Hypothyroidism in Dogs: Causes, Symptoms, and Treatment

Quick Summary

• Hypothryroidism is dogs is a disorder of the thyroid gland causing a dog’s metabolism to slow down abnormally.
• Symptoms of hypothyroidism in dogs include lethargy, weight gain, dry and flaky skin, bacterial skin infections, myxedema, hair loss, and many more.
• Canine hypothyroidism is treated by taking a “thyroid pill” every day. It contains levothyroxine, a synthetic version of the deficient hormone.

While one of the most popular forms of thyroid disease, hypothyroidism affects almost everyone at some point in their lives. It may surprise you to know that hypothyroidism in dogs is also quite common.

To help you understand the disease and how to help your dog suffering from hypothyroidism, I will discuss the causes, symptoms, and treatment in this article.

What is Hypothyroidism in Dogs?

Hypothyroidism is the most common hormone deficiency in dogs, according to Ron Hines, DVM. It occurs when the thyroid gland – two small lobes in your dog’s neck – is underactive and fails to secrete sufficient amounts of the hormone thyroxine. This affects your dog’s metabolism, causing him to slow down. (Hypothyroidism is the opposite of hyperthyroidism, which occurs when the thyroid overproduces thyroid hormone, making your dog, well, very hyper.)

We will also explore how lymphocytic thyroiditis can be a definitive diagnosis for the condition. Veterinary medicine has come a long way in recent years, and there are many treatments available for dogs with hypothyroidism.

Congenital hypothyroidism: This is the most common form of the disorder, and it occurs when a dog is born with a defective thyroid gland. In puppies, congenital hypothyroidism can cause stunted growth and delayed development. Adult dogs may experience weight gain, lethargy, and a dull coat.

What are the Symptoms of Hypothyroidism?

Hypothyroidism may have multiple symptoms. Every cell in your dog’s body is susceptible to thyroid hormone deficiency. It’s important to get an accurate diagnosis as soon as possible. Hypothyroidism can cause a number of health problems and even lead to death. Fortunately, thyroid function can be restored with proper treatment. Peteducation, thyroid-info and marvistavet list these symptoms as the most common:

•   Lethargy – Your dog isn’t interested in playing, Therefore it takes frequent naps and gets tired on long walks
•   Weight gain – Your dog may put on pounds although his appetite hasn’t increased
•   Dry, flaky skin and bacterial skin infections
•   Thickening of the facial skin (called “myxedema”), leading to more skin folds
•   Hair loss, especially on the tail, creating a “rat tail” appearance
•   Intolerance to cold – Your dog looks for warm places to lie down
•   Slow heart rate
•   Anemia and/or high cholesterol
•   Frequent ear infections
•   Extreme behavioral changes such as unprovoked aggression, head tilting, seizures, anxiety or compulsivity

What Causes Hypothyroidism?

According to experts hypothyroidism in dogs is typically caused by either lymphocytic thyroiditis or idiopathic thyroid gland atrophy . The former is the most common thyroid-related autoimmune disease and the later happens when normal thyroid tissue is replaced with fat tissue.

One of the most common triggers of hypothyroidism in dogs is a deficiency of levothyroxine sodium tablets. In dogs, the thyroid exists as two separate halves. It produces two forms of thyroid hormone, called T3 and T4. Thyroid hormones are essential for normal body function. T3 is the active form of the hormone. T4 is the inactive form that is created to circulate in the bloodstream; it’s converted into T3 when it is absorbed into tissue cells. In dogs, about half of the T3 comes from the thyroid gland. The remaining T3 comes from the body’s other tissues. (In humans, 80 percent of T3 comes from our body’s other tissues.)

Important point to consider

The pituitary gland at the base of your dog’s brain controls T4 production. The pituitary gland produces TSH (thyroid stimulating hormone), which stimulates the thyroid gland to produce more T4 when levels drop. Autoimmune thyroiditis is the most typical cause of hypothyroidism in dogs. According to Mary Shoman, a renowned expert on thyroid-info.com, autoimmune thyroiditis causes hypothyroidism in dogs.

“The dog’s own system attempts to compensate for this at first by secreting more and more of the thyroid hormone, but eventually the gland is unable to keep up with the attacks on its tissue, and the dog becomes hypothyroid and symptomatic,” Shoman writes. “While there is a genetic predisposition for thyroid disorders, environmental factors such as pollutants and allergies probably play a role as well.”Thyroid tumors can also cause hypothyroidism in dogs. Natural shrinkage of the thyroid gland, iodine deficiency, or a congenital condition are all possible causes. Most dogs become hypothyroid in midlife, between the ages of 4 and 10. It affects male and female dogs equally.

Medium- to large-sized breeds are more susceptible to the disease. According to marvistavet.com, some breeds with a definite predisposition to develop hypothyroidism are Doberman Pinschers, Golden Retrievers, Irish Setters, Great Danes, Dachshunds and Boxers. Hypothyroidism rarely occurs in toy and miniature breeds.

How is Hypothyroidism Diagnosed?

One of the most common ways to diagnose hypothyroidism is with a blood test. Your vet will examine your dog. If you suspect hypothyroidism, your doctor will perform urinalysis and other blood tests.:

•   Baseline T4 or Total T4 (TT4) – The most common test for hypothyroidism. A lowered level of the T4 hormone is an indication that the thyroid is underactive. Since other conditions and medications may cause a low T4 level – for example, dogs on antibiotics or heart medication may have low T4 levels, but are not actually hypothyroid – your vet may perform additional tests.
•   Baseline TSH – This test measures the level of thyroid stimulating hormone. In combination with T4 or T3, it provides a clearer indication of your dog’s thyroid activity.
•   Baseline T3 – Although T3 is the active thyroid hormone, its level can fluctuate into the normal range in hypothyroid dogs, according to marvistavet.com. Thyroid hormone production is frequently low in dogs with thyroid disease. Therefore this test is only reliable when it’s used in combination with the T4 or TSH tests.

What is the Treatment for Hypothyroidism?

Medical treatment: As with humans, hypothyroidism can be easily treated by taking a “thyroid pill” every day. It contains a synthetic version (called levothyroxine) of the deficient hormone. You should notice an improvement in your dog’s life within a few months of starting him on the medication.

According to pet education, your vet will initially place your dog on the standard dose for his weight, and then periodically draw blood samples to ensure the dosage is sufficient. If you notice your dog showing hypothyroidism symptoms while he is on the medication, you should take him to the vet for blood work.

Your dog will need to take the medication for the rest of his life…which, with this simple treatment, should be long and symptom-free.

FAQs

What are signs of hypothyroidism in dogs?

Signs of hypothyroidism in dogs include lethargy, weight gain, dry and flaky skin, bacterial skin infections, myxedema, hair loss, and many more.

Can hypothyroidism in dogs be cured?

Unfortunately, there is no cure for hypothyroidism in dogs. Treatment means lifetime medications also called thyroid hormone replacement therapy.

How long can dogs live with hypothyroidism?

The life expectancy for dogs that receives medical care for hypothyroidism is normal. Hypothyroidism in dogs, although incurable, can be managed so a dog can live a long and happy life.

How do you treat hypothyroidism in dogs?

To treat hypothyroidism, the dog is often given thyroid hormone replacement therapy typically with a pill called levothyroxine.