Endocrine Abstracts

Normocalcaemic hyperparathyroidism (NPHPT) is characterised by persistently normal calcium levels and elevated PTH values on at least two consecutive measurements, after excluding other causes of secondary hyperparathyroidism. This group of patients is challenging to identify and characterise. The prevalence of the disease in the literature varies significantly due to the various definitions used and the fact that not all causes of secondary hyperparathyroidism have been excluded. Its natural history is also quite unclear, with studies showing persistent normocalcaemia, progression to hypercalcaemia, or even intermittent hypercalcaemia. Clinical features of NPHPT can be similar to those in primary hyperparathyroidism (PHPT). Some, but not all studies from referral centres have shown that the frequency of skeletal complications, is similar to PHPT. The data on kidney stones and nephrolithiasis is also inconclusive. There have been some studies which showed potential benefit from surgical intervention, but the definitions in these studies vary, so, until more studies are available, the recommendation is to observe and follow up these patients with blood tests and BMD measurements