Hyperthyroidism in Cats

Following the Treatment of a Hyperthyroid Cat



November 21, 2002

Bubba has been recently diagnosed with hyperthyroidism, following a short period of rapidly-developing symptoms. He is a well-nourished 15 year old cat, having an excellent health history with only a couple of exceptions: a crisis with urinary crystals several years ago, and an idiopathic (undetermined) illness that struck when he was 12. He is also the alpha cat of our now 3-cat household, which was augmented in 2002 by the Guide Kittens Jaspurr and Joey, following the demise of our beloved Shannon in 2001, the previous Guide Cat for this About Cats site.

The Diagnosis

Because of Bubba's age, we keep a very close watch on his health, but this one slipped past us for awhile. He had become unusually grumpy recently, but we attributed this to his apparent dislike of little Joey (although he seems to love Jaspurr). But for the past week, Bubba had spent more time alone, and wanted to go outdoors for increasing periods of time. Bubba has always vomited after eating, but until recently, that had leveled off, due to food changes, and changes in the way it was served.

When he started vomiting several times a day and then went "off" his food, we whisked him to his veterinarian. I suspected IBD (Inflammatory Bowel Disease), because we had discussed the possibility in the past, so was taken aback when the veterinarian said he could feel Bubba's thyroid glands, and that hyperthyroidism was a possibility. The blood panel and T4 panel confirmed that diagnosis the next day. The laboratory results showed a T4 value of 6.5, compared to a "normal" reference range of 0.7 - 5.2. The footnotes to the report indicated that in a cat older than 10 years with clinical signs of hyperthyroidism, a T4 value greater than 2.5 is suspect for hyperthyroidism. This is because thyroid production normally decreases as animals age.

The Treatment

Bubba was given an antiemitic injection during the first veterinary visit, and was prescribed Reglan for the vomiting. Following the test results, he was started on Tapazole (methimazole), twice-daily. He will be re-tested with a full blood scan and T4 panel after two weeks of this treatment. He also was prescribed Periactin to help his appetite.

On just the second day of treatment, I am pleased to say that Bubba is already starting to resemble his "old self" again. He is eating heartily again, after a shaky start. The first meal he was served, after receiving his first dose of medication, he glanced at the food dish, then stared at me, as if to say, "Why do you hate me, Mom"? Shortly after, he visited the J-Boys' plate and finished off what they had left. I guess "stolen food tastes better" is the rule here, so that will be our feeding plan until his appetite returns in full.

The Follow-Up Visit

In researching hyperthyroidism in cats, I discovered that this disease can mask occult (hidden) kidney disease. So, although Bubba's kidney and liver values are excellent for a cat of his age, we will be relieved if the second blood panel remains consistent. He will also need tests for latent heart disease prior to making a decision for a treatment option. Pilling Bubba twice-daily, at exactly the same times every day is a daunting task, and because of our erratic lifestyle, I'm not sure that would be a viable option for a long-term treatment. We're leaning toward the radioactive iodine therapy, and are lucky to live within 50 miles of the Veterinary Teaching Hospital at U.C. Davis, where it could be performed. However, we really can't make a decision at this time, with so many unknown factors involved.

It's necessary to note at this time the importance of an annual full examination and blood panel for senior cats, a policy that I've preached, but didn't follow this year, for one reason or another. Had Bubba received a full examination when he received his three-year Rabies vaccination earlier this year (by another vet), we could have caught this disease quicker, and avoided the stress of a rush visit to the vet's office.

Bubba was diagnosed with hyperthyroidism a little over two weeks ago, after some very quick personality changes (increased grumpiness and disappearing for long periods of time), coupled with an unexplained aversion to food, and increased bouts of vomiting. His initial treatment was an antiemitic shot, Reglan tablets (also for the vomiting), Periactin (for appetite) and Tapezole (anti-thyroid drug) twice daily for a week, then once daily for a week. Bubba's kidney and liver values were checked and showed to be completely normal. However, since hyperthyroidism is known to mask hidden kidney disease, it is standard procedure to recheck thoase values once thyroid levels return to normal. The latter information was my biggest concern, since a cat with kidney failure is not a candidate for radioactive iodine therapy.

The Followup Tests

Exactly as planned, Bubba was retested at the end of the two weeks' preliminary Tapozole therapy. We could already see positive results, as his appetite had returned to normal and he appeared to even have gained a little weight.

We anxiously awaited the results of the second tests, and were excited to hear that Bubba's thyroid level (T-4) had dropped back to 3.3, (from 6.5 two weeks ago), which is mid-range of normal. The most encouraging news was that he has regained almost half a pound, and his kidney and liver values are still absolutely normal. This means he is a good candidate for the radioactive iodine therapy, which is our treatment of choice.

What Comes Next?

Although we had anticipated having the radioiodine therapy done at U.C. Davis, it appears that that service is no longer being offered in the veterinary teaching hospital. We were referred to a veterinarian in Sacramento (about 70 miles from our home), who appears to come very highly qualified. We had hoped to have the radioiodine treatment done as soon as possible, but, upon talking with Dr. Van Vechten, encountered a significant glitch: the clinic is out of the essential I-131 material, and it is not clear when it will be available. So, now, we're playing a waiting game, and can only wait until the call comes.

In the meantime, Bubba continues to thrive; he's pretty resigned to the pill-a-day routine, and eating well with minimal vomiting. He can survive indefinitely on the Tapazole, and except for the unknown (but unlikely, statistically) issue of the tumor being cancerous, there's no real rush, so we'll wait for that phone call.

To recap, we had decided to keep Bubba on the Tapazole therapy, pending a decision to go for a "permanent cure" via the more-expensive radioactive iodine therapy. After talking to the clinic manager in Sacramento, and discussing it with my husband, we agreed to continue on the Tapazole for an indefinite period of time. It seemed to be keeping Bubba's thyroid levels under control, but mainly, Asa was very concerned about Bubba's stress level, if he had to stay up to two weeks in a clinic 80 miles distant. It befell to Asa to become the pill-giver, as Bubba trusts him and considers Asa his "main man."

It has been a fairly uneventful year, punctuated only by one scare in mid-July. Bubba had again become anorexic, had apparently lost weight, and, in addition, seemed to be losing muscle mass in his hind quarters. We scheduled an appointment with his regular veterinary clinic, and subsequent blood tests were excellent. In fact, when the veterinarian (one who had not seen Bubba before) called with the results, he said, "If I didn't have the age of the cat on this chart (Bubba turned 16 on July 4th), I'd swear that this was the blood test of a young cat."

With that encouraging news, we continued the routine course of treatment, and experimented with several new foods. Bubba's appetite perked up, and he seemed to gain back some of those lost ounces.

Recently, however, because of a new episode of frequent vomiting, apparent weight loss, and because it was almost time for his annual checkup, we scheduled him for an appointment. I was also concerned, because I had been doing research on hypertension for a profile on that feline disease, and I saw what I interpreted to be small broken blood vessels in Bubba's eyes (Dr. Schnittker did not see anything untoward).

Once again, the veterinarian called with good news. Bubba's T4 is well within the "normal range," at 2.8 (although I noted it has dropped from last year's 3.3). His BUN and Creatine levels are also entirely normal.

We'll continue with the Tapazole treatment and increase the Reglan (for vomiting) to twice daily.

Because I write about cats, it's very possible that I overreact to symptoms with my own cats. However, I practice "better safe than sorry," because their health and welfare is extremely important to me.

Disclaimer : I am not a veterinarian, and this history is not necessarily a typical one for a hyperthyroid cat. Only your own veterinarian is qualified to treat your cat, based on a diagnosis after indicated lab work. I do hope that if you have a hyperthyroid cat, his condition will respond as readily as Bubba's has.

If you suspect your pet is sick, call your vet immediately. For health-related questions, always consult your veterinarian, as they have examined your pet, know the pet's health history, and can make the best recommendations for your pet.