Endocrine Abstracts

The kidney is an important target of primary hyperparathyroidism (PHPT). The 4th International Workshop for the management of Asymptomatic PHPT included the presence of hypercalciuria (24-h urinary calcium > 400 mg/day) and increased stone risk by biochemical stone risk profile as criteria for surgery. Increased stone risk profile was defined as at least one between ßCaOx>4 and ßHPO4>2, as defined in literature in a different study population. The aim of the present study was to evaluate the stone risk profile in 102 consecutive patients with asymptomatic PHPT, enrolled from October 2016-June 2017. We recorded clinical and biochemical data, kidney ultrasound and urinary stone risk profile by LithoRisk software, that calculates urine state of saturation for calcium oxalate (ßCaOx) and calcium hydrogen phosphate or brushite (ßHPO4). The group included 81 females and 21 males, mean age 55±15 years. In 93 (91%) patients were sporadic and in 9 (9%) had MEN1 syndrome. We found clearance of creatine <60 ml/min in 4.9% (n=5) and nephrolithiasis/nephrocalcinosis ultrasound detected in 18.3% (n=19). Hypercalciuria (24 h urinary calcium >400 mg/24 h) was detected in 29.4% (n=30). It was present in 57.9% (11 out of 19) patients with kidney stones detected at ultrasound (stone carriers) and in 22.9% (19 out of 83) of those patients without ultrasound detected stones. Either in the former and in the latter group all patients with hypercalciuria had also an increased stone risk profile. Moreover, we evaluated the stone risk profile also in those patients “stone carriers” without hypercalciuria (n=8) and we found that in 5 patients it was increased. In the whole group we found a positive correlation between ßCaOx and PTH (P=0.029, r=0.25) and between ßHPO4 and PTH (P=0.015, r=0.27). Our data suggest that hypercalciuria alone can identify all patients with positive stone risk profile. However, in the group of patients with stones detected at ultrasound and 24-h- urinary calcium <400 mg/24 h there is a proportion of patients in which Lithotest® can detect an increased stone forming risk.