyful lives, mirroring their undiagnosed counterparts in spirit and vitality.


The outlook for dogs diagnosed with hypothyroidism is overwhelmingly positive when the condition is identified early and managed effectively. With the initiation of hormone replacement therapy, most dogs show rapid improvement, regaining their former zest for life, shedding excess weight, and showcasing a healthier coat and skin.

Regular veterinary check-ups and periodic blood tests ensure that the treatment remains on track, adjusting dosages as needed to maintain optimal thyroid hormone levels. While hypothyroidism is a lifelong condition, with dedicated care and consistent treatment, it doesn't have to impede a dog's quality of life. In fact, many dogs with hypothyroidism, once stabilized on their medication, lead lives indistinguishable from those without the condition, enjoying every romp, fetch, and cuddle with the same enthusiasm and vigor as always.

Prevention and Risk Reduction

While the genetic underpinnings of hypothyroidism make it challenging to prevent outright, there are actionable steps dog owners can take to minimize risks and detect potential issues early. Responsible breeding practices, which prioritize health screenings and avoid breeding dogs with known thyroid issues, can play a pivotal role in reducing the prevalence of the condition in predisposed breeds. For individual dogs, regular veterinary check-ups, including thyroid function tests, can ensure early detection and timely intervention, even before overt symptoms manifest.

Nutritional considerations, such as providing a balanced diet with adequate iodine levels, can support healthy thyroid function. Additionally, being observant of subtle changes in behavior, coat quality, or energy levels can prompt timely evaluations. Empowerment through knowledge, combined with proactive veterinary care, lays the foundation for safeguarding our canine companions from the clutches of hypothyroidism and its associated challenges.

Case Studies

From u/ginowie97

“…We recently discovered our active 2 year old golden retriever is 15 pounds overweight and our vet advised us to begin a diet plan. We’ve done everything right with calorie tracking his food and training treats and absolutely no table scraps or any excess treats. With underfeeding and 3 walks a day his weight hasn’t budged even a pound in the last 2 months, so our vet made an appointment to get his blood work tested for possible hypothyroidism.”

From u/jeclin91092

“…Of course weight gain and difficulty losing it.

Also, thinning hair, dry skin, frequent ear infections, sudden personality changes like not wanting to listen, no energy.

A huge one for Milo was when he lost interest in the things he has always loved. We would hike for 6 miles, then suddenly he couldn't be bothered to go for a half mile walk.”

From u/Harley_Quinn_30

“…My poor pupper has not been herself lately and we took her to the vet, we thought she was just a little chunky but the blood work confirmed that it is hypothyroidism. (For that that don't know it means her thyroid is not working well enough). She will be on synthroid/levothyroxine for the rest of her life which is fine.

I just wanted to see if anyone has any experience with this in dogs. And if there are any tips you have. Also, if you have experienced this with a dog can you give me an idea of how long it took to notice a change?”


Hypothyroidism, with its diverse manifestations, underscores the intricate balance of health and well-being in our canine companions. While its onset might seem daunting, advancements in veterinary medicine and a deeper understanding of the condition have paved the way for effective treatments, allowing affected dogs to lead lives brimming with vigor and vitality. The journey from recognizing the subtle symptoms to navigating the treatment pathway emphasizes the unparalleled bond between dogs and their owners – one founded on care, vigilance, and mutual trust.

By staying informed, seeking timely veterinary intervention, and maintaining consistent treatments, dog owners can ensure that hypothyroidism becomes a manageable aspect of their pet's life, rather than an insurmountable hurdle. In this quest for optimal health, the shared moments of joy, play, and companionship stand testament to the resilience of the canine spirit and the depth of the human-dog bond.

About The Author

Bryan Huynh

Bryan Huynh

Product Tester & Writer

Bryan Huynh is a dedicated Product Tester & Writer. Just as insurance has your back, Bryan works to review and inform you about the wide range of insurance products available, ranging from business, auto, health, home, pet, to life insurance.

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