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(Scientific Name: Functional Thyroid Adenomatous Hyperplasia/Thyrotoxicosis)

Hyperthyroidism is a condition that exists when an enlarged thyroid is overactive and both the body’s metabolism and processes are shifted into overdrive. Over the last few years, hyperthyroidism in cats has increased approximately 25%. Female cats that are middle-aged or older are most affected. Nine out of ten cats that have hyperthyroidism are over ten years old.


Hyperthyroidism is created through an excess (“hyper”) hormonal imbalance. The thyroid (located in the front of the neck in front of the windpipe) is responsible for releasing hormones that control your cat’s metabolism. With hyperthyroidism, excess hormones are released into your feline’s body and consequently its body processes speed up and they become overly restless or hyperactive. Hyperthyroidism can be fatal if left untreated.


The list of possible causes of feline hyperthyroidism is extensive and includes: inflammation, infection, tumors, immunologic, autoimmune, imbalances or toxic substances, some ingredients and types of foods cats are being fed, immunological factors and some environmental influences.


Another possible theory concerns canned cat food. One of the first cases of feline hyperthyroidism was noted in 1979 – approximately two years after pop-top cat food cans were available. An EPA study in 2000 theorized there was a possible link between cats that ate canned foods (particularly those with fish flavor) and hyperthyroidism due to the chemical used to coat the inside of the cat food cans. However, it is important to also note cats that have only eaten dry food have also developed hyperthyroidism.


SYMPTOMS: When the thyroid begins to overproduce thyroid hormones, some or all of the following symptoms below will become noticeable in the feline with this disorder:


» Increased appetite;

» Unexplained weight loss and loss of muscle mass; » Increased thirst and urination;

» A rapid and pounding heart rate, panting;

» Frequent vomiting and diarrhea;

» Excitability, aggressiveness, agitation; hyperactivity;

» Increased body temperature;

» Tremors, weakness and lethargy; and

» Loss of hair and an unkempt appearance.


Not all the symptoms listed above will present themselves in every cat with hyperthyroidism. However, any one or two of these symptoms warrants a visit to your veterinarian for an examination and proper diagnosis. Since hyperthyroidism can predispose a feline to subsequent heart issues/disease, blood pressure problems and kidney damage/failure, early diagnosis and treatment by your veterinarian is critical. Both palpation of the feline’s thyroid gland and blood tests will be done to confirm hyperthyroidism.




Clinical treatments for cats with hyperthyroidism typically include the following three options:



» Daily treatment with an anti-thyroid drug (typically methimazole). The primary problem with this treatment is that it is not a cure. Treatment will be needed to be given every day (one pill given once or twice a day) for the rest of the feline’s life. Regular blood tests will also be necessary to closely monitor and regulate the feline hormone levels.


1.This is the most non-invasive option and relatively inexpensive (depending on the cat’s age when the condition develops).

2.Side effects may include vomiting, anorexia, fever, anemia and lethargy.


» Surgical intervention is another effective treatment using a procedure called a “thyroidectomy” (the removal of the thyroid gland). This option is usually selected when only one thyroid lobe is involved.


1.This option will cure the hyperthyroidism with no further need for daily drug treatment; but it is invasive and expensive.

2.It is possible for the hyperthyroidism to re-occur.

3.A cat with kidney disease cannot have this surgery.

4.A possible side effect is hypothyroidism (an underactive



» Radioactive Iodine Treatment is a fairly new treatment that provides a permanent cure in 95% of all feline hyperthyroidism cases. A single injection of radioactive iodine ‘finds’ and destroys all the diseased tissue while sparing the healthy tissue.


1.There are no known serious side effects and minimizes stress to the feline.

2.The procedure is invasive and requires radioactive material to be put in your feline’s body.

3.Your cat must be isolated away from you for a few days until the radioactivity is gone.

4.This treatment is expensive – approximately the same cost as the surgical option.

5.A possible side effect is hypothyroidism (an underactive thyroid) which will require life-long thyroid supplementation.


Integrative Medicine


Not all animals can use all natural remedies; allergic reactions to oils
and/or herbs and digestive problems are possible.
A natural remedy is not a substitute for veterinary care.


The following nutraceuticals or natural/herbal formulas can also provide effective treatment for your feline living with hyperthyroidism.


» Rehmannia Root (Cooked): An herbal root effective in treating auto-immune diseases in general and to also reduce hyperthyroid function.

» Cornus Fruit: A dried fruit pulp which helps balance an overactive thyroid.

» Poria Sclerotium (Hoelen): A mushroom that in many part of the world is used as a food instead of a medicine.

» And other herbal remedies such as: Dioscorea Root, Moutan Bark, Alisma Rhizome, Anemarrhena Rhizome, Phellodendron Bark, Kelp Thallus, Vervain Rhizome and Bugleweed Leaf.


– Feline Products –

(Reference: Veterinarians’ Desk Reference)

(Live Link)






Cats: ½-1 scoop/day

Inhibits thyroid, moisten tissues, decreases heat.


Cats: ½ capsule sid

If associated cardiomyopathy is present.


To help you quickly find the right Integrative Medicine formulas and manufacturers to help treat your dogs, cats and horses, please refer to the Veterinarians’ Desk Reference
(Click Here)


(Always consult with your veterinarian to properly diagnose any health problems. Misdiagnosis and/or mistreatment -- including OTC and/or homeopathic products -- can lead to dangerous complications.



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