ADOPTION OF THE FIFTH WORKSHOP URINARY CALCIUM THRESHOLD IN ASYMPTOMATIC PRIMARY HYPERPARATHYROIDISM

The clinical presentation of sporadic primary hyperparathyroidism (PHPT) has shifted over the last decades towards an asymptomatic disease (aPHPT). International workshops have refined surgical criteria, and urinary calcium excretion (24h-UCa) has been among the most controversial parameters. Notably, 24h-UCa was the only modified criterion between the Fourth and Fifth Workshops. The threshold was lowered from a single cut-off of 400 mg/24h (Fourth Workshop) to gender-specific cut-offs of 300 mg/24h for males and 250 mg/24h for females (Fifth Workshop).

We retrospectively analyzed our series of 540 patients with PHPT, focusing on the 225 patients with aPHPT and applying the surgical criteria dictated by the Fourth and Fifth International Workshops.

Patients with aPHPT who met the criteria for surgery increased from 186/225 (82.7%) to 199/225 (88.4%) by applying the Fourth and Fifth workshop criteria, respectively. The percentage of patients who exceeded the threshold for surgery according to the 24h-UCa criterion increased from 18.3% (34/186) to 45.2% (90/199), respectively. The percentage of those met only the 24h-UCa criterion increased from 8/186 (4.3%) to 13/199 (6.5%). Notably of the 39 patients with aPHPT who had not met any Fourth Workshop surgical criteria, 13 (33.3%) exceeded the new Fifth Workshop 24h-UCa threshold, thus newly qualifying for surgery.

Lowering the 24h-UCa threshold led to surgical reclassification in 13/39 patients (33.3%) with aPHPT who previously did not meet surgical indications. This revised criterion increased the overall proportion of patients meeting surgical criteria from 186/225 (82.7%) to 199/225 (88.4%), representing an absolute increase of 5.7% within the study cohort.