The Vit D intolerance started in my teens, it just was never identified as a problem. I have barfed if I drank milk since I was younger than 10, which the endo says is a sign that the intolerance started way back then. My mom said they had to go to soy formula rather than whole milk for me as a baby when she stopped nursing.
I would not be surprised if the parathyroids had been meddled with, mostly because very little would surprise me now.