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Objective: Patients with primary hyperparathyroidism (PHPT) are at risk of chronic kidney disease (CKD). Cystatin C (Cys-C) is considered a more reliable tool to assess glomerular filtration rate (GFR) than creatinine. The study aimed to assess circulating Cys-C and its relationships with biochemical PHPT and cardiometabolic parameters. Design and methods: The present cross-sectional study was performed in academic endocrine units on PHPT patients (nZ190) and non-hypertensive, non-diabetic, age-and sex-matched healthy controls (nZ135) with no established CKD. The main outcomes were creatinine by alkaline picrate method, Cys-C by immunonephelometry and calculation of estimated GFR based on creatinine and Cys-C (eGFRcr-cys) using the CKD-EPI equation. Results: In PHPT patients, circulating Cys-C ranged 0.45-3.13 mg/l and correlated with creatinine, age and BMI. Mean Cys-C level was higher in PHPT patients than in controls (0.93G0.02 vs 0.78G0.14 mg/l; PZ0.03). Cys-C levels in PHPT patients were predicted by age, BMI, ionized calcium, hypertension and HDL-cholesterol, the most significant determinant being ionized calcium. Cys-C positively correlated with cardiovascular disease (CVD) occurrence. Overall, 18.4% of PHPT patients with eGFRcr O60 ml/min per 1.73 m 2 (nZ169) had Cys-C levels higher than the 95th percentile in controls (1.03 mg/l), consistent with a preclinical CKD, which was associated with hypertension and insulin resistance. Considering eGFRcr-cys, CKD (stages G3a, G3b, 4) was diagnosed in 13.7% of PHPT patients. Estimated GFRcr-cys, but not eGFR based on creatinine, was predicted by insulin resistance and hypertension and positively correlated with CVD. Conclusions: Elevated Cys-C levels were associated with ionized calcium, cardiometabolic risk factors and CVD, and identified preclinical CKD in PHPT patients.

Purpose The study aimed to define the clinical, biochemical and genetic features of adult patients with osteopenia/osteoporosis and/or bone fragility and low serum alkaline phosphatase (sALP). Methods Twenty-two patients with at least two sALP values below the reference range were retrospectively enrolled after exclusion of secondary causes. Data about clinical features, mineral and bone markers, serum pyridoxal-5’-phosphate (PLP), urine phosphoethanolamine (PEA), lumbar and femur bone densitometry, and column X-ray were collected. Peripheral blood DNA of each participant was analyzed to detect ALPL gene anomalies. Results Pathogenic ALPL variants (pALPL) occurred in 23% and benign variants in 36% of patients (bALPL), while nine patients harbored wild-type alleles (wtALPL). Fragility fractures and dental anomalies were more frequent in patients harboring pALPL and bALPL than in wtALPL patients. Of note, wtALPL patients comprised women treated with tamoxifen for hormone-sensitive breast cancer. Mineral and bone markers were similar in the three groups. Mean urine PEA levels were significantly higher in patients harboring pALPL than those detected in patients harboring bALPL and wtALPL; by contrast, serum PLP levels were similar in the three groups. A 6-points score, considering clinical and biochemical features, was predictive of pALPL detection [P = 0.060, OR 1.92 (95% CI 0.972, 3.794)], and more significantly of pALPL or bALPL [P = 0.025, OR 14.33 (95% CI 1.401, 14.605)]. Conclusion In osteopenic/osteoporotic patients, single clinical or biochemical factors did not distinguish hypophosphatasemic patients harboring pALPL or bALPL from those harboring wtALPL. Occurrence of multiple clinical and biochemical features is predictive of ALPL anomalies, and, therefore, they should be carefully identified. Tamoxifen emerged as a hypophosphatasemic drug.

Hypercalciuria may represent a challenge during the workup for osteoporosis management. The present study aimed: (1) to describe the phenotype associated with hypercalciuria in vitamin D-sufficient (serum 25 hydroxyvitamin D (25OHD) > 20 ng/ml) patients with osteopenia/osteoporosis; (2) to analyze the effects of thiazides and anti-resorptive drugs on urine calcium excretion (UCa), mineral metabolic markers, and bone mineral density. Seventy-seven postmenopausal women with hypercalciuria (Uca > 4.0 mg/kg body weight/24 h on two determinations) were retrospectively evaluated in a real-life setting. Median UCa was 5.39 (4.75–6.70) mg/kg/24 h. Kidney stones occurred in 32.9% of patients, who had median UCa similar to that of patients without kidney stones. Clustering analysis considering the three variables, such as serum calcium, phosphate, and parathormone (PTH), identified two main clusters of hypercalciuric patients. Cluster 1 (n = 13) included patients with a primary hyperparathyroidism-like profile, suggesting a certain degree of autonomous PTH secretion from parathyroid glands. Within cluster 2 (n = 61), two subgroups were recognized, cluster 2A (n = 18) that included patients with relatively increased PTH and normophosphatemia, and cluster 2B (n = 43) that included patients with the normal mineral profile. After a follow-up of 33.4 ± 19.6 months, 49 patients treated with thiazidic diuretics (TZD) were reevaluated; 20 patients were treated with hydrochlorothiazide (HCT; 12.5–37.5 mg/day), 29 with indapamide (IND; 1.50–3.75 mg/day). Any significant difference could be detected in all the parameters both basal and treated conditions between patients treated with HCT or IND. TZD induced a mean 39% reduction in UCa and 63.3% of patients obtained Uca < 4.0 mg/kg/24 h, independent of their mineral metabolic profile. Moreover, TZD induced a significant decrease in PTH levels. TZD-treated patients normalizing UCa experienced an increase in bone mineral densities when concomitantly treated with anti-resorptives, while any gain could be observed in TZD-treated patients with persistent hypercalciuria. Finally, multiple regression analysis showed that UCa reduction was at least in part related to denosumab treatment. In conclusion, in postmenopausal osteoporotic women, hypercalciuria is associated with kidney stones in about one-third of patients and with a wide range of impaired PTH secretion, determining a diagnostic challenge. TZD efficiently reduces UCa and normalization contributes to increasing anti-resorptives positive effect on bone mineral density.