Endocrine Abstracts

Background: Primary hyperparathyroidism (PHPT) is an underdiagnosed metabolic cause of renal calculi, accounting for 3–5% of cases. This may lead to recurrent stone formation, pain, and repeated invasive interventions. Early detection and curative parathyroidectomy can prevent recurrence and reduce morbidity.

Methods: A single centre retrospective cohort study was performed including all patients presenting with renal calculi during 2023. Patients were stratified by serum calcium: hypercalcaemic (>2.6 mmol/l), high-normal (2.5–2.6 mmol/l), or normal (<2.5 mmol/l). Those with adjusted calcium >2.50 mmol/l were assessed for possible PHPT after exclusions including known alternative causes of hypercalcaemia and death. Eligible patients underwent testing for serum calcium, parathyroid hormone (PTH), 25-hydroxyvitamin D, and renal function. Patients with findings suggestive of PHPT were referred for endocrine surgical review and 24-hour urinary calcium analysis.

Results: Of 643 patients, 544 (84.6%) had serum calcium measured; 21% underwent lithotripsy or stenting. Elevated or high-normal calcium was found in 77 patients (14%; mean age 59 ± 17 years; 54% male). Following exclusions, 35 of 55 eligible patients (69%) completed further biochemical testing. Mean initial calcium was 2.57 mmol/l (SD 0.08; median 2.54, IQR 2.53–2.60). Mean PTH was 92.7 U/l (SD 57; median 83, IQR 53–118). 68% (n = 21) had elevated PTH (>68 U/l) of whom 76% (n = 16) had normal-range calcium on repeat testing. Vitamin D deficiency (<50 nmol/l) occurred in 31% (n = 11). Following endocrine surgical review; four underwent parathyroidectomy, and ten remain under evaluation for PHPT or normocalcaemic PHPT (nPHPT).

Conclusion: Targeted biochemical screening in renal stone patients enables early detection of PHPT, facilitating curative intervention and reducing recurrent stones disease. PTH and vitamin D testing should be considered in recurrent stone formers. nPHPT remains challenging to diagnose.