Cat Hyperthyroidism

by Dr. Kathryn Sarpong

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Your cat is losing weight, being hyperactive, no longer sleeping, and may be hungry all the time. What is going on?  Your cat may have something very treatable that can be found on a blood test. Your veterinarian will likely want to check your cat’s thyroid levels.  The thyroid is a gland located by the trachea in the neck that controls the body’s metabolic rate.  Sometimes it becomes hyperactive in cats as they age and can result in the symptoms above as well as immune problems, heart murmurs, vomiting, and drinking more and urinating more.

Luckily, hyperthyroidism can be treated!

Cats are usually given METHIMAZOLE – a tablet stops the excess production of thyroid.  If they will not swallow a pill, they can take a gel formulation of this medicine that goes inside the ears.  The tablet form of the medications is not expensive and has few side effects.  A few cats are allergic to it and develop a rash.  Some cats may have problems with vomiting from this medicine.

Another treatment option is radioactive iodine I131.  With this treatment, cats are given a special iodine that destroys the tissue that is making too much hormone.  Cats must stay at the hospital for a week after treatment, but they are generally medication free after this treatment.   This is very cost intensive for the first month, but then these cats do not require much ongoing monitoring or medication.

Some cats are treated with a special food that is iodine restricted (HILLS Y/DTM).  We use this in cats that cannot take methimazole and are not candidates for the radioactive iodine.

Rarely, surgery is recommended to remove the thyroid gland.  There can be complications from surgery, so it is rarely a first line option.

Each treatment option has pros and cons and your veterinarian can guide you on what is best for your kitty.  Once treated, cats tend to gain weight, normalize their heart rates, and appetite.   After treatment cats are rechecked to make certain no other organ dysfunction has been masked by the thyroid disease.  Some of these cats also have kidney disease that needs to be managed.  Many hyperthyroid cats live for years after the initial diagnosis.