From what I have seen with it, the Y/D is like pretty much any other 'medicine' out there, works great for some and not at all for others. I would highly reccomend it as an option, along with I-131 and Tapizole, but it may well be a trial and error to see what works for each cat.
One thing to keep in mind is that Tapizole and Y/D both treat the disease, while I-131 cures it. For some that is enough of a reason to fo the I-131 route, others don't care if it's treated or cured as long as the cat is doing well. ;-)
With the Hills, kitty must not get any other cat food because the other cat food will contain iodine.
Anyone know what the isolation period is for the radioactive treatment is?
If I had to treat it I'd do that because sometimes the thyroid cells are located outside of the thyroid, so surgery wouldn't work.
We usually do the I-131 treatments on Mondays and the cats go home on Thursdays, The litter needs to be put in a bag and left sitting for 3 weeks before putting in the trash (the iodine will break down then.) We tell people not to allow them on counters, next to your face, or in bed for about three weeks, The cats don't need to be iolated though.
The number of I-131 treatments we do has gone down a lot recently and our dr thinks it is do to the Y/D food...people are giving it a try first.
Last year, my cat was diagnosed with hyperthyroidism. I had noticed his water intake had increased for about 2 weeks, and with him being 14 years old, I wanted to check his blood levels. He came back with high T4 levels. My vet's recommendation was to first try the Y/D diet, second to try medication and third radioiodine treatment. He didn't overly push for the Y/D diet, but thought it was worth a shot. This diet has to be given as the sole diet for the cat. I have 4 cats and what I decided to do is feed them twice daily for 30 minutes to an hour at a time and feed them in separate areas that way my hyperthyroid kitty wouldn't get the wrong food. For the first few days, 2 of my 4 cats were very confused. My 2 boys were perfectly happy eating twice daily, but my 2 female cats (also my chubbier kitties haha) protested around midnight about the fact they didn't have food out. Within a week, everyone was on schedule and doing just fine with the twice daily feedings. I feed my hyperthyroid kitty in my bedroom with the door shut and the other three in three other parts of the house so they all have their own bowl and area to eat. He had absolutely no problem with the food. He loves it! I give him a mix of dry and canned. His T4 was rechecked at 4 weeks after he started eating it and it was within normal ranges. At 15 years old, he's been on Y/D for over a year now and his levels have been checked a couple times over the past year and every time he's within normal ranges. I haven't had any negative experiences with this food whatsoever. While the food is costly, I don't have to worry about the negative effects of pilling him daily. While pilling him wouldn't be hard (I would absolutely do it if the food wasn't regulating his levels correctly or if he didn't eat the food), I would hate to lose the bond I have with him because he's scared I'm going to be shoving something down his throat every day. That is another great thing about this diet!