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Tuesday, May 28, 2013

Feline Carpal Hyperextension And Hyperthyroidism

Did the big words in the title confuse my non-vet readers?  Today's entry links back to an entry from almost four years ago that I had honestly forgotten about!  Here's what Daphne wrote....

I had been trying to research my cat's condition online and had only found articles to do with injuries sustained from great heights, which is not the case here.  I started to get hopeful a bit after reading your blog:
My Billy will be 18 this summer.  We've been managing his hyperthyroid with Tapazole and two other supplements, rhemania 8 and Amino B-Plex (I've been seeing a holistic vet that practices chinese medicine as well).  One or two months ago, I started to notice Billy's left wrist quiver with effort to keep in its normal position.  Now both of them are noticeably hyperextended.  There is no known MOI as he's not as mobile in his old age, and has kept to the couch or bed (fairly low to the ground) for items to jump on for the last 2 - 3 years.  Other than a recent urinary tract issue, he's been eating and sleeping and being affectionate as normal.  I'm wondering if part of it is due to muscle wasting from his hyperthyroid?  Does hyperthyroidism affect ligaments?  Does hyperthyroidism lead to other neurological conditions or diabetes that could cause this?  I have an appointment with our vet. What are some good questions I could ask her, or how can I prepare myself and Billy for the appointment?

A complete and thorough exam is necessary here, Daphne.  Muscle wasting alone shouldn't lead to hyperextension, as the tendons and ligaments are what tend to cause such positioning.  Even with a loss of muscle mass the other connecting structures shouldn't be affected.  By itself hyperthyroidism shouldn't affect the ligaments, and only causes muscle reduction because of an increased metabolic rate causes the body to burn through fat and use muscle for energy.  Hypothyroidism can lead to ligament problems, but this is extraordinarily rare (I've never seen a case).

While diabetes can cause laxity in the ligaments and a "flat-footed" stance, this should not be caused by hyperthyroidism.  It is possible to have both disorders, but honestly diabetes is found in only about 1% of hyperthyroid cats.  We also don't tend to see direct neurological disorders as a cause of thyroid problems, so this wouldn't be likely.

Because the hyperextension is not likely to be caused by the high thyroid hormone I would suspect a secondary disorder, something likely unrelated.  I would plan on your vet wanting to run a full panel of blood tests, including rechecking the thyroid level.

On a secondary note this case illustrates the challenges vets often face.  We are taught to try and attribute all symptoms in a case to a single disorder.  It makes more sense that multiple symptoms are caused by one problem, rather than two or three going on at the same time.  Part of the diagnostic thought process is to figure out what one disease could cause everything that we're seeing.  However, sometimes there really are two different problems that happen to occur at the same time.  That makes the case much more complicated and harder to unravel as we try to figure out which symptoms go with which illness.

I hope this works out, Daphne.