Take a look at this website - especially at the chart that shows calcium and pth testing - and what results mean.
At one point I had looked into this. www.parathyroid.com
“ A blood calcium level that is too HIGH, and is associated with a HIGH parathyroid hormone level then one or more parathyroid gland tumors are almost surely present. That is, the high blood calcium is a result of the excess parathyroid hormone (PTH). It is a parathyroid gland tumor that is the problem. “
There is a chart somewhere on that website that shows levels of calcium and PTH that indicate a tumor is likely.