Hypothyroidism in Dogs

Hypothyroidism in Dogs

Hypothyroidism is a common endocrine disease in dogs. It can lead to unexplained weight gain, skin and coat problems, as well as a reduced level of energy in the dog. The cause of this disease is still poorly understood. Generally it is caused by the immune system attacking the thyroid (immune mediated lymphocitic thyroiditis) or sometimes by the gland's tissues being replaced by fat (idiopathic atrophy). The net result is that the thyroid does not produce enough thyroid hormones (designated T3 and T4). There are claims that the condition might be initiated by external factors, but the studies done to date are inadequate to draw strong conclusions from them.


Signs that your dog might suffer from this condition are:

  • Unexplained weight gain
  • Lack of energy
  • Intolerance for Cold
  • Thinning of coat, Post-clipping alopecia (hair loss)
  • Thickening of skin
  • Dull fur
  • Slow heart rate
  • Frequently recurring infections of the skin and ears (pyoderma or otitis externa)
Hypothyroid labrador showing hair loss
Hypothyroid Labrador showing signs of hair loss. Source: MediaWiki Commons

If you suspect that your dog might be suffering from this condition, you should have your vet perform a diagnosis. This will include a blood test to determine whether your dog's T3 and T4 hormones are within the normal range for your pet. If your pet is diagnosed with this condition he will receive a prescription of the synthetic thyroid hormone, called levothyroxine (L-T4). Unfortunately your dog will have to remain on this prescription for life. From personal experience, I can attest to the efficacy of this treatment. You will quickly see an improvement in your dogs energy levels, as well as his resistance to skin infections.

Breeds Affected

Hypothyroidism appears to affect medium to large-size breeds more than small dog breeds. Breeds that have been reported to be predisposed to this condition are2:

  • Golden Retriever
  • Doberman Pinscher
  • Irish Setter
  • Miniature Schnauzer
  • Dachshund
  • Cocker Spaniel
  • Airedale Terrier

Our boy Zeus, a brown Border Collie, also suffers from this condition, so other breeds can also be afflicted by this disease.


It is very important that a dog with hypothyroidism eat a balanced meal. Low fat, lean meats are easier to digest and the amino acids from the protein regulate the production of thyroid-stimulating hormones in the pituitary gland. Foods high in Omega-3 fatty acids are important as the fatty acids stimulate the production of TSH (thyroid-stimulating hormones). Dogs with hypothyroidism also frequently suffer from an iodine deficiency, it is therefore recommended that you consider supplements/foods with iodine to add to your dogs diet.

[1] - Copyright Creative Commons CC BY-SA 3.0 Derivative Work Original Sources: a) https://www.flickr.com/photos/petsadviser-pix/8655276316 b) https://upload.wikimedia.org/wikipedia/commons/5/5f/Levothyroxine2DCSD.svg
[2] - https://www.msdvetmanual.com/endocrine-system/the-thyroid-gland/hypothyroidism-in-animals
[3] - Copyright Creative Commons BY-SA 3.0 Source: https://commons.wikimedia.org/wiki/File:Hypothyroid_labrador_2.jpg
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