I had this happen when I was first being diagnosed with Crohn's. I was in really bad flare, didn't know what my condition was yet, and basically starved myself of nutrients being on an aggressive elimination diet for too long. My hair thinned but it did grow back when I got better and was in remission. That said, I was diagnosed at 31. I've had some thinning though that I think is part of natural aging.

This has happened to me when I start new medications or during flares!! My hair tends to grow back but my hair loss can still fluctuate

Yes my hair fell our in handfuls! My hair was quite long. I lost hair like a man would. Thinned on sides and ended with a bald spot on the back of my head. God is so good I found a great hair stylist who cut my hair to match the thinnest part. It has grown back a bunch and have had a haircut already! It would have been nice for my doc to mention this may happen for I could have been taking biotin!