Parathyroid hormone measurement in CKD

The Molecular Mechanisms Underlying the Systemic Effects Mediated by Parathormone in the Context of Chronic Kidney Disease

Chronic kidney disease (CKD) stands as a prominent non-communicable ailment, significantly impacting life expectancy. Physiopathology stands mainly upon the triangle represented by parathormone-Vitamin D-Fibroblast Growth Factor-23. Parathormone (PTH), the key hormone in mineral homeostasis, is one of the less easily modifiable parameters in CKD; however, it stands as a significant marker for assessing the risk of complications. The updated "trade-off hypothesis" reveals that levels of PTH spike out of the normal range as early as stage G2 CKD, advancing it as a possible determinant of systemic damage. The present review aims to review the effects exhibited by PTH on several organs while linking the molecular mechanisms to the observed actions in the context of CKD. From a diagnostic perspective, PTH is the most reliable and accessible biochemical marker in CKD, but its trend bears a higher significance on a patient's prognosis rather than the absolute value. Classically, PTH acts in a dichotomous manner on bone tissue, maintaining a balance between formation and resorption. Under the uremic conditions of advanced CKD, the altered intestinal microbiota majorly tips the balance towards bone lysis. Probiotic treatment has proven reliable in animal models, but in humans, data are limited. Regarding bone status, persistently high levels of PTH determine a reduction in mineral density and a concurrent increase in fracture risk. Pharmacological manipulation of serum PTH requires appropriate patient selection and monitoring since dangerously low levels of PTH may completely inhibit bone turnover. Moreover, the altered mineral balance extends to the cardiovascular system, promoting vascular calcifications. Lastly, the involvement of PTH in the Renin-Angiotensin-Aldosterone axis highlights the importance of opting for the appropriate pharmacological agent should hypertension develop.

Comparative Analysis of Vascular Calcification Risk Factors in Pre-Hemodialysis and Prevalent Hemodialysis Adult Patients: Insights into Calcification Biomarker Associations and Implications for Intervention Strategies in Chronic Kidney Disease

This retrospective study aimed to compare risk factors for vascular calcification (VC) between pre-hemodialysis (HD) and prevalent HD adult patients while investigating associations with calcification biomarkers. Baseline data from 30 pre-HD and 85 HD patients were analyzed, including iPTH, vitamin D, FGF 23, fetuin-A, sclerostin, and VC scores (Adragao method). Prevalence of VC was similar in both groups, but HD patients had more frequent VC scores ≥ 6. Pre-HD patients were older, with higher prevalence of hypertension and less frequent use of calcium phosphate binders. Both groups showed similar patterns of hyperphosphatemia, low vitamin D, and iPTH. Fetuin-A and sclerostin levels were higher in pre-HD, while FGF 23 was elevated in HD patients. Higher VC risk in pre-HD patients was associated with male gender, older age, lower fetuin-A and higher sclerostin, lower ferritin, and no vitamin D treatment, while in HD patients with higher sclerostin, FGF 23 and urea, and lower iPTH. Conclusion: Biomarkers could be measurable indicators of biological processes underlying VC in CKD patients that may serve as a potential guide for considering personalized therapeutic approaches. Further studies are needed to elucidate the underlying pathways.

Unveiling a new era with liquid chromatography coupled with mass spectrometry to enhance parathyroid hormone measurement in patients with chronic kidney disease

Precise determination of circulating parathyroid hormone (PTH) concentration is crucial to diagnose and manage various disease conditions, including the chronic kidney disease-mineral and bone disorder. However, the lack of standardization in PTH assays is challenging for clinicians, potentially leading to medical errors because the different assays do not provide equivalent results and use different reference ranges. Here, we aimed to evaluate the impact of recalibrating PTH immunoassays by means of a recently developed LC-MS/MS method as the reference. Utilizing a large panel of pooled plasma samples with PTH concentrations determined by the LC-MS/MS method calibrated with the World Health Organization (WHO) 95/646 International Standard, five PTH immunoassays were recalibrated. The robustness of this standardization was evaluated over time using different sets of samples. The recalibration successfully reduced inter-assay variability with harmonization of PTH measurements across different assays. By recalibrating the assays based on the WHO 95/646 International Standard, we demonstrated the feasibility for standardizing PTH measurement results and adopting common reference ranges for PTH assays, facilitating a more consistent interpretation of PTH values. The recalibration process aligns PTH results obtained from various immunoassays with the LC-MS/MS method, providing more consistent and reliable measurements. Thus, establishing true standardization across all PTH assays is crucial to ensure consistent interpretation and clinical decision-making.

Standardization of PTH measurement by LC-MS/MS: a promising solution for interassay variability

Parathyroid hormone measurement is critical in managing chronic kidney disease-mineral bone disorders. However, there are several commercially available immunoassays with interassay variability. To address this, Cavalier et al. developed standardization of parathyroid hormone measurement by establishing regression equations of each assay against the liquid chromatography coupled to tandem mass spectrometry method. The recalibration successfully reduced interassay variability, allowing for more consistent interpretation. The proposed approach may pave the way for accurate interpretation of parathyroid hormone in clinical practice.

Real-world usage of Chronic Kidney Disease - Mineral Bone Disorder (CKD-MBD) biomarkers in nephrology practices

Background

Chronic kidney disease mineral bone disorder (CKD-MBD) is a condition characterized by alterations of calcium, phosphate, parathyroid hormone (PTH), and fibroblast growth factor 23 (FGF-23) metabolism that in turn promote bone disorders, vascular calcifications, and increase cardiovascular (CV) risk. Nephrologists' awareness of diagnostic, prognostic, and therapeutic tools to manage CKD-MBD plays a primary role in adequately preventing and managing this condition in clinical practice.

Methods

A national survey (composed of 15 closed questions) was launched to inquire about the use of bone biomarkers in the management of CKD-MBD patients by nephrologists and to gain knowledge about the implementation of guideline recommendations in clinical practice.

Results

One hundred and six Italian nephrologists participated in the survey for an overall response rate of about 10%. Nephrologists indicated that the laboratories of their hospitals were able to satisfy request of ionized calcium levels, 105 (99.1%) of both PTH and alkaline phosphatase (ALP), 100 (94.3%) of 25(OH)D, and 61 (57.5%) of 1.25(OH)2D; while most laboratories did not support the requests of biomarkers such as FGF-23 (intact: 88.7% and c-terminal: 93.4%), Klotho (95.3%; soluble form: 97.2%), tartrate-resistant acid phosphatase 5b (TRAP-5b) (92.5%), C-terminal telopeptide (CTX) (71.7%), and pro-collagen type 1 N-terminal pro-peptide (P1NP) (88.7%). As interesting data regarding Italian nephrologists' behavior to start treatment of secondary hyperparathyroidism (sHPT), the majority of clinicians used KDOQI guidelines (n = 55, 51.9%). In contrast, only 40 nephrologists (37.7%) relied on KDIGO guidelines, which recommended referring to values of PTH between two and nine times the upper limit of the normal range.

Conclusion

Results point out a marked heterogeneity in the management of CKD-MBD by clinicians as well as a suboptimal implementation of guidelines in Italian clinical practice.

Agreement of Parathyroid Hormone Status Measured by Intact and Biointact Parathyroid Hormone Assays among Chronic Kidney Disease Patients and Its Correlation with Bone Turnover Parameters

Background

This study aimed to determine the agreement between intact parathyroid hormone (iPTH) and biointact parathyroid hormone (bio-PTH) assays and to correlate them with bone markers.

Methods

This cross-sectional study included 180 patients with chronic kidney disease (CKD) stages 3b, 4 and 5D. We measured their iPTH, bio-PTH, 25-hydroxyvitaminD (25(OH)D), C-terminal telopeptide collagen (CTX), procollagen 1 intact N-terminal propeptide (P1NP), calcium, phosphate and alkaline phosphatase (ALP).

Results

Higher iPTH than bio-PTH concentrations were seen in CKD stages 3b, 4 and 5D (58[62] versus 55[67] pg/mL, 94[85] versus 85[76] pg/mL and 378[481] versus 252[280] pg/mL, respectively). Both PTH assays showed good agreement among all the subjects, with an intraclass correlation coefficient of 0.832 (P-value < 0.001). The Passing-Bablok showed that the equation for the bio-PTH was PTH = 0.64 iPTH + 15.80, with r = 0.99. The Bland-Altman plots showed increased bias with an increasing PTH concentration. Both PTH assays showed a high positive correlation with CTX and P1NP, a moderate correlation with phosphate, a low correlation with ALP and calcium, and a negligible correlation with phosphate and 25(OH)D.

Conclusion

The iPTH and bio-PTH assays were in agreement, but their bias increased with the PTH concentration. The unacceptable large bias indicates that the two assays cannot be used interchangeably. They had a variable correlation with the bone parameters.

Intelligent and thermo-responsive Au-pluronic® F127 nanocapsules for Raman-enhancing detection of biomolecules

Thermo-responsive Raman-enhanced nanocapsules were successfully fabricated by Pluronic® F127 (F127) decorated with gold nanoparticles (AuNPs) for surface-enhanced Raman scattering (SERS) detection of biomolecules. F127 nanocapsules changes from hydrophilicity (swelling) to hydrophobicity (de-swelling) when the temperature increases from 15 °C to 37 °C, owing to the lower critical solution temperature (LCST) of F127 is about 26.5 °C. The size of nanocapsules would be enormous shrinking from 160 nm to 20 nm, resulting in a significant decrease in the distance between AuNPs to enhance hot spot effect, which increases the sensitivity of SERS detection. Based on the thermo-sensitive behavior, the ratio of AuNPs and F127 would be manipulated to find the optimal SERS enhancement effect. SERS nanocapsules can rapidly detect biomolecules (adenine and R6G) with limit of detection (LOD) lower than 10^-6 M. In addition, the relatively difficult to detect clinical samples, carboxyl-terminal parathyroid hormone fragments (C-PTH), can also be measured by the thermo-responsive SERS nanocapsules developed in this work. It is expected the biomolecules can be adsorbed at low temperature (15 °C), as well as collected and concentrated at high temperature (37 °C) for SERS detection, to increase the sensitivity and stability of SERS detection.

Tertiary and Postrenal Transplantation Hyperparathyroidism

Patients who have undergone kidney transplantation (KTx) (KTxps) are a distinctive population characterized by the persistence of some metabolic anomalies present during end-stage renal disease. Mineral metabolism (MM) parameters are frequently altered after KTx. These alterations involve calcium, phosphorus, vitamin D, and parathormone (PTH) disarrangements. At present, there is little consensus about the correct monitoring and management of PTH disorders in KTxps. This article presents the prevalence and epidemiologic and clinical impact of post-KTx hyper-PTH. The principal biochemical and instrumental investigations and the therapeutic options for these conditions are also reported.

Comparison of Second- and Third-Generation Parathyroid Hormone Test Results in Patients with Chronic Kidney Disease

BACKGROUND In patients with chronic kidney disease (CKD), secondary hyperparathyroidism is assessed by measuring serum parathyroid hormone (PTH) levels. Well-established, recommended, second-generation intact parathyroid hormone (iPTH) tests are typical; rarely are more recent third-generation PTH 1-84 assays used. The agreement between results of the 2 tests in patients with CKD has not been sufficiently defined. MATERIAL AND METHODS This study aimed to compare Roche second- and third-generation PTH assays by establishing a quantitative relationship between the results of assays in patients with CKD and assessing degree of their correlation with kidney function and calcium-phosphate and bone metabolism parameters. In 205 patients with stages 3 to 5D CKD and 30 healthy controls, we measured levels of iPTH and PTH (1-84), creatinine, urea, cystatin C, calcium, inorganic phosphate, magnesium, alkaline phosphatase, bone alkaline phosphatase, osteocalcin, and ß-CrossLaps. RESULTS The third-generation PTH assay results were more than 40% lower than those obtained with the second-generation test in patients undergoing dialysis and approximately 30% lower in patients in the pre-dialysis period. PTH concentrations determined with both assays were almost to the same extent correlated with calcium-phosphate and bone metabolism parameters, and renal function indices. Formulas have been developed enabling 2-way conversion of PTH results determined with both the second- and third-generation PTH assays: For dialyzed patients, PTH (1-84)=0.5181iPTH+18.0595. Serum osteocalcin, ß-CrossLaps, and total calcium were independent predictors of PTH levels. CONCLUSIONS Correcting for the established quantitative differences, the second-and third-generation PTH tests can be used interchangeably, given the almost identical pathophysiological correlations of their results with calcium-phosphate and bone metabolism parameters.

Vitamin D and subclinical cardiac damage in a cohort of kidney transplanted patients: a retrospective observational study

In 178-kidney transplanted patients (KTxp), the prevalence of hypovitaminosis-D, the presence and novel development of left ventricular hypertrophy(LVH) and the correlations between native Vitamin-D (25OHD) and LVH were evaluated during the 1st year of transplantation (KTx). Clinical and instrumental data were recorded at pre-KTx and at one (T1) and 12 (T12) months after KTx. 25OHD levels were considered sufficient (s25OHD, ≥ 30 ng/dL) or insufficient (i25OHD, < 30 ng/dL). 25OHD correlated at T1 with parathormone(PTH), and at T12 with 25OHD-T1 and PTH-(T1,T12). At T12, s25OHD (15%) had higher 25OH and alkaline phosphatase (ALP), lower Ca, at T1, and lower PTH-(T1, T12) than i25OH-T12. At T1, KTxp with LVH (LVH-T1pos, 42%) were older and with longer dialysis vintage than LVH-T1neg. At T12, KTxp with LVH (LVH-T12pos, 53%) were older, with higher systolic blood pressure (SBP) at T12 than LVH-T12neg. No relation between 25OHD and LVH were found. Novel LVH was found in 14% of KTxp. They were older, had higher SBP-T12 and lower serum albumin-T12 than the others. LVH-modifications and 25OHD were not correlated. Hypovitaminosis-D is highly prevalent in KTxp. LVH correlates with different risk factors according to the time elapsed from KTx. However, during the 1st year of KTx, no relationship between LVH and 25OHD was observed.

Renal Contributions in the Pathophysiology and Neuropathological Substrates Shared by Chronic Kidney Disease and Alzheimer's Disease

Chronic kidney disease and Alzheimer’s disease are chronic conditions highly prevalent in elderly communities and societies, and a diagnosis of them is devastating and life changing. Demanding therapies and changes, such as non-compliance, cognitive impairment, and non-cognitive anomalies, may lead to supplementary symptoms and subsequent worsening of well-being and quality of life, impacting the socio-economic status of both patient and family. In recent decades, additional hypotheses have attempted to clarify the connection between these two diseases, multifactorial in their nature, but even so, the mechanisms behind this link are still elusive. In this paper, we sought to highlight the current understanding of the mechanisms for cognitive decline in patients with these concurrent pathologies and provide insight into the relationship between markers related to these disease entities and whether the potential biomarkers for renal function may be used for the diagnosis of Alzheimer’s disease. Exploring detailed knowledge of etiologies, heterogeneity of risk factors, and neuropathological processes associated with these conditions opens opportunities for the development of new therapies and biomarkers to delay or slow their progression and validation of whether the setting of chronic kidney disease could be a potential determinant for cognitive damage in Alzheimer’s disease.

Mineral bone disorder and osteoporosis in hemodialysis patients

BACKGROUND

Bone disease is common in patients undergoing hemodialysis. It is the result of bone turnover abnormalities and the decrease of bone mineral density (BMD). We aimed to determine the usefulness of serum bone turnover markers and BMD measurement by dual-energy x-ray absorptiometry (DXA) in hemodialysis patients.

METHODS

We conducted a cross-sectional study including 90 hemodialysis for more than 12 months. Bone mineral density was assessed by DXA. Peripheral blood samples were obtained from each patient before dialysis in a fasting state within a week of the DXA. Biochemical variables of calcium and phosphate were measured. One bone formation marker (bone-specific alkaline phosphatase (bAP), one bone resorption marker (carboxy-terminal telopeptides of type 1 collagen (CTX)) were measured. Total alkaline phosphatase (TAP), intact parathyroid hormone (PTH) and fibroblast growth factor 23 (FGF23) which is a bone-derived hormone were also measured.

RESULTS

CTX values were 6.25 times higher than the normal limit of the assay. Bone alkaline phosphatase levels were less than 10 ng/mL in 28.8% of cases. 23% of patients have osteoporosis and 45% have osteopenia. Femoral BMD had negative correlations with age and PTH levels. FGF23 levels were significantly increased in patients with osteoporosis affecting the lumbar. The levels of bAP and CTX showed a positive correlation. Both circulating bAP and CTX levels showed also positive correlations with PTH levels. Fractures, observed in 12.2% of cases, were associated with low PTH values and the existence of osteoporosis.

CONCLUSIONS

Our study showed that osteoporosis and fracture are common in dialysis patients. The reduced BMD was associated with advanced age and elevated levels of PTH. Markers of bone turnover and FGF23 may play a role in the diagnosis of bone disease in hemodialysis patients. DXA measurement is necessary for the monitoring for bone loss.

Peptide hormone sensors using human hormone receptor-carrying nanovesicles and graphene FETs

Hormones within very low levels regulate and control the activity of specific cells and organs of the human body. Hormone imbalance can cause many diseases. Therefore, hormone detection tools have been developed, particularly over the last decade. Peptide hormones have a short half-life, so it is important to detect them within a short time. In this study, we report two types of peptide hormone sensors using human hormone receptor-carrying nanovesicles and graphene field-effect transistors (FETs). Parathyroid hormone (PTH) and glucagon (GCG) are peptide hormones present in human blood that act as ligands to G protein-coupled receptors (GPCRs). In this paper, the parathyroid hormone receptor (PTHR) and the glucagon receptor (GCGR) were expressed in human embryonic kidney-293 (HEK-293) cells, and were constructed as nanovesicles carrying the respective receptors. They were then immobilized onto graphene-based FETs. The two hormone sensors developed were able to detect each target hormone with high sensitivity (ca. 100 fM of PTH and 1 pM of GCG). Also, the sensors accurately recognized target hormones among different types of peptide hormones. In the development of hormone detection tools, this approach, using human hormone receptor-carrying nanovesicles and graphene FETs, offers the possibility of detecting very low concentrations of hormones in real-time.

Chronic Kidney Disease-Mineral and Bone Disorder (CKD-MBD): Current Perspectives

Despite the availability of global and regional guidelines to curtail the adverse clinical outcomes associated with chronic kidney disease–mineral and bone disorder (CKD-MBD), most CKD patients are still affected by the consequences of abnormalities of CKD-MBD. This important clinical complication of CKD continues to be studied, in order to improve the understanding and management of CKD-MBD. Some notable discoveries include the role of fibroblast growth factor 23 (FGF23) in the pathogenesis of CKD-MBD, leading to a shift from the previous well-established classic trade-off hypothesis to the updated trade-off hypothesis. More recently, there has been a shift from the treatment of CKD-MBD based on a single level of biomarkers to serial measurements of calcium, phosphate and parathyroid hormone (PTH). Furthermore, some clinical trials have emerged after the 2009 Kidney Disease-Improving Global Outcomes (KDIGO) Guidelines, leading to the 2017 KDIGO updated recommendations. Hence, this review gives an overview of the rapidly evolving trends in CKD-MBD, linking the past and current concepts of CKD-MBD.

Sclerostin within the chronic kidney disease spectrum

Sclerostin is sometimes presented as a promising biomarker in assessing bone health both in the general population and chronic kidney disease patients. However, it is still unclear whether it has any true added value compared to existing bone biomarkers in predicting bone turnover and/or bone density in chronic kidney disease patients. A wealth of papers has been published to evaluate the association between sclerostin and vascular calcifications development or even as prognostic biomarker for mortality, but often with conflicting results. Standardization and harmonization of analytical techniques is a prerequisite to advance clinical knowledge in sclerostin.

Bone biomarkers in de novo renal transplant recipients

Successful kidney transplantation (partly) corrects the physiologic and metabolic abnormalities driving chronic kidney disease - mineral and bone disorders. At the same time, renal transplant recipients are exposed to immunosuppressive agents that may affect bone metabolism. Bone biomarkers have been suggested as surrogates of or adjuncts to bone biopsy and imaging techniques to assess bone health and to classify risk of bone loss and fractures. Bone biomarkers may be classified as circulating factors that affect bone metabolism (commonly referred to as bone metabolism markers) or that reflect bone cell number and/or activity (commonly referred to as bone turnover markers). A growing body of evidence shows that successful renal transplantation has a major impact on both bone metabolism and bone turnover. Analytical issues, including the cross-reactivity with fragments, complicate the interpretation of bone biomarkers, especially in the setting of a rapid changing kidney function, as is the case after successful renal transplantation. Overall, bone turnover seems to decline following renal transplantation, but inter-individual variability is substantial. Preliminary evidence indicates that bone biomarkers may be useful in guiding mineral and bone therapy in renal transplant recipients.

The effect of vitamin D supplementation on plasma non-oxidised PTH in a randomised clinical trial

OBJECTIVE

PTH can be oxidised in vivo, rendering it biologically inactive. Non-oxidised PTH (n-oxPTH) may therefore give a better image of the hormonal status of the patient. While vitamin D supplementation decreases total PTH (tPTH) concentration, the effect on n-oxPTH concentration is unexplored. We investigated the effect of vitamin D on n-oxPTH concentration in comparison to tPTH and compared the correlations between parameters of calcium, bone and lipid metabolism with n-oxPTH and tPTH.

METHODS

N-oxPTH was measured in 108 vitamin D-insufficient (25(OH)D <75 nmol/L) hypertensive patients, treated with vitamin D (2800 IE daily) or placebo for 8 weeks in the Styrian Vitamin D Hypertension Trial (NCT02136771). We calculated the treatment effect and performed correlation analyses of n-oxPTH and tPTH with parameters of calcium, bone and lipid metabolism and oxidative stress.

RESULTS

After treatment, compared to placebo, 25(OH)D concentrations increased, tPTH decreased by 9% (P < 0.001), n-oxPTH by 7% (P = 0.025) and the ratio of n-oxPTH/tPTH increased (P = 0.027). Changes in phosphate and HDL concentration correlated with changes in n-oxPTH, but not tPTH.

CONCLUSIONS

tPTH and n-oxPTH decrease upon vitamin D supplementation. Our study suggests that vitamin D supplementation reduces the oxidation of PTH, as we observed a small but significant increase in the non-oxidised proportion of PTH upon treatment. In addition, we found that changes in phosphate and HDL concentration showed a relationship with changes in n-oxPTH, but not tPTH. This may be explained by the biological activity of n-oxPTH. Further research should be carried out to establish the clinical relevance of n-oxPTH.

A comparison of canine whole and intact parathyroid hormone concentrations as measured by different assays

OBJECTIVES

To compare an intact immunoradiometric parathyroid hormone assay with (1) a non-isotopic technique; and, (2) a whole parathyroid hormone immunoradiometric assay.

MATERIALS AND METHODS

Intact parathyroid hormone concentrations were measured using immunoradiometric (Scantibodies) and chemiluminescent (Immulite 2000) assays. Whole parathyroid hormone concentration was measured using an immunoradiometric assay (Scantibodies).

RESULTS

A total of 48 and 47 samples, respectively, were used to compare immunoradiometric and chemiluminescent intact parathyroid concentrations and intact and whole parathyroid hormone concentrations by immunoradiometric assays. Using chemiluminescence, 39 (81.3%) samples had intact parathyroid hormone concentrations at or below the reported limit of detection of the assay (0.3 pmol/L). Intact [6.3 (2.0 to 95.5) pmol/L] and whole [3.3 (0.8 to 125.2) pmol/L] immunoradiometric parathyroid hormone concentrations exhibited excellent correlation.

CLINICAL SIGNIFICANCE

Not all parathyroid hormone assays perform similarly. The chemiluminescent assay in this study cannot be recommended for use in dogs. The immunoradiometric intact parathyroid hormone assay proved to be a more reliable method. Given the correlation between intact and whole parathyroid hormone concentrations, it remains unclear which one is superior for routine clinical decision-making.

A Novel Perspective Linkage Between Kidney Function and Alzheimer's Disease

It has long been believed that kidney function is linked to brain activity. Clinical studies demonstrate that patients with chronic kidney disease (CKD) are more prone to cognitive impairment and Alzheimer's disease (AD), and the degree of cognitive impairment is closely related to CKD progression and renal failure. Moreover, the fact that cognitive function in CKD patients is significantly improved after successful kidney transplantation reveals a linkage between CKD and AD. However, the mechanisms behind this linkage are unclear. The physiological function of the kidney is to maintain the stability of the internal environment, including the cerebrovascular circulation, whereas abnormal kidney function often leads to ischemia and hypoxia. Many CKD patients experience chronic hypoxia, and many urinary toxins accumulate after renal function is impaired. In this mini review, we will propose a novel perspective on the association between AD and CKD and the connection between the kidney and brain.

Case Report of a Satin Guinea Pig with Fibrous Osteodystrophy That Resembles Human Pseudohypoparathyroidism

A case report of a 2-year-old female satin guinea pig with a history of dental overgrowth and lameness and radiological lesions of fibrous osteodystrophy is presented. The most relevant clinical findings were bone demineralization, high level of parathyroid hormone (PTH), normophosphatemia, normal ionized calcium, and low total thyroxine (tT4) with a normal renal function. Long-term treatment was based on teeth coronal reduction and maintaining a balanced diet. PTH measurement was performed with a kit suitable for rats to test 4 different paired samples of guinea pigs and resulted in similar results for each pair of measurements. Two kits routinely employed in dogs and cats failed in measuring PTH in guinea pig serum samples. The ionized calcium, PTH, and tT4 values, not previously reported in similar cases, were obtained. The determination of tT4 could be useful in the diagnosis of fibrous osteodystrophy in guinea pigs. The observed findings show similarity with human pseudohypoparathyroidism type Ia, a disease caused by an inactivating heterozygous mutation of the stimulatory G protein α subunit from the maternal genome that induces multiple hormone resistance and that courses with a syndrome called Albright hereditary osteodystrophy. Naturally occurring pseudohypoparathyroidism in animals has been reported previously only in a ferret.

Comparison of Intact PTH and Bio-Intact PTH Assays Among Non-Dialysis Dependent Chronic Kidney Disease Patients

BACKGROUND

The third-generation bio-intact parathyroid hormone (PTH) (1-84) assay was designed to overcome problems associated with the detection of C-terminal fragments by the second-generation intact PTH assay. The two assays have been compared primarily among dialysis populations. The present study evaluated the correlations and differences between these two PTH assays among patients with chronic kidney disease (CKD) stages 3 to 5 not yet on dialysis.

METHODS

Blood samples were collected from 98 patients with CKD stages 3 to 5. PTH concentrations were measured simultaneously by using the second-generation - PTH intact-STAT and third-generation bio-intact 1-84 PTH assays. Other serum biomarkers of bone mineral disorders were also assessed. CKD stage was calculated by using the CKD-Epidemiology Collaboration (EPI) formula.

RESULTS

Serum bio-intact PTH concentrations were strongly correlated but significantly lower than the intact PTH concentrations (r=0.963, P<0.0001). This finding was consistent among CKD stages 3 to 5. PTH concentrations by both assays (intact and bio-intact PTH) positively correlated with urea (r=0.523, r=0.504; P=0.002, respectively), phosphorus (r=0.532, r=0.521; P<0.0001, respectively) and negatively correlated with blood calcium (r=-0.435, r=-0.476; P<0.0001, respectively), 25(OH) vitamin D, (r=-0.319, r=-0.353; respectively, P<0.0001) and the estimated glomerular filtration rate (r=-0.717, r=-0.688; P<0.0001, respectively).

CONCLUSIONS

Among patients with CKD stages 3 to 5 not on dialysis, the bio-intact PTH assay detected significantly lower PTH concentrations compared with intact PTH assay. Additional studies that correlate the diagnosis and management of CKD mineral and bone disorders with bone histomorphometric findings are needed to determine whether bio-intact PTH assay results are better surrogate markers in these early stages of CKD.

Attainment of guideline targets in EURODOPPS haemodialysis patients: are differences related to a country's healthcare expenditure and nephrologist workforce?

Background

In the field of chronic kidney disease, global clinical practice guidelines have been developed and implemented with a view to improving patient care and outcomes. The attainment of international and European guideline targets for haemodialysis patients in European countries has not been audited recently. Hence, we sought to establish whether the attainment of the targets set out in guidelines and inappropriate care are similar across European countries and whether inter-country differences are related to disparities in national healthcare expenditures (as a percentage of gross domestic product) and/or the nephrologist workforce per capita.

Methods

EURODOPPS is the European part of an international, prospective study of a cohort of adult, in-centre, haemodialysed patients. For the current project, 6317 patients from seven European countries were included between 2009 and 2011. Data on laboratory test results and medication prescriptions were extracted from patient records, in order to determine the overall percentage of patients treated according to the international guidelines on anaemia, dyslipidaemia, metabolic acidosis and mineral bone disease. Data related to macroeconomic indices were collected from World Health Organization database and World Bank stats.

Results

Attainment of the targets set in international guidelines was far from complete; only 34.1% of patients attained their target blood pressure and 31.2% attained their target haemoglobin level. Overall, only 5% of the patients attained all of the studied guideline targets. We observed marked inter-country differences in levels of guideline uptake/application and the use of pharmacological agents. The levels of national healthcare expenditures and nephrologist workforce were not correlated with the percentage of patients on-target for ≥50% of the studied variables or with inappropriate care (except for anaemia).

Conclusions

Our analysis of EURODOPPS data highlighted a low overall level of guideline target attainment in Europe and substantial differences between European countries. These inter-country differences did not appear to be linked to macroeconomic determinants.

Hyaluronate - parathyroid hormone peptide conjugate for transdermal treatment of osteoporosis

Human parathyroid hormone 1-34 fragment (PTH_1-34) has been used as a FDA-approved therapeutics to treat osteoporosis by daily subcutaneous injection. In this work, we successfully developed PTH_1-34 conjugated hyaluronic acid (HA) for the transdermal treatment of osteoporosis with improved patient compliance. HA-PTH_1-34 conjugate was synthesized by the coupling reaction between aldehyde group introduced to HA and amine group of PTH_1-34. After characterization by gel permeation chromatography (GPC) and ELISA, the biological effect of HA-PTH_1-34 conjugate on the proliferation of human osteoblast cells was confirmed by in vitro calcium colorimetric assay and cAMP assay. Two-photon microscopy clearly visualized the effective skin penetration of FITC modified HA-PTH_1-34 conjugate. The transdermally delivered HA-PTH_1-34 conjugates elevated the blood calcium concentration for more than 2 days, reflecting the feasibility for the treatment of osteoporosis.

Multiphasic effects of blood pressure on survival in hemodialysis patients

Dialysis patients exhibit an inverse, L- or U-shaped association between blood pressure and mortality risk, in contrast to the linear association in the general population. We prospectively studied 9333 hemodialysis patients in France, aiming to analyze associations between predialysis systolic, diastolic, and pulse pressure with all-cause mortality, cardiovascular mortality, and nonfatal cardiovascular endpoints for a median follow-up of 548 days. Blood pressure components were tested against outcomes in time-varying covariate linear and fractional polynomial Cox models. Changes throughout follow-up were analyzed with a joint model including both the time-varying covariate of sequential blood pressure and its slope over time. A U-shaped association of systolic blood pressure was found with all-cause mortality and of both systolic and diastolic blood pressure with cardiovascular mortality. There was an L-shaped association of diastolic blood pressure with all-cause mortality. The lowest hazard ratio of all-cause mortality was observed for a systolic blood pressure of 165 mm Hg, and of cardiovascular mortality for systolic/diastolic pressures of 157/90 mm Hg, substantially higher than currently recommended values for the general population. The 95% lower confidence interval was approximately 135/70 mm Hg. We found no significant correlation for either systolic, diastolic, or pulse pressure with myocardial infarction or nontraumatic amputations, but there were significant positive associations between systolic and pulse pressure with stroke (per 10-mm Hg increase: hazard ratios 1.15, 95% confidence interval 1.07 and 1.23; and 1.20, 1.11 and 1.31, respectively). Thus, whereas high pre-dialysis blood pressure is associated with stroke risk, low pre-dialysis blood pressure may be both harmful and a proxy for comorbid conditions leading to premature death.

Achievement of Kidney Disease: Improving Global Outcomes mineral and bone targets between 2010 and 2014 in incident dialysis patients in France: the Photo-Graphe3 study

Background

Abnormal serum phosphate, calcium and parathyroid hormone (PTH) levels in patients with chronic kidney disease (CKD) undergoing haemodialysis have been associated with poor survival. The French Phosphorus and Calcium Observatory (Photo-Graphe^® 3) aimed to estimate the percentage of CKD patients achieving the three Kidney Disease: Improving Global Outcomes (KDIGO) targets about optimal serum phosphate, calcium and PTH over a 3.5-year follow-up period.

Methods

This was a prospective, multicentre, epidemiological observational study conducted with nephrologists in France, selected using a clustering approach. Eligible patients were adults undergoing intermittent haemodialysis or haemodiafiltration therapy started within the preceding 12 months. Data about clinical events, serum biochemistry and treatment were collected once every 6 months for 2.5 years and 12 months thereafter.

Results

Overall, 9010 incident patients were included (men, 63%; median age, 71 years) of whom 7515 (83.4%) were treated by haemodialysis and 1495 (16.6%) by haemodiafiltration. None had a history of fracture or revascularization while 89 (1%) patients had a history of parathyroidectomy >6 months. Overall, 874 (10%) patients received a kidney graft, 2183 (24%) died and 1148 (13%) were lost to follow-up. The proportion achieving the three KDIGO targets increased significantly from 11% to 16% (P < 0.0001) until Year 2, but remained stable afterwards. The percentage of incident dialysis patients with normal serum phosphate (P < 0.0001) or normal serum calcium (P < 0.0001) levels increased significantly over time, while no significant change was observed for those with controlled PTH.

Conclusion

Less than 20% of patients achieved the KDIGO recommendations although their proportion increased slightly over time.

[Management of bone and mineral metabolism disorders before the dialysis stage remains still perfectible. Data from the French Phosphorus and Calcium Survey Photo-Graphe]

Only limited data is available on the management of the chronic kidney disease-associated bone and mineral metabolism disorder (CKD-MBD) in the pre-dialysis stages of CKD in France. A better knowledge of current management habits could lead to an improvement in the implementation of international recommendations (KDIGO). The 3rd version of the French Phosphorus and Calcium Survey Photo-Graphe (Sanofi) included a cohort of CKD stages 4 and 5 patients, whose aim was to examine the prevalence of CKD-MBD and the quality of its management in patients under the care of 62 nephrologists from over 20 geographical regions in France. The study started in October 2011, i.e. one year after patient enrollment. We examined in particular the percentage of patients presenting with laboratory parameter abnormalities indicative of CKD-MBD who were not receiving adequate treatment. A total of 456 patients with CKD stage 4 and 154 with CKD stage 5 were studied. Their mean age was 72.9±14.2 years, and male/female ratio was 58/42. KDIGO targets of serum PTH for CKD stages 4 and 5 were not achieved in respectively 80 and 84% of the patients, for serum calcium in 8 and 22% and for serum phosphate in 12 and 46%. As a potential explanation, insufficient therapy was estimated to account for respectively 45 and 60% of insufficiently controlled secondary hyperparathyroidism, and for 36% of persistent hyperphosphatemia in stage 5. It should be noted that 55.5 and 57.5% of patients were receiving native vitamin D. In this national observatory, the management of CKD-MBD stages 4 and 5 appears suboptimal, especially as regards the control of secondary hyperparathyroidism, which remained untreated in nearly 50% of the patients. Hyperphosphatemia was also common and inadequately controlled in CKD stage 5. To improve the management of CKD-MBD, nephrologists need to be more aware of the importance of aiming for recommended laboratory targets and how this can be achieved.

Prospective cohort study: Cinacalcet-mediated lowering of PTH level and cardiovascular disease mortality in younger Korean patients with stage 5 CKD at a Korean secondary hospital

WHAT IS KNOWN AND OBJECTIVES

Cinacalcet may reduce cardiovascular disease (CVD) mortality in elderly patients with chronic kidney disease (CKD). However, previous studies of the clinical responses to cinacalcet have exhibited discrepancies due to highly variable baseline levels of parathyroid hormone (PTH), kidney function and age. Little is known about the true effect of cinacalcet on stage 5 CKD. The objective of the current observational study was to evaluate whether cinacalcet-mediated lowering of PTH levels improves all-cause mortality and cardiovascular disease mortality in younger stage 5 CKD patients (mean age <55 years).

METHODS

This prospective, cohort study reviewed the electronic medical records (EMRs) of CKD patients (n=540) with secondary hyperparathyroidism (SHPT) for a period of 36 months. Of 540 patients, 104 subjects met the inclusion criteria and were included in the final evaluation (mean serum iPTH 688.7 pg/mL). Patients were divided into a cinacalcet group (n=43) and a non-cinacalcet group (n=61).

RESULTS AND DISCUSSION

Comparing the cinacalcet group to the non-cinacalcet group, Cox proportional hazard modelling found that all-cause mortality was five (31.3%) in the cinacalcet group and three (15.8%) in the non-cinacalcet group for patients with serum levels of PTH>600 pg/mL [P=.277, hazard ratio 2.213, 95% confidence interval (CI): 0.529-9.262]. Cardiovascular disease mortality (CVD: heart disease) occurred in two (5.3%) in the cinacalcet group and one (2.1%) in the non-cinacalcet group [P=.425, HR 2.611, 95% CI: 0.228-9.939]. Overall, there were no significant differences in CVD mortality between the two groups.

WHAT IS NEW AND CONCLUSION

Cinacalcet was not associated with decreases in all-cause mortality or CVD mortality in younger stage 5 CKD patients with high PTH levels (>600 pg/mL). This could be explained by the diversity of the population in terms of the patient's age, health insurance policies, target serum level of biochemical and PTH, and glomerular filtration rate (GFR) at admission. These data, although based on an observational study, indicate that adding cinacalcet to the current standard care for younger stage 5 CKD patients should be re-evaluated.

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

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

Calcium and Bone Metabolism Indices

Calcium and inorganic phosphate are of critical importance for many body functions, thus the regulations of their plasma concentrations are tightly controlled by the concerted actions of reabsorption/excretion in the kidney, absorption in the intestines, and exchange from bone, the major reservoir for calcium and phosphate in the body. Parathyroid hormone (PTH) and 1,25-dihydroxyvitamin D (1,25(OH)₂D) control calcium homeostasis, whereas PTH, 1,25(OH)₂D, and bone-derived fibroblast growth factor 23 (FGF 23) control phosphate homeostasis. Hypoparathyroidism can cause hypocalcemia and hyperphosphatemia, whereas deficient vitamin D actions can cause osteomalacia in adults and rickets in children. Hyperparathyroidism, alternatively, can cause hypercalcemia and hypophosphatemia. Laboratory tests of calcium, phosphate, PTH, and 25-hydroxyvitamin D are very useful in the diagnosis of abnormalities associated with calcium and/or phosphate metabolisms. Bone is constantly remodeled throughout life in response to mechanical stress and a need for calcium in extracellular fluids. Metabolic bone diseases such as osteoporosis, osteomalacia in adults or rickets in children, and renal osteodystrophy develop when bone resorption exceeds bone formation. Bone turnover markers (BTM) such as serum N-terminal propeptide of type I procollagen (P1NP) and C-terminal collagen cross-link (CTX) may be useful in predicting future fracture risk or monitoring the response to anti-resorptive therapy. There is a need to standardize sample collection protocols because certain BTMs exhibit large circadian variations and tend to be influenced by food intakes. In the United States, a project to standardize BTM sample collection protocols and to establish the reference intervals for serum P1NP and serum CTX is ongoing. We anticipate the outcome of this project to shine lights on the standardization of BTM assays, sample collection protocols, reference intervals in relation to age, sex, and ethnic origins, and clinical utilities of BTMs. This review will briefly discuss the regulations of calcium and phosphate homeostasis, laboratory's role in the diagnosis, and monitoring of bone and calcium metabolism, as well as the usefulness and controversies of the utilities of BTMs in the diagnosis and monitoring of metabolic bone diseases.

Parathyroid hormone metabolism and signaling in health and chronic kidney disease

Circulating parathyroid hormone (PTH) shows a complex relationship with hard outcomes in subjects with chronic kidney disease (CKD). Moreover, intervention studies directly targeting PTH failed to yield unequivocal results. Disturbed PTH metabolism, posttranslational modifications of PTH, and end-organ hyporesponsiveness to PTH may explain the poor performance of PTH as an outcome biomarker and precise target of therapy in the setting of CKD, at least in the gray middle target zone. PTH fragments accumulate in CKD patients and may exert effects that are distinct from, if not opposite to biointact (1-84)PTH. Posttranslational modification of PTH and especially oxidation may alter the interaction of PTH with its receptor. Its clinical relevance, however, remains a matter of ongoing debate. Less controversial is the issue of end-organ hyporesponsiveness to PTH. This phenomenon, formally referred to as PTH resistance, has long been recognized in CKD, but factors and mechanisms contributing to it remain poorly defined. Subsequent evidence identified downregulation of the PTH receptor and competing downstream signals as underlying pathophysiologic mechanisms. End-organ hyporesponsiveness to PTH in CKD, along with important analytical and biological variability, renders defining the PTH target range in CKD challenging. Although this may still be accomplished at the population level, it may prove to be very difficult at the individual level. This is a disillusioning thought in an era of personalized medicine. Parallel to the search of a functional and readily available assay quantifying PTH signaling tone or sensitivity, additional biomarkers (or a panel of biomarkers) should be formally evaluated.

Clinical and Practical Use of Calcimimetics in Dialysis Patients With Secondary Hyperparathyroidism

CKD and CKD-related mineral and bone disorders (CKD-MBDs) are associated with high cardiovascular and mortality risks. In randomized clinical trials (RCTs), no single drug intervention has been shown to reduce the high mortality risk in dialysis patients, but several robust secondary analyses point toward important potential beneficial effects of controlling CKD-MBD-related factors and secondary hyperparathyroidism. The advent of cinacalcet, which has a unique mode of action at the calcium-sensing receptor, represented an important step forward in controlling CKD-MBD. In addition, new RCTs have conclusively shown that cinacalcet improves achievement of target levels for all of the metabolic abnormalities associated with CKD-MBD and may also attenuate the progression of vascular and valvular calcifications in dialysis patients. However, a final conclusion on the effect of cinacalcet on hard outcomes remains elusive. Tolerance of cinacalcet is limited by frequent secondary side effects such as nausea, vomiting, hypocalcemia and oversuppression of parathyroid hormone, which may cause some management difficulties, especially for those lacking experience with the drug. Against this background, this review aims to summarize the results of studies on cinacalcet, up to and including the publication of the recent ADVANCE and EVOLVE RCTs, as well as recent post hoc analyses, and to offer practical guidance on how to improve the clinical management of the most frequent adverse events associated with cinacalcet, based on both currently available information and personal experience. In addition, attention is drawn to less common secondary effects of cinacalcet treatment and advisable precautions.

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

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

Multiple biomarker strategy based on parathyroid hormone and natriuretic peptides testing for improved prognosis of chronic heart failure

Biomarkers offer new perspectives for a more personalized management of patients with heart failure (HF). Hyperparathyroidism is common in HF patients and parathyroid hormone (PTH) testing might provide added value for the prognostication of HF patients. Our objectives were therefore to determine the efficiency of multiple biomarker strategy based on PTH and natriuretic peptides measurement for the risk stratification of patients with HF. Circulating concentrations of bioactive PTH 1-84 and natriuretic peptides, B-type natriuretic peptide (BNP) and N-terminal proBNP (NT-proBNP), were measured with automated immunoassays in 45 healthy individuals and 137 HF patients with reduced left ventricular ejection fraction. Circulating levels of PTH 1-84 and natriuretic peptides were significantly increased in HF patients in comparison to HF patients. Over a long-term follow-up, baseline PTH 1-84 levels were related to the risk of cardiovascular death. Furthermore, in multiple biomarker approach, PTH measurement was additive to BNP and NT-proBNP testing for the cardiovascular risk assessment of HF patients. In conclusion, the combination of PTH 1-84 and natriuretic peptides testing improves the prognostication of HF patients and might allowed more personalized approach for risk stratification and treatment selection in HF patients.

News on biomarkers in CKD-MBD

The increased awareness of the potential role played by mineral and bone disorder in the appearance of cardiovascular disease in renal patients has produced research efforts aimed at discovering possible pathogenic links. Accordingly, the diagnostic significance of the classic bone markers of mineral disorders and of the new markers in the setting of chronic kidney disease-mineral and bone disorders (CKD-MBD) needs to be re-evaluated along with increasing information. In this article we include classic markers of bone metabolism and some of the noncollagenous bone proteins that are gaining experimental and clinical significance in CKD-MBD. Among classic markers of secondary hyperparathyroidism and of renal osteodystrophy, we analyzed parathyroid hormone, alkaline phosphatase, tartrate-resistant acid phosphatase, and bone collagen-derived peptides. We underlined, for each, the relevance of parent proteins (peptides or isoforms) that affect assay methods and, eventually, the diagnostic or prognostic significance. Also, we considered their relationship with cardiovascular mortality. Among the numerous noncollagenous bone proteins, we examined matrix Gla protein (MGP), osteocalcin (OC), osteoprotegerin, and the small integrin-binding ligand N-linked glycoprotein family. For MGP and OC we report the relevant involvement with the process of calcification (MGP) and with glucose and energy metabolism (OC). Both of these proteins require vitamin K to become active and this is a specific problem in renal patients who frequently are deficient of this vitamin. Finally, recent acquisitions on the fascinating family of the small integrin-binding ligand N-linked glycoprotein proteins are recapitulated briefly to underline their potential clinical interest and their complex involvement with all aspects of CKD-MBD. Their diagnostic role in clinical practice awaits further studies.

Long-term proton pump inhibitor use is associated with vascular calcification in chronic kidney disease: a cross-sectional study using propensity score analysis

BACKGROUND

Proton pump inhibitors (PPIs) are a class of drugs that is extensively used for common gastrointestinal disorders and often prescribed long-term for years. Long-term PPI treatment is associated with an increased risk of fractures in the general population. Several studies have suggested a relationship between vascular calcification, which is a predictor of cardiovascular morbidity and mortality, impaired bone metabolism and fractures. In dialysis patients, vascular calcifications are widespread and are connected to bone health.

OBJECTIVE

The aim of this study was to assess the association between the use of PPIs and vascular calcifications involving the aorta and iliac arteries in haemodialysis patients.

METHODS

Between November 2008 and November 2009, 387 patients receiving long-term dialysis treatment (≥1 year) were enrolled in a multicentre (18 Dialysis Units), cross-sectional study. Overall, 76.2 % of patients were receiving long-term PPI treatment. The main outcome measure was calcification of the aorta and iliac arteries in relation to PPI use. Standardized radiographs were sent to the coordinating centre for centralized evaluation in duplicate by two physicians who were blind to PPI status.

RESULTS

Arterial calcifications were significantly more common in the PPI group (p < 0.01). Also, the rates of aortic and iliac calcifications considered separately were higher (+12.2 %, p = 0.0254; and +13.6 %, p = 0.0211, respectively). After correction for the propensity score, the odds ratios [ORs] (95 % CI) related to PPI use were aorta 1.89 (1.01-3.54), p = 0.048; iliac arteries 2.27 (1.31-3.92), p = 0.003; aorta and iliac arteries 2.59 (1.48-4.53), p = 0.008. The ORs (95 % CI) related to the association of warfarin + PPI were aorta 2.19 (0.95-5.00), p = 0.06; iliac arteries 2.90 (1.07-7.86), p = 0.036; aorta and iliac arteries 2.69 (1.03-6.96), p = 0.042.

CONCLUSION

In haemodialysis patients, long-term treatment with PPIs, especially in the presence of warfarin treatment, is associated with vascular calcifications.

Elevated parathyroid hormone, but not vitamin D deficiency, is associated with increased risk of heart failure in older men with and without cardiovascular disease

BACKGROUND

Hyperparathyroidism and low vitamin D status have been implicated in the pathogenesis of heart failure (HF). We examined the prospective associations between parathyroid hormone (PTH), circulating 25-hydroxyvitamin D, and markers of mineral metabolism and risk of incident HF in older men with and without established cardiovascular disease.

METHODS AND RESULTS

Prospective study of 3731 men aged 60 to 79 years with no prevalent HF followed up for a mean period of 13 years, in whom there were 287 incident HF cases. Elevated PTH (≥55.6 pg/mL; top quarter) was associated with significantly higher risk of incident HF after adjustment for lifestyle characteristics, diabetes mellitus, blood lipids, blood pressure, lung function, heart rate, renal dysfunction, atrial fibrillation, forced expiratory volume in 1 second, and C-reactive protein (hazards ratio, 1.66; 95% confidence interval, 1.30-2.13). The increased risk was seen in both men with and without previous myocardial infarction or stroke (hazards ratio, 1.72; 95% confidence interval, 1.07-2.76; hazards ratio, 1.70; 95% confidence interval, 1.25-2.30, respectively). Elevated PTH was significantly associated with N-terminal probrain natriuretic peptide, a marker of left ventricular wall stress. By contrast, 25-hydroxyvitamin D and other markers of mineral metabolism including serum calcium and phosphate showed no significant association with incident HF after adjustment for age.

CONCLUSIONS

Elevated PTH, but not 25-hydroxyvitamin D or other markers of mineral metabolism, is associated with increased risk of HF in both older men with and without myocardial infarction/stroke. This increased risk was not explained by its association with known risk factors for HF. Further studies are now needed to elucidate the mechanisms underlying this association.

Hemodynamic markers and subclinical atherosclerosis in postmenopausal women with primary hyperparathyroidism

CONTEXT

Recent evidence suggests that primary hyperparathyroidism (pHPT) is linked with hypertension and subclinical atherosclerosis. These associations have not been examined in postmenopausal women, in whom cardiovascular risk steeply rises after menopausal transition.

OBJECTIVE

The objective of the study was to assess whether pHPT is associated with hemodynamic markers and subclinical atherosclerosis in postmenopausal women under a cross-sectional case-control design.

METHODS

One hundred two postmenopausal women with pHPT and 102 women matched 1:1 for age and menopausal status were consecutively recruited. In all patients, flow-mediated dilatation, carotid-femoral pulse wave velocity, reflected waves, aortic blood pressures (BP), intima-media thickness, and the presence of plaques in the carotid and common femoral arteries were measured.

RESULTS

Women with pHPT had higher aortic and peripheral BP (P < .05 for all), but no correlation was observed with subclinical atherosclerosis. After adjusting for possible confounders, pHPT was an independent determinant of peripheral and aortic diastolic BP (P < .05 for all). The association with systolic BP was lost after adjusting for C-reactive protein. Further adjustment for PTH and 25-hydroxyvitamin D levels revealed that PTH but not 25-hydroxyvitamin D was an independent determinant of all BP parameters. Both peripheral and aortic BP increased across PTH tertiles as compared with the control group, but this association lost significance after adjustment for C-reactive protein.

CONCLUSIONS

These results suggest that pHPT may increase peripheral and aortic BP through PTH and inflammatory-mediated mechanisms. A direct impact of the disease on the arterial wall cannot be implicated despite the large number of markers of subclinical atherosclerosis measured in this study.

The use of fibroblast growth factor 23 testing in patients with kidney disease

The emergence of fibroblast growth factor 23 as a potentially modifiable risk factor in CKD has led to growing interest in its measurement as a tool to assess patient risk and target therapy. This review discusses the analytical and clinical challenges faced in translating fibroblast growth factor 23 testing into routine practice. As for other bone mineral markers, agreement between commercial fibroblast growth factor 23 assays is poor, mainly because of differences in calibration, but also, these differences reflect the variable detection of hormone fragments. Direct comparison of readout from different assays is consequently limited and likely hampers setting uniform fibroblast growth factor 23-directed targets. Efforts are needed to standardize assay output to enhance clinical use. Fibroblast growth factor 23 is robustly associated with cardiovascular and renal outcomes in patients with CKD and adds value to risk assessments based on conventional risk factors. Compared with most other mineral markers, fibroblast growth factor 23 shows better intraindividual temporal stability, with minimal diurnal and week-to-week variability, but substantial interindividual variation, maximizing discriminative power for risk stratification. Conventional therapeutic interventions for the CKD-mineral bone disorder, such as dietary phosphate restriction and use of oral phosphate binders or calcimimetics, are associated with variable efficacy at modulating circulating fibroblast growth factor 23 concentrations, like they are for other mineral metabolites. Dual therapy with dietary phosphate restriction and noncalcium-based binder use achieves the most consistent fibroblast growth factor 23-lowering effect and seems best monitored using an intact assay. Additional studies are needed to evaluate whether strategies aimed at reducing levels or antagonizing its action have beneficial effects on clinical outcomes in CKD patients. Moreover, a better understanding of the mechanisms driving fibroblast growth factor 23 elevations in CKD is needed to inform the use of therapeutic interventions targeting fibroblast growth factor 23 excess. This evidence must be forthcoming to support the use of fibroblast growth factor 23 measurement and fibroblast growth factor 23-directed therapy in the clinic.

PTH: Potential role in management of heart failure

Biomarkers play an important role for the diagnosis and prognosis of heart failure (HF), a disease with high morbidity and mortality as well as a huge impact on healthcare budgets. Parathyroid hormone (PTH) is a major systemic calcium-regulating hormone and an important regulator of bone and mineral homeostasis. PTH testing is important for differential diagnosis of calcemia related disorders and for the management of patients with chronic kidney disease. As secondary hyperparathyroidism has been evidenced in HF patients, PTH testing might be relevant in HF patients for risk stratification and more personalized selection of treatment.

[Clinical value of two methods to measure parathyroid hormone in chronic renal insufficiency, considering vitamin D metabolism]

INTRODUCTION

Parathyroid hormone levels provide important information in chronic renal failure.

AIM

To compare parathyroid hormone levels measured by two assays in correlation with vitamin D supply.

METHOD

Parathyroid hormone and 25-hydroxi-vitamin-D were determined in 104 patients (31 patients with chronic renal failure without renal replacement therapy, 36 patients treated with peritoneal dialysis and 37 patients treated with hemodialysis).

RESULTS

Good correlation was found between results of the two parathyroid hormone methods, but the intact parathyroid hormone levels were higher than the biointact values. 87% and 13% of the patients had vitamin-D deficiency and insufficiency, respectively. The frequency of serious vitamin-D deficiency was higher in the peritoneal dialysis than in the hemodialysis group. Intact parathyroid hormone levels were different in dialysed patients having vitamin-D-deficiency and insufficiency, and the difference was higher for the biointact than intact values. Negative correlation was detected between biointact parathyroid hormone and 25-hydroxivitamin-D in the hemodialysis group.

CONCLUSIONS

Biointact parathyroid hormone levels better reflect the vitamin D supply and bone metabolism than intact levels, especially in hemodialysed patients.

Fibroblast growth factor 23

There is growing interest in the role of fibroblast growth factor 23 (FGF23) in various diseases of disordered mineral metabolism. In chronic kidney disease (CKD), where biochemical evidence of mineral disturbances is especially common, FGF23 measurement has been advocated as an early and sensitive marker for CKD-related bone disease. In this setting, FGF23 analysis may also improve the discrimination of risk of adverse renal and cardiovascular outcomes and aid targeting of those patients that are likely to benefit from interventions. Nonetheless, while the physiological relevance of FGF23 in the control of mineral metabolism is now firmly established, relatively little attention has been paid to important preanalytical and analytical aspects of FGF23 measurement that may impact on its clinical utility. Here we review these issues and discuss the suitability of FGF23 testing strategies for routine clinical practice. The current ‘state-of-the-art’ enzyme-linked immunosorbent assay methods for FGF23 measurement show poor agreement due to differences in FGF23 fragment detection, antibody specificity and calibration. Such analytical variability does not permit direct comparison of FGF23 measurements made with different assays and is likely to at least in part account for some of the inconsistencies noted between observational studies. From a clinical perspective, the lack of concordance has implications for the development of standardized reference intervals and clinical decision limits. Finally, the inherent assay-dependent biological variability of plasma FGF23 concentration can further complicate the interpretation of results and the design of FGF23-based testing protocols. Currently, it would be premature to consider incorporating FGF23 measurements into standard testing repertoires.

Harmonization in laboratory medicine: the complete picture

Evidence of the acute lack of interchangeable laboratory results and consensus in current practice among clinical laboratories has underpinned greater attention to standardization and harmonization projects. Although the focus is mainly on the standardization of measurement procedures, the scope of harmonization goes beyond method and analytical results: it includes all other aspects of laboratory testing, including terminology and units, report formats, reference intervals and decision limits, as well as test profiles and criteria for the interpretation of results. This review provides further insight on the issue of harmonization in laboratory medicine in view of the urgent need for a complete picture now that old and new drivers are calling for more effective efforts in this field. The main drivers for standardization and harmonization projects are first and foremost patient safety, but also the increasing trends towards consolidation and networking of clinical laboratories, accreditation programs, clinical governance, and advances in Information Technology (IT), including the electronic patient record. The harmonization process, which should be considered a three-tier approach involving local, national and international fronts, must go beyond the harmonization of methods and analytical results to include all other aspects of laboratory testing. A pertinent example of the importance of a complete picture in harmonization programs is given by the National Bone Health Alliance working in the field of bone turnover markers in cooperation with scientific societies including the International Federation of Clinical Chemistry and Laboratory Medicine (IFCC).

Variability in parathyroid hormone assays confounds clinical practice in chronic kidney disease patients

BACKGROUND

Intact parathyroid hormone (iPTH) measurements are used to guide therapy in renal patients, but variability in results can occur depending on the assay used. This study has investigated iPTH assay variation in North West England and paired data with regional audit data to determine clinical relevance of assay variability.

METHODS

Thirty-seven haemodialysis patients had blood taken (EDTA plasma, and serum), and samples were processed at 17 laboratories that analyse iPTH for North West dialysis patients. Correction factors were calculated and applied to the iPTH assay results to enable direct comparisons. These correction factors were also applied to Regional Audit data to determine if iPTH assay variability explains the variation in unit performance in achieving PTH targets.

RESULTS

The iPTH results from the 37 patients were significantly different when either analysed by different assays and/or different laboratories (P < 0.001). The Abbott Architect method consistently produced the highest iPTH results. Of the 37 patients, between 49% and 65% would achieve the Kidney Disease: Improving Global Outcomes (KDIGO) iPTH target depending on the assay used. When results were adjusted using correction factors, 21% of the patients would require a change of management according to guidelines. Data from all haemodialysis units submitted for the regional audit were adjusted to the Roche assay and this led to a small change in achievement of KDIGO iPTH targets in individual units when compared to each other.

CONCLUSIONS

A combination of iPTH assay variability and diversity in clinical management leads to variation in achieving iPTH targets. Both need to be improved and/or standardized to improve patient care.

Decreased expression of calcium-sensing receptor and parafibromin in secondary hyperparathyroidism with an abnormal whole PTH/intact PTH ratio

A 34-year-old female hemodialysis patient with an abnormal whole parathyroid hormone (PTH)/intact PTH ratio (ratio = 1.14) underwent parathyroidectomy for advanced secondary hyperparathyroidism. The abnormal PTH ratio indicated a relative increase in the serum N-terminus PTH, a new molecular form of PTH. The abnormal ratio normalized immediately after the largest parathyroid gland (PTG) was removed, proving the largest PTG as causative. An immunohistochemical analysis revealed extremely decreased expression of the calcium-sensing receptor and parafibromin in the largest PTG in comparison with the other PTGs. This case indicated the possible involvement of decreased calcium-sensing receptor and parafibromin signaling in the development of the abnormal PTH ratio.

Renal function, calcium regulation, and time to hospitalization of patients with chronic kidney disease

BACKGROUND

Chronic kidney disease is associated with disruption of the endocrine system that distorts the balance between calcitriol, calcium, phosphate and parathyroid hormone in the calcium regulation system. This can lead to calcification of the arterial tree and increased risk of cardiovascular disease and death. In this study we develop a health metric, based on biomarkers involved in the calcium regulation system, for use in identifying patients at high risk for future high-cost complications.

METHODS

This study is a retrospective observational study involving a secondary analysis of data from the kidney disease registry of a regional managed care organization. Chronic kidney disease patients in the registry from November 2007 through November 2011 with a complete set of observations of estimated glomerular filtration rate, calcitriol, albumin, free calcium, phosphate, and parathyroid hormone were included in the study (n = 284). Weibull regression model was used to identify the most significant lab tests in predicting "waiting time to hospitalization". A multivariate linear path model was then constructed to investigate direct and indirect effects of the biomarkers on this outcome.

RESULTS

The results showed negative significant direct effects of phosphate and parathyroid hormone on "waiting time to hospitalization". Base on this result, the risk of hospitalization increases 16.8% for each 0.55 mg/dl increase in phosphate level and 13.5% for each 0.467 increase in the natural logarithm of parathyroid hormone. Positive indirect effects of calcitriol surrogate (calcidiol), free calcium, albumin and estimated glomerular filtration rate were observed but were relatively small in magnitude.

CONCLUSION

Variables involved in the calcium regulation system should be included in future efforts to develop a quality of care index for Chronic Kidney disease patients.