Can you give some more info about the cat, such as age and about the cat's diet now and what it has been in the past?
What I read about hyperparathyroidism comes from hypocalceamia, not hypercalceamia, and can be corrected by diet, especially adding bones for calcium to a high protein diet.
Hypocalceamia may be linked to pancreatitis.
Many vets have the ability to do bloodwork in their office with results while you wait, otherwise they usually have results the next day.