Development and progression of secondary hyperparathyroidism in chronic kidney disease: lessons from molecular genetics

Current therapeutic approach of chronic kidney disease-mineral and bone disorder

Chronic kidney disease (CKD) has emerged as one of the leading noncommunicable diseases affecting >10% of the population worldwide. Bone and mineral disorders are a common complication among patients with CKD resulting in a poor life quality, high fracture risk, increased morbidity and cardiovascular mortality. According to Kidney Disease: Improving Global Outcomes, renal osteodystrophy refers to changes in bone morphology found in bone biopsy, whereas CKD-mineral and bone disorder (CKD-MBD) defines a complex of disturbances including biochemical and hormonal alterations, disorders of bone and mineral metabolism and extraskeletal calcification. As a result, the management of CKD-MBD should focus on the aforementioned parameters, including the treatment of hyperphosphatemia, hypocalcemia, abnormal PTH and vitamin D levels. Regarding the bone fragility fractures, osteoporosis and renal osteodystrophy, which constitute the bone component of CKD-MBD, anti-osteoporotic agents constitute the mainstay of treatment. However, a thorough elucidation of the CKD-MBD pathogenesis is crucial for the ideal personalized treatment approach. In this paper, we review the pathology and management of CKD-MBD based on the current literature with special attention to recent advances.

[The role of calcium sensitive and vitamin D receptors in the pathogenesis of sporadic multiple parathyroid gland disease]

BACKGROUND

Sporadic multiple parathyroid gland disease is ¼ cases of primary hyperparathyroidism (PHPT). However, a single tactic for diagnosing and operating volume in patients with this variant of PHPT has not yet been developed. One of the possible directions in the search for pathogenetically substantiated methods of diagnosis and treatment is the study of the molecular genetic features of the disease and associated clinical and laboratory factors.

AIM

To study the features of the expression of calcium sensitive (CaSR) and vitamin D (VDR) receptors on the surface of parathyroid cells in primary hyperparathyroidism with solitary and multiple lesions of the parathyroid glands, as well as its changes under the influence of a decrease in the filtration function of the kidneys.

MATERIALS AND METHODS

In a single center observational prospective study with retrospective data collection, there were patients who during 2019-2021. operated on for PHPT, secondary hyperparathyroidism (SHPT) and all cases of tertiary hyperparathyroidism (THPT) operated during 2014-2021. The expression of CaSR, VDR and its relationship with the main laboratory parameters, the clinical variant of hyperparathyroidism, and the morphological substrate were studied.

RESULTS

The study included 69 patients: 19 with multiple and 25 with solitary PTG near PHPT, 15 with SHPT, 10 with THPT. A statistically significant decrease in the frequency of detection of normal expression of CaSR and VDR receptors occurs in any morphological variant of hyperparathyroidism and is observed in 93-60% of drugs. A decrease in the normal expression of CaSR in hyperplasia is detected statistically significantly less frequently than in adenoma (p≤0.01). The median expression intensity in adenoma was 2.5 (2:3), in hyperplasia 3.5 (3-4) (p≤0.01). The difference in the molecular mechanisms of the development of hyperparathyroidism with a predominance of a morphological substrate in the form of adenoma (PHPT with solitary adenoma) or hyperplasia (SHPT and PHPT with multiple PTG lesions) is realized in the frequency of maintaining normal CaSR expression in the PTG tissue. These mechanisms are implemented at the local level, their variability does not change under the influence of RRT. A common molecular genetic mechanism for the development of hyperparathyroidism with a predominance of a morphological substrate in the form of adenoma or hyperplasia has been found to reduce the frequency of maintaining normal VDR expression in PTG (up to 7-13%), p<0.01. This mechanism is implemented at the local level, its variability changes under the influence of RRT, reaching statistically significant differences in patients with THPT.

CONCLUSION

The study demonstrates the features of changes in the expression of CaSR and VDR in PHPT with multiple lesions of the parathyroid glands. The relationship between the expression of these receptors and the clinical variant of hyperparathyroidism, the morphological substrate, the main laboratory parameters, and renal function was shown.

Kidney Failure Alters Parathyroid Pin1 Phosphorylation and Parathyroid Hormone mRNA-Binding Proteins, Leading to Secondary Hyperparathyroidism

BACKGROUND

Secondary hyperparathyroidism (SHP) is a common complication of CKD that increases morbidity and mortality. In experimental SHP, increased parathyroid hormone (PTH) expression is due to enhanced PTH mRNA stability, mediated by changes in its interaction with stabilizing AUF1 and destabilizing KSRP. The isomerase Pin1 leads to KSRP dephosphorylation, but in SHP parathyroid Pin1 activity is decreased and hence phosphorylated KSRP fails to bind PTH mRNA, resulting in high PTH mRNA stability and levels. The up- and downstream mechanisms by which CKD stimulates the parathyroid glands remain elusive.

METHODS

Adenine-rich high-phosphate diets induced CKD in rats and mice. Parathyroid organ cultures and transfected cells were incubated with Pin1 inhibitors for their effect on PTH expression. Mass spectrometry was performed on both parathyroid and PTH mRNA pulled-down proteins.

RESULTS

CKD led to changes in rat parathyroid proteome and phosphoproteome profiles, including KSRP phosphorylation at Pin1 target sites. Furthermore, both acute and chronic kidney failure led to parathyroid-specific Pin1 Ser16 and Ser71 phosphorylation, which disrupts Pin1 activity. Pharmacologic Pin1 inhibition, which mimics the decreased Pin1 activity in SHP, increased PTH expression ex vivo in parathyroid glands in culture and in transfected cells through the PTH mRNA-protein interaction element and KSRP phosphorylation.

CONCLUSIONS

Kidney failure leads to loss of parathyroid Pin1 activity by inducing Pin1 phosphorylation. This predisposes parathyroids to increase PTH production through impaired PTH mRNA decay that is dependent on KSRP phosphorylation at Pin1-target motifs. Pin1 and KSRP phosphorylation and the Pin1-KSRP-PTH mRNA axis thus drive SHP.

[Experience in using teriparatide for the treatment of postoperative hypoparathyroidism in hemodialysis patients]

The frequency of chronic postoperative hypoparathyroidism after total parathyroidectomy for secondary and tertiary hyperparathyroidism in patients with end-stage renal failure, according to various authors, can reach 20% or more. Prescribing active metabolites of vitamin D and calcium it is not always sufficient for achievement of target goals. This dictates the need for replacement therapy with recombinant parathyroid hormone. Teriparatide is the only drug of this series approved by the American Food and Drug Administration (FDA) and registered in the Russian Federation. However, it is registered as an anabolic anti-osteoporotic drug and is not indicated for the treatment of chronic hypoparathyroidism. The use of teriparatide in postoperative hypoparathyroidism in patients receiving renal replacement therapy with programmed hemodialysis in the Russian Federation has not been previously studied. Data on this issue is also limited in foreign literature. However, it is a potential treatment option for hemodialysis patients with chronic hypoparathyroidism and severe bone disorders. In this article, we present 2 clinical cases of substitution and anabolic therapy with teriparatide in this cohort of patients.

Update on imaging in chronic kidney disease-mineral and bone disorder: promising role of functional imaging

Disorders of mineral metabolism and bone disease are common complications in chronic kidney disease (CKD) patients and are associated with increased morbidity and mortality. Bone biopsies, bone scintigraphy, biochemical markers, and plain films have been used to assess bone disorders and bone turnover. Of these, functional imaging is less invasive than bone/marrow sampling, more specific than serum markers and is therefore ideally placed to assess total skeletal metabolism. ¹⁸F-sodium fluoride (NaF) PET/CT is an excellent bone-seeking agent superior to conventional bone scan in CKD patients due to its high bone uptake, rapid single-pass extraction, and minimal binding to serum proteins. Due to these properties, ¹⁸F-NaF can better assess the skeletal metabolism on primary diagnosis and following treatment in CKD patients. With the increased accessibility of PET scanners, it is likely that PET scanning with bone-specific tracers such as ¹⁸F-NaF will be used more regularly for clinical assessment and quantitation of bone kinetics. This article describes the pattern of scintigraphic/functional appearances secondary to musculoskeletal alterations that might occur in patients with CKD.

[Identification of microRNAs targeting vitamin D receptor and their effect on parathyroid hormone secretion in secondary hyperparathyroidism]

OBJECTIVE

To identify the miRNAs targeting vitamin D receptor (VDR) gene and their effect on parathyroid hormone (PTH) secretion in secondary hyperparathyroidism.

METHODS

Primary parathyroid cells with secondary hyperparathyroidism were isolated by collagenase digestion and cultured. The miRNAs targeting VDR were screened by bioinformatics methods and full transcriptome sequencing, and dual-luciferase reporter assay was used to verify the targeting relationship between VDR and the screened miRNA. The effects of overexpression or inhibition of the candidate miRNA on VDR mRNA and protein expressions and PTH secretion were evaluated using qRT-PCR and Western blotting. The expression levels of the candidate miRNAs and VDR mRNA in clinical specimens of parathyroid tissues were verified by qRT-PCR, and the expression of VDR protein was detected by immunohistochemistry.

RESULTS

We successfully isolated primary parathyroid cells. Dual-luciferase reporter assay verified the targeting relationship of hsa-miR-149-5p, hsa-miR-221-5p, hsa-miR-222-3p, hsa-miR-29a-5p, hsa-miR-301a-5p, hsa-miR-873-5p, hsa-miR-93-3p with VDR, and among them, the overexpression of hsa-miR-149-5p and hsa-miR-301a-5p significantly increased PTH secretion in the parathyroid cells. In patients with secondary hyperparathyroidism, hsa-miR-149-5p was highly expressed in the parathyroid tissues (P=0.046), where the expressions of VDR mRNA (P=0.0267) and protein were both decreased.

CONCLUSION

The two miRNAs, hsa-miR-149-5p and hsa-miR-301a-5p, may promote the secretion of PTH in patients with secondary hyperparathyroidism by down-regulating the expression of VDR gene.

Uremic Leontiasis Ossea in a Pediatric Patient

Uremic leontiasis ossea (ULO) is a rare disease characterized by extensive thickening of the cranium, resulting in a characteristic, lion-like facial appearance. It is considered the most severe osseous complication of renal dystrophy. Although rare, ULO can occur even in young patients, which can be catastrophic, as it can not only lead to life-threatening conditions but also multiple complications that cause severe determent to the quality of life.

Calcium Transport in the Kidney and Disease Processes

Calcium is a key ion involved in cardiac and skeletal muscle contractility, nerve function, and skeletal structure. Global calcium balance is affected by parathyroid hormone and vitamin D, and calcium is shuttled between the extracellular space and the bone matrix compartment dynamically. The kidney plays an important role in whole-body calcium balance. Abnormalities in the kidney transport proteins alter the renal excretion of calcium. Various hormonal and regulatory pathways have evolved that regulate the renal handling of calcium to maintain the serum calcium within defined limits despite dynamic changes in dietary calcium intake. Dysregulation of renal calcium transport can occur pharmacologically, hormonally, and via genetic mutations in key proteins in various nephron segments resulting in several disease processes. This review focuses on the regulation transport of calcium in the nephron. Genetic diseases affecting the renal handling of calcium that can potentially lead to changes in the serum calcium concentration are reviewed.

Molecular Mechanisms of Parathyroid Disorders in Chronic Kidney Disease

Secondary hyperparathyroidism (SHP) is a common complication of chronic kidney disease (CKD) that induces morbidity and mortality in patients. How CKD stimulates the parathyroid to increase parathyroid hormone (PTH) secretion, gene expression and cell proliferation remains an open question. In experimental SHP, the increased PTH gene expression is post-transcriptional and mediated by PTH mRNA–protein interactions that promote PTH mRNA stability. These interactions are orchestrated by the isomerase Pin1. Pin1 participates in conformational change-based regulation of target proteins, including mRNA-binding proteins. In SHP, Pin1 isomerase activity is decreased, and thus, the Pin1 target and PTH mRNA destabilizing protein KSRP fails to bind PTH mRNA, increasing PTH mRNA stability and levels. An additional level of post-transcriptional regulation is mediated by microRNA (miRNA). Mice with parathyroid-specific knockout of Dicer, which facilitates the final step in miRNA maturation, lack parathyroid miRNAs but have normal PTH and calcium levels. Surprisingly, these mice fail to increase serum PTH in response to hypocalcemia or uremia, indicating a role for miRNAs in parathyroid stimulation. SHP often leads to parathyroid hyperplasia. Reduced expressions of parathyroid regulating receptors, activation of transforming growth factor α-epidermal growth factor receptor, cyclooxygenase 2-prostaglandin E2 and mTOR signaling all contribute to the enhanced parathyroid cell proliferation. Inhibition of mTOR by rapamycin prevents and corrects the increased parathyroid cell proliferation of SHP. This review summarizes the current knowledge on the mechanisms that stimulate the parathyroid cell at multiple levels in SHP.

Activation of the Calcium Receptor by Calcimimetic Agents Is Preserved Despite Modest Attenuating Effects of Hyperphosphatemia

BACKGROUND

Phosphorus levels in the range seen clinically among patients undergoing dialysis have been reported to attenuate calcium receptor activation and modify parathyroid hormone (PTH) release from isolated parathyroid glands in vitro. Some clinicians and providers of dialysis thus have suggested that calcimimetic agents are ineffective and should not be used to manage secondary hyperparathyroidism among those undergoing dialysis when serum phosphorus concentrations exceed certain threshold levels.

METHODS

To determine whether hyperphosphatemia diminishes the therapeutic response to calcimimetic agents, we used data from large clinical trials to analyze the effects of etelcalcetide and cinacalcet to lower plasma PTH levels in individuals on hemodialysis who had secondary hyperparathyroidism and varying degrees of hyperphosphatemia.

RESULTS

Plasma PTH levels declined progressively during 26 weeks of treatment with either etelcalcetide or cinacalcet without regard to the degree of hyperphosphatemia at baseline. However, with each calcimimetic agent, the decreases in PTH from baseline were less at each interval of follow-up during the trials among participants with serum phosphorus levels above one of three prespecified threshold values compared with those with serum phosphorus levels below these thresholds.

CONCLUSIONS

These in vivo findings are the first in humans to support the idea that hyperphosphatemia attenuates calcium receptor activation by calcium ions and by calcimimetic agents. The effect of hyperphosphatemia on the responsiveness to calcimimetic agents appears relatively modest, however, and unlikely to be significant therapeutically. The efficacy of treatment with calcimimetic agents for lowering plasma PTH levels among those with secondary hyperparathyroidism remains robust despite substantial elevations in serum phosphorus.

Paricalcitol in hemodialysis patients with secondary hyperparathyroidism and its potential benefits

BACKGROUND

Secondary hyperparathyroidism (SHPT) is a common complication in patients with end-stage renal disease and it is also common in hemodialysis patients. SHPT can increase bone fragility and calcification of blood vessels and soft tissues, which greatly increases the risk of death.

AIM

To discuss the outcome, safety and other potential benefits of paricalcitol injection in hemodialysis patients with SHPT.

METHODS

We recruited 40 patients who received hemodialysis at our hospital for chronic renal failure with SHPT between March and December 2019. They received paricalcitol injection for 24 wk (starting dose, 0.06-0.08 μg/kg), three times per week. They were followed up at the baseline (week 0), week 4, week 12 and week 24. The primary outcome indicator was the percentage of patients with a > 30% decrease in intact parathyroid hormone (iPTH) levels at week 24 compared with the baseline. The secondary outcome indicators included percentage decrease in iPTH levels at week 24, standard-reaching rate of iPTH (percentage of patients with iPTH down to 130-585 pg/mL), changes in serum levels of calcium (Ca), phosphate (P), Ca × P product, alkaline phosphatase (ALP), creatinine (Cre), hemoglobin (Hb), and C-reactive protein (CRP), and incidence of adverse events (AEs).

RESULTS

After 24 wk of treatment, iPTH levels decreased significantly (598.88 ± 381.29 pg/mL vs 888.84 ± 376.88 pg/mL, P < 0.05). More than 30% decrease of iPTH was found in 21 of 36 (58.33%) patients. The average decrease in iPTH levels was 32.16 ± 4.33%; the standard-reaching rate of iPTH levels was 66.67% (24/36); and ALP levels decreased significantly compared with the baseline (113.72 ± 41.73 IU/L vs 133.45 ± 56.86 IU/L) (t = 2.798, P < 0.05). There were no significant differences in the serum levels of calcium, Hb, Cre and CRP compared with the baseline (P > 0.05). After 24 wk of treatment, serum P levels decreased compared with the baseline (1.91 ± 0.40 mmol/L vs 2.16 ± 0.66 mmol/L) (t = 2.830, P < 0.05). Ca × P product decreased significantly compared with the baseline (56.38 ± 13.22 mg2/dL2 vs 63.97 ± 20.30 mg2/dL2) (t = 2.717, P < 0.05). No serious adverse events occurred.

CONCLUSION

Paricalcitol was a safe and effective treatment for hemodialysis patients with SHPT. It decreased serum levels of iPTH, ALP and P and maintained stability of serum Ca levels.

Health Care Costs in Patients with and without Secondary Hyperparathyroidism in Spain

OBJECTIVE

To analyze the economic burden of secondary hyperparathyroidism (sHPT) in Spain by quantifying differences in costs of pharmacological treatments and associated cardiovascular events (CVE) between renal patients with and without sHPT.

METHODS

We used data collected in the NEFRONA cohort study and obtained treatment and CVE costs from the BOT PLUS database and Hospital Discharge Records in the Spanish Health System (CMBD-H), respectively. We examined data from 2445 renal patients followed during 2 years for chronic kidney disease (CKD) progression and 4 years for CVE, stratifying by presence of sHPT. Patient characteristics, administered treatments and CVE were directly extracted from NEFRONA registries. Dosage for each treatment regimen was assumed based on guidelines and multiplied by official unit costs to obtain treatment costs. Costs of CVE were based on ICD-9-CM.

RESULTS

Prevalence of sHPT in the cohort was 65.6% (63.6; 67.6). Average yearly pharmacological costs for patients without sHPT were 610.33€, while costs were 1483.17€ for sHPT patients (average increase of 143.0%). Two hundred three patients registered CVE, resulting in 4-year average costs of 582.57€ for non-sHPT patients compared to 941.87€ for sHPT patients (61.7% average increase). Bivariate analyses considering presence of dialysis, hypercalcemia or hyperphosphatemia and stratified by sHPT showed higher costs for sHPT patients.

CONCLUSIONS

These results show that sHPT is associated with substantially higher costs of both, pharmacological treatments and associated CVEs. Preventing the development of sHPT with early management in the course of CKD could possibly lead to better health outcomes and cost balance for health care systems.

Managing Anemia across the Stages of Kidney Disease in Those Hyporesponsive to Erythropoiesis-Stimulating Agents

BACKGROUND

Patients with CKD frequently have anemia that results from iron-restricted erythropoiesis and inflammation. Anemia of CKD is currently managed with iron supplements and erythropoiesis-stimulating agents (ESAs) to promote erythropoiesis and with RBC transfusion in severe cases. Hyporesponse to ESAs, or the need for larger than usual doses to attain a given hemoglobin (Hb) level, is associated with increased morbidity and mortality and presents a pressing clinical challenge, particularly for patients on dialysis. This paper reviews ESA hyporesponse and potential new therapeutic options in the management of anemia of CKD.

SUMMARY

The most common causes of ESA hyporesponse include iron deficiency and inflammation, and to a lesser degree, secondary hyperparathyroidism, inadequate dialysis, malnutrition, and concomitant medications. Management of ESA hyporesponse is multipronged and involves treating low level infections, ensuring adequate nutrition, and optimizing iron status and dialysis modality, although some patients can remain refractory. Inflammation directly increases production and secretion of hepcidin, contributes to an impaired response to hypoxia, and suppresses proliferation of erythroid progenitors. Coordination of renal and hepatic erythropoietin (EPO) production and iron metabolism is under the control of hypoxia-inducible factors (HIF), which are in turn regulated by HIF-prolyl hydroxylases (HIF-PHs). HIF-PHs and hepcidin are therefore attractive potential drug targets particularly in patients with ESA hyporesponse. Several oral HIF-PH inhibitors have been evaluated in patients with anemia of CKD and have been shown to increase Hb and reduce hepcidin regardless of inflammation, iron status, or dialysis modality. These sustained effects are achieved through more modest increases in endogenous EPO compared with ESAs. Key Messages: Treatments that address ESA hyporesponse remain a significant unmet clinical need in patients with anemia of CKD. New therapies such as HIF-PH inhibitors have the potential to address fundamental aspects of ESA hyporesponse and provide a new therapeutic option in these patients.

Etelcalcetide Utilization, Dosing Titration, and Chronic Kidney Disease-Mineral and Bone Disease (CKD-MBD) Marker Responses in US Hemodialysis Patients

RATIONALE AND OBJECTIVE

Clinical trial data have demonstrated the efficacy of etelcalcetide for reducing parathyroid hormone (PTH) levels in hemodialysis (HD) patients. We provide a real-world summary of etelcalcetide utilization, dosing, effectiveness, and discontinuation since its US introduction in April 2017.

STUDY DESIGN

New-user design within prospective cohort.

SETTING PARTICIPANTS

2596 new users of etelcalcetide from April 2017 through August 2019 in a national sample of adult, chronic HD patients in the US Dialysis Outcomes and Practice Patterns Study (DOPPS).

PREDICTORS

Baseline PTH, prior cinacalcet use, initial etelcalcetide dose.

OUTCOME(S)

Trajectories of etelcalcetide dose, use of mineral bone disorder (MBD) medications, and levels of PTH, serum calcium, and phosphorus in the 12 months following etelcalcetide initiation.

ANALYTICAL APPROACH

Cumulative incidence methods for etelcalcetide discontinuation and linear generalized estimating equations for trajectory analyses.

RESULTS

By August 2019 etelcalcetide prescriptions increased to 6% of HD patients from their first use in April 2017. Starting etelcalcetide dose was 15 mg/week in 70% of patients and 7.5 mg/week in 27% of patients; 49% of new users were prescribed cinacalcet in the prior 3 months. Etelcalcetide discontinuation was 9%, 17%, and 27% by 3, 6, and 12 months post-initiation. One year after etelcalcetide initiation, mean PTH levels declined by 40%, from 948 to 566 pg/mL, and the proportion of patients with PTH within target (150-599 pg/mL) increased from 33% to 64% overall, from 0% to 60% among patients with baseline PTH ≥600 pg/mL, and from 30% to 63% among patients with prior cinacalcet use. The proportion of patients with serum phosphorus >5.5 mg/dL decreased from 55% to 45%, while the prevalence of albumin-corrected serum calcium <7.5 mg/dL remained at 1%-2%. Use of active vitamin D (from 77% to 87%) and Ca-based phosphate binders (from 41% to 50%) increased in the 12 months following etelcalcetide initiation.

LIMITATIONS

Data unavailable for provider dosing protocols, dose holds, or reasons for discontinuation.

CONCLUSIONS

In the 12 months following etelcalcetide initiation, patients had large and sustained reductions in PTH levels. These results support the utility of etelcalcetide as an effective therapy to achieve the KDIGO recommended guidelines for CKD-MBD markers in HD patients.

Bone Disease in CKD in Children

This manuscript discusses mineral and bone disorders of chronic kidney disease (MBD-CKD) in pediatric patients with special emphasis on the underlying pathophysiology, the causes and clinical profile of growth retardation, the alterations in the growth plate, the strategies to optimize growth and the medical recommendations for prevention and treatment.

Decreased monocyte calcium sensing receptor expression in patients with chronic kidney disease is associated with impaired monocyte ability to reduce vascular calcification

In chronic kidney disease (CKD), calcium-sensing receptor (CaSR) expression and function have been extensively studied in parathyroid tissue and vascular tissues. To examine whether similar changes occurred in other tissues, we measured total and surface CaSR expression in monocytes of patients with various stages of CKD and healthy volunteers respectively in cross-sectional studies. We further explored in vitro the impact of uremic serum on CaSR expression in monocytes (U937 and THP-1 cell lines), and whether human peripheral blood mononuclear cells or U937 and THP-1 monocytes might modify vascular calcium deposition in rat carotid arteries in vitro. CKD was associated with a decrease in peripheral blood mononuclear cell CaSR expression both in total and at the monocyte surface alone (43% and 34%, respectively in CKD stages 4-5). This decrease was associated with a reduction in the ability of monocytes to inhibit vascular calcification in vitro. Pretreatment with the calcimimetic NPSR568 of peripheral blood mononuclear cells isolated from patients with CKD significantly improved monocyte capacity to reduce carotid calcification in vitro. The fewer peripheral blood mononuclear cells expressing cell surface CaSR, the more calcimimetic treatment enhanced the decrease of carotid calcium content. Thus, we demonstrate that monocyte CaSR expression is decreased in patients with CKD and provide in vitro evidence for a potential role of this decrease in the promotion of vascular calcification. Hence, targeting this alteration or following monocyte CaSR expression as an accessible marker might represent a promising therapeutic strategy in CKD-associated arterial calcification.

One-year safety and efficacy of intravenous etelcalcetide in patients on hemodialysis with secondary hyperparathyroidism

BACKGROUND

Secondary hyperparathyroidism (sHPT), a common complication of chronic kidney disease, is characterized by elevated serum parathyroid hormone (PTH). Etelcalcetide is an intravenous calcimimetic that increases sensitivity of the calcium-sensing receptor to calcium and decreases PTH secretion. This open-label extension (OLE) trial evaluated the long-term effects of etelcalcetide for sHPT treatment in patients receiving hemodialysis.

METHODS

This 52-week, multicenter, single-arm OLE enrolled patients from three parent trials: two randomized, double-blind, placebo-controlled trials and one open-label, single-arm, 'switch' study from cinacalcet to etelcalcetide. The primary endpoint was to investigate the nature, frequency, severity and relation to treatment of all adverse events (AEs) reported throughout the trial. Secondary endpoints included the proportion of patients with >30% reduction from baseline in PTH and the percentage change from baseline in PTH, albumin-corrected calcium (Ca), phosphate (P) and the calcium-phosphate product (Ca × P).ClinicalTrials.gov identifier: NCT01785875; Amgen study: 20120231.

RESULTS

Overall, 89.8% of the patients experienced one or more treatment-emergent AE. The most common were decreased blood Ca (43.3%), diarrhea (10.8%), vomiting (10.4%) and nausea (9.6%); symptomatic hypocalcemia occurred in 3.7% of the patients. Approximately 68% of patients achieved >30% reduction in PTH, and ∼56% achieved PTH ≤300 pg/mL. Mean percent changes from baseline ranged from -25.4% to -26.1% for PTH, -8.3% to -9.1% for Ca, -3.6% to -4.1% for P and -12.0% to -12.6% for Ca × P.

CONCLUSIONS

Etelcalcetide effectively lowered PTH and its effect was sustained, while no new safety concerns emerged over a 1-year treatment period.

Lower soluble Klotho levels in the pretransplant period are associated with an increased risk of renal function decline in renal transplant patients

Serum soluble Klotho levels are associated with renal function in predialysis patients with chronic kidney disease. However, few reports exist regarding the association between soluble Klotho levels and renal function in kidney transplant (KTx) recipients. This was a retrospective observational study of 41 living KTx recipients. The serum soluble Klotho levels were classed as "high" (>456 pg/mL [i.e., high-Klotho group]) or "low" (≤456 pg/mL [i.e., low-Klotho group]). Renal function decline was defined as a decrease in the estimated glomerular filtration rate (eGFR) of 30% or more from the baseline value within 3 months after KTx. A multivariable time-to-event analysis between the groups was conducted. Among the KTx recipients, the incidence of a 30% decrease in the eGFR was significantly higher in the low-Klotho group than in the high-Klotho group (P = .036). After adjusting for donor age, donor sex, the presence of rejection, and the number of cytomegalovirus infections, multivariable Cox models revealed that low soluble Klotho levels remained associated with a higher risk of a 30% decrease in the eGFR (hazard ratio, 2.38; 95% confidence interval, 1.02-6.41). These findings suggested that lower soluble Klotho levels in the pre-KTx period are associated with an increased risk of renal function decline in KTx recipients.

Cinacalcet studies in pediatric subjects with secondary hyperparathyroidism receiving dialysis

BACKGROUND

Secondary hyperparathyroidism (sHPT), a complication of chronic kidney disease (CKD) characterized by persistently elevated parathyroid hormone (PTH), alterations in calcium-phosphorus homeostasis, and vitamin D metabolism, affects 50% of children receiving dialysis. A significant proportion of these children develop CKD-mineral and bone disorder (CKD-MBD), associated with an increased risk of fractures and vascular calcification. The standard of care for sHPT in children includes vitamin D sterols, calcium supplementation, and phosphate binders. Several agents are approved for sHPT treatment in adults undergoing dialysis, including vitamin D analogs and calcimimetics, with limited information on their safety and efficacy in children. The calcimimetic cinacalcet is approved for use in adults with sHPT on dialysis, but is not approved for pediatric use outside Europe.

METHODS

This review provides dosing, safety, and efficacy information from Amgen-sponsored cinacalcet pediatric trials and data from non-Amgen sponsored clinical studies.

RESULTS

The Amgen cinacalcet pediatric clinical development program consisted of two Phase 3 randomized studies, one Phase 3 single arm extension study, one open-label Phase 2 study, and two open-label Phase 1 studies. Effects of cinacalcet on PTH varied across studies. Overall, 7.4 to 57.1% of subjects who received cinacalcet in an Amgen clinical trial attained PTH levels within recommended target ranges and 22.2 to 70.6% observed a ≥ 30% reduction in PTH. In addition, significant reductions in PTH were demonstrated in all non-Amgen-supported studies.

CONCLUSIONS

To help inform the pediatric nephrology community, this manuscript contains the most comprehensive review of cinacalcet usage in pediatric CKD patients to date.

Pharmacokinetic/pharmacodynamic data extrapolation models for improved pediatric efficacy and toxicity estimation, with application to secondary hyperparathyroidism

In most drug development settings, the regulatory approval process is accompanied by extensive studies performed to understand the drug's pharmacokinetic (PK) and pharmacodynamic (PD) properties. In this article, we attempt to utilize the rich PK/PD data to inform the borrowing of information from adults during pediatric drug development. In pediatric settings, it is especially crucial that we are parsimonious with the patients recruited for experimentation. We illustrate our approaches in the context of clinical trials of cinacalcet for treating secondary hyperparathyroidism in pediatric and adult patients with chronic kidney disease, where we model both parathyroid hormone (efficacy endpoint) and corrected calcium levels (safety endpoint). We use population PK/PD modeling of the cinacalcet data to quantitatively assess the similarity between adults and children, and use this information in various hierarchical Bayesian adult borrowing rules whose statistical properties can then be evaluated. In particular, we simulate the bias and mean square error performance of our approaches in settings where borrowing is and is not warranted to inform guidelines for the future use of our methods.

Parathyroid Cell Proliferation in Secondary Hyperparathyroidism of Chronic Kidney Disease

Secondary hyperparathyroidism (SHP) is a common complication of chronic kidney disease (CKD) that correlates with morbidity and mortality in uremic patients. It is characterized by high serum parathyroid hormone (PTH) levels and impaired bone and mineral metabolism. The main mechanisms underlying SHP are increased PTH biosynthesis and secretion as well as increased glandular mass. The mechanisms leading to parathyroid cell proliferation in SHP are not fully understood. Reduced expressions of the receptors for calcium and vitamin D contribute to the disinhibition of parathyroid cell proliferation. Activation of transforming growth factor-α-epidermal growth factor receptor (TGF-α-EGFR), nuclear factor kappa B (NF-kB), and cyclooxygenase 2- prostaglandin E2 (Cox2-PGE2) signaling all correlate with parathyroid cell proliferation, underlining their roles in the development of SHP. In addition, the mammalian target of rapamycin (mTOR) pathway is activated in parathyroid glands of experimental SHP rats. Inhibition of mTOR by rapamycin prevents and corrects the increased parathyroid cell proliferation of SHP. Mice with parathyroid-specific deletion of all miRNAs have a muted increase in serum PTH and fail to increase parathyroid cell proliferation when challenged by CKD, suggesting that miRNA is also necessary for the development of SHP. This review summarizes the current knowledge on the mechanisms of parathyroid cell proliferation in SHP.

Pattern of Laboratory Parameters and Management of Secondary Hyperparathyroidism in Countries of Europe, Asia, the Middle East, and North America

INTRODUCTION

This analysis explored laboratory mineral and bone disorder parameters and management of secondary hyperparathyroidism in patients undergoing hemodialysis in Belgium, Canada, China, France, Germany, Italy, Japan, Russia, Saudi Arabia, Spain, Sweden, the UK, and the USA.

METHODS

Analyses used demographic, medication, and laboratory data collected in the prospective Dialysis Outcomes and Practice Patterns Study (2012-2015). The analysis included 20,612 patients in 543 facilities. Descriptive data are presented as regional mean (standard deviation), median (interquartile range), or prevalence, weighted for facility sampling fraction. No testing of statistical hypotheses was conducted.

RESULTS

The frequency of serum intact parathyroid hormone levels > 600 pg/mL was lowest in Japan (1%) and highest in Russia (30%) and Saudi Arabia (27%). The frequency of serum phosphorus levels > 7.0 mg/dL was lowest in France (4%), the UK (6%), and Spain (6%), and highest in China (27%). The frequency of serum calcium levels > 10.0 mg/dL was highest in the UK (14%) and China (13%) versus 2% to 9% elsewhere. Dialysate calcium concentrations of 2.5 mEq/mL were common in the USA (78%) and Canada (71%); concentrations of 3.0-3.5 mEq/L were almost universal at facilities in Italy, France, and Saudi Arabia (each ≥ 99%).

CONCLUSIONS

Wide international variation in mineral and bone disorder laboratory parameters and management practices related to secondary hyperparathyroidism suggests opportunities for optimizing care.

A mathematical model of parathyroid gland biology

Altered parathyroid gland biology in patients with chronic kidney disease (CKD) is a major contributor to chronic kidney disease-mineral bone disorder (CKD-MBD). This disorder is associated with an increased risk of bone disorders, vascular calcification, and cardiovascular events. Parathyroid hormone (PTH) secretion is primarily regulated by the ionized calcium concentration as well as the phosphate concentration in the extracellular fluid and vitamin D. The metabolic disturbances in patients with CKD lead to alterations in the parathyroid gland biology. A hallmark of CKD is secondary hyperparathyroidism, characterized by an increased production and release of PTH, reduced expression of calcium-sensing and vitamin D receptors on the surface of parathyroid cells, and hyperplasia and hypertrophy of these cells. These alterations happen on different timescales and influence each other, thereby triggering a cascade of negative and positive feedback loops in a highly complex manner. Due to this complexity, mathematical models are a useful tool to break down the patterns of the multidimensional cascade of processes enabling the detailed study of subsystems. Here, we introduce a comprehensive mathematical model that includes the major adaptive mechanisms governing the production, secretion, and degradation of PTH in patients with CKD on hemodialysis. Combined with models for medications targeting the parathyroid gland, it provides a ready-to-use tool to explore treatment strategies. While the model is of particular interest for use in hemodialysis patients with secondary hyperparathyroidism, it has the potential to be applicable to other clinical scenarios such as primary hyperparathyroidism or hypo- and hypercalcemia.

Post-transcriptional mechanisms regulating parathyroid hormone gene expression in secondary hyperparathyroidism

Parathyroid hormone (PTH) regulates serum calcium levels and bone strength. Secondary hyperparathyroidism (SHP) is a common complication of chronic kidney disease (CKD) that correlates with morbidity and mortality. In experimental SHP, the increased PTH gene expression is due to increased PTH mRNA stability and is mediated by protein-PTH mRNA interactions. Adenosine-uridine-rich binding factor 1 (AUF1) stabilizes and K-homology splicing regulatory protein (KSRP) destabilizes PTH mRNA. The peptidyl-prolyl cis/trans isomerase Pin1 acts on target proteins, including mRNA-binding proteins. Pin1 leads to KSRP dephosphorylation, but in SHP, parathyroid Pin1 activity is decreased and phosphorylated KSRP fails to bind PTH mRNA, leading to increased PTH mRNA stability and levels. A further level of post-transcriptional regulation occurs through microRNA (miRNA). Dicer mediates the final step of miRNA maturation. Parathyroid-specific Dicer knockout mice that lack miRNAs in the parathyroid develop normally. Surprisingly, these mice fail to increase serum PTH in response to both hypocalcemia and CKD, indicating that parathyroid Dicer and miRNAs are essential for stimulation of the parathyroid. Human and rodent parathyroids share similar miRNA profiles that are altered in hyperparathyroidism. The evolutionary conservation of abundant miRNAs and their regulation in hyperparathyroidism indicate their significance in parathyroid physiology and pathophysiology. let-7 and miR-148 antagonism modifies PTH secretion in vivo and in vitro, suggesting roles for specific miRNAs in parathyroid function. This review summarizes the current knowledge on the post-transcriptional mechanisms of PTH gene expression in SHP and the central contribution of miRNAs to the high serum PTH levels of both primary hyperparathyroidism and SHP.

Is There a Gender Difference in Clinical Presentation of Renal Hyperparathyroidism and Outcome after Parathyroidectomy?

Introduction

Gender has been proven to influence the pathophysiology and treatment of numerous diseases, including kidney diseases and hormonal dysfunction like hyperparathyroidism. Thus, higher parathormone levels have been demonstrated in women with end-stage kidney disease, when compared to men.

Objectives

We questioned whether female gender is associated with an increased risk for parathyroid nodular hyperplasia and necessary parathyroidectomy in dialysis patients and assessed demographics as well as outcome data for women and men undergoing parathyroidectomy for renal hyperparathyroidism.

Patients and Methods

One hundred and thirty patients (men = 75, female = 55) with end-stage renal disease on chronic dialysis and advanced secondary hyperparathyroidism who underwent parathyroidectomy between 2008 and 2014 at our center were analyzed retrospectively. Perioperative characteristics and short-term outcome were evaluated with respect to biological gender.

Results

No differences could be demonstrated for patient demography, comorbidities and the perioperative course between males and females. Only preoperative calcium levels were lower in female than in male patients (2.3 ± 0.19 vs. 2.3 ± 0.26, p = 0.04). There were more women, however, with cerebrovascular complications during follow-up (p = 0.04). There was no postoperative mortality, and all complications and comorbidities with exception of cerebrovascular diseases were equally distributed between female and male patients.

Conclusion

Overall, we could not demonstrate many significant differences between male and female patients with end-stage renal diseases, chronic dialysis and operated secondary hyperparathyroidism. Only preoperative electrolyte levels were higher in male than in female patients, and cerebrovascular complications developed more often in females than in males during long-term follow-up.

Current Understanding of Mineral and Bone Disorders of Chronic Kidney Disease and the Scientific Grounds on the Use of Exogenous Parathyroid Hormone in Its Management

Chronic Kidney disease (CKD) disturbs mineral homeostasis leading to mineral and bone disorders (MBD). Serum calcium and phosphate (Pi) remain normal until the late stages of CKD at the expense of elevate fibroblast growth factor-23 (FGF-23), a phosphaturic hormone, followed by reduced 1,25-dihydroxy-vitamin D (1,25[OH]₂D) and finally elevated parathyroid hormone (PTH). Pi retention is thought to be the initial cause of CKD-MBD. The management of MBD is a huge clinical challenge because the effectiveness of current therapeutic regimens to prevent and treat MBD is limited. An intermittent regimen of PTH, when administered at the early stages of CKD, through its phosphaturic action, could prevent FGF-23 increases, the drop of 1,25(OH)₂D, and the development of renal osteodystrophy, including secondary hyperparathyroidism (HPT) and its catabolic effects on the skeleton. Even in more advanced stages of CKD that have not progressed to tertiary HPT, could be beneficial. Therapeutic effects could be achieved in vascular calcification as well. Limited experimental/clinical data support the effectiveness of PTH in CKD-MBD. Its safety, has been established only when it is used for the treatment of osteoporosis, including patients with CKD. The proposed intermittent PTH administration is biologically plausible but its effectiveness and safety has to be critically assessed in long term prospective studies in patients with CKD-MBD.

Disputable Issues of Etiology and Pathogenesis of Tertiary Hyperparathyroidism

Hyperparathyroidism is a clinical and laboratory syndrome characterized by high production of the chief cells of the parathyroid hormone, a calcium-phosphorus metabolism disorder and the organ failure (kidneys, bone tissue).There are primary, secondary and tertiary hyperparathyroidism.This literature review is focused on tertiary hyperparathyroidism and includes the following sections: definition of different forms of hyperparathyroidism, the role of vitamin D in the tertiary hyperparathyroidism development, the development of tertiary hyperparathyroidism in chronic kidney disease patients, the development of tertiary hyperparathyroidism in patients after kidney transplantation, differential diagnosis various forms of hyperparathyroidism, indications for surgical tertiary hyperparathyroidism treatment in patients with kidney disease, in patients with normal kidney function.Objective. The objective of this literature review is to study the current information about this definition, pathogenesis, diagnosis and treatment of tertiary hyperparathyroidism.Methodology. The literature review was taken in English data bases MEDLINE (Pubmed), Scopus, Cochlear library, using following keywords: “secondary hyperparathyroidism pathogenesis diagnosis treatment”, “tertiary hyperparathyroidism pathogenesis diagnosis treatment”, “development of tertiary hyperparathyroidism from secondary hyperparathyroidism”, “chronic vitamin D deficiency, hyperparathyroidism”, “early stages of chronic renal failure, hyperparathyroidism”. Also, search for the same keywords was completed in Russian data base Elibrary.Discussion. Both the lack of a common understanding of this problem, and the presence of diverse and contradictory data of the etiology and pathogenesis indicate the need for further study of tertiary hyperparathyroidism.

Bridging adults and paediatrics with secondary hyperparathyroidism receiving haemodialysis: a pharmacokinetic-pharmacodynamic analysis of cinacalcet

AIMS

The aims of this study were to develop a pharmacokinetic (PK) and PK-pharmacodynamic (PK/PD) model of cinacalcet in adults and paediatrics with secondary hyperparathyroidism (SHPT) on dialysis, to test covariates of interest, and to perform simulations to inform dosing in paediatrics with SHPT.

METHODS

Cinacalcet PK, intact parathyroid hormone (iPTH) and corrected calcium (cCa) time courses following multiple daily oral doses (1-300 mg) were modelled using a nonlinear mixed effects modelling approach using data from eight clinical studies. Model-based trial simulations, using adult or paediatric titration schemas, predicted efficacy (iPTH change from baseline and proportion achieving iPTH decrease ≥30%) and safety (cCa change from baseline and proportion achieving cCa ≤8.4 mg/dL) endpoints at 24 weeks.

RESULTS

Cinacalcet PK parameters were described by a two-compartment linear model with delayed first-order absorption-elimination (apparent clearance = 287.74 L h-1 ). Simulations suggested that paediatric starting doses (1, 2.5, 5, 10 and 15 mg) would provide PK exposures less than or similar to a 30 mg adult dose. The titrated dose simulations suggested that the mean (prediction interval) proportion of paediatric and adult subjects achieving ≥30% reduction in iPTH from baseline at Week 24 was 49% (36%, 62%), and 70.1% (62.5%, 77%), respectively. Additionally, the mean (confidence interval) proportion of paediatric and adult subjects achieving cCa ≤8.4 mg dL-1 at Week 24 was 8% (2%, 18%) and 23.6% (17.5%, 30.5%), respectively.

CONCLUSIONS

Model-based simulations showed that the paediatric cinacalcet starting dose (0.2 mg kg-1 ), titrated to effect, would provide the desired PD efficacy (PTH suppression <30%) while minimizing safety concerns (hypocalcaemia).

Predictors of cinacalcet discontinuation and reinitiation in hemodialysis patients: results from 7 European countries

Background

The putative benefits of cinacalcet therapy for management of secondary hyperparathyroidism (SHPT) are thought to be most manifested when patients are taking it consistently and as prescribed. Real-world descriptions of cinacalcet prescription discontinuation and reinitiation in European hemodialysis patients are lacking. To address this knowledge gap, we used Dialysis Outcomes and Practice Patterns Study (DOPPS) data, based on dialysis facility medical records, from seven European countries to estimate rates and predictors of cinacalcet prescription discontinuation and reinitiation in hemodialysis patients and to describe the trajectories of CKD-MBD laboratory values after discontinuation.

Methods

Cox regression analyses were used to predict (1) cinacalcet discontinuation among 613 patients with ≥3 consecutive months without cinacalcet prescription immediately prior to a new cinacalcet prescription and (2) cinacalcet reinitiation among 415 patients with a newly discontinued cinacalcet prescription immediately after ≥3 consecutive months of prescribed use.

Results

Cinacalcet was discontinued in 21 and 35% of new users after 6 and 12 months, respectively. Cinacalcet was reinitiated in 38 and 49% of newly-discontinued users after 6 and 12 months, respectively. Predictors of discontinuation included lower parathyroid hormone (PTH) in the previous month (< 150 pg/ml vs. 150–299, HR = 2.57 [95% CI: 1.52–4.33]) and lower serum calcium in the previous month (< 8.4 mg/dl vs. 8.4–10.19, HR = 1.67 [95% CI: 1.08–2.59]). Predictors of reinitiation included higher PTH in the previous month (300–599 pg/ml vs. 150–299, HR = 1.88 [95% CI = 1.19–2.97]; 600+ pg/ml, HR = 3.02 [95% CI = 1.92–4.76]). After cinacalcet discontinuation, mean serum PTH increased from 408 to 510 pg/ml, mean serum calcium briefly rose from 9.12 to 9.22 mg/dl before declining to 9.06 mg/dl, and mean serum phosphorus showed little change.

Conclusions

Nephrologist discontinuation of cinacalcet therapy is common in European countries. Additional research is needed to identify optimal cinacalcet treatment strategies for SHPT management, including comparisons of intermittent cinacalcet therapy versus sustained treatment with reduced dose or frequency.

Electronic supplementary material

The online version of this article (10.1186/s12882-019-1355-5) contains supplementary material, which is available to authorized users.

Plasma metabolite biomarkers related to secondary hyperparathyroidism and parathyroid hormone

BACKGROUND

Hyperphosphatemia, hypocalcemia, and elevation of parathyroid hormone (PTH) are typical abnormalities of uremic patients with Secondary hyperparathyroidism (SHPT). However, metabolic imbalance associated with SHPT is not well understood.

METHODS

A total of 15 SHPT patients with an intact parathyroid hormone (iPTH) level > 600 pg/mL were set as preoperative (PR) group, 15 age- and gender-matched controls who had undergone parathyroidectomy plus forearm transplantation because of hyperparathyroidism and achieved an iPTH level <150 pg/mL were set as postoperative (PO) group. Metabolite profiling of these 30 uremic patients and five healthy controls (HC) was performed using ultra performance liquid chromatography-mass spectrometry.

RESULTS

Five differential metabolites, including allyl isothiocyanate, L-phenylalanine, D-Aspartic acid, indoleacetaldehyde, and D-galactose correlated with PTH were identified in this study. Taking them as a biomarker signature, PR group can be distinguished from HC group with an area under the curve (AUC) of 0.947 (95% CI, 0.76-1) and PO group with an AUC of 0.6 (95% CI, 0.38-0.807).

CONCLUSIONS

The serum metabolome correlated with PTH is successfully demonstrated for a better understanding of the pathogenesis of SHPT.

An integrated analysis of safety and tolerability of etelcalcetide in patients receiving hemodialysis with secondary hyperparathyroidism

Background

Calcimimetics have been shown to be effective and safe therapies for the treatment of secondary hyperparathyroidism (sHPT), a serious complication of disordered mineral metabolism associated with dialysis-dependent chronic kidney disease. Etelcalcetide, a recently approved intravenous calcimimetic, reduces serum parathyroid hormone (PTH), calcium, phosphorus, and fibroblast growth factor-23 concentrations. Here we report the first integrated safety profile of etelcalcetide using pooled data from five pivotal clinical trials.

Methods

This analysis included data from patients receiving hemodialysis with moderate to severe sHPT enrolled in two randomized, placebo-controlled trials; a randomized active-controlled (with cinacalcet) trial; and two single-arm, open-label extension trials. Patients initially received etelcalcetide intravenously 5 mg three times weekly (TIW) after hemodialysis; with potential dose increases of 2.5 or 5 mg at 4-week intervals to a maximum dose of 15 mg TIW, depending on serum PTH and calcium levels. The nature, frequency, and severity of treatment-emergent adverse events (AEs) and changes in laboratory parameters were assessed.

Results

Overall, we evaluated 1023 patients from the placebo-controlled trials, 683 from the active-controlled trial, and 1299 from open-label extensions. The frequency and nature of common treatment-emergent AEs reported for the etelcalcetide arm were consistent among the placebo-controlled and active-controlled trials. The most common AEs were those related to mineral metabolism (decreased blood calcium, hypophosphatemia, muscle spasms) or gastrointestinal abnormalities (diarrhea, nausea, vomiting). Hypocalcemia leading to discontinuation of either calcimimetic was experienced in ≤ 1% of patients.

Conclusions

This integrated safety assessment of etelcalcetide across placebo- and active-controlled trials showed an overall favorable risk/benefit profile, with safety similar to that of cinacalcet. Consistent with its mechanism of action, the most important risks associated with etelcalcetide were serum calcium reductions and hypocalcemia-related AEs; no new safety findings were identified in the pooled long-term extension trials.

An open-label, single-dose study to evaluate the safety, tolerability, pharmacokinetics, and pharmacodynamics of cinacalcet in pediatric subjects aged 28 days to < 6 years with chronic kidney disease receiving dialysis

BACKGROUND

Calcimimetics, shown to control biochemical parameters of secondary hyperparathyroidism (SHPT), have well-established safety and pharmacokinetic profiles in adult end-stage renal disease subjects treated with dialysis; however, such studies are limited in pediatric subjects.

METHODS

In this study, the safety, tolerability, pharmacokinetics (PK), and pharmacodynamics (PD) of cinacalcet were evaluated in children with chronic kidney disease (CKD) and SHPT receiving dialysis. Twelve subjects received a single dose of cinacalcet (0.25 mg/kg) orally or by nasogastric or gastric tube. Subjects were randomized to one of two parathyroid hormone (PTH) and serum calcium sampling sequences: [(1) 2, 8, 48 h; or (2) 2, 12, 48 h] and assessed for 72 h after dosing.

RESULTS

Median plasma cinacalcet t_max was 1 h (range 0.5-4.0 h); mean (SD) C_max and AUC_last were 2.83 (1.98) ng/mL and 11.8 (8.74) h*ng/mL, respectively; mean (SD) half-life (t_1/2) was 3.70 (2.57) h. Dose adjustments, based upon body weight (mg/kg), minimized the effects of age, body weight, body surface area, and body mass index on cinacalcet PK. Reductions in serum PTH levels from baseline were observed at 2 to 8 h post-dose (median 10.8 and 29.6%, respectively), returned towards baseline by 12-72 h and were inversely related to changes in the plasma cinacalcet PK profile. Single-dose cinacalcet was well-tolerated with no unexpected safety findings and a PK/PD, safety profile similar to adults.

CONCLUSIONS

In conclusion, a single 0.25 mg/kg dose of cinacalcet was evaluated to be a safe starting dose in these children aged < 6 years.

Overview of the 2017 KDIGO CKD-MBD Update: Practice Implications for Adult Hemodialysis Patients

Renal dietitians play a pivotal role in the ongoing management of chronic kidney disease in patients on hemodialysis. Awareness of changes to clinical practice guidelines that may impact laboratory parameters associated with chronic kidney disease-mineral and bone disorder is important for optimal patient care. In this article, the Kidney Disease: Improving Global Outcomes 2017 Clinical Practice Guideline Update recommendations related to the treatment of secondary hyperparathyroidism in adults on hemodialysis are reviewed and treatment implications for renal dietitians discussed. Specific attention is given to the integration of updated recommendations such as the use of calcimimetics as part of a combination approach to the existing treatment paradigm. Renal dietitians can directly apply the updated clinical recommendations in the evaluation of diet composition; food additives; medication adherence challenges with phosphate binder type and use and serial monitoring of phosphorus, calcium, and parathyroid hormone levels to inform clinical decisions on treatment options for patients.

Interrelated role of Klotho and calcium-sensing receptor in parathyroid hormone synthesis and parathyroid hyperplasia

The pathogenesis of parathyroid gland hyperplasia is poorly understood, and a better understanding is essential if there is to be improvement over the current strategies for prevention and treatment of secondary hyperparathyroidism. Here we investigate the specific role of Klotho expressed in the parathyroid glands (PTGs) in mediating parathyroid hormone (PTH) and serum calcium homeostasis, as well as the potential interaction between calcium-sensing receptor (CaSR) and Klotho. We generated mouse strains with PTG-specific deletion of Klotho and CaSR and dual deletion of both genes. We show that ablating CaSR in the PTGs increases PTH synthesis, that Klotho has a pivotal role in suppressing PTH in the absence of CaSR, and that CaSR together with Klotho regulates PTH biosynthesis and PTG growth. We utilized the tdTomato gene in our mice to visualize and collect PTGs to reveal an inhibitory function of Klotho on PTG cell proliferation. Chronic hypocalcemia and ex vivo PTG culture demonstrated an independent role for Klotho in mediating PTH secretion. Moreover, we identify an interaction between PTG-expressed CaSR and Klotho. These findings reveal essential and interrelated functions for CaSR and Klotho during parathyroid hyperplasia.

Racial Variations in the Markers of Mineral Bone Disorders in CKD Patients in South Africa

Introduction

Several studies showed that serum intact parathyroid hormone (PTH), phosphate, and vitamin D levels differ across races. These comparative studies were largely carried out between Caucasians and black Americans. However, little is known of the existence of these associations in an African population with chronic kidney disease (CKD).

Methods

This cross-sectional multicenter study involved 293 CKD patients from 3 renal units in Johannesburg, South Africa.

Results

The 293 CKD patients (208 blacks, 85 whites) had an overall mean age of 51.1 ± 13.6 years, and black patients were significantly younger than the white patients (48.4 ± 13.6 years vs. 57.1 ± 15.5 years; P < 0.001). Compared with whites, blacks had higher median intact PTH (498 [range: 37–1084] pg/ml vs. 274 [range: 131–595] pg/ml; P = 0.03), alkaline phosphatase (122 [range: 89–192] U/L vs. 103 [range: 74–144] U/L; p = 0.03), and mean 25 OH vitamin D₃ (26.8 ± 12.7 ng/ml vs. 22.7 ± 12.2 ng/ml, P = 0.01) levels, whereas their median fibroblast growth factor (FGF) level was 23 (100 [range: 34–639] pg/ml vs. 233 [range: 80–1370] pg/ml; P = 0.002), and their mean serum phosphate (1.3 ± 0.5 vs. 1.5 ± 0.5; P = 0.001) levels were significantly lower. In multivariable analyses, black race was independently associated with increased log PTH (β = 0.488, P = 0.01) and decreased log FGF-23 (β = −0.636, P = 0.02). Similarly, blacks had a 3.08 times higher likelihood (95% confidence interval: 1.51–6.30; P = 0.002) of developing severe hyperparathyroidism than whites.

Conclusion

This study highlighted the existence of racial differences in the circulating markers of mineral bone disorders in an African CKD population.

Effect of Cinacalcet Combined with Calcitriol on the Clinical Outcome and Bone Metabolism in Patients on Hemodialysis with Severe Secondary Hyperparathyroidism

Objective: To observe the clinical outcome and the effect of bone metabolism of cinacalcet combined with calcitriol in maintenance hemodialysis (MHD) patients with severe secondary hyperparathyroidism (SHPT). Methods: Thirty MHD patients with SHPT were enrolled into the study. All patients were given cinacalcet 25–75 mg and 0.5 μg calcitriol daily. Serum Ca, P, intact parathyroid hormone (iPTH), and bone metabolic markers were measured. The clinical symptoms and their changes were investigated. Results: The baseline levels of iPTH, Ca, and P were 1,787.3 ± 1,321 pg/mL, 2.54 ± 0.19 mmol/L, and 2.06 ± 0.15 mmol/L respectively. After 3 months treatment, iPTH decreased by 70%. Serum Ca and P fell to 2.39 ± 0.17 and 1.56 ± 0.50 mmol/L (p < 0.05), respectively. After 6 months, the bone-specific alkaline phosphatase, osteocalcin, and β-cross levels were decreased by 50, 37, and 49% respectively compared with corresponding values before treatment. A decline in the bone density patients was inhibited. Conclusion: Cinacalcet combined with low dose calcitriol can improve high calcium, high phosphorus, and high iPTH in MHD patients with severe SHPT and also improve bone metabolism. It can be used as a favorable choice for SHPT treatment.

Treatment of secondary hyperparathyroidism: the clinical utility of etelcalcetide

Secondary hyperparathyroidism (SHPT), a very frequent, severe, and worsening complication of chronic kidney disease, is characterized by high serum parathyroid hormone (PTH), parathyroid gland hyperplasia, and disturbances in mineral metabolism. Clinically, SHPT shows renal osteodystrophy, vascular calcification, cardiovascular damage, and fatal outcome. Calcium-sensing receptor (CaSR) is the main physiological regulator of PTH secretion; its activation by calcium rapidly inhibits PTH. Another important player in regulating mineral metabolism is vitamin D receptor (VDR), which is under the influence of vitamin D and influences the intestinal absorption of calcium and phosphate, PTH gene expression, and bone calcium mobilization. Serum phosphate levels influence fibroblast growth factor 23 (FGF-23) production, a phosphatonin that modulates serum phosphate reabsorption, PTH synthesis, and vitamin D production. Current therapeutic approaches consist of 1) phosphate intake control by diet or phosphate binders, 2) vitamin D by VDR activation, and 3) calcimimetic agents that activate CaSR. Recently, a new long-acting peptide (etelcalcetide) belonging to the calcimimetics class was approved for intravenous use in hemodialysis patients with SHPT. Etelcalcetide binds directly to CaSR, by a sulfide bond, inhibiting the production and secretion of PTH by parathyroid glands. After intravenous administration in rats, etelcalcetide is quickly distributed to the tissues and eliminated by kidneys, while in uremic animals the nonrenal excretion is only 1.2%. In hemodialysis patients, the treatment itself is the main route of elimination. Etelcalcetide in hemodialysis patients with SHPT was more effective than placebo and cinacalcet, with a PTH reduction of >30% in 76% of patients with etelcalcetide versus 10% with placebo. Particular attention was paid to the safety of the drug; the most common adverse event was asymptomatic blood calcium reduction, similar to cinacalcet, while gastrointestinal symptoms were less frequent. This promising new drug available for better control of SHPT will, together with drugs already in use, optimize the treatment to normalize the biochemical parameters.

Tradeoff-in-the-Nephron: A Theory to Explain the Primacy of Phosphate in the Pathogenesis of Secondary Hyperparathyroidism

Chronic kidney disease (CKD) causes secondary hyperparathyroidism (SHPT). The cardinal features of SHPT are persistence of normocalcemia as CKD progresses and dependence of the parathyroid hormone concentration ([PTH]) on phosphate influx (IP). The tradeoff-in-the-nephron hypothesis integrates these features. It states that as the glomerular filtration rate (GFR) falls, the phosphate concentration ([P]CDN) rises in the cortical distal nephron, the calcium concentration ([Ca]CDN) in that segment falls, and [PTH] rises to maintain normal calcium reabsorption per volume of filtrate (TRCa/GFR). In a clinical study, we set GFR equal to creatinine clearance (Ccr) and IP equal to the urinary excretion rate of phosphorus (EP). We employed EP/Ccr as a surrogate for [P]CDN. We showed that TRCa/Ccr was high in patients with primary hyperparathyroidism (PHPT) and normal in those with SHPT despite comparably increased [PTH] in each group. In subjects with SHPT, we examined regressions of [PTH] on EP/Ccr before and after treatment with sevelamer carbonate or a placebo. All regressions were significant, and ∆[PTH] correlated with ∆EP/Ccr in each treatment cohort. We concluded that [P]CDN determines [PTH] in CKD. This inference explains the cardinal features of SHPT, much of the evidence on which other pathogenic theories are based, and many ancillary observations.

Associations of parathyroid hormone levels and mineral parameters with heart rate variability in patients with end-stage renal disease

PURPOSE

Parathormone (PTH) is a very potent uraemic toxin, which affects calcium/phosphate homeostasis in patients with end-stage renal disease (ESRD). It also plays the role in uraemic autonomic neuropathy. The aim of the study was to investigate the relationship between elevated PTH levels and cardiac autonomic neuropathy assessed by frequency-domain measures of heart rate variability.

METHODS

24-h ECG was performed in 106 ESRD patients and 65 healthy controls. Very-low-frequency (VLF), low-frequency (LF) and high-frequency (HF) bands were computed. LF/HF ratio was calculated.

RESULTS

We found that most heart rate variability indices were lower in ESRD patients than in healthy controls. Variables including demographics (age, sex, body mass index, dialysis vintage, systolic pressure, and diastolic pressure), laboratory values (Hb, Hct, glucose, Alb, and triglyceride), and bone metabolism panel (Ca, P, ALP, and iPTH) were selected as independent variables in the multivariable models. In multivariate analysis, serum intact PTH (iPTH) was correlated with mean normal-to-normal R-R intervals, mean heart rate, and VLF, serum calcium was correlated with standard deviation of 5-min average of normal R-R intervals (SDANN), and serum phosphorus was correlated with VLF and LF/HF. Serum iPTH was independently correlated with mean normal-to-normal R-R intervals (NN), mean HR, and VLF. Serum Ca was independently correlated with SDANN, and serum P was independently correlated with VLF and LF/HF. The results remained significant after the adjustment for iPTH.

CONCLUSIONS

In conclusion, high PTH levels and disorders of mineral metabolism are associated with decreased heart rate variability in ESRD patients.

Association of Beta-2 Microglobulin with Inflammation and Dislipidemia in High-Flux Membrane Hemodialysis Patients

BACKGROUND

Higher than expected cardiovascular mortality in hemodialysis patients, has been attributed to dyslipidemia as well as inflammation. Beta2-Microglobulin (β2M) is an independent predictor of outcome for hemodialysis patients and a representative substance of middle molecules.

RESULTS

In 40 patients in high-flux membrane hemodialysis, we found negative correlation of β2M with high density lipoprotein (r=-0.73, p<0.001) and albumin (r= -0.53, p<0.001) and positive correlation with triglycerides (r=0.69, p<0.001), parathyroid hormone (r=0.58, p < 0.05) and phosphorus (r= 0.53, p<0.001). There was no correlation of β2M with C- reactive protein (CRP) and interleukin-6 (IL-6). During the follow-up period of three years, 6 out of 40 patients have died from cardiovascular events.

CONCLUSION

In high-flux membrane hemodialysis patients, we observed a significant relationship of β2M with dyslipidemia and mineral bone disorders, but there was no correlation with inflammation.

Lanthanum carbonate oral powder: satisfaction, preference and adherence in French and Spanish patients with end-stage renal disease

BACKGROUND

Phosphate binders, such as lanthanum carbonate, control elevated serum-phosphate levels in patients with end-stage renal disease (ESRD). Lanthanum carbonate is available in oral powder and tablet form. The aim of this survey was to investigate satisfaction with, preference for, and adherence to lanthanum carbonate oral powder in patients with ESRD.

SCOPE

Patients from France and Spain who had been taking lanthanum carbonate powder for at least 4 weeks, and who had experience of other phosphate binders of any formulation, were asked to complete an online or telephone survey. Treatment satisfaction was measured using the Treatment Satisfaction Questionnaire for Medication-9; preference was measured using 5-point Likert scale agreement ratings; and adherence was measured using the Morisky Medication Adherence Scale-4. Data were evaluated using bivariate analyses.

FINDINGS

Overall, 160 patients participated (80 per country). Lanthanum carbonate powder was reported to have a higher effectiveness rating (p<0.05), be more convenient (p<0.05), and provide a higher level of satisfaction (p<0.01) than previous binders. There was an overall preference for lanthanum carbonate powder over previous binders of any formulation (p<0.001). Adherence to medication was similar for all binders analysed: 66.3% of French patients adhered to lanthanum carbonate powder, and 65.0% adhered to previous binder treatment (p=not significant); 52.5% of Spanish patients adhered to lanthanum carbonate powder, and 56.3% adhered to previous binder treatment (p=not significant).

LIMITATIONS

The survey enrolled patients who had already experienced phosphate binders before the study began. Information on patient preferences for and adherence to previous phosphate binders was therefore based on the patients' memories of these experiences, which may have been subject to change over time. Although most participants completed the online survey in this study, a telephone survey was used for individuals who could not access the online version; if only one method of data recording had been used, there may have been reduced variation in responses.

CONCLUSION

Patients with ESRD report increased satisfaction with and preference for lanthanum carbonate powder over other formulations, suggesting that lanthanum carbonate powder is more convenient and easier to use than other formulations.

Chronic Kidney Disease-Mineral and Bone Disorders (CKD-MBDs): What the Endocrinologist Needs to Know

OBJECTIVE

Chronic kidney disease-mineral and bone disorders (CKD-MBDs) are a spectrum of abnormalities involving skeletal hormones, minerals, and bone turnover and mineralization. This paper focuses on what the endocrinologist should know about the assessment and management of skeletal and metabolic disorders in CKD-MBDs.

METHODS

Relevant literature was reviewed to (1) define disturbances of minerals and hormones in the course of CKD; (2) identify the variable radiographic and histomorphometric changes of CKD-MBDs; (3) review the association among CKD-MBDs, vascular calcification, cardiovascular disease (CVD), and mortality; and (4) clarify issues in CKD-MBDs therapy.

RESULTS

Assessment and treatment of CKD-MBDs is complicated by progressive changes in bone minerals and skeletal regulatory hormones as kidney function declines. CKD-MBDs are associated with fracture risk, and studies demonstrate that bone mineral density can be used to assess bone loss and fracture risk in these patients. Treatment of CKD-MBDs continues to evolve. Use of calcium, phosphate binders, vitamin D, vitamin D-receptor analogs, and drugs for osteoporosis and CKD-MBDs treatment are discussed in the context of safety and efficacy for patients with CKD.

CONCLUSION

The association of CKD with bone disease, vascular calcification, CVD, and mortality mandates earlier recognition and treatment of CKD-MBDs. Osteoporosis as a distinct entity can be diagnosed and managed in CKD, although assessment of osteoporosis becomes challenging in late (stage 4 to 5) CKD. Diabetes is common in early (stage 1 to 3) CKD. In addition, 96% of all individuals identified as having CKD have early CKD. The endocrinologist is uniquely positioned to address and treat both diabetes and many of the metabolic and skeletal disorders associated with early CKD-MBDs, including osteoporosis.

Risk factors associated with secondary hyperparathyroidism in patients with chronic kidney disease

Secondary hyperparathyroidism (SHPT) is common in patients with chronic kidney disease (CKD), and its development and progression are affected by various factors. The aim of the present study was to identify the risk factors for SHPT in patients with CKD. A retrospective study was performed in 498 patients (305 males and 193 females) with CKD, observed in the The First Hospital of Jilin University between January 2008 and December 2012. The demographic, clinical and laboratory data were collected. Patients were divided into the SHPT group (n=424) with elevated serum parathyroid hormone (PTH) expression levels and the control group (n=74) with normal serum PTH expression levels. Univariate and multivariate regression analyses were employed to explore the risk factors for SHPT. Serum PTH expression levels in women with CKD were significantly higher than in men (P=0.047). Serum PTH expression levels were positively correlated with the expression levels of serum creatinine (P<0.01), phosphorus (P<0.01), C-reactive protein (P<0.05), triglyceride (P<0.05), cholesterol (P<0.05) and low-density lipoprotein cholesterol (P<0.05), but were negatively correlated with the expression levels of hemoglobin (P<0.05), calcium (P<0.01) and CO₂ combining power (P<0.01) in patients with CKD. Multivariate analysis showed that the serum expression levels of creatinine [µmol/l; odds radio (OR), 1.003; 95% confidence interval (CI), 1.002-1.004; P=0.001] and phosphorus (mmol/l; OR, 2.19; 95% CI, 1.254-3.826; P=0.006) in patients with CKD significantly influenced serum PTH expression levels. The SHPT risk factors include female gender, low calcium, high phosphorus, acidosis, anemia, hypertension, hyperlipidemia and micro-inflammation, with blood phosphorus and creatinine being independent risk factors.

A Prospective Cohort Study of Mineral Metabolism After Kidney Transplantation

Kidney transplantation corrects or improves many complications of chronic kidney disease, but its impact on disordered mineral metabolism is incompletely understood.

The prevalence of posttransplant hyperparathyroidism was 86% at 12 months (PTH >65 pg/ml) but only 40% (PTH >130 mg/dL) in the absence of cinacalcet, vitamin D sterols, or parathyroidectomy. Intact fibroblast growth factor 23 decreased rapidly to G40 pg/ml by 3 months posttransplant. Supplemental digital content is available in the text.