Tuesday, April 12, 2011

Happy old cat

Last weekend, I was presented with a 17 year old, female spayed kitty. She weighed in at a whopping 4.7 pounds! Her coat was greasy and unkempt. Her heart rate was very high. Worse, she was extremely ataxic (staggering) and unable to lift her head. Her head pointed straight at the ground, and she could not lift it.

Previously, this thin kitty (Ms Kitty) was diagnosed with hyperthyroidism. This is a fairly common condition in older cats in which the thyroid gland becomes overactive. As a result, excessive amounts of thyroid hormone are produced in the body. This causes a sharp increase in metabolism - leading to a cat with a sky-high metabolism: ravenous appetite but constant weight loss (due to the extremely high demands of the body for energy). The heart rate speeds up - sometimes to 250-300 beats per minute. As a result, the heart muscle thickens significantly, and the cat develops a secondary heart problem (hypertrophic cardiomyopathy). It's a very treatable condition - either with oral medications to down regulate the thyroid hormone, surgery to remove the thyroid glands, or radiation therapy to the glands to destroy them.

This cat was diagnosed with hyperthyroidism a year ago. She'd been on medications for a while, but the owner had stopped due to the side effects. She was supposed to see her veterinarian and start them back 4 months ago. She never did. Now, I was staring at the typical emaciated, weak hyperthyroid cat. She was worse than the usual though.

"Thyroid storm" is a well-described condition in humans. The thyroid hormones can spike and bring on an extremely high heart rate, a high body temperature (again, due to the high metabolic rate), increased respiratory rate, irregular behavior (aggression, hyperactivity), and weakness. Until recently, this condition was not really described in animals. It was then realized that this may indeed happen in animals - especially old cats with uncontrolled thyroid disease.

The syndrome is described as causing profound weakness, ataxia, cervical ventroflexion (inability to hold the head/neck up), high heart rate, respiratory distress, and changes in behavior (in cats). So...I was faced with a kitty possibly having a thyroid storm. On the other hand, cervical ventroflexion and weakness can arise secondary to changes in electrolyte status - specifically low potassium. Ms Kitty's potassium was indeed low. On the OTHER hand, hypokalemia can occur with hyperthyroidism...so - was it related to the thyroid problem? Was she hypokalemic for some other reason? Her urine was dilute, although her kidney values were normal, so I also suspected early renal insufficiency. There were many pieces to this puzzle, and I couldn't make them all fit.

So, I was left guessing. The test for hyperthyroidism must be sent to an outside laboratory. There is nothing I could do in-house to confirm my suspicion. I was left with treating the kitty with an anti-thyroid medication, potassium supplementation in her fluids, a beta blocker to slow down her heart rate some (as well as to interfere with the body's usage of all that extra thyroid hormone), and CROSSING MY FINGERS that I was doing the right thing.

When she left on Monday morning, she was purring, eating, and soliciting attention. Her potassium was in the normal range, finally. Hopefully, her owner will take her thyroid disease seriously, and she will live a few more happy, healthy kitty years.

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