In Search of the Truth

Canine behavioral problems are believed by some authorities to be associated with hypothyroidism (low thyroid levels). For example, in a study involving 1500 dogs with behavior problems, 62% of them had low or low-normal thyroid function. While the mechanism by which low thyroid levels contribute to aggression is not entirely clear, it has been suggested that hypothyroidism leads to low or unstable levels of the neurotransmitter serotonin, a brain chemical associated with mood, attention, emotion and sleep. Another possible mechanism could be that the stress hormone cortisol is increased in hypothyroid animals, mimicking a stress-like state.

Psychiatrists have noted a link between aggression and hypothyroidism since the 1940s and have used thyroid hormone replacement therapy in human psychiatric medicine for years. Recently, Drs. Nicholas Dodman and Linda Aronson, of Tufts Cummings School of Veterinary Medicine (TCSVM), with the diagnostic help of Dr. Jean Dodds (Hemopet/Hemolife Laboratories) began treating dogs with behavior problems for low, or borderline-low, thyroid levels and noting an improvement in behavior problems, most notably aggression. While case studies are helpful to point the way, more conclusive evidence - in the form of placebo-controlled, double blinded studies - is ultimately needed to demonstrate the therapeutic value of thyroid replacement therapy in the treatment of canine behavior problems. For a start, researchers at TCSVM are currently enrolling dogs with low or borderline low thyroid levels and also exhibit owner-directed aggression, into an 8-week clinical trial.

If you own a dog that growls, lifts a lip, snaps at, or otherwise “bites the hand that feeds,” please contact Ms. Nicole Cottam, Animal Behavior Service Coordinator at TCSVM ,at 508-887-4802 ([email protected]) for more information about enrolling your dog. Owners of behaviorally qualified dogs will receive a free thyroid test and free behavior modification advice. A visit to TCSVM is not necessary if your local veterinarian is involved.


Nicholas Dodman BVMS MRCVS DACVB Director of Animal Behavior Clinic
Professor, Dept Clinical Sciences
Tufts Cummings School of Veterinary Medicine
200 Westboro Road, North Grafton, MA 01536

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