Bone disease in idiopathic hypercalciuria

The Association Between Essential Metal Element Mixture and Sleep Quality in Chinese Community-Dwelling Older Adults

Previous studies have related single essential metal elements (EMEs) to sleep quality among older adults, however, the association of the EME mixture with sleep quality remained poorly understood. This study aimed to investigate the relationships between single EMEs and the EME mixture and sleep quality in older adults living in Chinese communities. This study consisted of 3957 older adults aged 60 years or over. Urinary concentrations of cobalt (Co), vanadium (V), selenium (Se), molybdenum (Mo), strontium (Sr), calcium (Ca), and magnesium (Mg) were detected using inductively coupled plasma mass spectrometry. Sleep quality was evaluated using Pittsburgh Sleep Quality Index (PSQI). The associations of single EMEs and EME mixture with sleep quality were assessed using logistic regression and Bayesian kernel machine regression (BKMR) models, respectively. Adjusted single-element logistic regression models showed that Mo (OR = 0.927, 95%CI:0.867-0.990), Sr (OR = 0.927, 95%CI:0.864-0.994), and Mg (OR = 0.934, 95%CI:0.873-0.997) were negatively related to poor sleep quality. BKMR models exhibited similar results. Also, higher levels of the EME mixture in urine were inversely related to the odds of poor sleep quality after adjustment for covariates, and Mo had the largest conditional posterior inclusion probability (condPIP) value in the mixture. Mo, Sr, and Mg were negatively related to poor sleep quality, separately and as the mixture. The EME mixture in urine was associated with decreased odds of poor sleep quality in older adults, and Mo was the greatest contributor within the mixture. Additional cohort research is warranted to clarify the relationship of multiple EMEs with sleep quality.

Urinary Calcium Is Associated with Serum Sclerostin among Stone Formers

BACKGROUND

Sclerostin plays an important role in bone metabolism and adipose tissue. Animal studies suggest that sclerostin influences urinary calcium (UCa), but this relationship has not been evaluated in stone formers (SFs). We aimed to investigate the association of UCa with serum sclerostin, bone mineral density (BMD), and body composition among SFs.

METHODS

Clinical and laboratorial data were retrieved from medical records. Determinants of UCa were studied using linear regression.

RESULTS

A total of 107 SFs (35.8 ± 9.3 years, 54% male) with eGFR 99.8 ± 14.5 mL/min/1.73 were studied. Subjects were split by sex and grouped into tertiles of UCa levels. Men in the highest UCa tertile had higher body mass index (BMI) and serum sclerostin, lower lean mass, and a trend towards higher fat mass. Women in the highest tertile had higher BMI and a trend towards higher serum sclerostin. Hypertension and metabolic syndrome, but not lower BMD, were more prevalent in the highest UCa tertile for both sexes. Sclerostin was positively correlated with fat mass and inversely correlated with lean mass among men, but not among women. BMD corrected for BMI at lumbar spine was inversely associated with UCa in a univariate analysis, but only serum sclerostin, hypertension, and NaCl intake were independent determinants of UCa in the multivariate model.

CONCLUSION

The present findings disclose that in addition to hypertension and salt intake, serum sclerostin is associated with urinary calcium in stone formers, suggesting that in addition to the hormones traditionally thought to alter calcium reabsorption in the kidney, sclerostin may play a significant additional role, warranting further investigation.

Correlation Between Renal Calculus Disease and Iliac Bone Thickness on a Single Non-contrast CT Scan

Background Renal calculi remain a major economic and health burden worldwide and are considered a systemic disorder associated with multiple other diseases. Several studies have observed that patients with idiopathic calcium renal stones show a reduction in bone mass. This study aimed to evaluate bone mass reduction on a non-contrast CT scan study in a group of idiopathic calcium-containing renal calculus disease patients in comparison with subjects without renal calculus disease. Methodology This non-interventional, cross-sectional study included a total of 300 patients with 150 cases (with renal calculi) and 150 controls (without renal calculi). Patients were divided according to age groups of 18-40, 40-60, and more than 60 years. The renal calculus size and the mean iliac bone thickness were calculated, and Spearman's correlation test was used to determine the correlation between them. Results The mean iliac bone thickness was significantly lower in the cases (3.29 mm) compared to the controls (9.73 mm with a standard deviation of 1.341 mm). There was a statistically significant negative correlation between the size of the renal calculus and the mean iliac bone thickness. Conclusions Renal calculus disease associated with hypercalciuria caused by increased bone resorption is reflected by the decreased iliac bone thickness on CT scans. Our study used the iliac bone (cancellous bone) in predicting bone mass reduction which shows changes early in the course of the disease compared to the neck of the femur and lumbar vertebrae (compact bones). It helps in predicting osteoporosis early and prevents the progression of the disease through early and appropriate clinical and urological intervention.

Bone density, microarchitecture and estimated strength in stone formers: a cross-sectional HR-pQCT study

BACKGROUND

Low areal bone mineral density (BMD), increased fracture risk and altered bone remodeling have been described among stone formers (SFs), but the magnitude of these findings differs by age, sex, menopausal status and urinary calcium (uCa). This study aimed to investigate volumetric BMD (vBMD), bone microarchitecture and biomechanical properties by high-resolution peripheral quantitative computed tomography (HR-pQCT) and finite element analysis (FEA) in young SFs, irrespective of calciuria, further distinguishing trabecular from cortical compartments.

METHODS

HR-pQCT/FEA was performed at the distal tibia (DT) and distal radius (DR) in 106 SFs (57 males and 49 premenopausal females; median age 37 years) and compared with 106 non-SFs (NSFs) retrieved from an existing database, matched for age, sex and body mass index (BMI). Biochemical/hormonal serum and urinary parameters were obtained from SFs.

RESULTS

SFs exhibited significantly lower trabecular number (TbN) and higher trabecular separation (TbSp) than NSFs at both anatomical sites and lower cortical porosity in the DR. In a subgroup analysis separated by sex, female SFs presented significantly lower TbvBMD, relative bone volume fraction (BV/TV) and TbN and higher TbSp than NSFs at both sites, while male SFs showed significantly lower stiffness and failure load. Multivariate analysis showed TbN to be independently associated with sex and BMI at both sites and with uCa at the DR.

CONCLUSIONS

The present findings suggest that bone disease represents an early event among SFs, associated at least in part with calcium excretion and mainly characterized by trabecular bone microarchitecture impairment, especially among women, but with reduced bone strength parameters in men.

Vascular Calcification Is Associated with Fetuin-A and Cortical Bone Porosity in Stone Formers

Background: Nephrolithiasis has been associated with bone loss and vascular calcification (VC), reflecting abnormal extraosseous calcium deposition. Fetuin-A (Fet-A) acts as a potent inhibitor of ectopic mineralization. The aim of the present study was to evaluate the prevalence of VC in stone formers (SF) and non-stone formers (NSF) and to investigate potential determinants of VC among SF, including circulating levels of Fet-A and bone microarchitecture parameters. Methods: Abdominal aortic calcification (AAC) was assessed using available computed tomography in SF and in age-, sex-, and BMI-matched NSF (potential living kidney donors). Serum Fet-A was measured in stored blood samples from SF. Bone microarchitecture parameters were obtained as a post hoc analysis of a cross-sectional cohort from young SF evaluated by high-resolution peripheral quantitative computed tomography (HR-pQCT). Results: A total of 62 SF (38.0 [28.0−45.3] years old) and 80 NSF (40.0 [37.0−45.8] years old) were included. There was no significant difference in AAC scores between SF and NSF. However, when dividing SF according to mean AAC score, below <5.8% (n = 33) or above ≥5.8% (n = 29), SF with higher AAC presented significantly higher BMI and tibial cortical porosity (Ct.Po) and significantly lower serum HDL, klotho, Fet-A, and eGFR. Urinary calcium did not differ between groups, but fractional excretion of phosphate was higher in the former. Upon multivariate regression, BMI, serum Fet-A, and tibial Ct.Po remained independently associated with AAC. Conclusions: This study suggests an association between reduced circulating Fet-A levels and increased bone Ct.Po with VC in SF.

Secondary Osteoporosis

Osteoporosis is a global public health problem, with fractures contributing to significant morbidity and mortality. Although postmenopausal osteoporosis is most common, up to 30% of postmenopausal women, > 50% of premenopausal women, and between 50% and 80% of men have secondary osteoporosis. Exclusion of secondary causes is important, as treatment of such patients often commences by treating the underlying condition. These are varied but often neglected, ranging from endocrine to chronic inflammatory and genetic conditions. General screening is recommended for all patients with osteoporosis, with advanced investigations reserved for premenopausal women and men aged < 50 years, for older patients in whom classical risk factors for osteoporosis are absent, and for all patients with the lowest bone mass (Z-score ≤ -2). The response of secondary osteoporosis to conventional anti-osteoporosis therapy may be inadequate if the underlying condition is unrecognized and untreated. Bone densitometry, using dual-energy x-ray absorptiometry, may underestimate fracture risk in some chronic diseases, including glucocorticoid-induced osteoporosis, type 2 diabetes, and obesity, and may overestimate fracture risk in others (eg, Turner syndrome). FRAX and trabecular bone score may provide additional information regarding fracture risk in secondary osteoporosis, but their use is limited to adults aged ≥ 40 years and ≥ 50 years, respectively. In addition, FRAX requires adjustment in some chronic conditions, such as glucocorticoid use, type 2 diabetes, and HIV. In most conditions, evidence for antiresorptive or anabolic therapy is limited to increases in bone mass. Current osteoporosis management guidelines also neglect secondary osteoporosis and these existing evidence gaps are discussed.

Thiazide and thiazide-like diuretics in nephrolithiasis

Thiazide and thiazide-like diuretics are widely used for the management of hypercalciuria among stone-forming patients. Although the effects of different thiazides should be relatively similar in terms of prevention of stone recurrence, their potency and side effects may differ. However, there is scarce data concerning the metabolic and bone effects of these agents among recurrent nephrolithiasis patients with hypercalciuria. The aim of this update article was to compare our experience in the use of thiazide and thiazide- like diuretics with that of the current literature, concerning their anticalciuric properties and consequent reduction of recurrent stone formation. Their impact on bone mass and potential side effects were also discussed.

Educational review: role of the pediatric nephrologists in the work-up and management of kidney stones

BACKGROUND

The incidence of nephrolithiasis in children and adolescents is increasing and appears to double every 10 years. The most important role of the pediatric nephrologist is to diagnose and modify various metabolic and non-metabolic risk factors, as well as prevent long-term complications especially in the case of recurrent nephrolithiasis.

OBJECTIVE

The purpose of this review is to summarize the existing literature on the etiology and management of pediatric nephrolithiasis.

RESULTS

The incidence of kidney stones is increasing; dietary and environmental factors are probably the main causes for this increased incidence. In most pediatric patients, the etiology for the kidney stones can be identified. Metabolic factors, such as hypercalciuria and hypocitraturia, urinary tract infection, and urinary stasis, constitute leading causes. Herein, we review the etiologies, diagnostic work-up, and treatment options for the most prevalent causes of kidney stones. The detrimental effects of excessive dietary sodium, reduced fluid intake, and the benefits of plant-based over animal-based protein consumption on urinary crystal formation are discussed. We also review the long-term complications.

CONCLUSIONS

Pediatric nephrologists have an important role in the diagnostic work-up and prevention of recurring nephrolithiasis.

CT-Based Diagnosis of Low Vertebral Bone Mineral Density Is Associated with Hypercalciuria and Hypocitraturia on Opportunistic Imaging

INTRODUCTION AND OBJECTIVES

Studies have demonstrated associations between nephrolithiasis and systemic conditions, including low bone mineral density (BMD), which may correlate with hypercalciuria in kidney stone formers (KSFs). Traditionally, low BMD is diagnosed with dual-energy X-ray absorptiometry. As a noncontrast CT (NCCT) scan is typically part of a stone evaluation, our objective was to evaluate the association of NCCT-based vertebral BMD with 24-hour urine parameters in KSF.

MATERIALS AND METHODS

This is a retrospective analysis of 99 KSFs who had CT imaging and 24-hour urine studies. For each patient, BMD was estimated at the L1 vertebral body and CT attenuation measured in HU. A threshold of 160 HU was chosen to distinguish normal from low BMD. Univariate and multivariate logistic regression analysis was performed to compare patients with low and normal BMD. Multivariate linear regression was performed to assess for variables associated with 24-hour urine parameters.

RESULTS

Patients with low BMD had higher 24-hour urine calcium (219 vs 147 mg/day, p < 0.0001) and larger stone volume (259 vs 78.4 mm³, p = 0.009). Multivariate analysis demonstrated age >60 years (odds ratio [OR] 9.3, p < 0.0001) and hypercalciuria (OR 4.34, p = 0.004) correlated with low BMD. Linear regression demonstrated that lower BMD was associated with higher urinary calcium (β-coefficient -0.268, p = 0.009) and lower urinary citrate (β-coefficient 0.332, p = 0.01).

CONCLUSIONS

CT-based diagnosis of low mineral bone density is associated with derangement in 24-hour urine calcium and citrate in KSFs, as well as larger stone volumes.

Characteristics and diagnostic workup of the patient at risk to sustain fragility fracture

The human body undergoes several physiological adaptations as a result of the aging process. Amongst other organs, the skeleton is also affected and when bone fragility is present, an increase in both morbidity and mortality has been reported. Identification of risk factors to calculate the probability for a given patient to develop a fragility fracture it is therefore of paramount importance. Moreover, the existence of an in house protocol for diagnostic work up using biochemical tests and imaging investigations is essential. In the herein study we discuss a diagnostic protocol that has been developed in our clinic based on knowledge from the literature and our clinical experience.

Idiopathic hypercalciuria and formation of calcium renal stones

The most common presentation of nephrolithiasis is idiopathic calcium stones in patients without systemic disease. Most stones are primarily composed of calcium oxalate and form on a base of interstitial apatite deposits, known as Randall's plaque. By contrast some stones are composed largely of calcium phosphate, as either hydroxyapatite or brushite (calcium monohydrogen phosphate), and are usually accompanied by deposits of calcium phosphate in the Bellini ducts. These deposits result in local tissue damage and might serve as a site of mineral overgrowth. Stone formation is driven by supersaturation of urine with calcium oxalate and brushite. The level of supersaturation is related to fluid intake as well as to the levels of urinary citrate and calcium. Risk of stone formation is increased when urine citrate excretion is <400 mg per day, and treatment with potassium citrate has been used to prevent stones. Urine calcium levels >200 mg per day also increase stone risk and often result in negative calcium balance. Reduced renal calcium reabsorption has a role in idiopathic hypercalciuria. Low sodium diets and thiazide-type diuretics lower urine calcium levels and potentially reduce the risk of stone recurrence and bone disease.

Bone remodeling markers as lithogenic risk factors in patients with osteopenia-osteoporosis

PURPOSE

To analyze the presence of phosphocalcic metabolism disorders in patients with osteopenia-osteoporosis without nephrolithiasis with respect to a control group.

METHODS

A cross-sectional study was conducted in patients with osteopenia-osteoporosis without nephrolithiasis (n = 67) in lumbar spine or femur and in a control group (n = 61) with no lithiasis or bone disorders. Blood bone markers, phosphocalcic metabolism, fasting urine, 24-h urine lithogenic risk factors, and densitometry were recorded in both groups. SPSS 20.0 was used for statistical analysis.

RESULTS

In comparison with the controls, significantly higher blood calcium (9.27 ± 0.36 vs. 9.57 ± 0.38, p = 0.0001), intact parathormone (45.6 ± 14.9 vs. 53.8 ± 18.9, p = 0.008), and alkaline phosphatase (61.9 ± 20.9 vs. 70.74 ± 18.9, p = 0.014) levels were found in patients with osteopenia-osteoporosis. In the 24-h urine test, citrate (1010.7 ± 647.8 vs. 617.6 ± 315.8, p = 0.0001) and oxalate (28.21 ± 17.65 vs. 22.11 ± 16.49, p = 0.045) levels were significantly lower in osteopenia-osteoporosis patients than in controls, with no significant difference in calcium (187.3 ± 106.9 vs. 207.06 ± 98.12, p = 0.27) or uric acid (540.7 ± 186.2 vs. 511.9 ± 167.06, p = 0.35) levels. Patients with osteopenia-osteoporosis had significantly higher levels of lithogenic risk factors associated with bone remodeling, including significantly increased β-crosslaps and osteocalcin values and higher β-crosslaps/osteocalcin ratios.

CONCLUSION

Patients with osteopenia-osteoporosis without nephrolithiasis showed phosphocalcic metabolism disorders as well as lower urinary citrate and higher β-crosslaps/osteocalcin and fasting calcium/creatinine ratios, which would increase the risk of nephrolithiasis. Hence, prospective studies are warranted to evaluate the long-term risks.

Gender Representation of Osteoporosis in Patients with Urolithiasis

Introduction:

A great number of clinical studies has indicated that the patients with calcium urolithiasis have a reduced mineral bone density.

Aim:

The aim of our research was to establish representation of osteoporosis, by measuring mineral bone density using the DEXA method, in patients with calcium urolithiasis, by gender.

Material and methods:

The research was a prospective one, performed at the University Hospital of the Clinical Center of Banja Luka, at the Urology Clinic and Clinic for Endocrinology, Diabetes and Metabolic Diseases. The material in this research were the patients divided into two groups: a working group (the patients suffering from calcium urolithiasis) and a control group (the patients without calcium urolithiasis). One hundred and twenty (120) patients were included in both these groups, divided in three age subgroups: 20-40, 40-60 and over 60. The total working group consisted of 63 men (52.2%) and 57 (47.5%) women. In the control group, the number of women was 72 (60%) and 48 (40%) of men. Establishing of mineral bone density at L2-L4 of lumbal spine vertebrae and hip was done for the patients in both these groups, using DEXA method.

Results:

Analysis of mineral bone density using DEXA method in patients by gender of working and control groups has shown that osteoporosis and osteopenia in patients of the working group is significantly more present in women (14% and 22.8%) compared to men (1.6% and 17.5%). When compared by gender in the control group, osteoporosis was present a lot more in women (36.1%) compared to men (2.1%). When observed for the total sample of both the working and control group, there was a statistically significant difference (p<0,01) related to gender structure, where the share of women with osteoporosis/osteopenia was significantly higher (36.1%) compared to men (4.2%).

Conclusion:

Representation of osteoporosis in women with urolithiasis, particularly of older age, is very expressed and this is why prevention measures should start as soon as possible, so as to avoid severe complications of this illness.

Management of endocrine disease: Secondary osteoporosis: pathophysiology and management

Osteoporosis is a skeletal disorder characterized by decreased mass and compromised bone strength predisposing to an increased risk of fractures. Although idiopathic osteoporosis is the most common form of osteoporosis, secondary factors may contribute to the bone loss and increased fracture risk in patients presenting with fragility fractures or osteoporosis. Several medical conditions and medications significantly increase the risk for bone loss and skeletal fragility. This review focuses on some of the common causes of osteoporosis, addressing the underlying mechanisms, diagnostic approach and treatment of low bone mass in the presence of these conditions.

Modeling hypercalciuria in the genetic hypercalciuric stone-forming rat

PURPOSE OF REVIEW

In this review, we discuss how the genetic hypercalciuric stone-forming (GHS) rats, which closely model idiopathic hypercalciuria and stone formation in humans, provide insights into the pathophysiology and consequences of clinical hypercalciuria.

RECENT FINDINGS

Hypercalciuria in the GHS rats is due to a systemic dysregulation of calcium transport, as manifest by increased intestinal calcium absorption, increased bone resorption and decreased renal tubule calcium reabsorption. Increased levels of vitamin D receptor in intestine, bone and kidney appear to mediate these changes. The excess receptors are biologically active and increase tissue sensitivity to exogenous vitamin D. Bones of GHS rats have decreased bone mineral density (BMD) as compared with Sprague-Dawley rats, and exogenous 1,25(OH)2D3 exacerbates the loss of BMD. Thiazide diuretics improve the BMD in GHS rats.

SUMMARY

Studying GHS rats allows direct investigation of the effects of alterations in diet and utilization of pharmacologic therapy on hypercalciuria, urine supersaturation, stone formation and bone quality in ways that are not possible in humans.

Calcium nephrolithiasis and bone demineralization: pathophysiology, diagnosis, and medical management

PURPOSE OF REVIEW

To establish the relationship between calcium nephrolithiasis, bone densitometry scoring, and bone mineral density (BMD) loss according to bone turnover markers (BTMs) and urinary metabolites.

RECENT FINDINGS

Patients with recurrent calcium nephrolithiasis and idiopathic fasting hypercalciuria (urinary calcium/creatinine ratio >0.11) are more likely to have BMD loss that may lead to osteopenia or osteoporosis. In these patients, BTMs may be used as a surrogate for both bone health and stone recurrence. Suspect higher lithogenic states when calcium stone formers have serum beta-crosslaps (resorptive marker) greater than 0.311 ng/ml, serum osteocalcin (formative marker) greater than 13.2 ng/ml, and beta-crosslaps/osteocalcin ratio greater than 0.024.

SUMMARY

Patients with recurrent calcium nephrolithiasis and fasting hypercalciuria have a higher incidence of osteopenia and osteoporosis, measured by the dual-energy X-ray absorptiometry. These patients present not only with hypercalciuria and increased BTMs (mainly resorptive), but also up to 30% have hypocitraturia and increased urinary calcium/citrate ratio (>0.25). On the basis of these results, a diagnostic algorithm was created, classifying hypercalciurics according to their fasting calcium/creatinine and calcium/citrate ratio. Medical therapy for these patients is aimed at improving the dietary habits (normocalcemic, low salt, low animal protein diet), prescribing combinations of potassium citrate, thiazides, and bisphosphonates, and correcting bone and urinary abnormalities that may lower future skeletal and kidney stone risk.

Retrospective review of serum and urinary lithogenic risk factors in patients with osteoporosis and osteopenia

OBJECTIVE

To analyze differences in bone remodeling markers, lithogenic factors and bone densitometry among the 3 groups of patients (controls, patients with relapsing calcium renal lithiasis, and patients with loss of bone mineral density without lithiasis).

MATERIAL AND METHODS

This is a cross-sectional study including 203 patients who were divided in 3 groups: group 1 (controls), group 2 (patients with relapsing calcium renal lithiasis), and group 3 (patients with osteopenia and/or osteoporosis in the lumbar spine or hip). Bone densitometry, calcium-phosphorous and bone metabolism analysis, and analysis of lithogenic risk factors in fasting urine samples and 24-hour urine samples were performed. Statistical analysis was performed with SPSS 17.0. A P ≤.05 was considered statistically significant.

RESULTS

Patients in group 2 presented greater calcium excretion and a lower citrate excretion in 24-hour urine samples as compared with the other 2 groups. The proportion of hypercalciuria and hypocitraturia was higher in group 2. In addition, patients in group 2 presented a lower loss of bone mineral density as well as altered bone remodeling markers as compared with those in group 1. Patients in group 3 also presented alterations in urine calcium and citrate excretion with respect to the control group, with elevated fasting calcium and citrate levels and calcium-to-citrateratio.

CONCLUSION

Lithogenic risk factors are altered in patients with osteopenia and/or osteoporosis without renal lithiasis although to a lesser extent than patients with calcium renal lithiasis.

Secondary osteoporosis: pathophysiology & diagnosis

Osteoporosis is a skeletal disease characterized by decreased bone mass and microarchitectural changes in bone tissue that increase the susceptibility to fracture. Secondary osteoporosis is loosely defined as low bone mineral density or increased risk of fragility fracture caused by any factor other than aging or postmenopausal status. The purpose of this review is to discuss the current understanding of the pathophysiology and contribution to fracture risk of many of the more common causes of secondary osteoporosis, as well as diagnostic considerations, outlined by organ system. While not comprehensive, included are a wide array of diseases, conditions, and medications that have been associated with bone loss and susceptibility to fractures. The hope is to highlight the importance to the general clinician of screening for and treating the osteoporosis in these patients, so to limit the resultant increased morbidity associated with fractures.

Expression of fibroblast growth factor 23, vitamin D receptor, and sclerostin in bone tissue from hypercalciuric stone formers

BACKGROUND AND OBJECTIVES

Increased bone resorption, low bone formation, and abnormal mineralization have been described in stone formers with idiopathic hypercalciuria. It has been previously shown that the receptor activator of NF-κB ligand mediates bone resorption in idiopathic hypercalciuria (IH). The present study aimed to determine the expression of fibroblast growth factor 23 (FGF-23), vitamin D receptor (VDR), and sclerostin in bone tissue from IH stone formers.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Immunohistochemical analysis was performed in undecalcified bone samples previously obtained for histomorphometry from 30 transiliac bone biopsies of idiopathic hypercalciuria stone-forming patients between 1992 and 2002 and 33 healthy individuals (controls). Serum parameters were obtained from their medical records.

RESULTS

Histomorphometry disclosed 21 IH patients with high and 9 IH patients with normal bone resorption. Importantly, eroded surfaces (ES/BS) from IH patients but not controls were significantly correlated with VDR immunostaining in osteoblasts (r=0.51; P=0.004), sclerostin immunostaining in osteocytes (r=0.41; P=0.02), and serum 1,25-dihydroxyvitamin D (r=0.55; P<0.01). Of note, both VDR and sclerostin immunostaining were significantly correlated with serum 1,25-dihydroxyvitamin D in IH patients (r=0.52; P=0.01 and r=0.53; P=0.02, respectively), although VDR and sclerostin expression did not differ between IH and controls. IH patients with high bone resorption exhibited a significantly stronger sclerostin immunostaining than IH patients with normal bone resorption. FGF-23 expression in osteocytes from IH patients did not differ from controls and was not correlated with any histomorphometric parameter.

CONCLUSIONS

These findings suggest the contribution of VDR and sclerostin, as well as 1,25-dihydroxyvitamin D, to increase bone resorption in idiopathic hypercalciuria but do not implicate FGF-23 in the bone alterations seen in these patients.

The relation between bone and stone formation

Hypercalciuria is the most common metabolic abnormality found in patients with calcium-containing kidney stones. Patients with hypercalciuria often excrete more calcium than they absorb, indicating a net loss of total-body calcium. The source of this additional urinary calcium is almost certainly the skeleton, the largest repository of calcium in the body. Hypercalciuric stone formers exhibit decreased bone mineral density (BMD), which is correlated with the increase in urine calcium excretion. The decreased BMD also correlates with an increase in markers of bone turnover as well as increased fractures. In humans, it is difficult to determine the cause of the decreased BMD in hypercalciuric stone formers. To study the effect of hypercalciuria on bone, we utilized our genetic hypercalciuric stone-forming (GHS) rats, which were developed through successive inbreeding of the most hypercalciuric Sprague-Dawley rats. GHS rats excrete significantly more urinary calcium than similarly fed controls, and all the GHS rats form kidney stones while control rats do not. The hypercalciuria is due to a systemic dysregulation of calcium homeostasis, with increased intestinal calcium absorption, enhanced bone mineral resorption, and decreased renal tubule calcium reabsorption associated with an increase in vitamin D receptors in all these target tissues. We recently found that GHS rats fed an ample calcium diet have reduced BMD and that their bones are more fracture-prone, indicating an intrinsic disorder of bone not secondary to diet. Using this model, we should better understand the pathogenesis of hypercalciuria and stone formation in humans to ultimately improve the bone health of patients with kidney stones.

Kidney stones: an update on current pharmacological management and future directions

INTRODUCTION

Kidney stones are a common problem worldwide with substantial morbidities and economic costs. Medical therapy reduces stone recurrence significantly. Much progress has been made in the last several decades in improving therapy of stone disease.

AREAS COVERED

This review discusses i) the effect of medical expulsive therapy on spontaneous stone passage, ii) pharmacotherapy in the prevention of stone recurrence and iii) future directions in the treatment of kidney stone disease.

EXPERT OPINION

Fluid intake to promote urine volume of at least 2.5 L each day is essential to prevent stone formation. Dietary recommendations should be adjusted based on individual metabolic abnormalities. Properly dosed thiazide treatment is the standard therapy for calcium stone formers with idiopathic hypercalciuria. Potassium alkali therapy is considered for hypocitraturia, but caution should be taken to prevent potential risk of calcium phosphate stone formation. For absorptive hyperoxaluria, low oxalate diet and increased dietary calcium intake are recommended. Pyridoxine has been shown effective in some cases of primary hyperoxaluria type I. Allopurinol is used in calcium oxalate stone formers with hyperuricosuria. Treatment of cystine stones remains challenging. Tiopronin can be used if urinary alkalinization and adequate fluid intake are insufficient. For struvite stones, complete surgical removal coupled with appropriate antibiotic therapy is necessary.

Association of severe calcium lithogenic activity and bone remodeling markers

OBJECTIVE

To establish cutoff points for markers of bone remodeling that allow for screening of patients at risk for serious lithogenic activity.

MATERIALS AND METHODS

We conducted a cross-sectional study with 182 patients (aged between 25 and 60 years) divided into 3 groups: group 1, 56 patients without lithiasis; group 2, 67 patients with light calcium lithiasis; and group 3, 59 patients with severe calcium lithiasis. The criteria for inclusion in and exclusion from the study were established, and light and severe lithogenic activity were defined. Metabolic variables in blood and urine, along with bone densitometry, were studied for the groups. Statistical analysis of the results and preparation of receiver operating characteristic curves to establish optimal cutoff points were performed.

RESULTS

The patients in group 3 showed the greatest bone mineral density loss and the highest values for markers of bone remodeling, together with increased 24-hour calciuria. Using the receiver operating characteristic curves developed and based on statistical significance (P = .0001), the following cutoff points for severe lithogenic activity, with a sensitivity between 75% and 85%, were established: β-crosslaps >0.331 ng/mL; osteocalcin >13.2 ng/mL; β-crosslaps/osteocalcin >0.024; 24-hour calciuria >306.6 mg; and fasting urine calcium/creatinine >0.105.

CONCLUSION

Patients with calcium lithiasis and elevated values for osteocalcin, β-crosslaps, β-crosslaps/osteocalcin, 24-hour calciuria, and fasting urine calcium/creatinine may present a high risk of severe lithogenic activity.

Optimum nutrition for kidney stone disease

We summarize the data regarding the associations of individual dietary components with kidney stones and the effects on 24-hour urinary profiles. The therapeutic recommendations for stone prevention that result from these studies are applied where possible to stones of specific composition. Idiopathic calcium oxalate stone-formers are advised to reduce ingestion of animal protein, oxalate, and sodium while maintaining intake of 800 to 1200 mg of calcium and increasing consumption of citrate and potassium. There are few data regarding dietary therapy of calcium phosphate stones. Whether the inhibitory effect of citrate sufficiently counteracts increasing urine pH to justify more intake of potassium and citrate is not clear. Reduction of sodium intake to decrease urinary calcium excretion would also be expected to decrease calcium phosphate stone recurrence. Conversely, the most important urine variable in the causation of uric acid stones is low urine pH, linked to insulin resistance as a component of obesity and the metabolic syndrome. The mainstay of therapy is weight loss and urinary alkalinization provided by a more vegetarian diet. Reduction in animal protein intake will reduce purine ingestion and uric acid excretion. For cystine stones, restriction of animal protein is associated with reduction in intake of the cystine precursor methionine as well as cystine. Reduction of urine sodium results in less urine cystine. Ingestion of vegetables high in organic anion content, such as citrate and malate, should be associated with higher urine pH and fewer stones because the amino acid cystine is soluble in more alkaline urine. Because of their infectious origin, diet has no definitive role for struvite stones except for avoiding urinary alkalinization, which may worsen their development.

DNA damage in human lymphocytes exposed to four food additives in vitro

In vitro genotoxic effects of antioxidant additives, such as citric acid (CA) and phosphoric acid (PA) and their combination, as well as antimicrobial additives, such as benzoic acid (BA) and calcium propionate (CP), on human lymphocytes were determined using alkaline single-cell gel electrophoresis. There was a significant increase in the DNA damage in human lymphocytes after 1 h of in vitro exposure to CA, PA, BA and CP (200, 25–200, 50–500, 50–1000 μg/mL, respectively). The combination of CA and PA significantly increased the mean tail intensity at all the concentrations used (25–200 μg/mL) and significantly increased the mean tail length mainly after higher concentrations (100 and 200 μg/mL). Data in this study showed that the concentrations of food additives used induce DNA damage and PA was the most genotoxic and CA was less genotoxic additives among them.

Metabolic evaluation of first-time and recurrent stone formers

Evaluation of stone formers should include careful attention to medications, past medical history, social history, family history, dietary evaluation, occupation, and laboratory evaluation. Laboratory evaluation requires at least serum chemistries and urinalysis. Twenty-four-hour urine collections are most appropriate for patients with recurrent stones or complex medical histories. However, these collections may be appropriate for some first-time stone formers, including those with comorbidities or large stones. Although twin studies demonstrate that heritability accounts for at least 50% of the kidney stone phenotype, the responsible genes are not clearly identified, and so genetic testing is rarely indicated.

Bisphosphonates in the management of idiopathic hypercalciuria associated with osteoporosis: a new trick from an old drug

Idiopathic hypercalciuria (IHC) is defined as a 24-hour urinary calcium excretion that exceeds 4 mg/kg/day, regardless of gender and in absence of systemic diseases or pharmacological treatments that may cause normocalcemic hypercalciuria (eg sarcoidosis, normocalcemic primary hyperparathyroidism, vitamin D intoxication, hyperthyroidism). Patients with IHC and nephrolithiasis often present increased bone turnover, decreased bone mineral density (BMD) and increased susceptibility to fragility fractures. Although the pathogenesis of IHC seems complex and multifactorial, recent evidences suggest that cells involved in bone resorption may play a critical role in the chain of events leading to the excessive urinary calcium excretion. Therefore, it has been proposed that bisphosphonates, potent inhibitors of bone resorption, may have beneficial effects in hypercalciuric patients with low BMD. This manuscript reports recent findings regarding the role of bone tissue in the pathogenesis of IHC, and supports the use of bisphosphonates in such conditions. It also reviews the literature on the effects of bisphosphonates in subjects with osteoporosis-associated IHC.

Osteoporosis in men: an Endocrine Society clinical practice guideline

OBJECTIVE

The aim was to formulate practice guidelines for management of osteoporosis in men.

EVIDENCE

We used the Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) system to describe the strength of recommendations and evidence quality.

CONSENSUS PROCESS

Consensus was guided by systematic evidence reviews, one in-person meeting, and multiple conference calls and e-mails. Task Force drafts were reviewed successively by The Endocrine Society's Clinical Guidelines Subcommittee and Clinical Affairs Core Committee; representatives of ASBMR, ECTS, ESE, ISCD; and members at large. At each stage, the Task Force received written comments and incorporated needed changes. The reviewed document was approved by The Endocrine Society Council before submission for peer review.

CONCLUSIONS

Osteoporosis in men causes significant morbidity and mortality. We recommend testing higher risk men [aged ≥70 and men aged 50-69 who have risk factors (e.g. low body weight, prior fracture as an adult, smoking, etc.)] using central dual-energy x-ray absorptiometry. Laboratory testing should be done to detect contributing causes. Adequate calcium and vitamin D and weight-bearing exercise should be encouraged; smoking and excessive alcohol should be avoided. Pharmacological treatment is recommended for men aged 50 or older who have had spine or hip fractures, those with T-scores of -2.5 or below, and men at high risk of fracture based on low bone mineral density and/or clinical risk factors. Treatment should be monitored with serial dual-energy x-ray absorptiometry testing.

Bone disease in pediatric idiopathic hypercalciuria

Idiopathic hypercalciuria (IH) is the leading metabolic risk factor for urolithiasis and affects all age groups without gender or race predominance. IH has a high morbidity with or without lithiasis and reduced bone mineral density (BMD), as described previously in pediatric patients as well as in adults. The pathogenesis of IH is complex and not completely understood, given that urinary excretion of calcium is the end result of an interplay between three organs (gut, bone and kidney), which is further orchestrated by hormones, such as 1,25 dihydroxyvitamin D, parathyroid hormone, calcitonin and fosfatonins (i.e., fibroblast growth-factor-23). Usually, a primary defect in one organ induces compensatory mechanisms in the remaining two organs, such as increased absorption of calcium in the gut secondary to a primary renal loss. Thus, IH is a systemic abnormality of calcium homeostasis with changes in cellular transport of this ion in intestines, kidneys and bones. Reduced BMD has been demonstrated in pediatric patients diagnosed with IH. However, the precise mechanisms of bone loss or failure of adequate bone mass gain are still unknown. The largest accumulation of bone mass occurs during childhood and adolescence, peaking at the end of the second decade of life. This accumulation should occur without interference to achieve the peak of optimal bone mass. Any interference may be a risk factor for the reduction of bone mass with increased risk of fractures in adulthood. This review will address the pathogenesis of IH and its consequence in bone mass.

Chlorthalidone improves vertebral bone quality in genetic hypercalciuric stone-forming rats

We have bred a strain of rats to maximize urine (u) calcium (Ca) excretion and model hypercalciuric nephrolithiasis. These genetic hypercalciuric stone-forming (GHS) rats excrete more uCa than control Sprague-Dawley rats, uniformly form kidney stones, and similar to patients, demonstrate lower bone mineral density. Clinically, thiazide diuretics reduce uCa and prevent stone formation; however, whether they benefit bone is not clear. We used GHS rats to test the hypothesis that the thiazide diuretic chlorthalidone (CTD) would have a favorable effect on bone density and quality. Twenty GHS rats received a fixed amount of a 1.2% Ca diet, and half also were fed CTD (4 to 5 mg/kg/d). Rats fed CTD had a marked reduction in uCa. The axial and appendicular skeletons were studied. An increase in trabecular mineralization was observed with CTD compared with controls. CTD also improved the architecture of trabecular bone. Using micro-computed tomography (µCT), trabecular bone volume (BV/TV), trabecular thickness, and trabecular number were increased with CTD. A significant increase in trabecular thickness with CTD was confirmed by static histomorphometry. CTD also improved the connectivity of trabecular bone. Significant improvements in vertebral strength and stiffness were measured by vertebral compression. Conversely, a slight loss of bending strength was detected in the femoral diaphysis with CTD. Thus results obtained in hypercalciuric rats suggest that CTD can favorably influence vertebral fracture risk. CTD did not alter formation parameters, suggesting that the improved vertebral bone strength was due to decreased bone resorption and retention of bone structure.

Determinants of osteopenia in male renal-stone-disease patients with idiopathic hypercalciuria

BACKGROUND AND OBJECTIVES

Bone demineralization is frequent in renal-stone formers with hypercalciuria. Although this pathologic link has been recognized for decades, the underlying mechanisms and risk factors associated with osteopenia/osteoporosis in this population remain partially understood.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

This study retrospectively analyzed determinants of low bone mineral density (BMD) in 65 idiopathic hypercalciuric male renal-stone formers. Clinical and biologic evaluation included BMD measurement, bone-remodeling markers, analysis of calcium metabolism with oral calcium load test, and dietary inquiry.

RESULTS

Patients with osteopenia (n=23, 35% of the population) presented significantly higher fasting calciuria as compared with normal bone density patients (n=42) (calcium/creatinine ratio was 0.32 versus 0.24 mmol/mmol; P=0.006). Analysis of the whole population revealed a negative association between fasting hypercalciuria and BMD (P = 0.003), independent of confounding variables including body-mass index and tobacco consumption. The fasting calcium/creatinine ratio above 0.25 mmol/mmol was associated with a 3.8-fold increase in the risk of low BMD.

CONCLUSION

In our study, fasting hypercalciuria after a 2-day calcium-restricted diet appears as the only biologic factor associated with low BMD, suggesting a bone-calcium efflux. Our results support the view of a parathyroid-independent pathologic process that remains to be identified. Hypercalciuric patients with low BMD do not excrete more calcium in 24-hour urine samples than patients without low BMD.

Phosphate toxicity: new insights into an old problem

Phosphorus is an essential nutrient required for critical biological reactions that maintain the normal homoeostatic control of the cell. This element is an important component of different cellular structures, including nucleic acids and cell membranes. Adequate phosphorus balance is vital for maintaining basic cellular functions, ranging from energy metabolism to cell signalling. In addition, many intracellular pathways utilize phosphate ions for important cellular reactions; therefore, homoeostatic control of phosphate is one of the most delicate biological regulations. Impaired phosphorus balance can affect the functionality of almost every human system, including musculoskeletal and cardiovascular systems, ultimately leading to an increase in morbidity and mortality of the affected patients. Human and experimental studies have found that delicate balance among circulating factors, like vitamin D, PTH (parathyroid hormone) and FGF23 (fibroblast growth factor 23), are essential for regulation of physiological phosphate balance. Dysregulation of these factors, either alone or in combination, can induce phosphorus imbalance. Recent studies have shown that suppression of the FGF23-klotho system can lead to hyperphosphataemia with extensive tissue damage caused by phosphate toxicity. The cause and consequences of phosphate toxicity will be briefly summarized in the present review.

The role of salt abuse on risk for hypercalciuria

Background

Elevated sodium excretion in urine resulting from excessive sodium intake can lead to hypercalciuria and contribute to the formation of urinary stones. The aim of this study was to evaluate salt intake in patients with urinary lithiasis and idiopathic hypercalciuria (IH).

Methods

Between August 2007 and June 2008, 105 lithiasic patients were distributed into 2 groups: Group 1 (n = 55): patients with IH (urinary calcium excretion > 250 mg in women and 300 mg in men with normal serum calcium); Group 2 (n = 50): normocalciuric patients (NC). Inclusion criteria were: age over 18 years, normal renal function (creatinine clearance ≥ 60 ml/min), absent proteinuria and negative urinary culture. Pregnant women, patients with intestinal pathologies, chronic diarrhea or using corticoids were excluded. The protocol of metabolic investigation was based on non-consecutive collection of two 24-hour samples for dosages of: calcium, sodium, uric acid, citrate, oxalate, magnesium and urinary volume. Food intake was evaluated by the three-day dietary record quantitative method, and the Body Mass Index (BMI) was calculated and classified according to the World Health Organization (WHO). Sodium intake was evaluated based on 24-hour urinary sodium excretion.

Results

The distribution in both groups as regards mean age (42.11 ± 10.61 vs. 46.14 ± 11.52), weight (77.14 ± 16.03 vs. 75.99 ± 15.80), height (1.64 ± 0.10 vs. 1.64 ± plusorminus 0.08) and BMI (28.78 ± 5.81 vs. 28.07 ± 5.27) was homogeneous. Urinary excretion of calcium (433.33 ± 141.92 vs. 188.93 ± 53.09), sodium (280.08 ± 100.94 vs. 200.44.93 ± 65.81), uric acid (880.63 ± 281.50 vs. 646.74 ± 182.76) and magnesium (88.78 ± 37.53 vs. 64.34 ± 31.84) was significantly higher in the IH group (p < 0.05). There was no statistical difference in calcium intake between the groups, and there was significantly higher salt intake in patients with IH than in NC.

Conclusions

This study showed that salt intake was higher in patients with IH as compared to NC.

The bone and the kidney

Renal tubular diseases may present with osteopenia, osteoporosis or osteomalacia, as a result of significant derangements in body electrolytes. In case of insufficient synthesis of calcitriol, as in renal failure, the more complex picture of renal osteodystrophy may develop. Hypothetically, also disturbed renal production of BMP-7 and Klotho could cause bone disease. However, the acknowledgment that osteocytes are capable of producing FGF23, a phosphaturic hormone at the same time modulating renal synthesis of calcitriol, indicates that it is also bone that can influence renal function. Importantly, a feed-back mechanism exists between FGF23 and calcitriol synthesis, while Klotho, produced by the kidney, determines activity and selectivity of FGF23. Identification of human diseases linked to disturbed production of FGF23 and Klotho underlines the importance of this new bone-kidney axis. Kidney and bone communicate reciprocally to regulate the sophisticated machinery responsible for divalent ions homeostasis and for osseous or extraosseous mineralisation processes.

Alendronate and indapamide alone or in combination in the management of hypercalciuria associated with osteoporosis: a randomized controlled trial of two drugs and three treatments

BACKGROUND

The role of bisphosphonates (BPs) in the management of patients with hypercalciuria (HC) associated with osteoporosis is still uncertain. The aim of the study was to evaluate the effect of alendronate and indapamide alone or in combination on bone mineral density (BMD) and 24-h urinary calcium excretion (24-CaU) in post-menopausal women with HC and low BMD.

METHODS

A total of 77 post-menopausal women with HC (24-CaU > 4 mg/kg/day) and low BMD [T-score < -2.0 at lumbar spine (LS), femoral neck (FN) or total hip (TH)] from two centres of Northern Italy were randomized to receive indapamide 2.5 mg daily alone (24 patients, IND group), alendronate 70 mg weekly alone (27 patients, ALN group) or the combination therapy (26 patients, ALN + IND group). Throughout the study, all subjects received daily calcium supplements, depending on their dietary intake, to maintain a daily input of 1000 mg. Patients were instructed to increase water intake up to 2000 mL daily. The percentage and absolute changes of BMD at LS, FN and TH, and the variation of 24-CaU from baseline at 1 year were the primary outcomes. Serum calcium, phosphate, parathyroid hormone and bone alkaline phosphatase were also measured.

RESULTS

Overall 67 women completed the study and were included in the final analysis. Patients in the three groups were similar with regard to baseline characteristics. BMD did not significantly change from baseline after 1 year of treatment with indapamide (LS: +1 +/- 3.1%; FN: -0.3 +/- 3.5%; TH: -0.4 +/- 3.1%), while it showed a significant increase from baseline in the other two groups (ALN; LS: +5.8 +/- 4.2%, P < 0.001; FN: +3.9 +/- 7.9%, P = 0.018; TH: +2 +/- 3.6%, P = 0.006) (ALN + IND; LS: +8.2 +/- 5.3%, P < 0.001; FN: +4.9 +/- 6.7%, P = 0.007; TH: +2.9 +/- 4.2%, P = 0.004). Patients in the combination group showed a significantly higher increase of BMD at LS compared to ALN (P = 0.04). After 1 year, 24-CaU values significantly decreased from baseline in all groups (IND, 239 +/- 78 versus 364 +/- 44, P < 0.001) (ALN, 279 +/- 68 versus 379 +/- 79, P < 0.001) (ALN + IND, 191 +/- 68 versus 390 +/- 55, P < 0.001). The mean percentage decrease of 24-CaU in ALN + IND group (-50%) was significantly greater compared to ALN (-24%, P < 0.001) and IND (-35%, P = 0.012).

CONCLUSIONS

These results show a benefit, in terms of BMD improvement and 24-CaU reduction, associated with BPs' therapy in combination with indapamide in HC associated with osteoporosis. The combination therapy demonstrated a reduction of 24-CaU and an increase in LS BMD superior to that observed with alendronate alone. Our results support a new potential approach with BPs associated with thiazide diuretics or indapamide in the management of post-menopausal women with HC and associated bone loss. Studies on the larger sample size are needed to demonstrate the efficacy on the fracture outcome.

RANKL is a mediator of bone resorption in idiopathic hypercalciuria

BACKGROUND AND OBJECTIVES

This study aimed to determine the expression of osteoprotegerin, receptor activator of nuclear factor kappaB ligand, interleukin-1alpha, transforming growth factor-beta, and basic fibroblast growth factor in stone-forming patients with idiopathic hypercalciuria.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Immunohistochemical analysis was performed in undecalcified bone samples previously obtained from 36 transiliac bone biopsies of patients who had idiopathic hypercalciuria and whose histomorphometry had shown lower bone volume, increased bone resorption, and prolonged mineralization lag time.

RESULTS

Bone expression of receptor activator of nuclear factor kappaB ligand and osteoprotegerin was significantly higher in patients with idiopathic hypercalciuria versus control subjects. Transforming growth factor-beta immunostaining was lower in patients with idiopathic hypercalciuria than in control subjects and correlated directly with mineralization surface. Interleukin-1alpha and basic fibroblast growth factor staining did not differ between groups. Receptor activator of nuclear factor kappaB ligand bone expression was significantly higher in patients who had idiopathic hypercalciuria and exhibited higher versus normal bone resorption.

CONCLUSION

A higher expression of receptor activator of nuclear factor kappaB ligand in bone tissue suggests that increased bone resorption in patients with idiopathic hypercalciuria is mediated by receptor activator of nuclear factor kappaB ligand. Osteoprotegerin bone expression might have been secondarily increased in an attempt to counteract the actions of receptor activator of nuclear factor kappaB ligand. The low bone expression of transforming growth factor-beta could contribute to the delayed mineralization found in such patients.