PetMeds® Treating Hyperthyroidism in Cats

Hyperthyroidism or an overactive thyroid is the most common hormonal disease seen in older cats. The most common symptoms include weight loss (despite an increased appetite), as well as increased thirst and urination. Some cats may become more restless and vocalize more, as well as develop inappropriate urination or defecation. If left untreated, hyperthyroidism can lead to high blood pressure, kidney damage or secondary heart disease.

Diagnosis is usually made by blood measurement of Thyroid levels, usually a T4 in conjunction with a free T4. There have been traditionally three options of treatment. The most common form of treatment is with a prescription medicine known as Methimazole.  This medicine must be given daily to twice daily, and periodic thyroid level  blood monitoring is needed every 3-6 months after initial control is obtained, , as well as monitoring of the blood count, and liver/kidney function  to make sure there are no ill effects of the medication.

Occasionally cats will become lethargic, vomit, or lose their appetite on Methimazole. However, with dose adjustments, most cats do tolerate Methimazole quite well, which needs to be maintained for the life of the cat. Other options of treatment include using radioactive iodine, which is preferred by many as a single dose curative treatment in most cases.  Surgical removal of the thyroid gland is no longer as common, due to surgical risk in many of these older cats.

In my experience there are not that many effective supplements for cats to treat the overactive thyroid, however, if your cat will accept cooked brassica veggies like broccoli or kale, these can sometimes have a thyroid-lowering effect. The herb bugleweed has been used by some, but data as to efficacy is limited.

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  1. I wanted to recommend topical DMSO for kitties with methimazole-induced cholestasis. Cannabidiol may help too.

  2. Hi. I wanted to share and ask for some basic recommendations for kitties with hyperthyroid and liver or renal disease.

    My cat was hyperthyroid for many years. She spent about a year on y/d then refused to eat it so I tried methimazole and almost killed her with it. The cholestasis, hepatitis improved and pancreatitis reversed after I experimented with topical DMSO and ionic silver. This isn’t surprising because DMSO is a powerful antiinflammatory andsupports the liver. The great news is that her T4 went into the normal range without my specifically attempting to remedy the thyroid. I may have found a non-junk-food, safe-for-compromised-kidneys remedy for hyperthyroidism. I will include info on how I treated her on my website when I have time to type it up.

    My question to you is, other than a raw diet- what do you recommend to support the liver and kidneys of hyperthyroid cats? What homeopathic/gentle remedies do you typically turn to? This cat hates milk thistle when added to food and I don’t like the idea of pilling her so many times a day so I’m looking for something to add to her water and that of the other renal/thyroid patients in my sanctuary. Some general ideas would be appreciated and I can do some research.

    Many thanks for the help you have provided thus far.

    • Dr. Michael Dym, VMD veterinarianNovember 2, 2014 at 2:51 pm · Reply

      Thanks for your sharing. the website has some interesting thyroid and other liquid herbal supplements. I would also see the book the Natural Cat by Anitra Frazier, who is a good friend of mine. You could try the supplement Senior blend, which is wonderful herbal support for liver/kidneys of older animals Hope this helps.

  3. My cat is 14 and on Methimazole 5 mg. twice daily. I give it to her morning and 12 hrs. later; attempting the same time everyday. Sometimes I loose track of time and am wondering how I should treat those times. Should I skip that first dose or give it to her late? Thank you.

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