Feline Hyperthyroidism
Friends and Neighbors,
Cats have two thyroid glands which are located on the underside of the neck. They play a vital role in regulating the body’s metabolic rate. Hyperthyroidism is the overproduction of thyroid hormone and a subsequent increase in metabolic rate. It is a common disease in adult cats, especially seniors. No individual breed is known to have greater risk of developing the disease and the exact cause has not been identified, although the role of dietary iodine continues to be investigated as an influencing factor.
Symptoms
Since the thyroid hormone is a major controller of the body’s metabolic rate, a common symptom is weight loss despite having an increased appetite. Vomiting and diarrhea may occur due to overeating and the changes in metabolism. Hyperactivity, vocalization and aggression are some common behavioral changes. Unfortunately, although this activity is appealing, the negative effects that come with it are harmful on the heart, muscles and skin. Treating the disease often causes a cat to “slow down” to a level that is more appropriate and is compatible with the functions of the organs. Heart muscles can be affected to meet the increased metabolic demands as they become enlarged and thickened. Cats can develop a her murmur associated with this.
Diagnosis
Most cases are diagnosed by routine blood testing for thyroid hormone (T4). Routine bloodwork and urinalysis are necessary to assess the effects on the other organs and to screen for other serious illness like renal disease or liver disease since it could mask these diseases and make it difficult to treat. Chest x-rays and sometimes echocardiograms to assess the effects on the heart from the disease are recommended.
Treatment
There are two ways to manage hyperthyroidism as a disease:
Daily Antithyroid Medication: Methimazole (Tapazole, Felimazole), given every 8-12 hours as prescribed for life. May take several weeks to restore normal thyroid function and bloodwork should be evaluated every 4-6 months. Wear gloves when administering this medication.
Radioactive Iodine Treatment (iodine-131): Injected it will collect in the thyroid gland, destroying the abnormal tissue. It is a very effective, very low-risk form of treatment and it can only be given in hospitals that are licensed to handle the radioactive substance. The chance of recurrence in the future is less than 1% and there are no daily medications to give thereafter. Normalizing the thyroid tissue can unveil underlying kidney disease and many specialists recommend a period of oral antithyroid medication and a recheck of kidney function to determine if a cat is a good candidate for permanent correction of hyperthyroidism with radioactive iodine.
In conclusion:
Administer any medications as prescribed on time, even if your cat seems normal. Often this may be due to the positive effect of the medication.
If you are giving your cat methimazole, watch for the symptoms of adverse effects (lack of appetite, inactivity, weight loss and intense facial itching), stop the medication and contact us!
Realize that hyperthyroidism is a lifelong condition that does not get better on its own. It will eventually cause life-threatening symptoms if not treated.
We hope you find these tips useful and that they help keep your pets happy and healthy. Contact us if you have any questions or would like to schedule a visit. We are always here for you and your pets!
Sincerely,
The BLVD Team