What Illnesses can be related to Hyperthyroid?

Hi,
I am getting ready to insure Ms. Gracie - she is 13 yrs old and has Hyperthyroid though, so not all companies will insure her. Also, evidently HT will not be covered NOR anything that is related to it.
Problem is, there is nothing in the policy that says WHAT is related to it . When I called the Company today (Trupanion, unfortunately PetsBest will not insure her, so I do not have a choice in the matter), she ran a Google search - yep, a google search! and only came up with behavior problems. When I said I am not concerned with behavioral problems, she said, sure, but they can cause stress, over grooming, blah blah blah.
She said the vet will decide what is related to HT and what is not related - and if the vet decides the illness is not related to HT, they cover, if the vet decides it is related, they do not cover.
So...... Here on TCS, for those with experience with Hyperthyroid - what does this disease bring? I know seniors do have more illness.... which is why I want to insure her FAST - she is healthy now - all her tests are 100% normal.
And please, lets not make this a "to insure or not insure" thread - I am an Insurance believer - my 3 other cats have insurance, and I am VERY happy they do it. I am a firm believer in it, and very glad to have it.
I just want to know the possible pitfalls of insuring Gracie, and if in the end, everything will ultimately be related to HT. I love that PetsBest is very Black and White, and I am not finding the same here... However, she is old, and having insurance for her would be a wonderful peace of mind....
Thanks!

Two things I remember reading about from when Cotton was first diagnosed that could come on as a result of Hyper-T:

1. CRF - Because Hyper-T keeps the kidneys running in top gear until it's treated, there can be some residual damage, or damage that was hidden while they were so high performing

2. Hypertophic Cardiomyopathy: Apparently it's not uncommon for Hyper-T kitties to have an increase heart rate, so there is a chance of damage to the heart itself

Out of the 2, kidney damage is the more likely, but you've had Gracie under control for awhile now, so if either of these existed you'd have found them. I think the only thing you'll need to watch for is any damage caused to her system if the Hyper-T were to get out of control again.

Hi Carolina! You might consider putting your question to these folks among whom I expect you will find people with actual experience with insurance companies.