How to establish the cause of hypercalcemia?

Ally Prebtani, MD, is a professor of medicine in the Division of Endocrinology and Metabolism at McMaster University.

What tests should be performed to diagnose the cause of hypercalcemia?

The most important test to have is a repeat calcium [test]. And at least once you should get an ionized calcium [test] to make sure the corrected calcium is actually accurate.

Then, the next step is to determine whether this is parathyroid hormone (PTH)–mediated or non-PTH mediated. So, you want to do PTH [testing]. But I really want to stress that before investigating further, you must do a nice history and a physical examination because that can help you with 2 things—actually 3 things—how acute it is, how severe the hypercalcemia is, and what the cause of the hypercalcemia is.

Once you do that and you have the calcium level and the PTH level, then you can do further investigations based on those 2 tests, such as imaging and things like the vitamin D level, etc.