Hi Joules. Welcome back though sorry under such circumstances :-(
The thyroid and diabetes link is a common one, unfortunately. I've been on synthroid for almost 25 years. Diabetes came 20 years after for me but the thyroid thing affects a number of my extended family, too. Researching "endocrinology and metabolism" might provide you some more specific glands and organs that are "auto-immune challenged" as I like to call them.
Thinking of you and hoping you can live life the best you can with your best friend beside you. We're here for ya, too
Kris