Normocalcemic primary hyperparathyroidism.

Normocalcemic primary hyperparathyroidism (PHPT) is a newer phenotype of PHPT defined by elevated PTH concentrations in the setting of normal serum calcium levels. It is increasingly being diagnosed in the setting of evaluation for nephrolithiasis or metabolic bone diseases. It is important to demonstrate that PTH values remain consistently elevated and to measure ionized calcium levels to make the diagnosis. A diagnosis of normocalcemic disease is one of exclusion of secondary forms of hyperparathyroidism, including vitamin D deficiency, renal failure, medications, malabsorption, and hypercalciuria. Lack of rigorous diagnostic criteria and selection bias of the studied populations may explain the different rates of bone and renal complications. The natural history still remains unknown. Caution should be used in recommending surgery, unless clearly indicated. Here we will review the diagnostic features, epidemiology, clinical presentation, natural history, medical and surgical management of normocalcemic PHPT.