PTH and Hypercalcemia: Indeed, when selecting a stringent criterion for NHPT based upon normal ionized calcium and not total calcium under a 2-day restricted diet and the onset of true hypercalcemia following a calcium load test with inappropriate PTH, our data pinpoint differences between NHPT and HPHPT in calcium homeostasis mainly related to better PTH inhibition and renal calcium excretion with no difference for intestinal calcium absorption or calcitriol regulation.