The receptor activator of nuclear factor-kappaB ligand inhibitor osteoprotegerin is a bone-protective agent in a rat model of chronic renal insufficiency and hyperparathyroidism

Control of phosphorus and prevention of fractures in the kidney patient

Patients with chronic kidney disease have a higher risk of fractures than the general population due to the added factor of uraemia. Although the mechanisms behind uraemia-associated fractures are not fully understood, it is widely accepted that the decrease in bone mineral content and alteration in bone architecture both increase bone fragility. As chronic kidney disease progresses, the risk of fracture increases, especially once the patient requires dialysis. Among the many causes of the increased risk are advanced age, amenorrhoea, steroid exposure, decreased vitamin D, increased PTH, malnutrition and chronic inflammation. Serum phosphorus, whether high or very low, seems to correlate with the risk of fracture. Moreover, increased serum phosphate is known to directly and indirectly affect bone metabolism through the development of adaptive hormonal mechanisms aimed at preventing hyperphosphataemia, such as the increase in PTH and FGF23 and the reduction in calcitriol. These adaptive mechanisms are less intense if the intestinal absorption of phosphorus is reduced with the use of phosphorus captors, which seem to have a positive impact in reducing the risk of fractures. We describe here the possible mechanisms associating serum phosphorus levels, the adaptive mechanisms typical in kidney disease and the use of drugs to control hyperphosphataemia with the risk of fractures. We found no studies in the literature providing evidence on the influence of different treatments on the risk of fractures in patients with chronic kidney disease. We suggest that control of phosphorus should be an objective to consider.

Control of phosphorus and prevention of fractures in the kidney patient

Patients with chronic kidney disease have a higher risk of fractures than the general population due to the added factor of uraemia. Although the mechanisms behind uraemia-associated fractures are not fully understood, it is widely accepted that the decrease in bone mineral content and alteration in bone architecture both increase bone fragility. As chronic kidney disease progresses, the risk of fracture increases, especially once the patient requires dialysis. Among the many causes of the increased risk are advanced age, amenorrhoea, steroid exposure, decreased vitamin D, increased parathyroid hormone (PTH), malnutrition and chronic inflammation. Serum phosphorus, whether high or very low, seems to correlate with the risk of fracture. Moreover, increased serum phosphate is known to directly and indirectly affect bone metabolism through the development of adaptive hormonal mechanisms aimed at preventing hyperphosphataemia, such as the increase in PTH and fibroblast growth factor 23 (FGF23) and the reduction in calcitriol. These adaptive mechanisms are less intense if the intestinal absorption of phosphorus is reduced with the use of phosphorus captors, which seem to have a positive impact in reducing the risk of fractures. We describe here the possible mechanisms associating serum phosphorus levels, the adaptive mechanisms typical in kidney disease and the use of drugs to control hyperphosphataemia with the risk of fractures. We found no studies in the literature providing evidence on the influence of different treatments on the risk of fractures in patients with chronic kidney disease. We suggest that control of phosphorus should be an objective to consider.

OPG-Fc treatment partially rescues low bone mass phenotype in mature Bgn/Fmod deficient mice but is deleterious to the young mouse skeleton

Biglycan (Bgn) and Fibromodulin (Fmod) are small leucine rich proteoglycans (SLRPs) which are abundant in the extra-cellular matrix (ECM) of mineralized tissues. We have previously generated a Bgn/Fmod double knock-out (DKO) mouse model and found it has a 3-fold increase in osteoclastogenesis compared with Wild type (WT) controls, resulting in a markedly low bone mass (LBM) phenotype. To try and rescue/repair the LBM phenotype of Bgn/Fmod DKO mice by suppressing osteoclast formation and activity, 3- and 26-week-old Bgn/Fmod DKO mice and age/gender matched WT controls were treated with OPG-Fc for 6 weeks after which bone parameters were evaluated using DEXA, micro-computed tomography (μCT) and serum biomarkers analyses. In the appendicular skeleton, OPG-Fc treatment improved some morphometric and geometric parameters in both the trabecular and cortical compartments in Bgn/Fmod DKO female and male mice, especially in the repair module. For many of the skeletal parameters analyzed, the Bgn/Fmod DKO mice were more responsive to the treatment than their WT controls. In addition, we found that OPG-Fc treatment was not able to prevent or ameliorate the formation of ectopic ossification, which are common lesions seen in aged joints and are one of the phenotypical hallmarks of our Bgn/Fmod DKO model. Analysis of skull bones, specifically the occipital bone, showed the treatment recovered some parameters of LBM phenotype in the craniofacial skeleton, more so in the younger rescue module. Using OPG-Fc as treatment alleviated, yet did not completely restore, the severe osteopenia and mineralized tissue structural abnormalities that Bgn/Fmod DKO mice suffer from.

Impact of denosumab on cardiovascular calcification in patients with secondary hyperparathyroidism undergoing dialysis: a pilot study

The receptor activator of nuclear factor-kappa B ligand (RANKL)/RANK/osteoprotegerin system is dysregulated in hyperparathyroid bone diseases. The introduction of denosumab preceding elective surgery as an alternative option when surgery is not possible immediately.

INTRODUCTION

The effects of denosumab on vascular calcification in patients with chronic renal failure and low bone mass have been a subject of interest. Therefore, this investigation aimed to determine the short-term changes in vascular calcification after denosumab treatment using a serial electrocardiography-gated computed tomography (CT) to measure coronary artery calcification (CAC) in patients with secondary hyperparathyroidism (SHPT) and low bone mass.

METHODS

This 6-month study enrolled patients with SHPT and low bone mass (T-score < - 2.5) owing to dialysis. The 2 groups administered denosumab at a dose of 60 mg (denosumab group), and conventional treatment (control group) had 21 patients each. All patients underwent CT scans at baseline and at the follow-up examination at 6 months to determine the bone mineral density and CAC.

RESULTS

The control group demonstrated a significant increase in Agatston scores (187.79 ± 72.27) (P = 0.004). However, no significant change was noted in the denosumab group (P = 0.41). In the denosumab group, only the baseline serum alkaline phosphatase levels correlated negatively with changes in the CAC score (P = 0.01); the baseline alkaline phosphatase levels were the deciding biomarkers for non-responsive CAC scores by Berry Criteria after denosumab treatment (P = 0.02). The denosumab group demonstrated significantly increased bone mineral density in the femoral neck and lumbar spine (P < 0.01).

CONCLUSION

The findings provide evidence that denosumab may suppress the progression of CAC and also regress osseous calcification in severe cases of high bone turnover.

Severe, Symptomatic Hypocalcemia due to Denosumab Administration: Treatment and Clinical Course

Denosumab is a receptor activator of nuclear factor kappa-B (RANK) ligand inhibitor used in the treatment of osteoporosis. Blockade of RANK ligand prevents osteoclastic resorption of bone, but in doing so impairs the parathyroid hormone (PTH)-driven maintenance of serum calcium. A subsequent elevation of PTH remains active at sites other than bone, potentially lowering serum phosphate by inhibiting proximal tubular reabsorption. We present 2 patients who developed severe, symptomatic hypocalcemia after administration of denosumab. These patients provide an opportunity to describe the clinical course and treatment, including the need to consider a continuous calcium infusion, of severe, symptomatic hypocalcemia caused by denosumab.

Management of Osteoporosis in CKD

CKD mineral and bone disease is a common complication of kidney disease, and it affects the majority of patients with moderate to severe CKD. Recently, prospective studies have shown that measurement of bone mineral density by dual energy x-ray absorptiometry predicts incident fracture, providing nephrologists the ability to risk classify patients for skeletal fragility and targeted antifracture strategies for the first time. Furthermore, an expanding body of literature and anecdotal evidence suggest that pharmacologic agents used to treat osteoporosis in the general population can be safely used in patients with CKD. This review highlights the effects of the Kidney Disease Improving Global Outcomes updates on the management of CKD-associated osteoporosis, discusses recent investigations on the effects of antiosteoporotic agents in patients with CKD, and provides an overview of novel antiosteoporosis agents and the potential challenges related to their use in CKD.

An open-label, prospective pilot clinical study of denosumab for severe hyperparathyroidism in patients with low bone mass undergoing dialysis

CONTEXT

Denosumab is widely used for bone diseases with increased bone resorption. Its effectiveness in patients with severe secondary hyperparathyroidism on dialysis is unclear.

OBJECTIVE

This study aimed to evaluate the efficacy and safety of denosumab in patients with severe secondary hyperparathyroidism who are on dialysis.

DESIGN

This 6-month prospective, open-labeled study evaluated 12 patients (five women, seven men; mean age 53.5 ± 3.8 y). All had intact PTH (iPTH; > 1000 pg/mL), low bone mass (T-score < -1.0 SD), and bone pain and were poor surgical candidates. Serum calcium, phosphorus, alkaline phosphatase (AP), and iPTH levels were assessed at baseline and every month thereafter. Vertebral spine x-rays and bone mineral densities (BMDs) (lumbar spine and femoral neck) were assessed at the start and end of the study. All patients received denosumab (60 mg), calcitriol, phosphate binders, and dialysate calcium that were adjusted according to the biochemistry data.

RESULTS

The BMD increased in both the femoral neck (mean increase 23.7% ± 4.0%) and lumbar spine (17.1% ± 2.6%) after 6 months. In the first month, most patients had increased iPTH levels, which dramatically decreased from 1702.1 ± 181.9 to 518.8 ± 126.8 pg/mL by the end of the study after increasing the calcitriol dose. All patients had significant decreases in AP, calcium × phosphorus, and bone pain. Changes in femoral neck BMD correlated only with AP and iPTH levels.

CONCLUSIONS

Denosumab is effective in restoring bone mass and reducing bone pain in patients on dialysis with secondary hyperparathyroidism. It also allows for a more aggressive use of calcitriol to control hyperparathyroidism.

Time Course of Calcium Concentrations and Risk Factors for Hypocalcemia in Patients Receiving Denosumab for the Treatment of Bone Metastases From Cancer

BACKGROUND

Severe hypocalcemia sometimes develops during denosumab treatment for bone metastases from cancer and is, therefore, an important issue. However, limited information is available on the risk factors for hypocalcemia and the appropriate interval for monitoring serum calcium concentration.

OBJECTIVE

The present study aimed to identify the risk factors for grade ≥2 hypocalcemia and to investigate the time course of serum calcium concentrations in patients receiving denosumab for bone metastases from cancer.

METHOD

The medical records of 66 cancer patients treated with denosumab between April 2012 and August 2013 were retrospectively reviewed.

RESULT

Of the 66 enrolled patients, 11, 5, and 1 developed grade 1, 2, and 3 hypocalcemia, respectively. All 4 patients with a baseline estimated glomerular filtration rate (eGFR) of <30 mL/min developed hypocalcemia. Hypocalcemia occurred in only 20%, 24%, and 15% of patients with an eGFR of 30 to 59, 60 to 89, and ≥90 mL/min, respectively. Multivariate logistic regression analysis revealed that lower eGFR values (odds ratio, 1.72 per 10 mL/min decrease, P = 0.02) were significantly associated with grade ≥2 hypocalcemia. In 11 patients who developed hypocalcemia during the first treatment course, the mean calcium concentrations decreased from 9.8 mg/dL at baseline to 8.4 mg/dL during the first week and reached a nadir of 8.1 mg/dL during the second week.

CONCLUSION

Our results support more frequent monitoring of serum calcium concentrations at baseline and during the first 2 weeks of treatment in patients receiving denosumab, especially those with an eGFR <30 mL/min.

Pharmacological management of osteogenesis

Osteogenesis and bone remodeling are complex biological processes that are essential for the formation of new bone tissue and its correct functioning. When the balance between bone resorption and formation is disrupted, bone diseases and disorders such as Paget's disease, fibrous dysplasia, osteoporosis and fragility fractures may result. Recent advances in bone cell biology have revealed new specific targets for the treatment of bone loss that are based on the inhibition of bone resorption by osteoclasts or the stimulation of bone formation by osteoblasts. Bisphosphonates, antiresorptive agents that reduce bone resorption, are usually recommended as first-line therapy in women with postmenopausal osteoporosis. Numerous studies have shown that bisphosphonates are able to significantly reduce the risk of femoral and vertebral fractures. Other antiresorptive agents indicated for the treatment of osteoporosis include selective estrogen receptor modulators, such as raloxifene. Denosumab, a human monoclonal antibody, is another antiresorptive agent that has been approved in Europe and the USA. This agent blocks the RANK/RANKL/OPG system, which is responsible for osteoclastic activation, thus reducing bone resorption. Other approved agents include bone anabolic agents, such as teriparatide, a recombinant parathyroid hormone that improves bone microarchitecture and strength, and strontium ranelate, considered to be a dual-action drug that acts by both osteoclastic inhibition and osteoblastic stimulation. Currently, anti-catabolic drugs that act through the Wnt-β catenin signaling pathway, serving as Dickkopf-related protein 1 inhibitors and sclerostin antagonists, are also in development. This concise review provides an overview of the drugs most commonly used for the control of osteogenesis in bone diseases.

Release of bone markers in immediately loaded and nonloaded dental implants: a randomized clinical trial

The aim of this study was to compare the release of bone markers during osseointegration of immediately loaded and nonloaded implants. Forty patients who were indicated for rehabilitation with dental implants randomly received either implant and prosthesis placement within 72 hours (group IM) or implant insertion and no prosthesis placement (group NL). Peri-implant crevicular fluid was collected immediately after implant insertion and 7, 15, 30, 60, 90, and 120 days after surgery and levels of osteoprotegerin, transforming growth factors, osteocalcin, osteopontin, and parathyroid hormone were evaluated using Luminex assay. Bleeding index and peri-implantar sulcus depth were also evaluated. The data were compared using statistical tests (α = 5%). No statistical difference was found regarding demographic and clinical parameters (p > .05). Transforming growth factors, osteoprotegerin, osteopontin, and parathyroid hormone presented an earlier release peak in group IM than in NL group (p < .05). Osteocalcin achieved higher levels in group IM versus group NL between 7 and 30 days of evaluation (p < .05). It may be concluded that earlier loading positively modulates bone mediators release around immediately loaded implants when compared with nonloaded dental implants.

The osteocyte: an endocrine cell ... and more

Few investigators think of bone as an endocrine gland, even after the discovery that osteocytes produce circulating fibroblast growth factor 23 that targets the kidney and potentially other organs. In fact, until the last few years, osteocytes were perceived by many as passive, metabolically inactive cells. However, exciting recent discoveries have shown that osteocytes encased within mineralized bone matrix are actually multifunctional cells with many key regulatory roles in bone and mineral homeostasis. In addition to serving as endocrine cells and regulators of phosphate homeostasis, these cells control bone remodeling through regulation of both osteoclasts and osteoblasts, are mechanosensory cells that coordinate adaptive responses of the skeleton to mechanical loading, and also serve as a manager of the bone's reservoir of calcium. Osteocytes must survive for decades within the bone matrix, making them one of the longest lived cells in the body. Viability and survival are therefore extremely important to ensure optimal function of the osteocyte network. As we continue to search for new therapeutics, in addition to the osteoclast and the osteoblast, the osteocyte should be considered in new strategies to prevent and treat bone disease.

High- and low-dose OPG-Fc cause osteopetrosis-like changes in infant mice

BACKGROUND

Receptor activator of nuclear factor-κB ligand (RANKL) inhibitors are being considered for use in children with osteogenesis imperfecta (OI). We sought to assess efficacy of two doses of a RANKL inhibitor, osteoprotegerin-immunoglobulin Fc segment complex (OPG-Fc), in a growing animal model of OI, the col1α2-deficient mouse (oim/oim) and its wild-type controls (+/+).

METHODS

Treated mice showed runting and radiographic evidence of osteopetrosis with either high- (20 mg/kg twice weekly) or low-dose (1 mg/kg/week) OPG-Fc. Because of this adverse event, OPG-Fc treatment was halted, and the mice were killed or monitored for recovery with monthly radiographs and assessment of serum osteoclast activity (tartrate-resistant acid phosphatase 5b, TRACP-5b) until 25 wk of age.

RESULTS

Twelve weeks of OPG-Fc treatment resulted in radiographic and histologic osteopetrosis with no evidence of bone modeling and negative tartrate-resistant acid phosphatase staining, root dentin abnormalities, and TRACP-5b activity suppression. Signs of recovery appeared 4-8 wk post-treatment.

CONCLUSION

Both high- and low-dose OPG-Fc treatment resulted in osteopetrotic changes in infant mice, an outcome that was not seen in studies with the RANKL inhibitor RANK-immunoglobulin Fc segment complex (RANK-Fc) or in studies with older animals. Further investigations of RANKL inhibitors are necessary before their consideration for use in children.

A single-dose study of denosumab in patients with various degrees of renal impairment

This 16-week study evaluated pharmacokinetics and pharmacodynamics of denosumab in 55 subjects with renal function ranging from normal to dialysis-dependent kidney failure. Participants received a single 60-mg subcutaneous dose of denosumab. Kidney function groups were based on calculations using the Cockcroft-Gault equation and U.S. Food and Drug Administration (FDA) guidance in place when the study was designed. Renal function did not have a significant effect on denosumab pharmacokinetics or pharmacodynamics. These findings suggest denosumab dose adjustment based on glomerular filtration rate is not required. Rapid decreases in serum C-telopeptide in all groups were sustained throughout the study. The most common adverse events were hypocalcemia (15%), pain in extremity (15%), and nausea (11%). Most adverse events were mild to moderate in severity. Calcium and vitamin D supplementation was not initially required by the study protocol, but was added during the trial. No subject who received adequate calcium and vitamin D supplementation became hypocalcemic. Seven subjects had nadir serum calcium concentrations between 7.5 and <8.0 mg/dL (1.9 and <2.0 mmol/L), and 5 subjects (4 with advanced renal disease) had nadir serum calcium <7.5 mg/dL (<1.9 mmol/L). Two subjects (1 symptomatic, 1 asymptomatic) were hospitalized for intravenous calcium gluconate treatment. At the recommended dose, denosumab is a useful therapeutic option for patients with impaired renal function. Supplementation of calcium and vitamin D is strongly recommended when patients initiate denosumab therapy, particularly in patients with reduced renal function.

Comparable outcomes in fracture reduction and bone properties with RANKL inhibition and alendronate treatment in a mouse model of osteogenesis imperfecta

We report a direct comparison of receptor activator of nuclear factor kappa B ligand (RANKL) inhibition (RANK-Fc) with bisphosphonate treatment (alendronate, ALN) from infancy through early adulthood in a mouse model of osteogenesis imperfecta. Both ALN and RANK-Fc decreased fracture incidence to the same degree with increases in metaphyseal bone volume via increased number of thinner trabeculae.

INTRODUCTION

The potential therapeutic benefit of RANKL inhibitors in osteogenesis imperfecta (OI) is under investigation. We report a direct comparison of RANKL inhibition (RANK-Fc) with bisphosphonate treatment (ALN) from infancy through early adulthood in a model of OI, the oim/oim mouse.

METHODS

Two-week-old oim/oim, oim/+, and wildtype (+/+) mice were treated with RANK-Fc 1.5 mg/kg twice per week, ALN 0.21 mg/kg/week or saline (n = 12-20 per group) for 12 weeks.

RESULTS

ALN and RANK-Fc both decreased fracture incidence (9.0 ± 3.0 saline 4.4 ± 2.7 ALN, 4.3 ± 3.0 RANK-Fc fractures per mouse). Serum TRACP-5b activity decreased to 65% after 1 month in all treated mice, but increased sacrifice with RANK-Fc to 130-200% at sacrifice. Metaphyseal density was significantly increased with ALN in +/+ and oim/oim mice (p < 0.05) and tended to increase with RANK-Fc in +/+ mice. No changes in oim/oim femur biomechanical parameters occurred with treatment. Both ALN and RANK-Fc significantly increased trabecular number (3.73 ± 0.77 1/mm for oim/oim saline vs 7.93 ± 0.67 ALN and 7.34 ± 1.38 RANK-Fc) and decreased trabecular thickness (0.045 mm ± 0.003 for oim/oim saline vs 0.034 ± 0.003 ALN and 0.032 ± 0.002 RANK-Fc) and separation in all genotypes (0.28 ± 0.08 mm for oim/oim saline vs 0.12 ± 0.010 ALN and 13 ± 0.03 RANK-Fc)., with significant increase in bone volume fraction (BVF) with ALN, and a trend towards increased BVF in RANK-Fc.

CONCLUSION

Treatment of oim/oim mice with either a bisphosphonate or a RANK-Fc causes similar decreases in fracture incidence with increases in metaphyseal bone volume via increased number of thinner trabeculae.

Rabbit model of primary hyperparathyroidism induced by high-phosphate diet

The objective of this study is to establish a new rabbit model of primary hyperparathyroidism (PHPT) induced by high-phosphate diet. One hundred twenty rabbits were divided into two groups of 60 each. The treatment group was fed a high-phosphate diet (Ca:P = 1:7) and the control group was given a normal animal diet (Ca:P = 1:0.7) for 1 to 6 mo. Serologic examinations, including parathyroid hormone (PTH), calcium and phosphorus levels, blood urea nitrogen, creatinine, and uric acid, and the histologic examination, including parathyroid, kidney, and bones, were performed at the end of each month for 6 mo. Compared with the control, serum PTH levels in the treatment groups were elevated at all six time points, whereas serum calcium levels were reduced, and serum phosphorus levels remain unchanged over the course of the first 3 mo. Serum calcium levels were increased, whereas serum phosphorus levels were reduced at 4, 5, and 6 mo. Parathyroid histopathological examination showed no change during the first month, whereas 60% of the animals exhibited mild hyperplasia starting at 2 mo, and 90% of the animals in the treatment group exhibited mild-to-moderate hyperplasia with gland enlargement starting from 3 mo through the end of the study. Histopathological examination of the kidneys showed no change at 1 mo, but focal parenchymal inflammation with calcium deposition was observed in the treatment groups at 2 to 6 mo. Fibrous tissue of the bone extended toward the cortex, and fibrosis was evident at the third month. The fibrous cells were found to be concentrated mainly on the inner and outer membranes of the bone cortex, and the amount of fibrous tissue increased as the disease progressed. We conclude that a new rabbit animal model of PHPT can be successfully created by the administration of a high-phosphate diet. This animal model can be used in various future studies related to PHPT.

The bone histology spectrum in experimental renal failure: adverse effects of phosphate and parathyroid hormone disturbances

Bone disease is a common disorder of bone remodeling and mineral metabolism, which affects patients with chronic kidney disease. Minor changes in the serum level of a given mineral can trigger compensatory mechanisms, making it difficult to evaluate the role of mineral disturbances in isolation. The objective of this study was to determine the isolated effects that phosphate and parathyroid hormone (PTH) have on bone tissue in rats. Male Wistar rats were subjected to parathyroidectomy and 5/6 nephrectomy or were sham-operated. Rats were fed diets in which the phosphate content was low, normal, or high. Some rats received infusion of PTH at a physiological rate, some received infusion of PTH at a supraphysiological rate, and some received infusion of vehicle only. All nephrectomized rats developed moderate renal failure. High phosphate intake decreased bone volume, and this effect was more pronounced in animals with dietary phosphate overload that received PTH infusion at a physiological rate. Phosphate overload induced hyperphosphatemia, hypocalcemia, and changes in bone microarchitecture. PTH at a supraphysiological rate minimized the phosphate-induced osteopenia. These data indicate that the management of uremia requires proper control of dietary phosphate, together with PTH adjustment, in order to ensure adequate bone remodeling.

RANKL inhibition for the management of patients with benign metabolic bone disorders

The receptor activator of NF-kappaB ligand (RANKL) is a member of the TNF receptor superfamily, essential for osteoclastogenesis. It binds to its receptor activator of NF-kappaB on the surface of osteoclast precursors and enhances their differentiation, survival and fusion, while it activates mature osteoclasts and inhibits their apoptosis. The effects of RANKL are counteracted by osteoprotegerin (OPG), a neutralizing decoy receptor. Derangement of the balance in RANKL/OPG action is implicated in the pathophysiology of metabolic bone diseases, including osteoporosis. Current therapies used to prevent or treat metabolic bone diseases are thought to act, at least in part, through modification of the RANKL/OPG dipole. The idea of using a molecule that could specifically bind and neutralize RANKL to decrease bone resorption and subsequent bone loss is appealing. Recombinant OPG was initially tested. Denosumab, a fully human monoclonal antibody against RANKL, is a promising antiresorptive agent under investigation. It rapidly decreases bone turnover markers resulting in a significant increase in bone mineral density and reduction in fracture risk. However, because receptor activator of NF-kappaB activation by RANKL is also essential for T-cell growth and dendritic-cell function, inhibition of its action could simultaneously affect the immune system, leading to susceptibility in infections or malignancies.

Unusual case of calciphylaxis associated with primary hyperparathyroidism without coexistent renal failure

OBJECTIVE

To report a case of calciphylaxis in a patient with primary hyperparathyroidism without coexistent renal failure.

METHODS

The clinical, laboratory, and radiographic details of this case are reviewed, and the pathogenesis of calciphylaxis and the associated prognosis are discussed.

RESULTS

A 52-year-old woman had progressive fatigue, cachexia, severe osteoporosis, and necrotizing skin lesions. Her serum calcium level was 16 mg/dL, serum phosphorus level was 2.13 mg/dL, and parathyroid hormone level was 2,257 pg/mL (reference range, 15 to 65). On physical examination, gangrenous skin lesions with black crusts were noted on her legs, abdomen, and gluteal region. A mass lesion was detected in the parathyroid region by both ultrasonography and a parathyroid scan. The patient underwent a bilateral neck exploration, and a parathyroid adenoma measuring 3.5 by 1.5 by 1.2 cm was found on pathologic examination. After the operation, biochemical findings normalized, and the skin lesions progressively improved.

CONCLUSION

Severe primary hyperparathyroidism may be a factor leading to calciphylaxis, even in the absence of renal failure and a high calcium-phosphate product. This potentially life-threatening condition should not be left untreated if the levels of serum calcium and parathyroid hormone are severely elevated.

Effects of parathyroidectomy on bone remodeling markers and vitamin D status in patients with chronic kidney disease–mineral and bone disorder

BACKGROUND/AIMS

Chronic renal failure (CRF) is often associated with bone disorders including chronic kidney disease-mineral and bone disorder (CKD-MBD). Parathyroid hormone (PTH) has a relationship to bone remodeling, and so this study was undertaken to evaluate changes in bone remodeling markers after parathyroidectomy (PTX).

METHODS

Twelve adult patients, mean age 43.4 +/- 12.7 years, of both genders, were evaluated, prior to and six months after PTX. Analysis of biochemical markers of bone metabolism, such as total and ionized calcium, phosphorus, 25(OH)D(3), total alkaline phosphatase (TAP), bone-specific alkaline phosphatase (BAP), intact PTH, osteoprotegerin (OPG), and tartrate-resistant acid phosphatase isoform 5b (TRAP), were measured.

RESULTS

No changes were observed after PTX in the serum total and ionized calcium, TAP, BAP, and 25(OH)D(3). After surgery there was a significant decrease in serum phosphorus, iPTH, and TRAP (P < 0.001). No significant change was observed in OPG; however there was a positive correlation between OPG and 25(OH)D(3) before and after surgery (r = 0.774, P = 0.014; and r = 0.706, P = 0.01, respectively). The percentage of patients with vitamin D deficiency decreased from 16.7% to 8.3%, while those with sufficient levels increased from 41.7% to 58.3%.

CONCLUSION

The small number of patients in the study notwithstanding, the present study is unique because it provides information on bone metabolism and vitamin D status six months after PTX. The removal of parathyroid glands significantly decreased bone resorption and indicated a tendency of 25(OH)D(3) concentration to increase. However, the precise role of OPG and BAP in the improvement in bone remodeling in patients with CKD-MBD requires further study.