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Hyperthyroidism

             Mr. Smith had the telltale bags under his eyes, which complimented his slack, pale expression, which made it clear that he hadn’t been getting much sleep recently.  “ Its this cat.” he told me.  “Muffin has always been a nice, easygoing companion, but recently she has been getting me up every hour or so with the most obnoxious and insistent yowling.  Ignoring her doesn’t work.  She wont stop until I have poured her a fresh glass of water and topped off her food bowl.  She dives in like she has been lost in the desert for five days, and then she settles down for a while, but in another hour she is up and insisting again.  I’m beginning to think that I offended an evil spirit somewhere and now the cat has been charged with tormenting me for the remainder of my life.”

          I had bee seeing Muffin for years.  She had always been a relaxed patient with a Rubenesque silhouette that reflected the life of luxury that she lead.  The cat in front of me now was four pounds lighter than the last time she was in.  She was a little wild-eyed, and her heart rate was 250 beats per minute, a full 70 beats per minute higher than I would expect for a normal stressed out cat in the exam room.  The little lump I could feel at the base of her throat helped confirm my suspicions about what was going on.  I don’t know much about demonic possession in cats, but I can recognize the signs of hyperthyroidism when I see them.

          Confirmation of the diagnosis required some bloodwork to be sent out, and when we got the answers back it was clear that an overactive thyroid was the cause of  all these symptoms.  Fortunately for everyone involved we now had a variety of options to improve the situation.

          Hyperthyroidism in cats happens when one of the pair of thyroid glands located at the base of the throat develops a benign tumor that starts producing large amounts of thyroid hormone and ignores all the feedback signals that are telling it to stop.  Thyroid hormone is responsible for revving up the metabolism and keeping everything ticking along at a brisk pace.  Cats with too much thyroid hormone will typically lose weight in spite of having voracious appetites, drink enormous amounts of water and urinate more than usual, and often develop a frantically pushy attitude that can manifest itself with a lot of loud yowling at night.  As attention getting as these symptoms are, it is actually the unseen effects of too much thyroid hormone that cause the most serious problems.  Blood pressure rises, which can lead to kidney damage and blindness from retinal detachment.  Heart rate speeds up which causes a thickening of the heart muscle and leads to heart failure and potentially fatal blood clots.  These symptoms usually manifest in cats that are 14 years old or older. 

          There are three main options for treatment: medication, surgery, and radioactive iodine therapy.  Methimazole is a medication that blocks the action of excess thyroid hormone.  It does not stop the growth of the tumor that is producing the extra hormone, so as time goes on the dosage of Methimazole may need to be increased in order to stay effective.  Regular monitoring of thyroid, liver, and kidney values is needed.

         Surgery involves removing  the malfunctioning thyroid gland.  The remaining normal gland can then take back over producing a normal amount of thyroid hormone.  The up front cost of surgery is greater, but in the long run it may allow resolution of the problem without the continual medication and monitoring.  Unfortunately for a small number of  cats  the remaining thyroid gland will develop a tumor itself and start the whole process over again. 

           The best treatment available is radioactive iodine.  When a cat is given an injection of radioactive iodine the bad thyroid gland takes up the radiation which kills the abnormal cells.  The good thyroid gland gets almost no radiation and the normal cells are left functioning.  The treatment itself is not much more involved than giving a subcutaneous injection, like a vaccine, and it does not tend to make the cats feel sick at all,  but a special facility is needed to deal with the radioactive materials and with the radioactive patients until they are safe to go back to their families.  Because of the complexity of managing the radiation the treatment is the most expensive up front, but it is the most gentle for the cat and the most effective in the long run.  We are fortunate to have a facility for radioactive iodine treatment as close as Monument.

          Now that Muffin has gotten treatment for her hyperthyroidism everyone in her household is doing much better, and Mr. Smith can rest easier knowing that it wasn’t just an evil plan from his cat to drive him to insanity.

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