Dear Dennis,

One day it occurred to me that you, a fat cat in your youth, had become skinny. Initially it was good to see you becoming more svelte. We’d been trying for years to get weight off of you, and so when you reached your teens and began to finally slim down, it was kind of nice. Until you went past ‘nicely slim’ to skinny.

You were still eating well, and there didn’t seem to be any more vomiting than usual, but something was obviously going on. It was time for a car ride to the clinic!

There are several reasons why an older cat might start to unexpectedly lose weight, beyond food management issues. The list includes: heart disease, respiratory disease, diabetes, thyroid disease, gastrointestinal diseases, kidney disease and cancer.

First, we did general blood testing to screen for kidney and liver disease, anemia and thyroid disease. I wasn’t surprised to find you had high thyroid levels. This is a disease called Hyperthyroidism, and there is lots of information available on this condition in cats.

There are different options available to deal with this condition in cats and they all have pros and cons. There is medication, surgery, radioactive iodine therapy and diet therapy available. Surgery and radioactive iodine therapy have the advantage of being a one-time treatment that ideally returns your cat to good health, but there are risks and side effects with these options. They are also not usually available at a regular clinic and would require referral and travel. Diet therapy was not a good option for you Dennis, because we had two other cats in the household at the time and making sure you and only you at the prescription food would be difficult.

Because you were easy to pill (hiding the pill inside anything edible worked very well), that’s where we started, and your thyroid levels returned to the normal range fairly quickly.

With any hyperthyroid cat, kidney health needs to be checked when the thyroid levels return to normal. High thyroid levels cause increased blood pressure, which can mask kidney disease in an older cat. We were lucky, your kidney values were also good when we rechecked your blood work.

Overall, hyperthyroidism in an older cat is one of the conditions that can be managed well, but once they are on medication they will need to stay on it for life.

I knew we were on the right track when you started to gain back some weight.