I’ve been opining on feline hyperthyroidism a LOT in the past 18 months or so. It all started with Latifah. Something seemed amiss with her back in January/February 2007, as although her diabetes was well controlled, even went into sporadic remissions, she had a ravenous hunger and her fur/coat wasn’t as smooth and glossy as I’d expect in a cat on an all-wet diet. Bloodwork looked pretty good, but I had this nagging feeling – and she just “felt” hyperthyroid, I’d tell the veterinarians. They’d usually dismiss the idea, saying her T4 values (in her bloodwork) were well within the reference range.
In a conversation with Dr. Hogkins, I noted my misgivings and I got quite the education. T4 values in an older cat (over age ten) should not *just* be in the reference range, but in the lower half to third of the reference range and decreasing over time. Other ailments, such as CRF (kidney disease), IBD (inflammatory bowel disease), etc. deflate T4 values as well as age.
Latifah’s T4 in January 2007 was 2.2, well within the lab’s range of 1 to 4, but it was up from 1.2 in January of 2006. I decided to get her in to a nearby specialty center for a technitium (or scintrigraphic) scan, which enables the imaging veterinarian to see the thyroid glands and any potential tumor causing hyperthyroidism.
I’ll admit, I was fully prepared to be told she was not hyperthyroid and I was off my rocker – but the day of the scan came and I got the call there was significant hyperthyroidism. I opted have her treated via radioactive iodine therapy immediately – and she stayed there five days until the radioactivity reached levels deemed “safe” by the government.
It was only about a month later, in February of 2007, that Omaha had routine bloodwork which showed his T4 value of 3.7. Again, within the lab’s range of 1 to 4, but up significantly from his last test and near the top of the range. We had him scanned, and he was hyperthyroid as well, which we treated with radioactive iodine. The only symptom I can recall was some excessive thirst – I rarely see most of my cats drink water, due to their all-wet diet, but I recall seeing Omaha at the water dish several times.
A year later, March 2008, and I noticed Afer’s T4 was up in her bloodwork. It was only 2.6, within range of 0.5 to 5.8, but up from 1.8 the prior September, and 1.0 the year before that. Afer’s about 20 years old, and has CRF (renal or kidney insufficiency) and a history of IBD (currently controlled by diet). These three factors should result in decreased T4 levels. Again, we got a scan and again it showed significant hyperthyroidism. After a consult with a nephrologist (kidney specialist) we got her radioactive iodine treatment in July of 2008. Her kidney values per bloodwork did worsen a bit post-treatment (as expected) but she looks great overall. (Hyperthyroidism can “mask” some kidney insufficiency.)
The story doesn’t quite end there – Ralphie also had T4 values increased in his last bloodwork and I had him scanned. This time the scan showed only slight hyperthyroidism and we opted to wait and retest in four to six months. I could have opted for a trial of methimazole (Tapazole), the oral or transdermal medication, but with Ralph’s history of anemia and IBD I was not willing to chance the side effects.
The reason I have such a ‘bug in my bonnet’ about hyperthyroidism isn’t just my personal experiences (which so far all had very happy endings). I’ve met some caregivers whose cats show EVERY symptoms of hyperthyroidism, but when I ask if they’ve considered whether their cat may be hyperthyroid they declare that their veterinarian “ruled it out”. When I inquire further, I find out “the T4 values were in range”. T4 VALUES WITHIN REFERENCE RANGE DOES NOT RULE OUT HYPERTHYROIDISM! Cats with untreated hyperthyroidism can suffer hypertension (high blood pressure, which can lead to blindess or stroke) or heart failure. A hyperthyroid cat’s system is in overdrive, causing pressure to all the organs. In one case, the caregiver opted to drive the cat five hours to another imaging center that would do the scan (after a nearby vet school refused to do the scan as T4 values were in range, and suggested she put the cat to sleep) and the cat had significant hyperthryoidism and was treated and is now fine. Another case had a sadder ending where the caregiver consulted specialist after specialist looking for one to help her cat – it was *finally* diagnosed with hyperthyroidism despite it’s bloodwork values – but too late, and the cat lost its life.
I know I’ll be watching my cats’ T4 values like a HAWK.
Discussion of possible causes of hyperthyroidism (including discussion of the pop-top can research and more recent research indicating fire retardants) here
More information on hyperthyroidism available at Feline Outreach:
Life of the Lintee Bean 
I have been through hyperthyroid sickness with one older cat. She did well on methimazole (sic) for a few years but then just collapsed. I have another cat with diabetes that is showing all the same signs.
You write that your cats only ate wet food. I am very suspicious of the white liner in the cat food cans that is made of bisphenol A (not sure of the spelling) and which has been outlawed in many countries for use in baby bottles. It is a carcinogen and is used to soften plastic.
My diabetic cat ate for many years from a diabetic maintenance food that was packaged in such a can with that white lining.
All my vets tell me that this sickness was unknown when they went to med school.
What do you think?
Hi Barbara!
I think you should take a look at my post on just this subject: pop-top cans.
https://meowmeowmom.wordpress.com/2008/08/28/pop-goes-the-pop-top-can/
In it, I note that flame retardants (present in fish, household dust, etc.) are a MUCH more likely suspect in hyperthyroidism than the can lining.
Lynette
[…] hyperthyroidism is the most underdiagnosed feline ailment, kidney disease is probably the most overdiagnosed. […]
[…] started dropping off Omaha dramatically. So quickly, the vet became nervous he may have become hyperthyroid. His thyroid was fine, though, and I found myself in a position of INCREASING his food portions! […]
We just had a second of our 3 cats diagnosed hyper-T as well… and she’s only 9. You may have seen this research from a few years ago linking the fire retardants PBDEs and hyper-T in cats:
http://www.sciencedaily.com/releases/2007/08/070815122354.htm
http://www.ncbi.nlm.nih.gov/sites/entrez
There is ongoing research on the link between PBDEs and hyper-T in cats, our cats will be providing blood samples for analysis. We lived in student housing in the past, where fire retardants are heavily used.
Hi Tina,
Thanks for the comments.
I discuss the subject of fire retardants and hyperthyroidism here:
https://meowmeowmom.wordpress.com/2008/08/28/pop-goes-the-pop-top-can/
Lynette
I would also like to add that the statistical occurrence of cats who eat canned food from pop-top cans “especially fish” is more likely due to the contamination of fish such as tuna and large mackerel with fire retardants and other persistent organic pollutants, not from the nature of the food or the can itself.
I agree – as I hopefully make clear in this post:
https://meowmeowmom.wordpress.com/2008/08/28/pop-goes-the-pop-top-can/
Lynnette,
I’m so glad you provide this information. My 14-year-old cat, Chocolate, had hyperthyroid disease and a dual-lobe thyroidectomy about 2 years ago. Within the last 3 months, she has begun exhibiting all of the signs again: excessive water drinking, constant hunger, and constant crying. I had her bloodwork done only to find out that she was “perfect” with a T4 level of 3.4. I even asked them if they were sure her blood didn’t get mixed up with another cat’s. The treatment was to dose her with a wormer, attributing her excessive hunger to parasites (which is really unlikely).
However, every day I was bothered by the fact that something is wrong with her. The excessive crying disturbs everyone in the house and keeps us up all night. Luckily I found this post and just called my vet to find out where I can get a scan done. Thank you.
[…] it a lot, and I just didn’t know. T4 bloodwork in reference range doesn’t rule out hyperthyroidism by any means. In an older cat, it should be in the lower half of the range and decreasing over […]
I’m seeking information for post radiation iodine
treatment, ie., time touching my cat, sleeping on the bed, etc. Also, I have an 8 year old daughter, and the clinic says she can’t touch or be in the same room with our cat for FIVE weeks. She is heartbroken, as am I, because this is our “cling-on”
cat. I would appreciate any information about post
care that you may have experienced. Thank you!
Hi Carole,
If I remember correctly, I was told by my clinic I had to flush their bodily fluids (urine, feces, any vomit, etc) for 30 days – or store it for 30 days before putting it in the garbage. I was also told to avoid prolonged contact for that time.
Honestly, I didn’t. The cats are getting such a low dose of radiation – similar to getting several x-rays. By the end of the five-day quarantine period, risk is slim. I let my cats sleep with me, etc. I only separated them because I didn’t want to have to flush ALL the waste for ALL cats and I had no way of telling it all apart!
I know PEOPLE that had radioactive iodine treatment – they obviously get a much larger dose than cats… and they still slept with their spouses, etc.
Now, I don’t have children. If I did, I might allow them to visit the kitty and pet kitty – but maybe not sleep touching kitty. (I wouldn’t worry if kitty was just on the bed nearby – but prolonged touching… if I had children I’d probably err on the side of caution).
Here’s a quote from a vet specializing in felines – one of my FAVORITE VETS OF ALL TIME!
“They will tell you to treat Latifah as though she were 8 pounds of pure plutonium when she gets home (BTW, my favored center keeps the cats 4-5 days). This doesn’t make any sense, however. The cat got the WHOLE dose, and then peed the vast majority of that out for the next several days. There is little residual radiation at that point, and what there is continues to diminish greatly every 48 hours or so (don’t forget, the cat got the whole dose yet we never see any negative effects to the rest of the cat’s body). So, within 10-14 days of the injection, the amount of radiation at the level of the cat’s insides is miniscule. Still, by state and federal regulation the centers have to give these incredible warnings that would make most folks send their cats to Iceland for a month. It’s pretty over the top, but they fear that if they don’t give all these warnings you will sue them 20 years from now should you develop any kind of problem that might remotely be linked to this treatment….”
Hope that helps.
Lynette
Carole,
I have had 2 cats treated successfully with I131 now, and I’ve also fostered 2 other cats who were successfully treated and then adopted out (one lived to be 21, the other is still alive). The information you have received is *extremely* over-cautious. the treatment facilities are not allowed to release your cat until their radiation levels have fallen to acceptable, safe public exposure levels. The amount of radiation given off by your cat after release from the hospital is lower than the amount you’d receive by taking a cross country airplane trip.
The main exposure to radiation post-treatment would be the urine, since the radioactive decay products are excreted in the urine – however the type of radiation excreted in the urine is a low energy radiation that is only harmful if ingested. So if you avoid getting urine on your hands, and wash your hands after cleaning the litter box or any accidents, you will be fine.
As for the cats sleeping on you etc, I let all the cats sleep on my bed and sit on my lap after treatment, less radiation than getting all those dental x-rays so really I am not worried!
I guess with children, they are always going to be very over-cautious just because radiation exposure is a lifetime cumulative risk, but if your child gets dental x-rays or flies on a plane they are exposed to more radiation from those sources. If she does not get frequent x-rays and does not fly often, the small exposure from the cat is not going to be a risk.
Personally I’d probably say 2 weeks of no close contact with the cat (ie lap sitting) to be absolutely safe… but not even being able to touch her is ridiculous! It’s going to come down to what you personally feel comfortable with.
[…] beat my sweet girl. She started losing weight a while back, and I thought it was the beginnings of hyperthyroidism. We knew she needed her teeth cleaned (again, something we went through about twice a year). After […]