Surgical treatment of secondary hyperparathyroidism in children with chronic kidney disease. Experience in 19 patients

OBJECTIVES

Secondary hyperparathyroidism (sHPT) is an important contributor to bone disease and cardiovascular calcifications in children with chronic kidney disease (CKD). When conservative measures are ineffective, parathyroidectomy is indicated. The aim of our study was to evaluate the efficacy and safety of subtotal parathyroidectomy (sPTX) in pediatric and adolescent patients, and to provide a rationale for considering this aggressive treatment in CKD patients with uncontrolled sHPT.

METHODS

We retrospectively analyzed the medical records of 19 pediatric CKD patients on dialysis with refractory sHPT who underwent sPTX at our institution between 2010 and 2020. All patients had clinical, radiological, and biochemical signs of renal osteodystrophy.

RESULTS

One year after sPTX, parathyroid hormone (PTH) levels (median and interquartile range (IQR)) dropped from 2073 (1339-2484) to 164 (93-252) pg/mL (p=0.0001), alkaline phosphatase (ALP) levels from 1166 (764-2373) to 410 (126-421) IU/L (p=0.002), and the mean (±SDS) calcium-phosphate (Ca*P) product from 51±11 to 41±13 mg2/dL2 (p=0.07). Postoperatively, all patients presented with severe hungry bone syndrome (HBS) and required intravenous and oral calcium and calcitriol supplementation. None of them had other postoperative complication. Histological findings had a good correlation with preoperative parathyroid ultrasound imaging (n: 15) in 100 % and with technetium-99m (99mTc) sestamibi scintigraphy (n: 15) in 86.6 %. Clinical and radiological signs of bone disease improved in all patients.

CONCLUSIONS

Pediatric sPTX is effective and safe to control sHPT and calcium-phosphate metabolism in children with CKD on dialysis and may mitigate irreversible bone deformities and progression of cardiovascular disease.

Diagnosis and management of mineral and bone disorders in infants with CKD: clinical practice points from the ESPN CKD-MBD and Dialysis working groups and the Pediatric Renal Nutrition Taskforce

BACKGROUND

Infants with chronic kidney disease (CKD) form a vulnerable population who are highly prone to mineral and bone disorders (MBD) including biochemical abnormalities, growth retardation, bone deformities, and fractures. We present a position paper on the diagnosis and management of CKD-MBD in infants based on available evidence and the opinion of experts from the European Society for Paediatric Nephrology (ESPN) CKD-MBD and Dialysis working groups and the Pediatric Renal Nutrition Taskforce.

METHODS

PICO (Patient, Intervention, Comparator, Outcomes) questions were generated, and relevant literature searches performed covering a population of infants below 2 years of age with CKD stages 2-5 or on dialysis. Clinical practice points (CPPs) were developed and leveled using the American Academy of Pediatrics grading matrix. A Delphi consensus approach was followed.

RESULTS

We present 34 CPPs for diagnosis and management of CKD-MBD in infants, including dietary control of calcium and phosphate, and medications to prevent and treat CKD-MBD (native and active vitamin D, calcium supplementation, phosphate binders).

CONCLUSION

As there are few high-quality studies in this field, the strength of most statements is weak to moderate, and may need to be adapted to individual patient needs by the treating physician. Research recommendations to study key outcome measures in this unique population are suggested. A higher resolution version of the Graphical abstract is available as Supplementary information.

Phase 1, single-dose study to assess the safety, tolerability, pharmacokinetics, and pharmacodynamics of etelcalcetide in pediatric patients with secondary hyperparathyroidism receiving hemodialysis

BACKGROUND

Data on the safety, efficacy of etelcalcetide in children with secondary hyperparathyroidism (sHPT) are limited.

METHODS

This phase 1 study (NCT02833857) evaluated the safety, tolerability, pharmacokinetics (PK), pharmacodynamics (PD) of single-dose etelcalcetide (0.035 mg/kg intravenously) in pediatric hemodialysis patients (two cohorts; 1: 12-< 18 years; 2: 2-< 12 years). Treatment-emergent adverse events (AEs), PK/PD were assessed post-dose on D1 at 10 min and 4 h, on multiple days until D10, and at end of study (D30).

RESULTS

Etelcalcetide administered to 11 patients (mean [SD] age 10.3 [4.3] years; cohort 1, n = 6; cohort 2, n = 5) was well tolerated. AEs were consistent with established safety profiles in adults. Two patients (1 per cohort) reported treatment-related AEs (cohort 1: hypocalcemia; cohort 2: headache, paresthesia, vomiting). No serious AEs or deaths were reported. Mean serum corrected calcium (cCa) for all patients was maintained > 2.25 mmol/L. After etelcalcetide dosing, PK exposures declined, with mean C_max, AUC_last, and AUC_inf exposures higher in cohort 1. Median percent change in serum intact parathyroid hormone (iPTH) from baseline (cohort 1: 51.2 pmol/L; cohort 2: 84.0 pmol/L) reached the nadir on D1 at 4 h (cohort 1: - 33.4%; cohort 2: - 64.2%). Mean total calcium and cCa reached nadirs on D3 at 2.39 mmol/L, and ionized Ca on D1 at 4 h.

CONCLUSIONS

Single-dose etelcalcetide (0.035 mg/kg) was well tolerated with expected PK and safety profiles. Overall pattern of changes in serum iPTH and serum calcium was similar between cohorts and consistent with expected responses to etelcalcetide.

Cinacalcet use in paediatric dialysis: a position statement from the European Society for Paediatric Nephrology and the Chronic Kidney Disease-Mineral and Bone Disorders Working Group of the ERA-EDTA

Secondary hyperparathyroidism (SHPT) is an important complication of advanced chronic kidney disease (CKD) in children, which is often difficult to treat with conventional therapy. The calcimimetic cinacalcet is an allosteric modulator of the calcium-sensing receptor. It has proven to be effective and safe in adults to suppress parathyroid hormone (PTH), but data on its use in children are limited. To date, studies in children only consist of two randomized controlled trials, nine uncontrolled interventional or observational studies, and case reports that report the efficacy of cinacalcet as a PTH-lowering compound. In 2017, the European Medical Agency approved the use of cinacalcet for the treatment of SHPT in children on dialysis in whom SHPT is not adequately controlled with standard therapy. Since evidence-based guidelines are so far lacking, we present a position statement on the use of cinacalcet in paediatric dialysis patients based on the available evidence and opinion of experts from the European Society for Paediatric Nephrology, Chronic Kidney Disease-Mineral and Bone Disorder and Dialysis Working Groups, and the ERA-EDTA. Given the limited available evidence the strength of these statements are weak to moderate, and must be carefully considered by the treating physician and adapted to individual patient needs as appropriate. Audit and research recommendations to study key outcome measures in paediatric dialysis patients receiving cinacalcet are suggested.

Pathogenesis and treatment of electrolyte problems post transplant

PURPOSE OF REVIEW

Electrolyte abnormalities posttransplant are common occurrences that can have significant short-term and long-term effects on graft outcome and patient quality of life. Understanding the pathophysiology of these electrolyte derangements can help guide management to optimize bone health and minimize cardiovascular disease. This review explores the pathogenesis of the most common postrenal transplant electrolytes abnormalities as well as current treatment options.

RECENT FINDINGS

Clarifications of the role of FGF-23 has improved our understanding of posttransplant bone disease in addition to the known roles of hyperparathyroidism and vitamin D. The mechanisms of renal electrolyte wasting by immunosuppressive agents give insight into potential treatment options for hyperkalemia and hypomagnesemia.

SUMMARY

Understanding the pathogenesis of the common electrolyte abnormalities found post renal transplant may lead to targeted treatment options that in turn may improve transplant complications. Further studies are required to evaluate the effects on long-term outcomes of renal allografts.

Cinacalcet ameliorates aortic calcification in uremic rats via suppression of endothelial-to-mesenchymal transition

AIM

Experimental studies found that cinacalcet (CINA) markedly attenuated vascular calcification in uremic rats, but its underlying mechanisms are still largely unknown. Recent evidence have demonstrated that endothelial cells (ECs) participate in ectopic calcification in part by mediating endothelial-to-mesenchymal transition (EndMT). In this study, we investigated whether CINA ameliorated aortic calcification in uremic rats via suppression of EndMT.

METHODS

Uremia was induced in rats by feeding rats a 0.75% adenine diet for 4 weeks. After adenine withdrawal, the rats were maintained on a 1.03% phosphorus diet for next 8 weeks. At initiation of the adenine diet, rats were orally administered CINA (10mg/kg one day) for 12 weeks. The aortic expression of EndMT- and chondrocyte- markers was examined. The effect of elevated PTH on EndMT was also studied in aortic ECs.

RESULTS

In uremic rats, CINA treatment significantly decreased the serum PTH concentrations, but did not affect the elevated levels of serum calcium (Ca), phosphorus (P) and Ca×P product. Besides, CINA significantly attenuated aortic calcification, and inhibited the expression of chondrocyte markers (SOX9 and COL2A1) and chondrocyte proteoglycan in uremic aortas. Moreover, CINA treatment largely abolished the up-regulation of mesenchymal markers (FSP1 and α-SMA) and down-regulation of the endothelial marker (CD31), which accompanied aortic calcification in uremic aorta samples. In vitro, PTH increased the expression of EndMT-markers in a concentration- and time-dependent manner.

CONCLUSION

These findings suggest that strategies aiming at reducing serum PTH might prevent uremic aortic calcification by abrogating EndMT.

[Surgical treatment of secondary hyperparathyroidism: a systematic review of the literature]

Secondary hyperparathyroidism (HPT) has a high prevalence in renal patients. Secondary HPT results from disturbances in mineral homeostasis, particularly calcium, which stimulates the parathyroid glands, increasing the secretion of parathyroid hormone (PTH). Prolonged stimulation can lead to autonomy in parathyroid function. Initial treatment is clinical, but parathyroidectomy (PTx) may be required. PTx can be subtotal or total followed or not followed by parathyroid tissue autograft. We compared the indications and results of these strategies as shown in the literature through a systematic literature review on surgical treatment of secondary HPT presented in MedLine and LILACS from January 2008 to March 2014. The search terms were: hyperparathyroidism; secondary hyperparathyroidism; parathyroidectomy and parathyroid glands, restricted to research only in humans, articles available in electronic media, published in Portuguese, Spanish, English or French. We selected 49 articles. Subtotal and total PTx followed by parathyroid tissue autograft were the most used techniques, without consensus on the most effective surgical procedure, although there was a preference for the latter. The choice depends on surgeon's experience. There was consensus on the need to identify all parathyroid glands and cryopreservation of parathyroid tissue whenever possible to graft if hypoparathyroidism arise. Imaging studies may be useful, especially in recurrences. Alternative treatments of secondary HPT, both interventional and conservative, require further study.

Severe secondary hyperparathyroidism and panoramic radiography parameters

OBJECTIVES

Renal osteodystrophy (RO) are skeletal abnormalities seen in patients with secondary hyperparathyroidism (SHPT). This study aims to evaluate the effects of RO using panoramic radiography parameters. Furthermore, the correlation between these parameters and parathyroid hormone (PTH) levels was tested.

MATERIALS AND METHODS

Qualitative (mandibular cortical index/trabecular bone pattern) and quantitative parameters (mental index/calcification and resorption foci) were applied from panoramic radiographs of chronic kidney disease (CKD) patients and controls. Frequency distribution and descriptive analysis were used to compare the results of both groups. Spearman's correlation coefficient evaluated the correlation between serum PTH levels of CKD patients and the radiographic parameters. Intra- and interobserver agreement was tested using the intraclass correlation coefficient and kappa index.

RESULTS

Intra- and interobserver agreement was respectively excellent (0.81-1.00) and good (0.61-0.80). Qualitative parameters demonstrate significant difference compared with the control group. Mean mental index was lower in patients with CKD (3.17 ± 1.35 mm), but the difference was not significant. Calcification/resorption foci (3.63 ± 2.07) of CKD patients were significantly more present than in the control group (p = 0.0001). PTH levels were correlated with mental index, mandibular cortical index and trabecular bone pattern (respectively, 0.0034, 0.0315, and 0.0370).

CONCLUSIONS

RO presented a number of characteristic bone metabolic effects in the jaws that could be observed on panoramic radiographs. Radiographs of CKD patients demonstrate significantly more calcification and resorption.

CLINICAL RELEVANCE

The mental index, mandibular cortical index, and trabecular bone pattern are good parameters for evaluating the effects of RO on severe secondary hyperparathyroidism.

Parathyroid hormone levels in long-term renal transplant children and adolescents

Secondary hyperparathyroidism is a common complication of chronic renal failure. Kidney transplantation corrects renal insufficiency and most metabolic abnormalities but hyperparathyroidism persists in 50% of children after transplantation. The aim of this study was to investigate parathyroid hormone (PTH) course and potential risk factors for hyperparathyroidism in children after renal transplant. We collected data from 145 transplanted children (mean follow-up 4.7 years). Intact PTH level (iPTH) rapidly decreased in the first 6 months post-transplant and continued to decline in the following years. iPTH was above the normal range in 69.1% of the patients at the time of transplant and in 47% 1 year later, this improvement continuing thereafter. Hypercalcemia was present in 20.3% of the patients before transplant and in 6.3 and 4.1% of patients 6 months and 1 year after transplant, respectively. Hypophosphatemia was present in 5.5% of the patients at 6 months, and 45.5% of the patients needed phosphorus supplements during the first 6 months after transplant. Multivariate analysis indicated pre-transplant hyperparathyroidism, dialysis duration, creatinine clearance and hypophosphatemia as predictors of persistent hyperparathyroidism. In kidney transplanted children, serum iPTH normalized in the long term in the majority of cases. Thus, parathyroidectomy should be reserved for selected patients.

Mineral and bone disorders in children with chronic kidney disease

As children with chronic kidney disease (CKD) have a long lifespan, optimal control of bone and mineral homeostasis is essential not only for the prevention of debilitating skeletal complications and for achieving adequate growth but also for preserving long-term cardiovascular health. As the growing skeleton is highly dynamic and at particular risk of deterioration, close control of bone and mineral homeostasis is required in children with CKD. However, assessment of bone disease is hampered by the limited validity of biochemical parameters-major controversy exists on key issues such as parathyroid hormone target ranges and the lack of useful imaging techniques. The role of newly discovered factors in bone and mineral homeostasis, such as fibroblast growth factor 23, is not yet established. Even though scientific evidence is limited in children with CKD, ergocalciferol or cholecalciferol supplementation and the use of calcium-free phosphate binders is recommended. The new drug cinacalcet is highly promising; however, pediatric experience is still limited to observational data and the effect of cinacalcet on longitudinal growth and pubertal development is unknown. Randomized, controlled trials are underway, including studies of cinacalcet pharmacokinetics and pharmacodynamics in infants.

Uraemic vasculopathy in children with chronic kidney disease: prevention or damage limitation?

Since the inception of pediatric dialysis programmes nearly 50 years ago, there have been vast improvements in both the technology and expertise in the care of children with chronic kidney disease (CKD). Nevertheless, children on dialysis continue to have a significantly higher mortality than their healthy peers and cardiovascular disease (CVD) is the most common cause of death in this group. Chronic kidney disease is described as the "perfect storm" of risk factors for CVD development, and vascular calcification is a highly regulated cell-mediated process with several promoters and inhibitors of calcification. CVD begins early in the course of CKD and there is an independent and graded association between cardiovascular morbidity and renal decline. Also, it is shown that once vascular damage and calcification begin, they progress inexorably in the uraemic milieu and may only be partially reversed after successful transplantation. Thus, preventing the development of CVD is key, and early identification and management of specific CVD-related risk factors should begin from the early stages of CKD. While the vasculopathy of childhood CKD is clearly multifactorial, clinical, epidemiological and cell biology studies provide converging evidence pointing to the role of dysregulated mineral metabolism as an important modifiable risk factor in the development of vascular calcification. In this review we focus on the role of calcium, phosphate, parathyroid hormone and vitamin D in ectopic vascular calcification, and discuss the role of screening, early intervention and management of established vascular calcification.

Molecular regulation of phosphate metabolism by fibroblast growth factor-23-klotho system

Phosphorus is an essential nutrient and is routinely assimilated through consumption of food. The body's need of phosphate is usually fulfilled by intestinal absorption of this element from the consumed food, whereas its serum level is tightly regulated by renal excretion or reabsorption. Sodium-dependent phosphate transporters, located in the luminal side of the proximal tubular epithelial cells, have a molecular control on renal phosphate excretion and reabsorption. The systemic regulation of phosphate metabolism is a complex multiorgan process, and the identification of fibroblast growth factor-23 (FGF23)-Klotho system as a potent phosphatonin has provided new mechanistic insights into the homeostatic control of phosphate. Hypophosphatemia as a result of an increase in urinary phosphate wasting after activation of the FGF23-Klotho system is a common phenomenon, observed in both animal and human studies, whereas suppression of the FGF23-Klotho system leads to the development of hyperphosphatemia. This article will briefly summarize how delicate interactions of the FGF23-klotho system can regulate systemic phosphate homeostasis.