Tim - Who Developed Hyperthyroidism
Hyperthyroidism (overactive thyroid) in cats is most commonly caused by a benign tumor located on one or both lobes of the thyroid gland. In cats the thyroid gland is located in the neck beside the trachea. It consists of two lobes and produces the thyroid hormone thyroxine (T4), which is converted into triiodothyronine (T3). The benign tumor on the thyroid gland causes excessive production of thyroid hormone. This condition most commonly occurs in older cats.
The following symptoms are associated with feline hyperthyroidism:
- weight loss despite increased appetite
- increased activity
- increased thirst
- increased urine output
- decreased grooming leading to dull, unkempt fur
Many of the above symptoms are common to other diseases in cats and so you need to take your cat to the veterinarian for an accurate diagnosis. Also, not every cat will have every symptom. For example, I have an older cat that developed hyperthyroidism, but he did not throw up.
How is Hyperthyroidism Diagnosed?
If you suspect that your cat has an overactive thyroid then your veterinarian may be able to feel a nodule on your cats neck in the thyroid area. However, a blood test is the best way to know what is going on with your cat's health. Because the above symptoms are common to so many different diseases in older cats it is best to have a complete chemistry panel and a complete blood count (CBC) done. The specific blood test for thyroid function test the levels of T3 and T4, but it is good to have a complete blood work-up in case your cat's symptoms are caused by something other than thyroid disease. If your cat's tests come back with a significantly elevated T3 and/or T4 then your cat has hyperthyroidism. Thankfully, there are treatments available.
How is Hyperthyroidism in Cats Treated?
It is very important to get your cat treated for hyperthyroidism. This condition can cause several health problems, such as heart disease and hypertension. There are currently three treatments available to treat your cat's overactive thyroid gland:
- Thyroidectomy (surgical removal of the thyroid gland)
- Radioactive Iodine
Pros and Cons of Medication
As a first treatment your veterinarian will most likely prescribe medication that will cause your cat's thyroid gland to produce less thyroid hormone. Methimazole (Tapazole) is commonly given. Unfortunately this means that you will need to give your cat a pill everyday for the rest of his or her life. Also, some cats don't tolerate the medication well. My cat who developed hyperthyroidism became ill (gastrointestinal distress) from the medication and had to stop taking it, although some cats do tolerate the medication well. In cats that do tolerate the medication, thyroid hormone levels are reduced (you'll need to get these checked periodically by your veterinarian) and the medication is relatively inexpensive (around $20 a month).
Pros and Cons of Thyroid Surgery
Surgery is another option for a cat with hyperthyroidism. This option works well for cats who can't take the pills. This option works especially well if only one lobe of the thyroid is affected. The surgical procedure is done under general anesthesia, which is sometimes risky for an older cat, but your veterinarian can advise you on whether or not surgery is the best option for your hyperthyroid cat. The benefit to having surgery is that once the thyroid is removed your cat will not have to take the medication to reduce thyroid hormone levels and will no longer have an overactive thyroid.
However, you will need to get your cat's thyroid levels tested again after the surgery to make sure that his or her thyroid hormone levels are within the normal range. Also, if both lobes are removed, then you may have to give your cat medication for an underactive thyroid. Also, if the parathyroid glands are accidentally removed or damaged during the surgery then your cat may suffer from hypocalcemia (low blood calcium). The symptoms of hypocalcemia are muscle temors and weakness, and convulsions. This is a serious complication, but can be treated with vitamin D and calcium supplements.
Because my cat Tim couldn't take the pills he had thyroid surgery. His thyroid levels have been fine ever since. He is currently 17.5 years old. He had the surgery last year. His surgical incision looked pretty bad, however, he recovered very quickly. The cost of the surgery will vary depending on the area you live in and your particular veterinarian, however, my cat's surgery was around $300. He had no complications and has not had to take any pills since the surgery.
The photo shows Tim (the black and white cat) playing with the other household cats. As you can see from the photo, he gained back all of his weight after the thyroid surgery and is doing fine.
Pros and Cons of Radioactive Iodine Treatment
This treatment is often said to be the best for hyperthyroidism in cats because it destroys the overactive thyroid gland without the worry that the parathyroid glands will accidentally be damaged. Another benefit is that the cat doesn't have to be under general anesthesia for this procedure.
The drawbacks of this procedure is that not every veterinarian is equipped to perform this procedure (mine wasn't) and that the cat must be quarantined for a period of time due to the radioactive iodine used that will be shed through your cat's feces and urine. The expense is another drawback as this procedure is much more expensive than the other two treatments.