An association has recently been reported between aberrant behavior and thyroid dysfunction in the dog. Typical clinical signs include unprovoked aggression towards other animals and/or people, sudden onset of a seizure disorder at puberty or in adults, disorientation, moodiness, erratic temperament, periods of hyperactivity, hypoattentiveness, depression, fearfulness and phobias, anxiety, submissiveness, passivity, compulsiveness, and irritability. After the episodes, most of the animals appeared to be coming out of a trance-like state and were unaware of their previous behavior.

The study involves more than 1500 cases of dogs presented to veterinary clinics for aberrant behavior. The first 499 cases have been analyzed independently by a neural network correlative statistical program. Results showed a significant relationship between thyroid dysfunction and seizure disorder, and thyroid dysfunction and dog/to/human aggression. Treatment outcome followup in 95 cases showed a significant behavioral improvement in 61% of the dogs.

Based on these findings, we advise including thyroid antibody testing as part of the laboratory and clinical work up of any behavioral case.

A recent study of 20 healthy research Beagles and 16 healthy pet dogs was undertaken to determine whether routine multivalent and/or rabies vaccination induced production of antibodies against canine thyroglobulin. Antibodies against bovine thyroglobulin were also measured. Published results indicated that a significant increase in antibovine thyroglobulin antibodies was found in all vaccinated research dogs in comparison with unvaccinated control dogs. Anticanine thyroglobin antibodies were significantly increased in all research dogs receiving rabies vaccine but not in the group that received only the multivalent vaccine without a rabies vaccine. In the pet dogs, a significant increase in anticanine but not antibovine thyroglobulin antibodies was seen 2 weeks after vaccination with combined multivalent and rabies vaccines. In some of the dogs, the level of anticanine thyroglobulin antibodies was in the range observed in dogs with spontaneous thyroiditis. While the duration of these vaccine-induced anticanine thyroglobulin antibodies is unclear, we recommend retesting the dogs in 4-6 months.

The clinical importance of these findings is unknown at the present time, although vaccine administration has been implicated as a contributing factor in autoimmune diseases such as thyroiditis, immune-mediated hemolytic anemia and thrombocytopenia, and immune arthropathies.