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Behavioral Changes Associated with Thyroid Dysfunction in Dogs

"Another interesting association which has been increasing in frequency is the link between thyroid dysfunction and aberrant behavior.

Typical clinical signs include unprovoked aggression towards other animals and/or people, sudden onset of a seizure disorder in adulthood, disorientation, moodiness, erratic temperament, periods of hyperactivity, hypoattentiveness, depression, fearfulness and phobias, anxiety, submissiveness, passivity, compulsiveness and irritability.

After the episodes, a majority of the animals were noted to behave as if they were coming out of a trance like state, and were unaware of their previous behavior....

Hypothyroid patients have reduced cortisol clearance, and the constantly elevated levels of circulating cortisol mimic the condition of an animal in a constant state of stress, as well as suppressed TSH output and the production of thyroid hormones.

In humans and seemingly in dogs, mental function is impaired and the animal is likely to respond to stress in a stereotypical rather than a reasoned fashion. Chronic stress in humans has been implicated in the pathogeneiss of affective disorders such as depression.

Major depression has been shown in imaging studies to produce changes in neural activity or volume in areas of the brain which regulate aggressive and other behaviors. Dopamine and serotonin receptors have been clearly demonstrated to be involved in aggressive pathways in the CNS.

Hypothyroid rats have increased turnover of serotonin and dopamine receptors and an increased sensitivity to ambient neurotransmitter levels. In dogs with aberrant aggression, a large collaborative study at Tufts University has shown a favorable response to thyroid replacement therapy within the first week of treatment, whereas it took about three weeks to correct their metabolic deficit.

Dramatic reversal of behavior with resumption of previous problems has occurred in some cases if only a single dose is missed. (In a 634 case group with aberrant behavior, thyroid dysfunction was found in 62% of the aggressive dogs.)"

Behavioral Changes Associated with Thyroid Dysfunction in Dogs - W. Jean Dodds and Linda P. Aronson (proceedings of the 1999 American Holistic Veterinary Medical Association Annual Conference, pgs 80 - 82)

"Aberrant Behavior and Thyroid Dysfunction An additional noteworthy clinical finding in dogs affected with thyroid or polyglandular autoimmune disease has been the sudden or progressive onset of aberrant behavior including aggression, submissiveness, shyness, fearfulness, passivity, seizure disorder, excitability, sensitivity to noise, anxiety, irritability, compulsiveness, chewing, moodiness, lethargy, depression and unstable temperament.

A similar association between behavioral and psychologic dysfunction has been recognized in humans since the 19th century...(charts and tables on canine cases of diagnostic profiling of over 300 dogs of aberrant behavior compiled by this author (Dr. Dodds) in collaboration with Drs. Nicholas Dodman, Linda Aronson and Jean DeNapoli of Tufts).

...these initial results are so promising that complete thyroid diagnostic profiling and treatment with thyroid supplement, where indicated, is warranted for all cases presenting with aberrant behavior."

What's New in Thyroid Disease - W. Jean Dodds (Proceedings of the 1997 American Holistic Veterinary Medical Association Annual Conference, pgs 82 - 95)

Thyroid Can Alter Behavior - W. Jean Dodds (published in DogWorld October 1992)

" the onset of puberty which varies from seven months to a year in age, sudden major changes in personality are observed. Typical signs may include incessant whining, nervousness, schizoid behavior, fear in the presence of strangers, hyperventilation, undue sweating, occasional disorientation and failure to be attentive.

These can progress to sudden unprovoked aggressiveness in unfamiliar situations with other animals and with people, especially children....for a significant proportion of these animals, however, neutering does not alter the symptoms and they intensify progressively to the point that the adult can be described as flaky, unable to handle any kind of stress, frantically circling, hyperventilating and not able to settle down....

In some cases affected animals do not show aggression but become very shy and fearful to the point that they are social outcasts...experience seizure or seizurelike some cases the animals become aggressive and attack those around them shortly before or after having on of these seizure episodes....

If your otherwise healthy young or adult dog experiences sudden behavioral changes, you should consult your vet and check for an underlying thyroid imbalance...."

Thyroid Dysfunction as a Cause of Aggression in Dogs and Cats - L.P. Aronson and N. H. Dodman, August 1997 veterinary conference in Germany

Here are a couple of additional links

I would like to thank Therese McClain for compiling this information.

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