Normocalcemic Hyperparathyroidism

Primary hyperparathyroidism (PHPT) is characterized by hyperactivity of one or more parathyroid glands, hypercalcemia and elevated or inappropriately normal parathyroid hormone (PTH) concentrations. Normocalcemic PHPT (NPHPT) has been recently recognized as a distinct phenotype with persistently elevated PTH concentrations, but normal levels of ionized and albumin-corrected total calcium. In countries where serum calcium is measured as part of a biochemical-screening panel, with the widespread availability of PTH assays, NPHPT has gained increased scientific interest. NPHPT presents primarily as an asymptomatic disease. In parts of the world like many South Asian countries where calcium is not routinely measured, the disease is more likely to be symptomatic, with skeletal and renal complications. In NPHPT patients, multiglandular disease may be more common. No guidelines regarding management of this entity exist. Parathyroidectomy is recommended for those with symptomatic disease and for those with asymptomatic PHPT who meet guidelines or prefer surgery. This article reviews the current state of the NPHPT, with emphasis on recently published literature.