Schini M, et al. - In this retrospective study, researchers characterized the prevalence of normocalcemic hyperparathyroidism (NPHPT) and its natural history in a referral population and contrasted the variability of serum calcium with a group of patients with primary hyperparathyroidism (PHPT). Six thousand two hundred eighty patients referred for a BMD measurement. Using data from the day of the BMD measurement, NPHPT patients were identified. Patients with low eGFR or vitamin D, or with no measurements available were excluded. Compared with the PHPT group, the mean adjusted calcium was found to be significantly lower in the NPHPT group but higher than the control group. PTH was comparable to NPHPT and PHPT. Such two groups were experiencing similar variations in serum calcium. Patients with NPHPT often have episodes of hypercalcemia. They consider NPHPT to be a mild form of primary hyperparathyroidism.