Hyperthyroidism is probably the most common endocrine disease affecting older cats.

Hyperthyroidism is caused by excessive thyroid gland production and secretion of

thyroxine (T4) and triiodothyronine (T3) hormones.

The condition rarely appears in cats under 8 years of age.

Owner observations for cats with Hyperthyroidism may include some of the following signs:

Clinical Sign                                 % of Cats

Weight loss                                           93

Increased appetite                                 56

Rough hair coat                                     46

Increased thirst / urination                      44

Vomiting                                               44

Nervous/hyperactive                               34          

Abnormal stools (feces)                           25

Panting                                                12

Decreased appetite                                 6

Increased Vocalization

Itching

Important Points in Treatment

1.  Blood tests are necessary to diagnose the condition and monitor treatment.

When your cat is first diagnosed with hyperthyroidism, treatment options available are:

¨ Methimazole therapy (usually twice daily doses).

¨ Radioactive iodine therapy (best treatment if kidneys are OK)

¨ Surgery

Methimazole is initially recommended to verify the kidney status prior to a more permanent correction of the thyroid problem.

A second blood test will be necessary in 3 to 4 weeks to ensure the correct dosage for your pet is being given.

Do not let the pills run out before rechecking the T4 or a false high reading will occur.

On the day of recheck appointment, be sure to give medication at the usual times prior to blood testing.

If depression, vomiting or soft stool occurs prior to recheck, please call the clinic.

After a normal T4 level is found with supplementation, a blood test will

be requested periodically to ensure dosage requirements do not change.

2. Thyroid pill supplementation is a lifetime therapy.

3. You may notice a slight decrease in your pet’s activity and appetite after treatment.

This is normal.

Notify the Doctor if Any of the Following Occur

¨ Your cat becomes depressed, not eating, has vomiting or diarrhea.
¨ Your cat’s condition does not improve.
¨ Your cat continues to lose weight or general health deteriorates.

Click on the blue hyperthyroidism link below to read an article from

the University of Illinois College of Veterinary Medicine about this disease.

Hyperthyroidism