Hyperthyroidism in Cats – What YOU Need To Know!
23 July, 2013

As our cats get older, there are various ailments that are very typical among our senior cats.  Hyperthyroidism is very common in cats and simply means that your cat has an overactive thyroid. The typical signs of hyperthyroidism usually include weight loss (despite increased appetite), increased energy or irritability, and increased thirst and urination to name a few.

Below are the treatments available today to help your cat.

1. Hyperthyroid Prescribed Food

Hills Nutrition makes a prescribed food to help keep your cat’s thyroid balanced.  While this treatment is still yet to be proven, it makes an easy alternative to the below treatments.   The food is supposed to improve your cat’s thyroid in three weeks as it supports kidney health with controlled phosphorus and low sodium.   While the food can be expensive, it is a nice alternative to the other treatments listed below.

The only con is that the food is still very new and yet to be tested for the long term.  And, while your cat is eating this food, he can not eat or snack on anything but the food.  Because iodine intake from other food sources — treats, another pet’s food, etc. — can compromise the effectiveness of low-iodine nutrition, it’s critical that you follow your veterinarian’s feeding instructions carefully and feed only the prescribed food.

2.  Medication for your cat: Methimazole

This medication is in the form of a pill that needs to be given by mouth one to three times daily, depending on each cat’s case. Alternatively, compounding pharmacies can create a tasty liquid medication or a paste that is applied to the inside of the ears for absorption if pilling the cat is difficult or not an option.  This drug works by suppressing the thyroid gland’s production of thyroid hormone, but does not cure the disease. If treatment is stopped, the hyperthyroid condition will recur.

Methimazole Pros:

Does not require hospitalization or anesthesia and the initial costs are less; Initial costs are less

Can adjust the dose up or down fairly easily to control signs; and the side effects are usually mild and resolve over time (lethargy, anorexia, vomiting)

Methimazole Cons:

This medication is not a cure; signs will recur if the medication is stopped.  Blood test monitoring and the cost of pills can add up.  Some cats can experience more severe side effects (itching, liver failure, blood changes). Administering pills twice daily may be too difficult for the owner or the cat.

3.  Thyroid removal surgery

The thyroid gland consists of two parts, or lobes. Some vets remove only the visibly diseased lobe, others recommend removing both, since there is a high probability of the other lobe becoming diseased. Make sure that you have a skilled, recommended veterinary surgeon, and your kitty will be under a general anesthesia for the surgery. Careful pre-operative evaluation must be completed prior to surgery to assess kidney, liver and hyperthyroidism.

Surgery Pros:

The surgery is very often a curative for hyperthyroidism; No daily medications to administer.

Surgery Cons:

Anesthetic risk is higher for senior patients (and who often have compromised health of the heart or kidneys); more expense at one time and for post surgery monitoring; if any thyroid tissue is left behind, it may become hyperthyroid.

4. Radioiodine therapy

Treatment is via a single injection of radioiodine under the skin. The hyperactive thyroid tissue takes up large amounts of this substance via the bloodstream, and the diseased thyroid cells die.

Radioiodine Therapy Pros:

This is a curative for all diseased thyroid tissue in the body, even in atypical locations; No daily medications to administer; Safe – very few side effects; Parathyroid glands left intact; No anesthesia or surgery necessary

Radioiodine Therapy Cons:

Treatment must be given at a special facility; your cat must be boarded for a number of days post treatment due to radioactive wastes in litter box; Special disposal of litter box waste required for a period of weeks post treatment at home; A few cats may become hypothyroid post treatment Cats with underlying or latent problems, such as kidney failure, may have a rapid exacerbation of signs.

I hope that your cat never has hyperthyroidism, but if he or she does, it can be maintained. Good luck!

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