Normocalcaemic primary hyperparathyroidism: a diagnostic and therapeutic algorithm.

In recent years, there has been increasing interest in understanding the implications of diagnosing normocalcaemic primary hyperparathyroidism (nPHPT). Many patients hope that nPHPT might explain some of their symptoms, but surgeons hesitate to offer treatment to patients whose calcium levels are normal but whose parathyroid hormone (PTH) levels are elevated in the absence of secondary causes of hyperparathyroidism. This potential new diagnosis is not well understood and may lead to inappropriate investigation and possible unnecessary operations. However, because a significant number of patients with nPHPT progress to hypercalcaemic primary hyperparathyroidism (PHPT), some consider nPHPT to be an early or mild form of hypercalcaemia. Rather than being an indolent disease, nPHPT was reported to be associated with systemic complications similar to 'classical' PHPT, and hence there is growing interest to understand who should be offered surgical treatment and who should be monitored. Further standardisation of diagnostic definition, associated complications, patient selection, surgical management and long-term outcomes are necessary. The recommendations outlined in this review are based on limited evidence from non-randomised cohort studies and expert opinion.