Today I learned about a 14 year old cat diagnosed with hyperthyroid condition. Her vet is treating her with Tapazole tablets. However, this resulted in the cat becoming very lethargic and refusing to eat. Apparently these are common side effects of this medication. Reducing the dose didn’t help. After stopping the treatment, the cat started eating again. The pet corner columnist vet wasn’t too helpful. He just confirmed that the pet owner’s experience indeed reflects the side effects of Tapazole and he recommended reducing the dose by cutting the daily dose into half and then slowly raising it up again to the originally prescribed dose of 2.5 to 5 mg every 12 hours. Did I say “today I learned”? Actually, you will agree with me, I didn’t learn a lot here, at least not anything as to how the owner’s particular problem can be solved. So I did a little more research on my own. Hyperthyroidism is the most common hormone disorder that affects cats. It comes with a wide variety of signs resulting from the overproduction of thyroid hormone made by the thyroid gland. The thyroid gland is small and consists of two lobes, one on each side of the trachea/windpipe in the neck. This gland produces the major thyroid hormone called thyroxine (T4) and a small amount of another hormone, triiodothyronine (T3). These hormones regulate the body's metabolic rate and affect every system in the body. Production of the thyroid hormones is controlled by the hormone called thyroid stimulating hormone (TSH). TSH is produced by the pituitary gland found at the base of the brain. If the thyroid gland produces excessive amounts of the thyroid hormones, a condition called hyperthyroidism is the result. Most common cause is a non cancerous increase in the number of cells in the thyroid gland. Groups of these abnormal cells form small nodules on the thyroid gland and are termed adenomas. Multiple adenomas may form in the same lobe. In approximately 70% of the cases, both lobes are involved. Note that only 1 to 2% of hyperthyroid conditions in cats are caused by malignancy (cancer).
The number of incidents of hyperthyroidism in cats has increased very noticeable over the last 25 years. Reasons for this increase are unknown. Probably they are due to multiple factors, some of the sounding very familiar on this blog: The ingredients and types of foods fed, immunological factors, and environmental influences may be involved.
Hyperthyroidism occurs most commonly in middle to old-age cats with a reported range of onset between 4 and 22 years. Median age for acquiring the disorder is just under 13 years. Only 5% of hyperthyroid cats develop the disease before 8 years of age. There is no indication that specific breed or genders are more than others are impacted.
Signs that a cat may have this disease are numerous. Research finds the most common ones with the frequency to be: Weight loss 90%, increased food consumption 53%, vomiting 44%, increased water consumption/ urination 40%, increased activity, behavior changes, nervousness 34%, unkempt hair coat/hair loss 30%, diarrhea 20%, tremors 15%, weakness 13%, panting or labored breathing 12%, decreased activity 12% and loss of appetite 7%. Rapid heart rates are common in cats with hyperthyroidism, and heart murmurs and high blood pressure can also occur. If not treated, cats with hyperthyroidism may and do quite frequently develop a heart condition called hypertrophic cardiomyopathy. In this condition the muscle of the heart becomes excessively thick which may lead to heart failure and death.
The disease initially is diagnosed by watching the signs as described above. There are currently three ways to treat hyperthyroidism in cats: Medical treatment with Methimazole, a human anti thyroid drug, surgical removal of the affected gland or treatment with radioactive iodine. The advantages of a medical treatment with Methimazole (Tapazole) are easy availability, low short term cost, does not require anesthesia or surgery, hospitalization or special facilities, treatment is reversible if need be, development of hypothyroidism is very rare, it is preferred in cats with kidney failure or other serious disease and used prior to radiation or surgery to stabilize cat. The disadvantages include that it is not a cure since the adenoma will continue to grow, it requires a lifelong therapy, it may have to be given more than once daily, comes with the typical difficulties of giving meds to a pet and may have side effects (for example, as we have learned on the very top of this comment, loss of appetite). It also requires periodic blood work.
Surgical removal ensures that the condition is cured if all of the abnormal tissue is removed. The cost is approximately the same as what you would spend for years of treatment with Methimazole. Hospitalization is short and after surgery there is no longer a need for daily medication. It does require anesthesia and that the animal is a good surgical candidate. Post operative complications can occur to parathyroid gland or nerves in the area. Though it happens rarely it may cause hypothyroidism. Surgical removal is not possible if the thyroid tissue is located within the chest and finally the last disadvantage is that it may have to be repeated if removal wasn’t complete during the first attempt.There are also radioactive iodine treatments available, having the advantages that they don’t require anesthesia, sedation, or surgery, all abnormal tissue is treated, again no need for daily medication, don’t destroy healthy tissue or other organs and normal thyroid function returns within a month. They are a preferred treatment if malignancy is present or the thyroid tissue is located within the chest . Availability of this expensive ($1,000+) option is limited. It requires a specialized facility, hospitalization and quarantine. During the initial days following the procedure treatment of other diseases is not possible. In rare cases it may need to be repeated and it, though rarely, could cause hypothyroidism.
Finally, there is chemical ablation. However, this procedure is still considered to be experimental with only limited availability. Therefore II decided not to exploit this venue any further. I wanted to find out more as to how I would help that pet owner who was asking the vet in the pet corner. We still don’t have a great answer for that yet. But here is where I would start:
Earlier in the above comment I talked about the reasons for this disease and, isn’t it so typical, named the food and its ingredients as a possible cause for this disease. Since I promised no advertising on this blog, I am not going to mention any products here. However, I would recommend a nourishing growth formula combined with raw elements and meat only varieties out of a can combined with supplements for adequate nourishment. e-mail me if you have specific questions regarding this recommendation.