The prevalence and natural history of normocalcaemic hypoparathyroidism in a United Kingdom referral population

Context

Normocalcaemic hypoparathyroidism (NHYPO) is characterised by persistently low levels of parathyroid hormone (PTH) with normal levels of calcium. There is little in current literature on this disease, with only two studies published on its prevalence whilst its natural history remains relatively unknown.

Objectives

to identify the prevalence of NHYPO in a UK referral population and to study the natural history of the disorder.

Design

Retrospective study. Follow up five years

Patients

6280 patients referred for a BMD measurement in a Metabolic Bone referral centre

Measurements

Prevalence of NHYPO and variability of calcium

Results

Based on laboratory results on the index day, 22 patients with NHYPO were identified. Four patients were excluded due to non‐PTH induced hypocalcaemia and unconfirmed data. The final prevalence was 0.29%. Only 67% had persistent normocalcaemia, the rest having intermittent hypocalcaemia. Two of these patients also had persistently low PTH on two occasions. Most of the patients had one PTH measurement available. No patient developed permanent hypoparathyroidism.

Conclusions

The prevalence calculated from this UK referral population is lower when compared to results from previous studies. NHYPO patients often have episodes of hypocalcaemia with some cases having no apparent reason for calcium levels below the reference range.