Feline Hyperthyroidism Study

When I post a paper/story, I usually put the title of the story in the subject line of my post. Not this time. I want you to have the same surprise as I had. :-)

Over the past three decades, the number of cats diagnosed with hyperthyroidism has increased. According to research reports, many factors such as exposure to flame retardants could be responsible, and now a new study in ACS' journal Environmental Science & Technology points in another direction. It suggests that fish-flavored cat food could be among the culprits.

Hyperthyroidism is a hormonal disorder that can cause weight loss, hyperactivity, aggression, vomiting and other symptoms in cats. No one knows for sure what causes it. But some studies have suggested a connection between environmental pollutants including polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs), which have been banned in many countries because they could potentially harm humans. Previous studies have detected these compounds and their byproducts in blood samples from cats. But the byproducts, which can also have toxic effects, could come naturally from other sources such as fish, a common ingredient in cat food. Hazuki Mizukawa, Kei Nomiyama and colleagues wanted to investigate whether cats were getting exposed from their fish-flavored food.

The researchers tested cat food and blood samples from cats. They also simulated how a feline's body would process various PCB- and PBDE-related compounds. Based on their results, the team concluded that the byproducts that were detected at high levels in cats' blood samples likely came from fish-flavored food and not exposure to PCBs or PBDEs. The researchers say further work is needed to clarify whether these metabolites specifically contribute to hyperthyroidism.

The authors acknowledge funding from the Japan Society for the Promotion of Science.

Story Source:

The above post is reprinted from materials provided by American Chemical Society. Note: Materials may be edited for content and length.

Journal Reference:

Hazuki Mizukawa, Kei Nomiyama, Susumu Nakatsu, Hisato Iwata, Jean Yoo, Akira Kubota, Miyuki Yamamoto, Mayumi Ishizuka, Yoshinori Ikenaka, Shouta M. M. Nakayama, Tatsuya Kunisue, Shinsuke Tanabe. Organohalogen Compounds in Pet Dog and Cat: Do Pets Biotransform Natural Brominated Products in Food to Harmful Hydroxlated Substances? Environmental Science & Technology, 2016; 50 (1): 444 DOI: 10.1021/acs.est.5b04216


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We have 2 hyperthyroid cats but they didn't get it from fishy cat food as we don't buy it.

Helvella, wonder whether there is a lot of iodine in the fish flavouring?

I think that is not the cause, though what many of us will instantaneously wonder, this link says a bit more (but full paper still paywalled):


Helvella, Tricky innit? Pet foods fortified with vitamins have undoubtedly led to better health and longevity in many pets but this suggests processed foods may also be causing problems in animals.

"but this suggests processed foods may also be causing problems in animals."

There's actually a growing trend for natural food for pets nowadays, without all the additives. A few years ago, you couldn't buy the stuff - now vets are promoting it. Our two cats have a raw human-grade meat called Natural Instinct - and the improvement in their health as a result is amazing. One of the cats is a black and white. We thought the black parts of her coat were quite shiny before - but we really noticed the difference when they started eating this.

I firmly believe, just as processed food is no good for us, it's no good for animals either.

CarolineC57, yes I'm aware people people who eat a natural diet are inclined to extend the same to their pets and the raw food diet has been very good for dogs with digestive issues.

Yes raw tripe definately reduced whippet wind in my homeπŸ˜‚πŸ˜‚πŸ˜‚

It amazes me how terrible supermarket cat food is. 3% meat? Yuck, what's all the rest of it?

I just give my cat raw meat (plus a few other things), organic when I can afford it. If I'm really stuck, I buy blocks of frozen ground raw meat and bone from Pets at Home. I use the recipe from RawPaws Yahoo group. Cat has been fed like that for more than 10 years now. He's been ill once.

One of the possible treatments is a prescription food which is low iodine, its expensive but so are the other options, tablets, surgery or RAI.

Yes, it is. I have posted about it.

But, if the cause can be identified and (possibly) proved not to be due to relatively high iodine intake, there could be alternative treatments. These might even help without restricting iodine intake.

One of my cats ended up dying of this at age 18.5. Drugs did nothing. Her levels kept going up anyway.

I wonder if the catfood containing fish also contains a lot of fluoride from the ground up fish bones. Cats need a much higher calcium intake than dogs or humans. So their cat food is high in ground up bones. If these bones are from ocean fish, then the fluoride level would be high.

Maybe even though fluoride is anti-thyroid, something happens to overstimulate the thyroid due to the suppressant effect of the fluoride.

just wondering out loud.

I now feed my sighthounds raw tripe, it is what they would favour in the wild - they wolf it down and seem a lot more healthy on it than the stuff out of cans. Their fur is noticeably improved really luxurious and shiny. I wonder if it might have helped avoid the hypo three of mine got if I had fed it from the get go. This info confirms my suspicion that it has to be better, given the additives they adulterate tinned cat and dog food with. I had always understood cats were less easy to trick with supposed additive 'appetisers' than dogs and tinned cat food was a lot better that dog equivalents. Clearly that is a complete myth. Perhaps the situation is no better or even worse with tinned dog food.

Fascinating article Rob, thanks for posting

We used to get what was called 'lights' from the butcher. It was the windpipe and lungs I think, of cows. We'd simmer it for a couple of hours and cut it up into bite sized pieces and the cats loved it! A huge bag was about 6d (old money!) It's hard now to find stuff like that - I don't think butchers sell it any more??

Yes I can remember whole shops devoted to tripe with it neatly displayed in trays in the window. That was in Sheffield. I don't think any one eats it anymore and all the sweet breads (as I know them as but I have heard of 'lights').

Perhaps some old fashioned butcher up north might have them but they probably belong to a bygone era of coal miners, flat caps and whippets!

I think that Wiki has it more or less right here:

Sweetbreads or ris are culinary names for the thymus (also called throat, gullet, or neck sweetbread) or the pancreas (also called heart, stomach, or belly sweetbread), especially of calf (ris de veau) and lamb (ris d'agneau), and, less commonly, of beef and pork.[1] Various other glands used as food may also be called "sweetbreads," including the parotid gland ("cheek" or "ear" sweetbread), the sublingual glands ("tongue" sweetbreads or "throat bread"), and testicles (cf. Rocky Mountain oyster, prairie oyster, or lamb fries).[2][3] The "heart" sweetbreads are more spherical in shape, and surrounded symmetrically by the "throat" sweetbreads, which are more cylindrical in shape.



Lights are the lungs of game or livestock as used in cooking and butchery. Although technically offal, lights are rarely used in English-speaking culinary traditions, with the exception of the Scottish national dish haggis.


We sometimes see people claiming that thyroid is regarded as sweetbread - it shouldn't be and if it has been it's impact on the consumer could be very significant - see hamburger thyrotoxicosis.

Great to have all the detail of what the sweetbreads comprise. That is what I call attention to detai!l πŸ˜‰

I'm in Sheffield - maybe I'll get lucky if I scout around the old areas!

My cats (brother and sister aged 13) have always had dry food from the vet (Science Plan) and don't really know what to do with wet food. I get the chicken flavour but I wonder now if it has any fish bones in it - must read the label!

My vet mentioned hyperthyroidism when I took Jennifer for her flea jab as she'd lost a bit of weight but the blood test came back normal. I think it's because Oliver is twice the size and eats faster hahaha. Oliver will eat pink salmon from a tin but not red! Fussy old feline!

It was near Crooksmoor Road on the corner of Spring Hill Road and Commonside, Walkley way, as I remember from many moons ago and it was full of tripe of all kinds honeycombe tripe seemed to be the deluxe one! I can't imagine it still exists I should try street view! Funny about the salmon preference and red is more expensive!

Page is somewhat old, but some places might still exist:


The one I knew has gone πŸ™

I shall go and search it out. Thanks x

I am definitely going to look into this. Thanks for posting.

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