
Not a chance - if you want it covered, you'll need to stick with them. I have yet to find an insurer who will cover an existing condition, no matter what it is.
I would also be VERY wary of assuming it won't cost you much and might be worth just not having it covered - I made that mistake with Remy, not the same condition but his thyroid, I figured thyroids are always pretty straightforward with dogs so I changed policy.
I now have a dog with an extremely unusual form of thyroid trouble, on a medication that very few dogs go on, costing me £30 a month in meds only, and around £100 minimum per test because I HAVE to check his T3, the standard tests are pointless.