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Common Illness in Dogs – Hypothyroidism

By Colleen Williams and medically reviewed by JoAnna Pendergrass, DVM
published: February 3, 2012 - updated: January 17, 2023 • 3 min. read
Dog with hyperthyroidism

Hypothyroidism is caused by a deficiency of hormones produced by the thyroid gland. These hormones affect your dog’s metabolism – the biochemical process that changes food into energy. Hypothyroidism is not curable, but it is easily manageable. With loving, patient care from a pet parent, a dog with hypothyroidism can lead a long, happy life.

Causes of Hypothyroidism

There is no virus, bacteria, or parasite that causes hypothyroidism. There are several factors that increase a dog’s risk of developing the disease:

  • Age. Dogs between the ages of four and ten are at a higher risk.
  • Size. If your dog is mid-sized to large, their chances of developing hypothyroidism are heightened.
  • Breed. Some breeds of dogs are more prone to developing hypothyroidism. These breeds include Doberman pinschers, Irish setters, Golden Retrievers, Great Danes, dachshunds, Miniature Schnauzers, boxers, poodles, and Cocker Spaniels.
  • Neuter/spay status. Male dogs that have been neutered and female dogs that have been spayed have been shown to develop hypothyroidism more often.
  • Genetics. In some cases, hypothyroidism can be traced through generations and passed down to offspring.
  • Other illnesses. Thyroid cancer, thyroid inflammation, and thyroid gland shrinkage can also contribute to a dog’s chances of developing hypothyroidism.

Hypothyroid Symptoms in Dogs

There are many outward signs of hypothyroidism; most are either behavioral or affect the animal’s skin and fur. Lethargy and inactivity, weakness, and mental dullness are the most common. When these are coupled with excessive hair loss and shedding, a dry/dull coat, and scaly skin, the diagnosis is most often hypothyroidism. Sudden, unexplained weight gain is the most distinctive symptom.

Dogs with hypothyroidism also become intolerant to cold and can develop ear infections. In severe cases of hypothyroidism, dogs can develop a “tragic face” when the skin on the face swells and sags.

Diagnosis and Treatment for Hypothyroidism

A thorough physical exam will be performed and a detailed medical history will need to be provided, including onset of symptoms. Diagnostic tests, including blood work, a urinalysis, and several thyroid hormone tests, will be run.

Since hypothyroidism cannot be cured, only managed, your dog will need loving care for the rest of their life. Your veterinarian will prescribe medications that contain synthetic thyroid hormones to correct your dog’s thyroid hormone deficiency. A diet plan may also be constructed to promote weight loss or prevent obesity; animals with hypothyroidism often experience frequent weight fluctuations.

It usually takes four to eight weeks of thyroid hormone replacement therapy before improvements in weight and skin condition can be observed. Your vet will need to measure your dog’s thyroid hormone levels regularly to monitor how your dog is responding to treatment and make dosage adjustments if needed.

Managing Your Dog’s Hypothyroidism

Stick to the medication and diet regimen your vet constructed; never change anything unless directed by your veterinarian. It doesn’t take long for your pooch to return to their old ways.

Hypothyroidism is a condition that inhibits your dog’s thyroid glands from producing hormones that control metabolism. This can lead to symptoms like obesity and decreased mental function. If you see any of the signs of hypothyroidism, make an appointment with your vet. The symptoms of hypothyroidism can also be present with other illnesses, so your vet will need to run tests to confirm that your dog has hypothyroidism. The condition can be easily managed, but it does take life-long care from loving pet parents.

The content is not intended to be a substitute for professional veterinarian advice, diagnosis, or treatment. Always seek the advice of your veterinarian or other qualified health provider with any questions you may have regarding a medical diagnosis, condition, or treatment options.

colleen williams
By Colleen Williams

Over the past decade, Colleen has written about health, wellness, beauty, and even pets for The New York Times, The Cut, Refinery29, xoVain, Healthy Paws Pet Insurance, and Seattle Met Magazine, as well as many beauty brands. She has a BFA in Art History from the University of New Mexico and an AAS in Fashion Design from Parsons School of Design in New York.

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joanna pendergrass
By JoAnna Pendergrass, DVM

JoAnna Pendergrass, DVM, is a veterinarian and freelance medical writer in Atlanta, GA. After graduating from the Virginia-Maryland College of Veterinary Medicine with her veterinary degree, JoAnna completed a 2-year research fellowship in neuroscience at Emory University. During this fellowship, she learned that she could make a career out of combining her loves of science and writing. As a medical writer, JoAnna is passionate about providing pet parents at Healthy Paws with clear, concise, and engaging information about pet care. Through her writing, she strives not only to educate pet parents, but also empower them to make good health decisions for their pets. JoAnna is a member of the American Medical Writers Association and Dog Writers Association of America.

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