El-Husseini Amr, Chakraborty Amit, Yuan Qingcong, Inayatullah Saqib, Bush Heather, Sawaya B Peter
Clin Nephrol. 2017 Nov;88(11):239-247. doi: 10.5414/CN109144.
It is well documented that patients with osteoporosis (OP) have high incidence of hypercalciuria (HC). However, the mechanism of HC in patients with OP is not well established. It is thought to be the result of high bone turnover (HBT) with excessive bone resorption. OP also frequently presents with low bone turnover (LBT). At this time, it is not clear whether OP with LBT is also associated with hypercalciuria.
The purpose of this study is to evaluate urinary calcium excretion in osteoporotic patients with HBT and LBT.
This is a retrospective study of 132 patients with osteoporosis who underwent bone biopsy at the University of Kentucky between January 2010 and December 2012. Based on bone biopsy results, patients were divided into HBT or LBT groups. Demographic data, medical history, bone mineral density, serum creatinine, calcium, phosphorus, estimated glomerular filtration rate (eGFR), filtered calcium load, fractional excretion of calcium and phosphorus, 25-hydroxy vitamin D levels, and 24-hour urinary calcium excretion and creatinine were obtained from the patients' medical records. Also, intact parathyroid hormone (iPTH), serum osteocalcin, bone-specific alkaline phosphatase, N-telopeptide of type I collagen, and urine pyridinium levels were measured.
Hypercalciuria was present in approximately half of the patients in both the HBT and LBT groups. Patients with HBT OP were significantly younger than those with LBT OP (p = 0.013). There was no difference between HBT and LBT patients in 24-hour urinary calcium excretion, serum creatinine, calcium, phosphorus, eGFR, filtered calcium load, and fractional excretion of phosphorus. Mean values of serum osteocalcin and serum N-telopeptide of type I collagen were significantly lower in the LBT compared to the HBT group (p = 0.000 and 0.0152, respectively). There was a significant correlation between filtered calcium load and urinary calcium excretion in HBT patients but not in patients with LBT. Fractional excretion of calcium significantly correlated with urinary calcium excretion in both groups. There was no correlation between kidney function and 24-hour urinary calcium excretion. There was no correlation between dual-emission X-ray absorptiometry T-scores and 24-hour urinary calcium excretion.
CONCLUSION: HC is frequently present in patients with OP regardless of the underlying bone turnover status. This may suggest the presence of a bone-derived renal calcium regulating factor(s). Further studies are needed to understand the exact mechanism and the potential consequences of HC in OP patients. .
有充分文献记载，骨质疏松症（OP）患者高钙尿症（HC）的发生率很高。然而，OP患者发生HC的机制尚未完全明确。一般认为这是高骨转换（HBT）伴骨吸收过多的结果。OP也常表现为低骨转换（LBT）。此时，尚不清楚LBT的OP患者是否也与高钙尿症有关。
本研究的目的是评估HBT和LBT的骨质疏松症患者的尿钙排泄情况。
这是一项对2010年1月至2012年12月间在肯塔基大学接受骨活检的132例骨质疏松症患者的回顾性研究。根据骨活检结果，将患者分为HBT组或LBT组。从患者的病历中获取人口统计学数据、病史、骨密度、血清肌酐、钙、磷、估计肾小球滤过率（eGFR）、滤过钙负荷、钙和磷的排泄分数、25-羟维生素D水平以及24小时尿钙排泄量和肌酐。此外，还测量了完整甲状旁腺激素（iPTH）、血清骨钙素、骨特异性碱性磷酸酶、I型胶原N-端肽以及尿吡啶水平。
HBT组和LBT组中均约有一半的患者存在高钙尿症。HBT型OP患者比LBT型OP患者明显年轻（p = 0.013）。HBT组和LBT组患者在24小时尿钙排泄量、血清肌酐、钙、磷、eGFR、滤过钙负荷以及磷的排泄分数方面没有差异。与HBT组相比，LBT组血清骨钙素和I型胶原血清N-端肽的平均值显著更低（分别为p = 0.000和0.0152）。HBT组患者的滤过钙负荷与尿钙排泄之间存在显著相关性，而LBT组患者则不存在。两组中钙的排泄分数与尿钙排泄均显著相关。肾功能与24小时尿钙排泄之间没有相关性。双能X线吸收法T值与24小时尿钙排泄之间没有相关性。
无论潜在的骨转换状态如何，OP患者中经常存在HC。这可能提示存在一种骨源性肾钙调节因子。需要进一步研究以了解OP患者中HC的确切机制及其潜在后果。
