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The Thyroid Gland

The Thyroid Gland is responsible for metabolism, Body Temperature and Heart Function; it is also associated with behaviour changes in dogs. It is the most Common disorder in the Endocrine System and causes genetic implications for breeding.

Hypothyroidism is an underactive gland, where as Hyperthyroidism is an overactive gland. The thyroid is located at either side of the throat and stimulated by a Thyroid Stimulating Hormone or TSH for short.


Hypothyroidism is the most common disorder in dogs, 80% comes from Autoimmune Lymphocytic Thyroiditis. Autoimmune diseases are when the immune systems attacks itself, it mistakes healthy cells as damaged and starts to wipe them out,


It effects mostly large breed dogs and is relatively unheard of in Small/miniature Dog Breeds. Dogs are usually diagnosed between the ages of 4 – 10 years. Clinical findings as quoted in the MSDVet Manual

Breeds reported to be predisposed include the Golden Retriever, Doberman Pinscher, Irish Setter, Miniature Schnauzer, Dachshund, Cocker Spaniel, and Airedale Terrier. There does not appear to be a sex predilection, but spayed females appear to have a higher risk of developing hypothyroidism than intact females.


Thyroid Disorders must be carefully diagnosed as the symptoms can mimic other diseases and misdiagnosis is very possible. It is in fact the most over diagnosed disease in dogs.


Hypothyroidism will slow the metabolism down, due to poor oxygen levels in the cells, there is not enough TSH or Cortizol available, this will cause symptoms of lethargy, weight gain, dry flaky skin, it can cause reproductive problems in female dogs, Seizures and mental dullness are other symptoms.


Hyperthyroidism on the other hand, will cause more TSH production, which will cause excess energy, just thinking about that can be worrying, it can cause Jitters in the dog, increased heart rate, the same in humans, ADHD in Human Children, has also been associated with Hyperthyroidism, shaking due to the excess energy. Weight loss and nervousness are other symptoms, its like the dog is in constant fight or flight, this could be dangerous and the cause of aggression in some dogs, so a vet would need to be seen as soon as any new behaviour is noticed, especially with any of the above symptoms,


A vet should be seen with any behaviour changes in the dog.


The causes can be brought on after trauma or Iodine deficiency or after cancer treatment when the immune system is at its weakest. Not forgetting hereditary passing.


Early diagnosis is imperative as when the symptoms have appeared the Gland is usually already damaged, noticing even the slightest physical or behavioural change could save a dogs life.