Usually these are benign adenomas of one of the parathyroid glands, these are 4 tiny glands located in the thyroid. When it produces too much parathyroid hormone (PTH), it can raise calcium levels, which usually causes a lot of issues, various pain and calcium deposits in places they don't belong.

They usually order a sestamibi scan to look.

See website
https://www.parathyroid.com/
In there somewhere the website mentions often it is a low Vitamin D leading to some of these kinds of diagnoses.