Equine Cushings & Iodine?

Hi,
Has anyone used Iodine successfully in Equine Cushings cases and if so, what where the changes you saw? Also was the horse on pergolide at the time?

I am especially wondering about mares, as they tend to be harder to stabilize on diet and pergolide, unlike geldings and I believe it is probably due to their hormones.

Thank you!