Parathyroid hormone and growth in children with chronic renal failure

Tumor necrosis factor-alpha is associated with mineral bone disorder and growth impairment in children with chronic kidney disease

BACKGROUND

Mineral and bone disorder (MBD) and growth impairment are common complications of pediatric chronic kidney disease (CKD). Chronic inflammation detrimentally affects bone health and statural growth in non-CKD settings, but the impact of inflammation on CKD-MBD and growth in pediatric CKD remains poorly understood. This study assessed associations between inflammatory cytokines with biomarkers of CKD-MBD and statural growth in pediatric CKD.

METHODS

This is a cross-sectional study of children with predialysis CKD stages II-V. Cytokines (IL-1b, IL-4, IL-6, IL-8, IL-10, IL-12, IL-13, TNF-α, interferon-γ), bone alkaline phosphatase (BAP), and procollagen type 1 N-terminal propeptide (P1NP) were measured at the same time as standard CKD-MBD biomarkers. Associations between cytokines, CKD-MBD biomarkers, and height z-score were assessed using linear regression analysis.

RESULTS

Among 63 children, 52.4% had stage 3 CKD, 76.2% non-glomerular CKD etiology, and 21% short stature. TNF-α was the only cytokine associated with parathyroid hormone (PTH) independent of glomerular filtration rate. After stratification by low, medium, and high TNF-α tertiles, significant differences in PTH, serum phosphorus, alkaline phosphatase, BAP, P1NP, and height z-score were found. In a multivariate analysis, TNF-α positively associated with phosphorus, PTH, and alkaline phosphatase and inversely associated with height z-score, independent of kidney function, age, sex, and active vitamin D analogue use.

CONCLUSIONS

TNF-α is positively associated with biomarkers of CKD-MBD and inversely associated with height z-score, indicating that inflammation likely contributes to the development of CKD-MBD and growth impairment in pediatric CKD. Prospective studies to definitively assess causative effects of inflammation on bone health and growth in children with CKD are warranted.

Twenty years of growth hormone treatment in dialyzed children in Poland-Results of national multicenter study

PURPOSE

The aim of the study was to analyze the effect of recombinant human growth hormone (rhGH) therapy and to establish factors influencing growth rate in dialyzed children in Poland.

METHODS

We retrospectively analyzed medical records of 81 children with end-stage renal disease (ESRD) on chronic dialysis treated with rhGH for ≥12 months between 1994 and 2014. The following data were recorded: cause of ESRD, dialysis modality, age at the dialysis and rhGH initiation [years]. In addition, growth [cm], [standard deviation score - SDS], body mass index [SDS], skeletal age [years], bone mineral density [SDS], hemoglobin, total protein, albumin, urea, creatinine, calcium, phosphorus, calcium phosphorus product, PTH, and alkaline phosphatase were measured at the baseline and after 12 months.

RESULTS

Growth velocity in 81 children during one-year rhGH treatment was 7.33 ± 2.63 cm (ΔSDS 0.36 ± 0.43). Height SDS increased significantly (-3.31 ± 1.12 vs. -2.94 ± 1.15, p < 0.001). Children on peritoneal dialysis (PD) (n = 51) were younger than children on hemodialysis (HD) (n = 30) (9.92 ± 3.72 vs. 12.32 ± 3.11 years, p = 0.003). ΔSDS did not differ between PD and HD children (0.40 ± 0.33 vs. 0.30 ± 0.47, p = 0.311). Growth velocity (ΔSDS) correlated with age at dialysis initiation (r=-0.30, p = 0.009), age at rhGH treatment initiation (r=-0.35, p = 0.002), skeletal age (r=-0.36, p = 0.002), BMI SDS (r=-0.27, p = 0.019), and PTH (r=-0.27, p = 0.017). No correlation between growth velocity and other parameters was observed.

CONCLUSIONS

Treatment with rhGH in children with ESRD is effective and safe irrespective of dialysis modality. Early initiation of rhGH therapy is a crucial factor determining response to the treatment in children with ESRD.

RANKL/OPG system regulation by endogenous PTH and PTH1R/ATF4 axis in bone: Implications for bone accrual and strength in growing rats with mild uremia

Osteoprotegerin (OPG), receptor activator of NF-κB ligand (RANKL), and parathyroid hormone (PTH) play a central role in the regulation of bone turnover in chronic kidney disease (CKD), but their influence on bone mineral density (BMD) and strength remains unclear, particularly in children. We studied the clinical significance of OPG and RANKL in relation to PTH, femur weight, BMD, and bone biomechanical properties in growing rats after one month (CKD-1) and three months (CKD-3) of surgically-induced mild CKD. Gene expression of parathyroid hormone 1 receptor (PTH1R) and activating transcription factor 4 (ATF4), major regulators of anabolic PTH response in bone, was also determined. Serum PTH and bone PTH1R/ATF4 expression was elevated in CKD-3 compared with other groups, and it positively correlated with femur weight, BMD, and the biomechanical properties of the femoral diaphysis reflecting cortical bone strength. In contrast, bone RANKL/OPG ratios were decreased in CKD-3 rats compared with other groups, and they were inversely correlated with PTH and the other abovementioned bone parameters. However, the PTH-PTH1R-ATF4 axis exerted an unfavorable effect on the biomechanical properties of the femoral neck. In conclusion, this study showed for the first time an inverse association between serum PTH and the bone RANKL/OPG system in growing rats with mild CKD. A decrease in the RANKL/OPG ratio, associated with PTH-dependent activation of the anabolic PTH1R/ATF4 pathway, seems to be responsible for the unexpected, beneficial effect of PTH on cortical bone accrual and strength. Simultaneously, impaired biomechanical properties of the femoral neck were observed, making this bone site more susceptible to fractures.

Prevention of Dialysis Disequilibrium by use of CVVH

Objective.

Dialysis disequilibrium occurs due to a rapid shift of osmols when hemodialysis is used in cases of extreme uremia. Continuous veno-venous hemofiltration (CVVH) with citrate anticoagulation may offer a safe method of urea reduction.

Design.

Retrospective, clinical observation.

Setting.

Tertiary pediatric intensive care unit and nephrology program.

Patients

Two males, ages 10 and 12 years of age.

Intervention.

CVVH with citrate anticoagulation.

Results.

Three to four day reduction of BUN from 180 mg/dL to 22 mg/dL and from 279 mg/dL to 23 mg/dL.

Conclusion.

Slow and safe improvement of severe urea, hyperphosphatemia, hypocalcemia, and anemia without untoward side effects.

Clinical practice recommendations for treatment with active vitamin D analogues in children with chronic kidney disease Stages 2-5 and on dialysis

In patients with chronic kidney disease (CKD), renal synthesis of active vitamin D [1,25-dihydroxyvitamin D (1,25(OH)2D)] declines and is associated with hypocalcaemia, secondary hyperparathyroidism and the spectrum of CKD-mineral and bone disorder (MBD). In advanced CKD, active vitamin D analogues, including alfacalcidol, calcitriol and paricalcitol, are routinely administered. There are few studies on the use of vitamin D analogues in children with CKD and on dialysis. It is difficult to define bone-specific outcomes that can guide treatment with active vitamin D analogues in children with CKD-MBD. A core working group (WG) of the European Society for Paediatric Nephrology (ESPN) CKD-MBD and Dialysis WGs has developed recommendations for the use of active vitamin D therapy in children with CKD and on dialysis. A second document in parallel with this one covers treatment recommendations for native vitamin D therapy. The WGs have performed an extensive literature review to include systematic reviews and randomized controlled trials in adults and children with CKD and prospective observational studies in children with CKD. The Grading of Recommendation, Assessment, Development and Evaluation (GRADE) system was used to develop and grade the recommendations. In the absence of applicable study data, the opinion of experts from the ESPN CKD-MBD and Dialysis WGs is provided, but clearly GRADE-ed as such and must be carefully considered by the treating physician and adapted to individual patient needs as appropriate.

Lack of hepcidin ameliorates anemia and improves growth in an adenine-induced mouse model of chronic kidney disease

Growth delay is common in children with chronic kidney disease (CKD), often associated with poor quality of life. The role of anemia in uremic growth delay is poorly understood. Here we describe an induction of uremic growth retardation by a 0.2% adenine diet in wild-type (WT) and hepcidin gene (Hamp) knockout (KO) mice, compared with their respective littermates fed a regular diet. Experiments were started at weaning (3 wk). After 8 wk, blood was collected and mice were euthanized. Adenine-fed WT mice developed CKD (blood urea nitrogen 82.8 ± 11.6 mg/dl and creatinine 0.57 ± 0.07 mg/dl) and were 2.1 cm shorter compared with WT controls. WT adenine-fed mice were anemic and had low serum iron, elevated Hamp, and elevated IL6 and TNF-α. WT adenine-fed mice had advanced mineral bone disease (serum phosphorus 16.9 ± 3.1 mg/dl and FGF23 204.0 ± 115.0 ng/ml) with loss of cortical and trabecular bone volume seen on microcomputed tomography. Hamp disruption rescued the anemia phenotype resulting in improved growth rate in mice with CKD, thus providing direct experimental evidence of the relationship between Hamp pathway and growth impairment in CKD. Hamp disruption ameliorated CKD-induced growth hormone-insulin-like growth factor 1 axis derangements and growth plate alterations. Disruption of Hamp did not mitigate the development of uremia, inflammation, and mineral and bone disease in this model. Taken together, these results indicate that an adenine diet can be successfully used to study growth in mice with CKD. Hepcidin appears to be related to pathways of growth retardation in CKD suggesting that investigation of hepcidin-lowering therapies in juvenile CKD is warranted.

Pre-treatment considerations in childhood hypertension due to chronic kidney disease

Hypertension (HTN) develops very early in childhood chronic kidney disease (CKD). It is linked with rapid progression of kidney disease, increased morbidity and mortality hence the imperative to start anti-hypertensive medication when blood pressure (BP) is persistently > 90^th percentile for age, gender, and height in non-dialyzing hypertensive children with CKD. HTN pathomechanism in CKD is multifactorial and complexly interwoven. The patient with CKD-associated HTN needs to be carefully evaluated for co-morbidities that frequently alter the course of the disease as successful treatment of HTN in CKD goes beyond life style modification and anti-hypertensive therapy alone. Chronic anaemia, volume overload, endothelial dysfunction, arterial media calcification, and metabolic derangements like secondary hyperparathyroidism, hyperphosphataemia, and calcitriol deficiency are a few co-morbidities that may cause or worsen HTN in CKD. It is important to know if the HTN is caused or made worse by the toxic effects of medications like erythropoietin, cyclosporine, tacrolimus, corticosteroids and non-steroidal anti-inflammatory drugs. Poor treatment response may be due to any of these co-morbidities and medications. A satisfactory hypertensive CKD outcome, therefore, depends very much on identifying and managing these co-morbid conditions and HTN promoting medications promptly and appropriately. This review attempts to point attention to factors that may affect successful treatment of the hypertensive CKD child and how to attain the desired therapeutic BP target.

The consequences of pediatric renal transplantation on bone metabolism and growth

PURPOSE OF REVIEW

During childhood, growth retardation, decreased final height and renal osteodystrophy are common complications of chronic kidney disease (CKD). These problems remain present in patients undergoing renal transplantation, even though steroid-sparing strategies are more widely used. In this context, achieving normal height and growth in children after transplantation is a crucial issue for both quality of life and self-esteem. The aim of this review is to provide an overview of pathophysiology of CKD-mineral bone disorder (MBD) in children undergoing renal transplantation and to propose keypoints for its daily management.

RECENT FINDINGS

In adults, calcimimetics are effective for posttransplant hyperparathyroidism, but data are missing in the pediatric population. Fibroblast growth factor 23 levels are associated with increased risk of rejection, but the underlying mechanisms remain unclear. A recent meta-analysis also demonstrated the effectiveness of rhGH therapy in short transplanted children.

SUMMARY

In 2013, the daily clinical management of CKD-MBD in transplanted children should still focus on simple objectives: to optimize renal function, to develop and promote steroid-sparing strategies, to provide optimal nutritional support to maximize final height and avoid bone deformations, to equilibrate calcium/phosphate metabolism so as to provide acceptable bone quality and cardiovascular status, to correct all metabolic and clinical abnormalities that can worsen both bone and growth (mainly metabolic acidosis, anemia and malnutrition), promote good lifestyle habits (adequate calcium intake, regular physical activity, no sodas consumption, no tobacco exposure) and eventually to correct native vitamin D deficiency (target of 25-vitamin D >75 nmol/l).

Medication adherence and growth in children with CKD

BACKGROUND AND OBJECTIVES

Poor growth is a consequence of CKD, but can often be partially or fully prevented or corrected with the use of a number of medications. The extent of nonadherence with medications used to treat or mitigate growth failure in CKD has not been examined prospectively in children with CKD.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

The prevalence of both prescription of and nonadherence to recombinant human growth hormone (rhGH), phosphate binders, alkali, active vitamin D, nutritional vitamin D, iron, and erythrocyte-stimulating agents was summarized over the first seven visits of the Chronic Kidney Disease in Children cohort study. The association between self-reported nonadherence to each medication group and the mean annual change in age- and sex-specific height z score was quantified using seven separate linear regression models with generalized estimating equations.

RESULTS

Of 834 participants, 597 reported use of at least one of these medication groups and had adherence data available. Nonadherence ranged from 4% over all visits for erythrocyte-stimulating agents to 22% over all visits for nutritional vitamin D. Of the study participants, 451 contributed data to at least one of the analyses of adherence and changes in height z score. Children nonadherent to rhGH had no change in height z score, whereas those adherent to rhGH had a significant improvement of 0.16 SDs (95% confidence interval, 0.05 to 0.27); the effect size was slightly larger and remained significant after adjustment. Among participants with height≤3rd percentile and after adjustment, adherence to rhGH was associated with a 0.33 SD (95% confidence interval, 0.10 to 0.56) greater change in height z score. Nonadherence with other medication groups was not significantly associated with a change in height z score.

CONCLUSIONS

Self-reported nonadherence to rhGH was associated with poorer growth velocity in children with CKD, suggesting an opportunity for intervention and improved patient outcome.

Chronic kidney disease: mineral and bone disorder in children

Childhood and adolescence are crucial times for the development of a healthy skeletal and cardiovascular system. Disordered mineral and bone metabolism accompany chronic kidney disease (CKD) and present significant obstacles to optimal bone strength, final adult height, and cardiovascular health. Early increases in bone and plasma fibroblast growth factor 23 (FGF23) are associated with early defects in skeletal mineralization. Later in the course of CKD, secondary hyperparathyroidism--caused by a combination of declining calcitriol values and phosphate retention--results in high-turnover renal osteodystrophy whereas increased levels of both phosphate and FGF23 contribute to cardiovascular disease. Treatment of hyperphosphatemia and secondary hyperparathyroidism improves high-turnover bone disease but fails to correct defects in skeletal mineralization. Because overtreatment may result in adynamic bone disease, growth failure, hypercalcemia, and progression of cardiovascular calcifications, therapy therefore must be titrated carefully to maintain optimal serum biochemical parameters according to stage of CKD. Newer therapeutic agents and new treatment paradigms may suppress serum PTH levels effectively while limiting intestinal calcium absorption and skeletal FGF23 stimulation and may provide future therapeutic alternatives for children with CKD.

Vitamin D in chronic kidney disease

Vitamin D deficiency is widespread in both the pediatric and adult chronic kidney disease (CKD) population. CKD is characterized by dysregulation of vitamin D and mineral metabolism. Secondary hyperparathyroidism and its management puts patients with CKD at increased cardiovascular risk. Emergence of experimental and some clinical data suggesting beneficial effects of vitamin D on proteinuria, blood pressure, inflammation and cardiovascular outcomes has pushed it to the center stage of CKD research. Pediatric data on vitamin D dysregulation and its consequences are still in its infancy. Ongoing prospective studies such as Chronic Kidney disease in Children (CKiD) and the Cardiovascular Comorbidity in Children with CKD (4 C) should help to delineate the evolution of disturbances in mineral metabolism and its adverse effects on growth, CKD progression and cardiovascular outcomes.

The consequences of chronic kidney disease on bone metabolism and growth in children

Growth retardation, decreased final height and renal osteodystrophy (ROD) are common complications of childhood chronic kidney disease (CKD), resulting from a combination of abnormalities in the growth hormone (GH) axis, vitamin D deficiency, hyperparathyroidism, hypogonadism, inadequate nutrition, cachexia and drug toxicity. The impact of CKD-associated bone and mineral disorders (CKD-MBD) may be immediate (serum phosphate/calcium disequilibrium) or delayed (poor growth, ROD, fractures, vascular calcifications, increased morbidity and mortality). In 2012, the clinical management of CKD-MBD in children needs to focus on three main objectives: (i) to provide an optimal growth in order to maximize the final height with an early management with recombinant GH therapy when required, (ii) to equilibrate calcium/phosphate metabolism so as to obtain acceptable bone quality and cardiovascular status and (iii) to correct all metabolic and clinical abnormalities that can worsen bone disease, growth and cardiovascular disease, i.e. metabolic acidosis, anaemia, malnutrition and 25(OH)vitamin D deficiency. The aim of this review is to provide an overview of the mineral, bone and vascular abnormalities associated with CKD in children in terms of pathophysiology, diagnosis and clinical management.

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.

Parathyroid hormone and growth in chronic kidney disease

Growth failure is common in children with chronic kidney disease, and successful treatment is a major challenge in the management of these children. The aetiology is multi-factorial with "chronic kidney disease-metabolic bone disorder" being a key component that is particularly difficult to manage. Parathyroid hormone is at the centre of this mineral imbalance, consequent skeletal disease and, ultimately, growth failure. When other aetiologies are treated, good growth can be achieved throughout the course of the disease when parathyroid hormone (PTH) levels are in the normal range or slightly elevated. A direct correlation between PTH levels and growth has not been convincingly established, and the direct effect of PTH on growth has not been adequately described; furthermore, direct actions of PTH on the growth plate are unproven. The effects of PTH on growth stem from the pivotal role that PTH plays in the development of renal osteodystrophy. In severe secondary hyperparathyroidism, the growth plate is altered and growth is affected. At the other end of the spectrum, with an over-suppressed parathyroid gland, the rate of bone turnover and remodelling is markedly diminished, and some data suggest this is associated with poor growth. Most of the data available suggests that avoiding the development of significant bone disease through the strict control of PTH levels permits good growth. Absolute optimal ranges for PTH that maximise growth or minimise growth failure are not yet established.

Vitamin D status of Inuit preschoolers reflects season and vitamin D intake

Rickets ascribed to hypovitaminosis D remains a public health concern among Aboriginal children in Canada and the United States. Our primary objective in this study was to investigate the prevalence and risk factors (gender, age, vitamin D intake, and socioeconomic status) for low vitamin D status of Inuit preschoolers living in 16 Arctic communities (51(o)N-70(o)N) and participating in the 2007-2008 Nunavut Child Inuit Health Survey. Children were selected randomly in summer (n = 282) and a follow-up was performed in winter for a subsample (n = 52). Dietary intake was assessed through the administration of a 24-h dietary recall and a FFQ. Anthropometric measurements (height, weight) were assessed. Plasma 25-hydroxy vitamin D was measured using a chemiluminescent assay (Liaison, Diasorin). Prevalence of vitamin D insufficiency (<75 nmol/L) among preschoolers was 78.6% and 96.8% in summer and winter, respectively. Median vitamin D concentrations and interquartile ranges in summer and winter were 48.3 (32.8-71.3) and 37.7 (21.4-52.0) nmol/L, respectively. The prevalence of vitamin D deficiency < 25 and < 37.5 nmol/L was 13.6 and 36.5%, respectively. Children who met or exceeded the adequate intake, those who consumed 2 or more milk servings (1 serving = 250 mL), and those who lived in households without crowding (47.7%) had a better vitamin D status than those who did not. The predictors of vitamin D status were dietary intake and age. Given low traditional food consumption and low consumption of milk, interventions promoting vitamin D supplementation may be required.

Long-term outcome of infants with severe chronic kidney disease

BACKGROUND AND OBJECTIVES

In 2000, we reported the outcome of 101 children with a GFR <20 ml/min per 1.73 m2 at 0.3 yr of age (range 0.0 to 1.5 yr). Long-term data on such young children are scarce.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Mortality, treatment modalities, and growth were reanalyzed 9.9 yr later.

RESULTS

Of the 101 patients, 28 died and three were lost to follow-up during 13.90 yr (range 0.03 to 22.90 yr). One-, 2-, 5-, 10-, 15-, 20-, and 22-yr survivals were 87, 81, 77, 75, 73, 72, and 64%, respectively. Fifty-one children had comorbidities. Sixty-six percent were tube fed for 1.7 yr (range 0.1 to 6.9 yr), 37% had a gastrostomy, and 13% had a Nissen fundoplication. Mean height SD score (SD) was -0.42 (2.33) at birth (n = 40), -2.07 (1.34) at 0.5 (n = 62), -1.93 (1.38) at 1 (n = 72), -1.14 (1.14) at 5 (n = 67), -1.04 (1.15) at 10 (n = 62), -1.84 (1.32) at 15 (n = 40), and -1.68 (1.52) at age > or =18 yr (n = 32). Comorbidities adversely influenced growth (P < 0.01) and final height (P = 0.02): Mean height SD score (SD) was -1.16 (1.38) in otherwise normal adults.

CONCLUSIONS

Growth and final height in infants with severe chronic kidney disease are influenced by comorbidity. Intensive feeding and early transplantation resulted in a mean adult height within the normal range in patients without comorbidities. Overall mortality is comparable to that of older children.

Response of different PTH assays to therapy with sevelamer or CaCO3 and active vitamin D sterols

Amino-terminally truncated parathyroid hormone (PTH) fragments are detected to differing degrees by first- and second-generation immunometric PTH assays (PTH-IMAs), and acute changes in serum calcium affect the proportion of these fragments in circulation. However, the effect of chronic calcium changes and different vitamin D doses on these PTH measurements remains to be defined. In this study, 60 pediatric dialysis patients, aged 13.9 +/- 0.7 years, with secondary hyperparathyroidism were randomized to 8 months of therapy with oral vitamin D combined with either calcium carbonate (CaCO(3)) or sevelamer. Serum phosphorus levels did not differ between groups. Serum calcium levels rose from 9.3 +/- 0.1 to 9.7 +/- 0.1 mg/dl during CaCO(3) therapy (p < 0.01 from baseline) but remained unchanged during sevelamer therapy. In the CaCO(3) and sevelamer groups, baseline serum PTH levels (1st PTH-IMA; Nichols Institute Diagnostics, San Clemente, CA) were 964 +/- 75 and 932 +/- 89 pg/ml, and levels declined to 491 +/- 55 and 543 +/- 59 pg/ml, respectively (nonsignificant between groups). Patients treated with sevelamer received higher doses of vitamin D than those treated with CaCO(3). The PTH values obtained by first- and second-generation PTH-IMAs correlated closely throughout therapy and the response of PTH was similar to both PTH-IMAs, despite differences in serum calcium levels.

Bone histomorphometry in children prior to commencing renal replacement therapy

Renal osteodystrophy (ROD) develops early in the course of chronic kidney disease (CKD). With improving patient survival it's importance and relevance has increased. The last published bone biopsy data in children prior to renal replacement therapy (RRT) was in 1982, which demonstrated abnormal histology in all patients with a glomerular filtration rate (GFR) <20 ml/min per 1.73 m(2). Studies investigating the relationship between bone histology and parathyroid hormone levels (PTH) and/or growth in children with CKD are few (seven). These were mostly undertaken in patients already initiated on RRT-dialysis. We investigated the presence of ROD in children at the commencement of RRT and to investigate any relationship between histology, growth and PTH levels. Following double tetracycline labelling, bone biopsies were taken from patients at the time of RRT surgery. Histological classification was based on the newly proposed turnover/mineralisation/volume (TMV) system. Eleven patients underwent bone biopsy. Patients were followed for an average of 1.1 years (0.5-1.8) prior to biopsy over an average of eight clinic visits (3-14), when routine biochemical data were collected. Time-integrated median calcium, phosphate and PTH levels were calculated. PTH levels were within the normal range in two patients with low turnover, 1.1-1.4 times the upper limit of normal (ULN) in three with mixed osteodystrophy and >2.9 times the ULN in four patients with high bone turnover. There was no relationship between bone turnover and growth. The presence of ROD was universal in these children with severe CKD. Low bone turnover was associated with normal-range mean PTH levels, and high bone turnover occurred at lower PTH levels than current guidelines would suggest.

Management of Renal Osteodystrophy: THe Heart and Bone of Pediatric Dialysis

Control of mineral homeostasis is a particularly challenging task in children and adolescents on dialysis. Treatment efforts must not only ensure patient survival and the absence of debilitating complications of bone disease, but in view of a potentially long lifespan, must also consider how to best promote long-term cardiovascular health and successful psychosocial transition into adult life. In that context, avoidance of cardiovascular calcifications and accomplishment of adequate statural growth and a normal final height are major objectives of uremic bone disease management in children. Unfortunately, current pediatric management guidelines operate on a small evidence base, and major controversy surrounds key issues such as optimal target ranges for serum parathyroid hormone, calcium, and phosphorus in the individual childhood phases, and individual risk–benefit ratios for the use of phosphate binders, vitamin D analogs, and calcimimetics in children. The present review summarizes the current state of knowledge and outlines future research requirements in bone disease associated with pediatric end-stage renal disease.

Chronic kidney disease mineral and bone disorder in children

Childhood and adolescence are crucial times for the development of a healthy skeletal and cardiovascular system. Disordered mineral and bone metabolism accompany chronic kidney disease (CKD) and present significant obstacles to optimal bone strength, final adult height, and cardiovascular health. Decreased activity of renal 1 alpha hydroxylase results in decreased intestinal calcium absorption, increased serum parathyroid hormone levels, and high-turnover renal osteodystrophy, with subsequent growth failure. Simultaneously, phosphorus retention exacerbates secondary hyperparathyroidism, and elevated levels contribute to cardiovascular disease. Treatment of hyperphosphatemia and secondary hyperparathyroidism improves growth and high-turnover bone disease. However, target ranges for serum calcium, phosphorus, and parathyroid hormone (PTH) levels vary according to stage of CKD. Since over-treatment may result in adynamic bone disease, growth failure, hypercalcemia, and progression of cardiovascular calcifications, therapy must be carefully adjusted to maintain optimal serum biochemical parameters according to stage of CKD. Newer therapeutic agents, including calcium-free phosphate binding agents and new vitamin D analogues, effectively suppress serum PTH levels while limiting intestinal calcium absorption and may provide future therapeutic alternatives for children with CKD.

Mineral metabolism and vascular damage in children on dialysis

Cardiovascular disease is increasingly recognized as a life-limiting problem in young patients with chronic kidney disease, but there are few studies in children that describe its determinants. We studied the association of intact parathyroid hormone (iPTH) levels and their management on vascular structure and function in 85 children, ages 5-18 years, who had received dialysis for > or =6 months. Compared to controls, dialysis patients had increased carotid intima-media thickness and pulse-wave velocity. All vascular measures positively correlated with serum phosphorus levels, while carotid intima-media thickness and cardiac calcification score also correlated with iPTH levels. Patients with mean time-integrated iPTH levels less than twice the upper limit of normal (n = 41) had vascular measures that were comparable to age-matched controls, but those with iPTH levels greater than twice the upper limit of normal (n = 44) had greater carotid intima-media thickness, stiffer vessels, and increased cardiac calcification than controls. Patients with increased carotid intima-media thickness had stiffer vessels and a greater prevalence of cardiac calcification. There was a strong dose-dependent correlation between vitamin D and all vascular measures, and calcium intake from phosphate binders weakly correlated with carotid intima-media thickness. In conclusion, both iPTH level and dosage of vitamin D are associated with vascular damage and calcification in children on dialysis.

Nutrition in children with CRF and on dialysis

The objectives of this study are: (1) to understand the importance of nutrition in normal growth; (2) to review the methods of assessing nutritional status; (3) to review the dietary requirements of normal children throughout childhood, including protein, energy, vitamins and minerals; (4) to review recommendations for the nutritional requirements of children with chronic renal failure (CRF) and on dialysis; (5) to review reports of spontaneous nutritional intake in children with CRF and on dialysis; (6) to review the epidemiology of nutritional disturbances in renal disease, including height, weight and body composition; (7) to review the pathological mechanisms underlying poor appetite, abnormal metabolic rate and endocrine disturbances in renal disease; (8) to review the evidence for the benefit of dietetic input, dietary supplementation, nasogastric and gastrostomy feeds and intradialytic nutrition; (9) to review the effect of dialysis adequacy on nutrition; (10) to review the effect of nutrition on outcome.

Growth and PTH in prepubertal children on long-term dialysis

Growth failure is an important complication for children on dialysis. One possible influence on growth is renal bone disease. We reviewed the case notes of 35 children (23 boys), mean (range) age at inclusion 2.8 (0.25-8.9) years (17 children age <2 years), on dialysis for 2.0 (1-4.8) years, for growth, PTH, calcium and phosphate levels and medications. Data collection ended at age 10 years, commencement of growth hormone (rhGH) or renal transplantation. The mean (range) height standard deviation score (HtSDS) at the start of dialysis was -2.06 (-5.90 to 0.63). No change in HtSDS per year was observed; the median was -0.06 (-1.07 to 2.39). Children aged <2 years showed catch-up growth in the first year on dialysis; median change in HtSDS was 0.31 (-0.78 to 3.13). Mean plasma calcium and ionised calcium were approximately at the mid-point and phosphate just above the mid-point of the respective normal ranges. The median PTH level was 1.52 times the upper limit of normal and levels did not correlate with growth. Our results indicate that intensive nutritional therapy and phosphorus control aiming to keep PTH within the normal range prevents further loss of HtSDS in short children on dialysis. In some children under 2 years of age catch-up growth can be observed in the first dialysis year.

Parathormone et maladie rénale chronique

The serum parathyroid hormone (PTH) rises in chronic kidney disease (CKD) and induces renal bone disease as well as other organ damage. The bone disease guidelines were released by the K-DOQI in 2003 in order to help physicians to improve bone management at all different CKD stages. However, many different PTH commercial assays are available today and some questions are raised concerning the interpretation, the validity and the practical choice of these different measurements. After reviewing PTH biosynthesis and metabolism, we will describe the regulation of different PTH fragments (particularly 1-84 and 7-84) and the various types of PTH assays. In compromised clinical situations, bone biopsy still remains the golden standard assessment of bone disease, and it will be helpful to clarify the interest of new 3rd generation PTH measurements. At present, we do not dispose of valid therapeutic recommendations using 3rd generation tests, as well as the relevance of the ratio PTH 1-84/7-84.

Parathyroid hormone assay: problems and opportunities

The assay of parathyroid hormone continues to remain problematic as a result of the presence in the circulation of a variety of parathyroid hormone (PTH) peptides derived from secretion and from peripheral metabolism. The detection of these PTH fragments to varying degrees leads to widely differing results in the various assays used, particularly in the setting of chronic kidney disease, where PTH fragments accumulate as glomerular filtration rate (GFR) falls. The differing results not only lead to problems in comparing values from various laboratories but also limit efforts to develop useful clinical practice guidelines. At the same time, research into the precise identification of the PTH fragments which contribute to the assay problems has uncovered a relatively new area of parathyroid research that has pointed to potential biologic activity of PTH peptides previously thought to be biologically inactive and which may act on a novel PTH receptor. These issues have brought new focus to the difficulties in standardization of PTH assays and have provoked efforts to provide standards to help in the characterization of PTH assays and to facilitate the development of clinical practice guidelines.

Bone mineral density in children with chronic renal failure

Bone mineral density (BMD) is important in children and adolescents because of its relationship to long-term skeletal health, and because, in adults with chronic renal failure (CRF), a relationship between low BMD and vascular calcification has been suggested. To investigate the relationship between BMD and manipulable factors that might affect it, i.e. plasma calcium, phosphate and parathyroid hormone (PTH), 64 patients with a median glomerular filtration rate (GFR) of 31 (range 7-60) ml min(-1) 1.73 m(-2) and median age of 10.0 (4.1-16.9) years were followed over 1.3 (0.7-1.7) years at an average of 5 (3-14) clinic visits. At one visit, BMD of the lumbar spine was measured by dual energy X-ray absorptiometry. The mean BMD Z-score was normal (=0.0). Overall mean calcium, phosphate and PTH levels were in their respective normal ranges. The majority of the patients (72%) were treated with calcium carbonate, mean dose 65 mg kg(-1) day(-1); prescription was positively related to serum calcium levels and calcium-phosphate product (P=0.012 and P<0.01 respectively). Almost all patients (98%) were treated with alfacalcidol, mean dose 12 ng kg(-1) day(-1); prescription was not related to investigated factors. Patients grew well; there was no change in height standard deviation score (DeltaHtSDS=0.0). Normal BMD Z-score for age and sex can be achieved in children with CRF managed with the aim of maintaining normal PTH levels by dietary phosphate restriction, calcium-based phosphate binders and small doses of alfacalcidol. Further investigation of the underlying bone by the use of biopsy and histomorphometry is required to determine actual bone health.

Serum osteocalcin and parathyroid hormone in healthy children assessed with two new automated assays

BACKGROUND

The recent introduction of new automated assays needs careful definition of reference values in healthy children. The aim of this study was to determine serum parathyroid hormone (PTH) and osteocalcin in a large group of healthy children according to age.

METHODS

We selected 2,288 healthy children (1,079 girls, 1,209 boys), aged 2-16 years. Serum PTH and osteocalcin were assayed with a two-site immunochemiluminometric assay adapted on an automated analyzer, the Liaison.

RESULTS

Significant differences were found between the mean serum values of PTH and osteocalcin in boys and girls in all age groups (p <0.001). Boys' and girls' PTH values ranged from 3.42-22.30 ng/l and 2.31-24.49 ng/l, respectively; serum osteocalcin ranged from 3.85-17.80 nmol/l in boys and 3.74-17.38 nmol/l in girls.

CONCLUSIONS

The results of this study contribute to the establishment of reference values in healthy children for PTH and osteocalcin assays.