Endocrine Abstracts

Introduction: Normocalcemic hyperparathyroidism is a less recognised variation of primary hyperparathyroidism (pHPT). Patients present with normal calcium and elevated level of PTH.

Case: A 70 years old woman presented to her general practitioner with left sided loin pain. She had no past medical history of note and she was not taking any medications. Ultrasound of the urinary tract showed bilateral nephrocalcinosis. Her blood tests showed raised PTH level 62 ngm/L (7–53), adjusted calcium 2.54 mmol/L (2.20–2.60), 25-Hydroxy Vitamin D 78.4 nmol/L (>50). Plasma creatinine was 73 micromol/L (51–107), eGFR 69 mL/min/1.73 m², phosphate 1.30 mmol/L (0.70–1.50), and alkaline phosphatase 65 iu/L (30–125). 24 hours urinary calcium and creatinine excretion was not suggestive of familial hypocalciuric hypercalcaemia; urine calcium 7.1 mmol (2.5–7.5), urine creatinine 10.2 mmol (9.0–17.0), Ca/cr E=0.02. Bone DXA scan showed relatively low cortical bone density at the wrist (left distal third of radius: BMD 0.453 g/cm², T score −3.7, Z score −1.8; right femur neck: BMD 0.752 g/cm², T score −1.9, Z score −0.3; AP spine L2-L4: BMD 0.948 g/cm², T score −2.1, Z score −0.4). Her PTH was persistently elevated and plasma calcium remained normal during 6 months of follow up.

Discussion: With increased biochemical screening, pHPT is often discovered incidentally while patients are asymptomatic. Normocalcaemic hyperparathyroidism is a newly recognised phenotype of asymptomatic pHPT. The diagnosis is made after excluding secondary causes of pHPT and these patients are more commonly seen in the bone clinic. It is not clear how many of them will progress to frank hypercalcaemic hyperparathyroidism or remain normocalcaemic; and there are no clear guidelines with regards to indications for parathyroidectomy.

Conclusion: Normocalcaemic hyperparathyroidism is a less recognised form of primary hyperparathyroidism and more research is needed to shed light on how best to manage these patients.

Declaration of interest: There is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported.

Funding: No specific grant from any funding agency in the public, commercial or not-for-profit sector.