Thyroid hormone affects so many body functions. It
definitely is known to affect some sensory functions and some emotional functions.
Low thyroid levels in humans are known to be able to cause symptoms of full blown major depression. Some
humans with depression who do not respond to anti depressant drugs will respond to those same drugs if they
also get thyroid supplement. Children who are depressed can act in ways
that the parents and teachers perceive as "irritable" or as "aggressive" rather
than as "sad" or "depressed" . so possibly a child with low thyroid would
behave similarly. likewise a dog.
Definitely have been cases where low thyroid in dogs has caused dog to behave irritably,
aggressively, or in a spooky or "paranoid" manner. When I say cause, I mean that supplementation has resulted in major
improvement. Sometimes these dogs are only borderline low or have levels
in the "gray zone" between what is considered to be normal and what is considered to be deficient.
There has been some publications in the vet lit
about this, especially from Jeann Dodds. My own vet had a case of a dog who had
begun behaving aggressively and because she had seen in the vet lit that low thyroid could
cause such behavior she tested him. came out borderline low, so she put him on
supplement. behavior improved fairly soon. later on the owners for some reason
stopped the supplement and soon after the dog's behavior deteriorated. resumed supplement and behavior again improved.
In the tracking world it is fairly well known that dogs who are low thyroid can have deficient sense of smell or at any rate can be
hard to train to track because they seem to have trouble perceiving
the track. when supplemented to normal range, these dogs improve in ability
to learn to track. no one knows if the effect is occurring at the level of the
sensory receptor cells or if it is occurring at higher brain levels.
I have personally observed that dogs who are low in thyroid levels will exhibit an
insensitivity to electrical stimuli. I have trained a lot of dogs of all kinds of temperament to acquire a solidly reliable
recall under conditions that can include major distraction (running rabbit
etc) by use of low level negative reinforcement , i.e. use of remote collar
working at the lowest level that the dog can perceive as mildly uncomfortable -- the level of a particularly annoying and
persistent flea. flea starts to bite as I give the recall command and immediately I use the
long leash to draw the dog in to me (a distance of just a few steps) and
the flea stops biting as soon as the dog arrives at my feet. later at longer distances the flea stops biting as soon as the dog has made a few
steps towards me. Now what I have found is that for the low thyroid dogs,
the lowest level of stimulus that they can perceive as annoying, lowest level that
causes a twitch of neck muscles or other subtle reaction, is higher than average -- and more importantly, after these dogs have been on
thyroid supplement a few weeks , then the level of stimulation needed to
get this same response will drop by at least one level (one Tritronics collar insert button) and sometimes by two levels. again there is no way
to know whether this effect is occurring at the levels of the sensory receptor cells or
whether it occurs at a higher CNS level.
I'm not aware of as much info in the vet lit or the training lit about behavioral effects of high thyroid. but it stands to
reason that if low levels have some behavior or sensory effects, high levels would also have effects. Kevin's reports (quoted below) of Dragon's
behavior when an unauthorized use of thyroid supplement by show handler resulted in the dog being artificially high
thyroid and the results when removal of this supplementation restored the dog to normal thyroid levels
constitutes valuable observations worthy of serious attention. Here is a
case of high thyroid levels apparently causing a dog to behave more aggressively. If so then both high
and low levels can cause aggressive behavior.
For our Bouvier breed, where low thyroid is not uncommon, it seems to me that any time a dog is behaving irritably,
aggressively, depressedly, or spooky/schizo, the veterinary "rule outs" should include a
blood test for thyroid level. Hey it's a minimally invasive test (i.e. minor
inconvenience to dog of having a tablespoon of blood drawn) and very modest in cost, and it just might yield the
answer or an important part of the answer.
Those rescue groups able to afford to include a thyroid test in their
basic pre-adoption health protocol ( spay/neuter plus shots being of course the imperative elements ; heartworm test and prevention
being highly desirable ) would probably do well to do so fairly early in the
fostering process. If the dog's behavior is iffy, then the thyroid test becomes a higher priority.
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Thyroid
