Can a tapeworm in a cat cause a false high thyroid level?

cat has been on methimazole 5 mg bid for a month with no visibal improvement in weight gain, threw up a tapeworm with a hairball and is now gaining weight. she wanted to eat all the time and is now only eats canned food when offered 2 x a day. Dry food is available 24/7 but has not been eating like before. Could thyroid medication be working now too or was weight loss related to tapeworm?

  • Vetinfo

    By: Julie Ann El Segundo, CA

    Replied on 04/19/2011

    Tapeworms rarely cause weight loss nor do they cause a false high thyroid level.   The vomited tapeworm and then the weight gain are probably not related.  You are likely seeing the changes due to the effects of the methimazole bringing the thyroid level down to a more normal level.

    A high thyroid level makes a cat eat much more than normal.  When the thyroid level goes down after beginning the medication the cat's appetite should go back to normal or near normal.

    It is generally recommended to recheck the cat's thyroid level and kidney function tests about a month after starting the methimazole.  The dosage of methimazole may need to be changed if the thyroid level is not in the normal range.  Kidney function can be affected by hyperthyroidism due to the hypertension (high blood pressure) that occurs as part of the disease.  Think of it as someone pushing water under force through a filter.  When the "force" is reduced to the normal level water goes through the filter slower.  When the hyperthyroidism is treated and the kidneys return to the normal filtering rate evidence of pre-existing kidney disease may be present. 

    Weight gain following treatment for the high thyroid is exactly what you want.  That is a good sign.  Feeding canned food to older cats is recommended by many cat specialists because it increases the cat's water intake due to the water content of canned food.   Extra water can help aging kidneys maintain their normal function longer.

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