Dear Dr. John,
We have a 12-year-old spayed female Kerry Blue Terrier that has gotten especially untrustworthy and nasty over the last few years. She is somewhat thin but otherwise has always been in good health. Just last week, she attacked my college-age son and bit him on the wrist without provocation.
How common is it for an older dog or any dog to suddenly start to become aggressive like this?
She has had a good life in our home along with our two other smaller dogs that she sometimes also terrorizes. This never used to happen!
I had her seen by my vet, who discussed several possibilities and ran some blood tests.
She sometimes looks about aimlessly, so the vet’s thoughts were that she could have dog dementia and that she might benefit from a drug for that or possibly from Prozac for her aggression.
Then the blood tests came back and it turns out that she has a low thyroid condition. He said that this could be the cause of her mean streak, and he put her on a thyroid supplement.
Any thoughts, and will this cure her, or will we have to continue to live afraid of her attacks?— M.R.
It is not very common for any dog to suddenly become aggressive, but it surely can happen and for many possible reasons. They can include viruses and bacterial infections that can affect the central nervous system, trauma, rabies, metabolic disorders, tumors, seizures and even genetics.
Proper diagnostics should include blood work and urinalysis as well as possible X-rays, MRIs or CT scans. Sometimes one even needs to analyze cerebrospinal fluid to make a diagnosis.
Your veterinarian wisely did some blood work and found the hypothyroidism, which can cause aggression in dogs. These dogs can have cognitive dysfunction signs similar to dementia as well as strange fears and sudden outbursts of aggression. Strangely though, most hypothyroid dogs are overweight, lethargic and have thin, dull hair coats. The fact that your dog is thin is odd but surely possible.
I would suspect that the thyroid supplement will help, and hopefully it will completely resolve your problem. If not, other medications might be necessary as well, but I would start with what you have been directed. Good luck!Source URL: http://bostonherald.com/entertainment/lifestyle/2013/09/thyroid_problem_could_cause_dog_s_aggression