PTH and adenoma: The finding that pooled preload and postload iCa were strongly negatively associated with serum PTH only in the NHPT and not the HPHPT group suggests preserved CaSR signaling within parathyroid cells following proliferation into adenoma or hyperplasia, conversely to patients with HPHPT where a significant contingent of parathyroid cells more likely underwent CaSR downregulation disturbing normal calcium homeostasis.