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Hypothyroidism in Dogs: Symptoms & Treatment

Nicole Cosgrove

Just like humans, dogs have a thyroid gland that releases hormones to control metabolic rate. When the thyroid’s production of these hormones is impaired and secretion reduces, it causes a drop in the metabolic rate. This condition is known as hypothyroidism, and it affects many species of animal. It’s the opposite of hyperthyroidism, in which excessive levels of hormones are secreted and cause the metabolism to skyrocket, leading to a loss of weight, increase in anxiety, and more.

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What Causes Hypothyroidism?

In the vast majority of hypothyroidism cases, the condition seems to stem from the destruction of the thyroid gland. Most of the time, either lymphocytic thyroiditis or idiopathic atrophy of the thyroid gland are the reasons for this. Lymphocytic thyroiditis is the more common culprit of the two, and it’s believed to be an immune-mediated disease. Essentially, this means that the immune system has wrongly identified the thyroid as a foreign body and has begun attacking it. Idiopathic atrophy of the thyroid gland is when the tissue of the gland degenerates, being replaced with fat tissue instead.

fat golden retriever lying on grass
Image Credit: Barbara Danázs, Pixabay

Signs and Symptoms of Hypothyroidism in Dogs

When hypothyroidism starts to set in and your dog’s metabolism drops, several signs should be visible. Some of these symptoms are experienced almost universally by dogs that suffer from hypothyroidism while other symptoms are much rarer and are considered to be abnormal symptoms, though they do occur with enough frequency to warrant listing.

Common Signs of Hypothyroidism

  • Hair doesn’t grow back after being cut
  • Reduced heart rate
  • Excessive shedding
  • Dry and dull coat
  • Dark pigmentation in the skin increases
  • Skin and ear infections become more prevalent
  • Loss of energy and desire to play or exercise
  • High blood cholesterol
  • Gaining weight without eating more
  • No tolerance to the cold
  • Thinning hair – the coat may even be practically bald in places

Less Common Symptoms of Hypothyroidism

  • Facial skin becomes thick, forcing the face into a grimace
  • Fat deposits form in the corneas
  • Lack of tear production causing dry eye
  • Reduced libido and infertility (only applies to non-fixed males)
  • Infertility, miscarriage, cessation of heat periods (applies only to females)
  • Nerves stop functioning properly
  • Lameness
  • Dragging the feet
  • Loss of coordination
  • Tilted head

Diagnosing Hypothyroidism in Dogs

You’ll need to schedule a vet visit for a proper diagnosis of hypothyroidism. Your vet will most likely perform a total thyroxin level test known as TT4. It measures the concentrations of thyroxin, the main thyroid hormone, in the blood. If thyroxin levels are low and other clinical signs are present, then the vet may continue testing with a free T4 by equilibrium dialysis test or a panel test that measures concentrations of several thyroxin forms.

Should this second test also come back showing your dog has decreased levels of thyroxin, then a positive diagnosis of hypothyroidism has been made. On the other hand, if your dog showed low levels on the first test but not the second, then it does not have hypothyroidism and additional testing could be administered to determine what the cause of your dog’s symptoms is.

ear infection on dog
Image Credit: dawi88888, Shutterstock

How Is Hypothyroidism Treated in Dogs?

Unfortunately, hypothyroidism cannot be cured in dogs, though it can be managed with proper treatment, which will be ongoing for the remainder of your dog’s life. Treatment involves daily dosing of an oral thyroid replacement hormone that should allow your dog’s metabolism to function like normal. Dosing starts at a standard level based on your dog’s weight.

One month into treatment, a blood sample will be used to determine whether the medication is returning hormone levels to where they should be, allowing the vet to adjust the dosage as needed. Over time, your dog’s body might change, which will necessitate another adjustment to the dosage, so thyroid hormone levels are generally tested every six months to ensure that hypothyroidism management is still going as planned.

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Conclusion

If undiagnosed and untreated, hypothyroidism can make your dog’s life miserable and drastically reduce its quality of life. Thankfully, this is a manageable condition, even though it’s incurable. With daily medication, your dog could live a long, healthy life free of hypothyroidism’s effects. If you believe your dog is exhibiting signs of a reduced metabolism, take it to the vet for screening and proper diagnosis so you can begin administering medication and return your dog’s quality of life to normal levels.


Featured Image Credit: Marut Sayannikroth, Shutterstock

Nicole Cosgrove

Nicole is the proud mom of Baby, a Burmese cat and Rosa, a New Zealand Huntaway. A Canadian expat, Nicole now lives on a lush forest property with her Kiwi husband in New Zealand. She has a strong love for all animals of all shapes and sizes (and particularly loves a good interspecies friendship) and wants to share her animal knowledge and other experts' knowledge with pet lovers across the globe.