Methimazole Helps Many. Consider the Cures Carefully


My 10 year old female cat was diagnosed with hyperthyroidism 2 years ago and placed on oral methimazole 10mg. The dose was too high (she wouldn’t eat or play and she was always cold) so she has been taking 5mg. for the past year.  Now our vet is saying that her dose needs to be increased again even though neither her behavior nor weight have changed. I am very concerned about the increase, but I certainly don’t want to shorten her life span. Is a surgical option worth the risks involved?


Dr. Nichol:

Hyperthyroidism, caused by benign thyroid tumors, is usually seen in older cats. Most affected kitties have a rapid heart rate and weight loss in the face of an increasing appetite. Methimazole tablets usually work well. But even with appropriate dosing the tumors continue to grow slowly, hence the need for more methimazole. Surgery, radioactive iodine, and “chemical ablation” are alternative treatments that can cure the disease but there are additional considerations.


Thyroid hormone is important because it’s responsible for managing our metabolic rate. It impacts every part of the body. With regard to the kidneys, more thyroid hormone means more blood flow. Reducing your cat’s thyroid level could mean kidney damage and ultimately, kidney failure. It can be a delicate balance.


Your veterinarian’s advice should be based on your cat’s overall health. Assuming that all internal systems are functioning nicely one of the curative treatments could be just right. If continued methimazole is still best for your kitty, it can be made easier by applying it in gel form once daily to the skin. Whatever the management, continued monitoring is essential because nothin’s perfect.





More on Feline Hyperthyroidism


Taz is my 16 year old spayed female Siamese cat. For at least a year, she has had an overactive appetite. She eats three cans of food a day. She does not have diabetic symptoms, anemia, diarrhea, or weight loss. I am assuming it is some sort of metabolic disorder, but I don’t know what it could be.


Dr. Nichol:

You are right to consider diabetes, usually a straight forward diagnosis with blood and urine tests. I am also concerned about hyperthyroidism, caused by high hormone levels produced by benign tumors of the thyroid glands. Like diabetes, it is potentially fatal but most cases respond well to treatment.


There is no substitute for competent medical care. Fast Taz and prevent access to cat litter for a few hours so her doctor can take blood and urine for testing. If she is hyperthyroid she’s likely to do fine with tablets or radioactive iodine treatment.


Your feline senior should still have a few good miles ahead. Trust your veterinarian to make an accurate diagnosis and prescribe the best treatment.





Elderly Cat Owner has Difficulty Caring for Hyperthyroid Cat


I have an elderly, hyperthyroid cat (Flo) who needs daily meds and I am having trouble caring for her. It may not be such a good idea for elderly people with severe arthritis to have pets. What will become of Flo when I can no longer care for her?


Dr. Nichol:

You and Flo are good for each other. The devotion of a pet helps many senior citizens maintain a positive outlook in spite of their health struggles. Your kitty’s needs are a challenge but we can make it easier.


Hyperthyroidism is caused by slow growing thyroid tumors that produce too much hormone. Most cats like Flo have a growing appetite in the face of weight loss. Left untreated these kitties end up with heart and kidney failure. Most respond well to medication.


I can see how your arthritis would make it hard to pill a wiggly kitty. Ask your veterinarian to have a compounding pharmacist prepare her medication (methimazole) in a tasty triple fish suspension or a transdermal gel that can be applied to her ear flaps. Keep the faith; you and Flo need each other.





Vomiting Hyperthyroid Cat


My eight year-old kitty is on medication for hyperthyroid disease.  Josie has always had problems with eating and throwing it up a short time later. The thyroid medication does seem to have cut down on this problem but she will still get sick every couple of weeks.  I would really like to see this sweet but thin kitty put on some weight.


Dr. Nichol:

The best place to start would be to reevaluate sweet Josie’s methimazole dose-the medication she takes for her hyperthyroidism. A thyroid blood level is an accurate yardstick that’s easy to check.


Feline hyperthyroidism is serious business but nearly every affected cat does well if it’s carefully managed. These kitties are subjected to excessive amounts of hormone caused by slowly growing benign tumors of their thyroid glands. We see it most often in cats over age 8. Common symptoms include a rapid heart rate and weight loss in the face of a voracious appetite. Some become hyperactive or aggressive. Without treatment many develop heart, liver, or kidney failure from runaway high blood pressure.


Josie’s vomiting could be a side effect of the medication. Her weight loss, on the other hand, may be a signal that her dose should be increased. Cats who react badly to methimazole at any dose can be treated with radioactive iodine instead.


There may be other, unrelated, reasons for Josie’s vomiting and weight loss. Organ failure, chronic intestinal disease, and malignant cancer should also be ruled out. Don’t gamble; your girl needs special care.





A New Diet-Hill’s y/d can make Treatment Easier


My almost 17 year old cat Katy has started eating voraciously–she is hungry all the time. I feed her all day but she is not gaining weight and still looks thin the way old cats tend to look. Otherwise she is active and seems her usual self.


Dr. Nichol:

I am concerned that Katy has hyperthyroidism-too much thyroid hormone. There is a high incidence in cats over age 10. The most common symptom is a ravenous appetite in the face of weight loss. Many drink and urinate excessively and vomit periodically; some talk a lot more and a few are hyperactive.


Diagnosis is usually straight-forward but thoroughness is essential. Katy’s doctor needs to check every part of her including a careful palpation of her thyroid glands. Lab work should include a thyroid profile. Because hypertension is a feature of this disease a Doppler blood pressure measurement will be essential. Most hyperthyroid cats have rapid heart rates. Press gently with your fingertips on the sides of Katy’s chest just behind her front legs. Over 180 beats/minute is highly suspicious. Greater than 200 and you almost have the diagnosis.


Treatment is usually effective. A good method is radioactive iodine but we no longer have a licensed facility in New Mexico. An oral tablet called methimazole has been used reliably for years. Enlarged thyroid glands can also be surgically removed. My recommendation would be to feed Katy a new iodine-restricted prescription diet called Hill’s y/d.


We are always careful with elderly cats. Kidney disease accompanies hyperthyroidism for many. As treatment for hyperthyroidism reduces thyroid hormone levels, blood pressure usually diminishes too-which decreases blood delivery to marginal kidneys. If we aren’t careful we can succeed with one disease while the patient succumbs to another.