Biochemical characterization of primary hyperparathyroidism with and without kidney stones

Abstract

The exact metabolic-physiological background for kidney stone formation in primary hyperparathyroidism (PHPT) is unclear. To obtain clarification, this retrospective data analysis was conducted in 131 patients with PHPT who had undergone a detailed ambulatory evaluation on a random diet since 1980. The baseline biochemical presentation of 78 patients with PHPT with stones was compared with that of 53 patients without stones. Compared to those without stones, the stone-forming patients had a more marked hypercalciuria (343 +/- 148 vs. 273 +/- 148 mg/day, P < 0.01). Urinary saturation of calcium oxalate and brushite was significantly higher in stone-formers. Serum PTH and fasting urinary calcium were similar between the two groups, but serum phosphorus was significantly lower in stone-formers. Serum calcitriol (available in some patients) showed a slightly higher mean value in stone-formers but the difference was not significant. The increment in urinary calcium after oral load of 1-g calcium was twofold higher among stone-formers. Radial shaft and L2-L4 bone mineral densities resided within the normal ranges. Stone-formers with PHPT display exaggerated urinary calcium excretion due to intestinal hyperabsorption of calcium, contributing to a greater enhancement of the saturation of stone-forming calcium salts.

Renal stones and calcifications in patients with primary hyperparathyroidism: associations with biochemical variables

“…This is in contrast to the findings of Odvina et al (17) who reported a frequency of 60% found by a history of passing stone, removal of stone or roentgenogram. They retrieved data from 131 patients aged R18 years and diagnosed with PHPT by hypercalcaemia, high PTH levels and no secondary cause of hyperparathyroidism.…”

“…This may suggest that a CT scan in a cross-sectional setting is more sensitive than sonography in the diagnosis of nephrocalcinosis and should be used for the routine examination of the patients. It is difficult to conclude on the prevalence of renal stones in PHPT as the reports vary from 7% (18) to 60% (17). The wide range in reported prevalence of stones is difficult to explain but may be based on the differences between studies in study populations, assessment of previous clinical stones and methodology used to identify calcifications and persistent stones.…”

“…In accordance, PHPT is a known risk factor for renal stone formation, which is observed with an estimated prevalence of 7-40% (17,18). Furthermore, among patients presenting with renal stones, the prevalence of concurrent PHPT is around 2% (19).…”

“…However, the precise relationship between the clinical presentation of PHPT and the increased formation of renal stones is not completely understood as only some (20), but not all (19,21) studies have shown an increased renal calcium excretion in PHPT patients with renal stones. Young age at the time of diagnosis (17,20,21,22,23,24) and male gender (17,20,23,25) have often been associated with renal stones, whereas divergent results have been reported for other variables including parathyroid pathology (17,21,22,23,26,27), plasma calcium (17,20,21,22,23,27), plasma PTH (17,20,22,27), plasma calcitriol (13,17,27), diuresis (17,26) and other biochemical variables such as urinary citrate (17,26). To prevent stone formation in the urinary tract, there are inhibitors and among these citrate is the most important.…”

Polymorphisms at the regulatory regions of the CASR gene influence stone risk in primary hyperparathyroidism

“…Kidney stones that are generally related to hypercalciuria are a common complication in PHPT patients (9). Nonconservative Arg990Gly polymorphism (SNP) of the CASR gene is associated with a specific phenotype in PHPT patients, characterized by kidney stones, lower serum concentrations of PTH, and higher urine calcium excretion (10,11).…”