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Primary hyperparathyroidism (PHPT) is a common endocrinopathy referred to the endocrinology outpatient clinic. Distinguishing between PHPT and familial hypocalciuric hypercalcaemia (FHH) using a urinary calcium/creatinine clearance ratio (CCCR) is important, as FHH does not warrant surgical intervention. A urinary CCCR<0.01 favours FHH.

In this study, Sharma et al. describe 88 patients who were referred over a 4-year period with parathyroid hormone (PTH)-dependent hypercalcaemia. In total, 81 of the 88 patients completed diagnostic work-up, with 86% diagnosed with PHPT.

In the series, 66 out of 70 patients with PHPT had untimed spot urine sampling. Of these, 56/66 had a positive urinary CCCR>0.01. Of the patients with a urinary CCCR<0.01, 7/10 were found to have a ratio >0.01 on subsequent 24-hour urine sampling.

Based on their findings, the authors demonstrate the clinical utility of untimed spot urine sampling in making a diagnosis of PHPT in 84% of patients in their series. This provides a quicker, more convenient and patient-friendly investigation in an outpatient setting. The authors also provide a proposed diagnostic algorithm for PTH-dependent hypercalcaemia, which includes untimed spot urine CCCR sampling.

Read the full article in Clinical Endocrinology 2024 101 203–205 https://doi.org/10.1111/cen.15116