Your 12-year-old cat is suddenly zooming around at 3am and emptying the bowl. Feeling young again? Maybe. Or maybe it's the thyroid.
What the study found
Vets at Chungbuk National University in South Korea went through the records of 152 indoor cats with hyperthyroidism, treated between 2018 and 2025. That's the most common hormone problem in older cats: a small gland in the neck makes too much thyroid hormone and the body runs in fast-forward.
The typical patient was 12. And 30% of the cats were diagnosed by chance, during a check-up for something else, not because anyone spotted the illness.
The signs to watch
The most common signs were weight loss (88% of cats), vomiting (68%), being more active or restless (66%), a racing heart (60%), eating more (56%) and drinking more (55%). The authors say owners, and even vets, can easily blame these on old age.
Timing matters. The longer the disease went on, the higher the hormone levels and the more often pills stopped working.
One more surprise
Most cats had been on methimazole, the usual anti-thyroid pill. 84% got human or generic versions, not the cat-licensed one, and those cats had itchy skin more often. The study can't say why yet.
Six in ten owners asked for radioactive iodine treatment on their own, without the vet suggesting it first.
What it means for you
If your senior cat eats like a teenager but looks thinner, book a vet visit and ask for a thyroid blood test. The authors suggest older cats should get routine checks anyway.
Your cat will hate the trip. It will forgive you. Eventually. Probably.