Bone Age X-Ray

We went to my duaghter's quarterly endo visit yesterday and I was shocked that she wants my daughter to get a Bone x-ray of her hand. Endo is concerned that she has not really grown since the last visit (a little over 3 months ago.) My daughter is 12 and 5'2" and has been growing like a weed, and now she has stopped. Has anybody had any experience with somethink like this?

I don't know much about this but I do know a family who's mentioned it to me. Their daughter has t1d and had told me something about her having a bone age test and that they'd found out she was totally done growing. I didn't understand how they knew, but only that she was 16, was sort of shorter for her age and they knew that that was as tall as she'd get.
Sorry I'm no help, but just wanted you to know, you're not the only ones going through it.