Adynamic bone disease: clinical and therapeutic implications:

Predictors of functional impairment and mortality in patients on maintenance hemodialysis

INTRODUCTION

Numerous factors impact the mortality and functional abilities of patients with end-stage renal disease (ESRD) receiving maintenance hemodialysis (MHD). We aimed to determine the mortality rate at 1 year of MHD, identify predictors of mortality, and assess functional impairments concerning activities of daily living (ADLs) and instrumental ADL (IADL).

METHODS

Our study was prospective, observational cohort study that enrolled patients receiving MHD. We collected demographic, clinical, and laboratory data. We also assessed ADLs and IADLs for daily performance.

RESULTS

Our study included 167 patients with a mean age of 51.6 ± 13.1 years, and 56.9% were male. Of these, 80 (47.9%) were diabetic, and 145 (86.8%) were hypertensive. The mortality rate after 1 year of MHD was 10.8%, and cardiovascular causes accounted for over 70% of total deaths. Sudden cardiac death was the most frequent cause (38.9%), followed by cardiogenic shock (22.2%). Older age and low parathormone levels (<300 pg/mL) were significantly associated with higher mortality rates. Mean ADL and IADL scores were 4.5 ± 1.3 and 6.3 ± 2.7, respectively. Eighteen (10.8%) and 56 (33.5%) patients had low ADL and IADL scores, respectively. Although statistically insignificant, a higher proportion of non-survivors exhibited low IADL and ADL scores. Older age, longer diabetes duration, and higher BMI levels were significantly associated with lower IADL scores.

CONCLUSIONS

Older age and suppressed PTH levels are predictors of mortality in ESRD patients receiving MHD. These patients require regular follow-ups to rule out cardiovascular morbidity. Functional impairment is prevalent but remains underdiagnosed in MHD patients. It should be monitored regularly to improve quality of life in ESRD.

Pathophysiology of bone disease in chronic kidney disease: from basics to renal osteodystrophy and osteoporosis

Chronic kidney disease (CKD) is a highly prevalent disease that has become a public health problem. Progression of CKD is associated with serious complications, including the systemic CKD-mineral and bone disorder (CKD-MBD). Laboratory, bone and vascular abnormalities define this condition, and all have been independently related to cardiovascular disease and high mortality rates. The "old" cross-talk between kidney and bone (classically known as "renal osteodystrophies") has been recently expanded to the cardiovascular system, emphasizing the importance of the bone component of CKD-MBD. Moreover, a recently recognized higher susceptibility of patients with CKD to falls and bone fractures led to important paradigm changes in the new CKD-MBD guidelines. Evaluation of bone mineral density and the diagnosis of "osteoporosis" emerges in nephrology as a new possibility "if results will impact clinical decisions". Obviously, it is still reasonable to perform a bone biopsy if knowledge of the type of renal osteodystrophy will be clinically useful (low versus high turnover-bone disease). However, it is now considered that the inability to perform a bone biopsy may not justify withholding antiresorptive therapies to patients with high risk of fracture. This view adds to the effects of parathyroid hormone in CKD patients and the classical treatment of secondary hyperparathyroidism. The availability of new antiosteoporotic treatments bring the opportunity to come back to the basics, and the knowledge of new pathophysiological pathways [OPG/RANKL (LGR4); Wnt-ß-catenin pathway], also affected in CKD, offers great opportunities to further unravel the complex physiopathology of CKD-MBD and to improve outcomes.

A feasibility study of avoiding positive calcium balance and parathyroid hormone increase in patients on peritoneal dialysis

Background

The effect of the dialysate calcium concentration (D[Ca]) on mineral and bone metabolism in patients on peritoneal dialysis (PD) is overlooked. D[Ca] of 1.75 mmol/L is still prescribed to many patients on PD around the world. Previous studies on the effects of reducing D[Ca] have been carried out before the incorporation of calcimimetics in clinical practice. We hypothesized that a reduction in D[Ca] is safe and without the risk of a rise in serum parathyroid hormone (PTH).

Methods

In this non-randomized clinical trial, the D[Ca] was reduced from 1.75 mmol/L to 1.25 mmol/L for one year in prevalent patients on PD. Demographic, clinical, and CKD-MBD-related biomarkers were evaluated at baseline, 3, 6, and 12 months of follow-up.

Results

20 patients completed 1-year follow-up (56 ± 16 years, 50 % male, 25 % diabetic, 55 % with baseline parathyroid hormone – PTH >300 pg/mL). Over time, there was no significant change in calcium, phosphate, total alkaline phosphatase, 25(OH)-vitamin D or PTH, although adjustments in calcitriol and sevelamer prescription were required. After 1 year, absolute and percentual change in PTH levels were 36 (−58, 139) pg/mL, and 20 % (−28, 45) respectively. The proportion of patients with PTH > 300 pg/mL did not change during the follow-up (p = 0.173).

Conclusion

Knowing the risk of a positive calcium balance in patients on PD, reducing the D[Ca] concentration is a safe and valuable option, although medication adjustments are needed to detain PTH rising.

High calcium, phosphate and calcitriol supplementation leads to an osteocyte-like phenotype in calcified vessels and bone mineralisation defect in uremic rats

A link between vascular calcification and bone anomalies has been suggested in chronic kidney disease (CKD) patients with low bone turnover disease. We investigated the vascular expression of osteocyte markers in relation to bone microarchitecture and mineralization defects in a model of low bone turnover CKD rats with vascular calcification. CKD with vascular calcification was induced by 5/6 nephrectomy followed by high calcium and phosphate diet, and vitamin D supplementation (Ca/P/VitD). CKD + Ca/P/VitD group (n = 12) was compared to CKD + normal diet (n = 12), control + normal diet (n = 8) and control + Ca/P/VitD supplementation (n = 8). At week 6, tibia, femurs and the thoracic aorta were analysed by Micro-Ct, histomorphometry and for expression of osteocyte markers. High Ca/P/VitD treatment induced vascular calcification only in CKD rats, suppressed serum parathyroid hormone levels and led to higher sclerostin, DKK1 and FGF23 serum levels. Expression of sclerostin, DKK1 and DMP1 but not FGF23 were increased in calcified vessels from CKD + Ca/P/VitD rats. Despite low parathyroid hormone levels, tibia bone cortical thickness was significantly lower in CKD + Ca/P/VitD rats as compared to control rats fed a normal diet, which is likely the result of radial growth impairment. Finally, Ca/P/VitD treatment in CKD rats induced a bone mineralization defect, which is likely explained by the high calcitriol dose. In conclusion, Ca/P/VitD supplementation in CKD rats induces expression of osteocyte markers in vessels and bone mineralisation anomalies. Further studies should evaluate the mechanisms of high dose calcitriol-induced bone mineralisation defects in CKD.

Teriparatide Treatment for Hypercalcemia Associated With Adynamic Bone Disease

Hypercalcemia most often results from primary hyperparathyroidism and malignancy. Adynamic bone disease (ABD) is a form of renal osteodystrophy characterized by reduced bone turnover, which can limit the ability of bone to release or store calcium, potentially leading to low, normal, or high serum calcium levels. We describe a 51‐year‐old dialysis‐dependent female with hypercalcemia after parathyroidectomy. A demeclocycline‐labeled bone biopsy confirmed adynamic bone disease. Teriparatide, a recombinant form of parathyroid hormone (PTH) used to treat postmenopausal osteoporosis, was prescribed for 12 months and normalized serum calcium levels. Although previous case reports and series have described favorable changes in spine bone mineral density when teriparatide was prescribed for ABD, ours is the first documented case in which teriparatide resolved hypercalcemia due to ABD. © 2019 The Authors. JBMR Plus published by Wiley Periodicals, Inc. on behalf of American Society for Bone and Mineral Research.

Hypoalbuminemia differently affects the serum bone turnover markers in hemodialysis patients

Renal osteodystrophy (ROD) represents bone disorders related to chronic kidney disease (CKD) and several bone biomarkers are used clinically to predict ROD in CKD and hemodialysis (HD) patients. Serum albumin associates with inflammation other than nutritional status in these patients. Chronic inflammation is proved to relate with bone loss, however, the influence of hypoalbuminemia on bone biomarkers is still unclear. In this study, we evaluated the pattern of bone biomarker changes and further studied the influence of hypoalbuminemia on these biomarkers. A total of 300 maintenance HD patients were evaluated and 223 HD patients were included in the study. The patients were grouped according to serum parathyroid hormone (PTH) levels (PTH ≤150 pg/mL, PTH 150-300 pg/mL, PTH 300-600 pg/mL and PTH >600 pg/mL). Bone biomarkers and inflammatory markers were measured and their relation with PTH levels was determined. Significantly increased interleukin-6 (IL-6) and lower albumin levels were noted among PTH>600 pg/mL group. Bone turnover markers were significantly higher in PTH >600 pg/mL group (p< 0.05). Hypoalbuminemia significantly increased the fibroblast growth factor-23 (FGF-23) and procollagen type 1N-terminal propeptide (P1NP) in PTH ≤150 pg/mL, PTH 150-300 pg/mL, PTH 300-600 pg/mL groups, whereas no such relation was noted among PTH> 600 ng/dL group. In conclusion, hypoalbuminemia represents a chronic inflammation which differently relates to bone turnover markers according to serum PTH levels in SHPT patients. Thus, serum albumin measurement should be considered in determining bone disorders among these patients.

The Diet and Haemodialysis Dyad: Three Eras, Four Open Questions and Four Paradoxes. A Narrative Review, Towards a Personalized, Patient-Centered Approach

The history of dialysis and diet can be viewed as a series of battles waged against potential threats to patients' lives. In the early years of dialysis, potassium was identified as "the killer", and the lists patients were given of forbidden foods included most plant-derived nourishment. As soon as dialysis became more efficient and survival increased, hyperphosphatemia, was identified as the enemy, generating an even longer list of banned aliments. Conversely, the "third era" finds us combating protein-energy wasting. This review discusses four questions and four paradoxes, regarding the diet-dialysis dyad: are the "magic numbers" of nutritional requirements (calories: 30-35 kcal/kg; proteins > 1.2 g/kg) still valid? Are the guidelines based on the metabolic needs of patients on "conventional" thrice-weekly bicarbonate dialysis applicable to different dialysis schedules, including daily dialysis or haemodiafiltration? The quantity of phosphate and potassium contained in processed and preserved foods may be significantly different from those in untreated foods: what are we eating? Is malnutrition one condition or a combination of conditions? The paradoxes: obesity is associated with higher survival in dialysis, losing weight is associated with mortality, but high BMI is a contraindication for kidney transplantation; it is difficult to limit phosphate intake when a patient is on a high-protein diet, such as the ones usually prescribed on dialysis; low serum albumin is associated with low dialysis efficiency and reduced survival, but on haemodiafiltration, high efficiency is coupled with albumin losses; banning plant derived food may limit consumption of "vascular healthy" food in a vulnerable population. Tailored approaches and agreed practices are needed so that we can identify attainable goals and pursue them in our fragile haemodialysis populations.

Differentially expressed miR-3680-5p is associated with parathyroid hormone regulation in peritoneal dialysis patients

Mineral and bone disorder (MBD) is observed universally in patients with chronic kidney disease (CKD). Detrimental MBD-related skeletal changes include increased prevalence of fracture, cardiovascular disease, and mortality. MicroRNAs (miRNAs) have been identified as useful biomarkers in various diseases, and the aim of this study was to identify miRNAs associated with parathyroid hormone level in peritoneal dialysis (PD) patients. Fifty-two PD patients were enrolled and grouped by their intact parathyroid hormone (iPTH) level; 11 patients had low iPTH (<150 pg/mL) and 41 patients had high iPTH (≥150 pg/mL). Total RNA was extracted from whole blood samples. Total RNA from 15 patients (7 and 8 patients in the low and high iPTH groups, respectively) underwent miRNA microarray analysis, and three differentially upregulated (>2-fold change) miRNAs previously associated with human disease were selected for real-time quantitative PCR (qPCR) analysis. Interaction analyses between miRNAs and genes were performed by using TargetScan and the KEGG pathway database. Microarray results revealed 165 miRNAs were differentially expressed between patients with high iPTH levels and low iPTH levels. Of those miRNAs, 81 were upregulated and 84 were downregulated in patients with high iPTH levels. Expression levels of miR-1299, miR-3680-5p, and miR-548b-5p (previously associated with human disease) in 52 patients were analyzed by using qPCR. MiR-3680-5p was differentially expressed in low and high iPTH patients (P < 0.05). The predicted target genes of miR-3680-5p were USP6, USP32, USP46, and DLT, which are involved in the ubiquitin proteolysis pathway. This pathway has roles in PTH and parathyroid hormone related protein degradation and proteolysis. The mechanisms involved in the associations among low PTH, adynamic bone disease, miR-3680-5p, and the target genes should be explored further in order to elucidate their roles in CKD-MBD development.

Changing bone patterns with progression of chronic kidney disease

It is commonly held that osteitis fibrosa and mixed uremic osteodystrophy are the predominant forms of renal osteodystrophy in patients with chronic kidney disease. Osteitis fibrosa is a high-turnover bone disease resulting mainly from secondary hyperparathyroidism, and mixed uremic osteodystrophy is in addition characterized by a mineralization defect most often attributed to vitamin D deficiency. However, there is ancient and more recent evidence that in early chronic kidney disease stages adynamic bone disease characterized by low bone turnover occurs first, at least in a significant proportion of patients. This could be due to the initial predominance of bone turnover-inhibitory conditions such as resistance to the action of parathyroid hormone (PTH), reduced calcitriol levels, sex hormone deficiency, diabetes, and, last but not least, uremic toxins leading to repression of osteocyte Wnt/β-catenin signaling and increased expression of Wnt antagonists such as sclerostin, Dickkopf-1, and sFRP4. The development of high-turnover bone disease would occur only later on, when serum PTH levels are able to overcome peripheral PTH resistance and the other inhibitory factors of bone formation. Whether FGF23 and Klotho play a direct role in the transition from low- to high-turnover bone disease or participate only indirectly via regulating PTH secretion remains to be seen.

The Study of Low Calcium Dialysate on Elderly Hemodialysis Patients with Secondary Hypoparathyroidism

OBJECTIVE

The study aimed to study the safety and efficacy of 1.25 mmol/l calcium dialysate on maintenance hemodialysis (MHD) in elderly patients who suffered from secondary hypoparathyroidism.

METHODS

Eighty-two elderly patients (ages ≥65) who had been in MHD with dialysate calcium at 1.5 mmol/l over 6 months and had 2 consecutive serum intact parathyroid hormone (iPTH) measurements at level below 100 pg/ml were selected and randomized into 2 groups: treatment group (41 patients, with dialysate calcium at 1.25 mmol/l) and control group (41 patients, still with dialysate calcium at 1.5 mmol/l). Both groups were studied for the duration of 12 months. The changes of serum iPTH, calcium, phosphorus, calcium and phosphorus product and other indicators as well as related adverse reactions were recorded at the following time points: before the study and 1, 3, 6 and 12 months into the study. In addition, the intimal media thickness (IMT) of carotid artery and abdominal aorta calcification score (AACS) were measured in the 0, 6 and 12 months during the study.

RESULTS

(1) In the treatment group, the levels of serum corrected calcium, phosphorus and calcium-phosphate product began to decline after 1 month and exhibited further decrease 3 months later. Serum iPTH level increased significantly after 1 month into the study and the trend continued. The above markers stabilized after month 6. Compared with pre-study markers, the changes of the above markers were significant after study (p < 0.05). (2) The average IMT and AACS were evidently decreased during the 6 and 12 months of study in the treatment group. There was statistical significance (p < 0.05) when compared with the above indexes of the pre-study and the control group. (3) In the control group, there were no significant differences in above laboratory markers over the 12-month study period. (4) There was no significant difference in the adverse events observed between the 2 groups.

CONCLUSION

Safety of low calcium dialysate (dialysate calcium 1.25 mmol/l) in elderly MHD patients with iPTH <100 pg/ml is good, as well as improving carotid IMT, resistance index and AACS as indexes of vascular calcification in the small study group and warrants further investigation.

Adynamic bone disease: from bone to vessels in chronic kidney disease

Adynamic bone disease (ABD) is a well-recognized clinical entity in the complex chronic kidney disease (CKD)-mineral and bone disorder. Although the combination of low intact parathyroid hormone (PTH) and low bone alkaline phosphatase levels may be suggestive of ABD, the gold standard for precise diagnosis is histomorphometric analysis of tetracycline double-labeled bone biopsies. ABD essentially is characterized by low bone turnover, low bone volume, normal mineralization, and markedly decreased cellularity with minimal or no fibrosis. ABD is increasing in prevalence relative to other forms of renal osteodystrophy, and is becoming the most frequent type of bone lesion in some series. ABD develops in situations with reduced osteoanabolic stimulation caused by oversuppression of PTH, multifactorial skeletal resistance to PTH actions in uremia, and/or dysregulation of Wnt signaling. All may contribute not only to bone disease but also to the early vascular calcification processes observed in CKD. Various risk factors have been linked to ABD, including calcium loading, ageing, diabetes, hypogonadism, parathyroidectomy, peritoneal dialysis, and antiresorptive therapies, among others. The relationship between low PTH level, ABD, increased risk fracture, and vascular calcifications may at least partially explain the association of ABD with increased mortality rates. To achieve optimal bone and cardiovascular health, attention should be focused not only on classic control of secondary hyperparathyroidism but also on prevention of ABD, especially in the steadily growing proportions of diabetic, white, and elderly patients. Overcoming the insufficient osteoanabolic stimulation in ABD is the ultimate treatment goal.

Normocalcaemic hypoparathyroidism: prevalence and effect on bone status in older women. The OPUS study

OBJECTIVE

There are no consistent data on the prevalence and bone status of normocalcaemic hypoparathyroidism (NHYPO) as defined by normal adjusted calcium and low PTH level. Our aim was to determine the prevalence and the metabolic bone profile of NHYPO in older women, assessing its evolution over time. The second objective was to evaluate the prevalence of other calcium metabolic disorders.

DESIGN

The Osteoporosis and Ultrasound Study (OPUS) is a 6-yr prospective study of fracture-related factors.

PARTICIPANTS

A total of 2419 older women (age 55-79 yrs) and 258 younger women (age 30-40 yrs) participated. Complete follow-up data were available in 1416 subjects.

MEASUREMENTS

After calculating the adjusted calcium according to James' formula, we identified 'abnormal' calcium and PTH using Mahalanobis distances and allocated older women into different pathological categories using reference intervals from the healthy young women.

RESULTS

We identified 57 subjects with NHYPO (2·4%). These women had lower than expected bone turnover as assessed by bone alkaline phosphatase (-14·5%, 95% CI: -26·2 to -3·0, P = 0·007), CTX (-66·3%, 95% CI: -74·0 to -56·4, P < 0·001) and osteocalcin (-36·8%, 95% CI: -45·6 to -26·6, P < 0·001). After 6 years, of the 35 NHYPO subjects with follow-up data, none developed overt hypoparathyroidism and only 15 (0·6%) subjects had persistent evidence of NHYPO. We also identified 86 subjects (3·6%) affected by hyperparathyroid hypercalcaemia.

CONCLUSION

This is the first large population-based study to investigate NHYPO in older women. NHYPO is fairly common, not always persistent and is characterized by low bone turnover.

Chronic kidney disease and bone metabolism

Chronic kidney disease-related mineral and bone disease (CKD-MBD) is a syndrome defined as a systemic mineral metabolic disorder associated with CKD, and the term renal osteodystrophy indicates a pathomorphological concept of bone lesions associated with CKD-MBD. Cortical bone thinning, abnormalities in bone turnover and primary/secondary mineralization, elevated levels of circulating sclerostin, increased apoptosis in osteoblasts and osteocytes, disturbance of the coupling phenomenon, iatrogenic factors, accumulated micro-crackles, crystal/collagen disorientation, and chemical modification of collagen crosslinks are all possible candidates found in CKD that could promote osteopenia and/or bone fragility. Some of above factors are the consequences of abnormal systemic mineral metabolism but for others it seem unlikely. We have used the term uremic osteoporosis to describe the uremia-induced bone fragility which is not derived from abnormal systemic mineral metabolism. Interestingly, the disease aspect of uremic osteoporosis appears to be similar to that of senile osteoporosis.

Histomorphometric diagnostics of renal osteopathy in chronic dialysis patients at high risk of cardiovascular disease

Chronic kidney disease-mineral and bone disorder (CKD-MBD) ranks among clinically and pathogenetically significant complications in patients with CKD. Numerous factors are involved in its development, and histomorphometric analysis of the bone tissue is still necessary for accurate diagnosis.

METHODS

The open, pilot, prospective study aimed at performing a comprehensive histomorphometric bone analysis in 26 dialysis patients and assessing the relationships of different types of CKD-MBD to selected parameters of calcium and phosphate metabolism, densitometry, activity of parathyroid glands, presence of diabetes mellitus, and duration of dialysis treatment.

RESULTS

Comparison of the histomorphometric characteristics demonstrated statistically significant correlations between the volume of bone trabeculae and s-procollagen 1 (.754) as well as s-calcitonin (.856). Similarly, there was a positive correlation between the size of tetracycline lines and volume of bone trabeculae (.705) and a strong negative correlation with the thickness of trabeculae (-.442). When assessing the serum levels of s-osteoprotegerin and serum RANKL, there was a correlation with osteoid thickness and bone trabeculae thickness. In case of s-osteoprotegerin, a statistical power was demonstrated in relation to osteoid thickness (.880); in case of s-RANKL, a statistical power was demonstrated in relation to the thickness of trabeculae (.830). When assessing the influence of dialysis duration, relationships to the volume of trabecular bone (.665) and volume of bone trabeculae (.949) were demonstrated. Finally, a relationship between s-1,25-hydroxyvitamin D and s-osteoprotegerin was observed (.739); also the relationships demonstrated were significantly lower volume of bone trabeculae in men (p = 0.067) and lower values of s-osteocalcin and s-procollagen 1 in diabetic patients (p = 0.014).

CONCLUSION

The results provide new noninvasive possibilities of CKD-MBD detection that are based on selected serum parameters of bone metabolism. Presented are possibilities of noninvasive assessment of different types of CKD-MBD using serum osteomarkers in relation to comprehensive CKD-MBD histomorphometry.

Chronic kidney disease and the skeleton

Fractures across the stages of chronic kidney disease (CKD) could be due to osteoporosis, some form of renal osteodystrophy defined by specific quantitative histomorphometry or chronic kidney disease-mineral and bone disorder (CKD-MBD). CKD-MBD is a systemic disease that links disorders of mineral and bone metabolism due to CKD to either one or all of the following: abnormalities of calcium, phosphorus, parathyroid hormone or vitamin D metabolism; abnormalities in bone turnover, mineralization, volume, linear growth or strength; or vascular or other soft-tissue calcification. Osteoporosis, as defined by the National Institutes of Health, may coexist with renal osteodystrophy or CKD-MBD. Differentiation among these disorders is required to manage correctly the correct disorder to reduce the risk of fractures. While the World Health Organization (WHO) bone mineral density (BMD) criteria for osteoporosis can be used in patients with stages 1-3 CKD, the disorders of bone turnover become so aberrant by stages 4 and 5 CKD that neither the WHO criteria nor the occurrence of a fragility fracture can be used for the diagnosis of osteoporosis. The diagnosis of osteoporosis in stages 4 and 5 CKD is one of the exclusion-excluding either renal osteodystrophy or CKD-MBD as the cause of low BMD or fragility fractures. Differentiations among the disorders of renal osteodystrophy, CKD-MBD or osteoporosis are dependent on the measurement of specific biochemical markers, including serum parathyroid hormone (PTH) and/or quantitative bone histomorphometry. Management of fractures in stages 1-3 CKD does not differ in persons with or without CKD with osteoporosis assuming that there is no evidence for CKD-MBD, clinically suspected by elevated PTH, hyperphosphatemia or fibroblast growth factor 23 due to CKD. Treatment of fractures in persons with osteoporosis and stages 4 and 5 CKD is not evidence-based, with the exception of post-hoc analysis suggesting efficacy and safety of specific osteoporosis therapies (alendronate, risedronate and denosumab) in stage 4 CKD. This review also discusses how to diagnose and manage fragility fractures across the five stages of CKD.

Renal safety in patients treated with bisphosphonates for osteoporosis: a review

Bisphosphonates are widely used for the treatment of osteoporosis and are generally well tolerated. However, the United States Food and Drug Administration safety reports have highlighted the issue of renal safety in bisphosphonate-treated patients. All bisphosphonates carry labeled "warnings" or a contraindication for use in patients with severe renal impairment (creatinine clearance <30 or <35 mL/min). Data from pivotal trials and their extension studies of bisphosphonates approved for the management of osteoporosis were obtained via PubMed, and were reviewed with support from published articles available on PubMed. Renal safety analyses of pivotal trials of oral alendronate, risedronate, and ibandronate for postmenopausal osteoporosis showed no short-term or long-term effects on renal function. Transient postinfusion increases in serum creatinine have been reported in patients receiving intravenous ibandronate and zoledronic acid; however, studies showed that treatment with these agents did not result in long-term renal function deterioration in clinical trial patients with osteoporosis. All bisphosphonate therapies have "warnings" for use in patients with severe renal impairment. Clinical trial results have shown that even in elderly, frail, osteoporotic patients with renal impairment, intravenous bisphosphonate therapy administration in accordance with the prescribing information did not result in long-term renal function decline. Physicians should follow guidelines for bisphosphonate therapies administration at all times.

Effects of pamidronate and calcitriol on the set point of the parathyroid gland in postmenopausal hemodialysis patients with secondary hyperparathyroidism

BACKGROUND/AIMS

Secondary hyperparathyroidism may worsen after the administration of pamidronate in postmenopausal hemodialysis (HD) patients. The aim of this study was to evaluate the short-term effect of coadministration of calcitriol and pamidronate on dynamic parathyroid hormone (PTH) secretion.

METHODS

Fifteen postmenopausal women undergoing regular HD with serum intact PTH levels of >200 pg/ml were enrolled. The PTH-ionized calcium (iCa) curve was evaluated by the response to hypo- and hypercalcemia induced with 1 and 4 mEq/l of dialysate calcium, respectively. Parameters were compared after pamidronate was administered and after coadministration of pamidronate and calcitriol. Changes in serum levels of maximal serum PTH (PTHmax), basal PTH (PTHbase) and minimal PTH (PTHmin) were evaluated.

RESULTS

Pamidronate therapy resulted in a decrease in predialysis basal plasma iCa (p < 0.05) and an increase in PTHmax (p < 0.01), PTHbase (p < 0.01) and PTHmin (p < 0.01). The change in serum iCa and PTH was reversed after the coadministration of calcitriol and pamidronate.

CONCLUSION

Our study demonstrated that pamidronate therapy is associated with a reduced plasma iCa and increased PTH secretion. These adverse effects may be reversed by calcitriol. These findings suggest that in considering pamidronate treatment in postmenopausal patients with osteoporosis receiving HD, it might be safer to add calcitriol to prevent the increased PTH secretion.

Bone turnover markers predict changes in bone mineral density after parathyroidectomy in patients with renal hyperparathyroidism

OBJECTIVE

Patients on long-term dialysis may develop secondary hyperparathyroidism (SHPT), which causes varying degrees of bone mass loss. This condition is treated with parathyroidectomy (PTX). We investigated whether serial serum bone turnover markers could predict changes in bone mineral density (BMD) after PTX.

DESIGN AND PATIENTS

Renal patients on maintenance haemodialysis who received PTX for refractory SHPT (n = 26, male/female: 13/13; mean age: 48·6 ± 10·7 year) and control subjects without SHPT (n = 25) were prospectively followed for 1 year at two tertiary hospitals in Taiwan.

MEASUREMENTS

Serum intact parathyroid hormone (iPTH), bone-specific alkaline phosphatase (BAP) and type 5b tartrate-resistant acid phosphatase (TRAP) were measured serially. Additionally, femoral neck (FN) and lumbar spine (LS) BMD were measured before and 1 year after PTX.

RESULTS

After PTX, iPTH levels decreased markedly and persistently. BMDs increased in both the FN and LS, but particularly in the LS. Serum BAP progressively increased to a peak at 2 weeks after PTX. Serum TRAP levels progressively decreased over 6 months after PTX. In univariate correlation analyses, baseline iPTH correlated positively with T-score changes in FN (r = 0·45, P = 0·021) and LS (r = 0·48, P = 0·013). In multivariate regression models, changes in FN T-scores were negatively predicted by baseline BAP levels (r = -0·615, P = 0·005) and baseline FN T-scores (r = -0·563, P = 0·012), and they were positively predicted by baseline TRAP(r = 0·6, P =  0·007). Changes in LS T-scores were positively predicted by baseline TRAP values (r = 0·528, P = 0·01) and negatively predicted by the percentage change in BAP after 2 weeks (r = -0·501, P = 0·015).

CONCLUSIONS

Parathyroidectomy provided marked, sustained improvements in BMD for up to 1 year. Furthermore, markers of bone turnover predicted 1-year changes in FN and LS BMDs after PTX.

Bone-specific alkaline phosphatase concentrations are less variable than those of parathyroid hormone in stable hemodialysis patients

Abnormalities of bone mineral metabolism and vascular calcification are prevalent in patients with kidney failure. Clinical management is based on biochemical targets, in particular parathyroid hormone (PTH) concentrations, but this has many limitations including high biological variation. A possible alternative is bone-specific alkaline phosphatase (ALP); therefore, we evaluated the biological variation of this marker in patients undergoing hemodialysis. Bone ALP was measured in non-fasting serum samples taken twice a week over a 6-week period in 22 stable hemodialysis patients and 12 healthy volunteers. The within-individual coefficients of variance were calculated and used to derive the critical difference required to be certain that an observed change was significant. The coefficient of variance for bone ALP was significantly higher in hemodialysis patients compared to healthy individuals. Seven samples were required to estimate the homeostatic set point of bone ALP, within 10%, in a hemodialysis patient. The concentration of serial bone ALP measurements would need to change by 36% between any two measurements before it can be considered a significant change. Since the biological variation of bone ALP is less than half that reported for PTH, our study provides further support for the use of bone ALP as an alternative marker of bone mineral metabolism in the setting of chronic kidney disease–mineral and bone disorder.

Association between increased serum osteoprotegerin levels and improvement in bone mineral density after parathyroidectomy in hemodialysis patients

Secondary hyperparathyroidism (SHPT) is a common complication in chronic renal disease. Osteoprotegerin (OPG), an extracellular cytokine receptor secreted by osteoblasts, can promote bone formation by inhibiting the function of osteoclasts. Hemodialysis (HD) patients have elevated serum OPG levels. OPG secretion can be suppressed with high parathyroid hormone (PTH) levels. HD patients with refractory SHPT can benefit from parathyroidectomy (PTX) treatment, but the changes of serum OPG, bone turnover markers and bone mineral density (BMD) following PTX in HD patients remain unclear. In this study, patients on maintenance HD who received PTX for refractory SHPT (n = 28) were prospectively followed for 1 year. Serum intact PTH (iPTH), alkaline phosphatase (Alk-P), and OPG were measured serially; BMD was measured pre-PTX and at 1 year after PTX. After PTX, serum iPTH levels reduced profoundly. Serum Alk-P levels increased rapidly, peaking at 2 weeks post-PTX, while serum OPG levels gradually increased at 2 weeks after PTX and peaked at 2 months. BMD improved in both femoral neck (FN; cancellous and cortical bone) and lumbar spine (LS; cancellous bone). Higher baseline iPTH levels were associated with greater FN and LS BMD improvements at one year after PTX. The increment of serum OPG was correlated with the increase in LS BMD, implying that inhibition of osteoclastic bone resorption may improve BMD within the first year after PTX. These findings suggest that PTX removes the suppressive effects of high PTH on OPG secretion, resulting in the increased serum OPG levels that may contribute to BMD improvement.

PTH--a particularly tricky hormone: why measure it at all in kidney patients?

Plasma parathyroid hormone (PTH) concentrations are commonly measured in the context of CKD, as PTH concentration elevation is typical in this clinical context. Much has been inferred from this raised PTH concentration tendency, both about the state of skeletal integrity and health and also about the potential clinical outcomes for patients. However, we feel that reliance on PTH concentrations alone is a dangerous substitute for the search for, and use of, more precise and reliable biomarkers. In this article, we rehearse these arguments, bringing together patient-level and analytical considerations for the first time.

Efficacy and safety of a short course of very-high-dose cholecalciferol in hemodialysis

BACKGROUND

Vitamin D deficiency is highly prevalent among hemodialysis patients, but little data exist in support of an optimal repletion regimen.

OBJECTIVE

The objective was to ascertain the efficacy of weekly very-high-dose cholecalciferol (vitamin D(3)) in correcting vitamin D insufficiency and deficiency in patients with stage 5D chronic kidney disease.

DESIGN

We conducted a prospective, double-blind, randomized controlled pilot study that compared placebo with very high doses of oral cholecalciferol for 3 wk (200,000 IU/wk) in hemodialysis patients. We examined the rate of correction of vitamin D insufficiency or deficiency and the effect of treatment on markers of mineral metabolism and routine laboratory variables.

RESULTS

Twenty-seven subjects received placebo, and 25 received cholecalciferol. The majority (94%) of subjects had serum 25-hydroxyvitamin D [25(OH)D] concentrations <30 ng/mL. Study groups were similar with respect to baseline clinical characteristics, with the exception of hemoglobin concentrations, which were lower in the cholecalciferol-treated group (P < 0.04). At follow-up, 90.5% of subjects treated with cholecalciferol achieved serum 25(OH)D concentrations ≥30 ng/mL in contrast to 13.6% of the placebo group. There were no significant changes in serum calcium, phosphate, or intact parathyroid hormone during the study.

CONCLUSION

Short-term, high-dose oral cholecalciferol treatment of vitamin D deficiency in hemodialysis patients appears to be effective and with no evidence of toxic effects. This trial was registered at clinicaltrials.gov as NCT00912782.

Mineral and bone disorders in chronic kidney disease and end-stage renal disease patients: new insights into vitamin D receptor activation

Progressive loss of kidney function leads to reduced production of calcitriol (1,25-dihydroxyvitamin D; active vitamin D) and an imbalance in serum calcium (Ca) and phosphorus (P) levels, which are associated with progression of renal failure as well as increased rates of cardiovascular (CV) events and mortality. In addition, multifactorial hypocalcemia and resistance to parathyroid hormone (PTH) can lead to prolonged and excessive synthesis and secretion of PTH, eventually leading to development of secondary hyperparathyroidism and renal osteodystrophy. These changes associated with chronic kidney disease (CKD), extending beyond bone and related biochemical abnormalities, have prompted the development of the term CKD–mineral and bone disorder to describe its systemic nature. Excessive P loading, among other factors, will promote vascular calcification (VC), and PTH production will affect bone remodeling. Although administration of calcitriol increases serum Ca levels and decreases PTH, it is also associated with elevated Ca × P product. Therefore, compounds that selectively activate vitamin D receptors (VDR activators), potentially reducing Ca–P toxicity and distinctly affecting pathogenic mechanisms of VC, might enhance CV and renal protection, increase the vitamin D therapeutic window, and thus provide a significant clinical benefit. Moreover, selective VDR activators have been associated with improvement in survival, at least among dialysis patients. Thus, selective VDR activators should be considered a novel and interesting approach to enhance the standard of care in CKD patients.

Vitamin D deficiency and toxicity in chronic kidney disease: in search of the therapeutic window

Both vitamin D deficiency and vitamin D toxicity are associated with cardiovascular complications in chronic kidney disease (CKD). Clinical and experiment data indicate that the association of vitamin D levels with cardiovascular disease is best illustrated as a biphasic, or U-shaped, curve. Children and adolescents with CKD need vitamin D due to the demands of a growing skeleton, to prevent renal rickets. However, this therapy carries the risk of severe side effects and chronic toxicity. Observational studies show that vitamin D deficiency and toxicity are frequently present in patients with CKD. In view of the importance of cardiovascular complications for the long-term survival of young patients, these findings demand a judicious use of vitamin D preparations. In clinical practice, the therapeutic window is rather small, presenting a therapeutic challenge to avoid both vitamin D deficiency and toxicity.