Racial differences in parathyroid hormone levels in patients with secondary hyperparathyroidism

Current treatment options for secondary hyperparathyroidism in patients with stage 3 to 4 chronic kidney disease and vitamin D deficiency

Introduction: Secondary hyperparathyroidism (SHPT) represents a complication of chronic kidney disease (CKD). Vitamin D system is altered since early CKD, and vitamin D deficiency is an established trigger of SHPT. Although untreated SHPT may degenerate into tertiary hyperparathyroidism with detrimental consequences in advanced CKD, best treatments for counteracting SHPT from stage 3 CKD are still debated. Enthusiasm on prescription of vitamin D receptor activators (VDRA) in non-dialysis renal patients, has been mitigated by the risk of low bone turnover and positive calcium-phosphate balance. Nutritional vitamin D is now suggested as first-line therapy to treat SHPT with low 25(OH)D insufficiency. However, no high-grade evidence supports the best choice between ergocalciferol, cholecalciferol, and calcifediol (in its immediate or extended-release formulation).Areas covered: The review discusses available data on safety and efficacy of nutritional vitamin D, VDRA and nutritional therapy in replenishing 25(OH)D deficiency and counteracting SHPT in non-dialysis CKD patients.Expert opinion: Best treatment for low 25(OH)D and SHPT remains unknown, due to incomplete understanding of the best homeostatic, as mutable, adaptation of mineral metabolism to CKD progression. Nutritional vitamin D and nutritional therapy appear safest interventions, whenever contextualized with single-patient characteristics. VDRA should be restricted to uncontrolled SHPT by first-line therapy.

Racial differences in the relationship between high-normal 25-hydroxy vitamin d and parathyroid hormone levels in early stage chronic kidney disease

Aim:

Current guidelines do not address between-person variability in markers of bone and mineral metabolism across subgroups of patients, nor delineate treatment strategies based upon such factors.

Methods:

A cross sectional study was carried out to analyze data from 20,494 United States Veterans and verify the variability of Vitamin D (25(OH)D) and parathyroid hormone (PTH) levels across race and stage of chronic kidney disease.

Results:

PTH levels were higher in Black Americans (BA) than White Americans (WA) at all levels of 25(OH)D and across eGFR strata. There was a progressive decline in PTH levels from the lowest (25(OH)D < 20) to highest quartile (25(OH)D >=40) in both BA (134.4 v 90 pg/mL, respectively) and WA (112.5 v 71.62 pg/mL) (p<0.001 for all comparisons).

Conclusion:

In this analysis, higher than normal 25(OH)D levels were well tolerated and associated with lower parathyroid hormone values in both blacks and whites. Black Americans had higher PTH values at every level of eGFR and 25(OH)D levels suggesting a single PTH target is not appropriate.

Racial-ethnic differences in chronic kidney disease-mineral bone disorder in youth on dialysis

BACKGROUND

Studies in healthy pediatric populations and adults treated with dialysis demonstrate higher parathyroid hormone (PTH) and lower 25-hydroxyvitamin D levels in African-Americans. Despite these findings, African-Americans on dialysis demonstrate greater bone strength and a decreased risk of fracture compared to the Caucasian dialysis population. The presence of such differences in children and young adult dialysis patients is unknown.

METHODS

Differences in the markers of mineral and bone metabolism (MBM) were assessed in 661 incident dialysis patients (aged 1 month to < 21 years). Racial-ethnic differences in PTH, calcium, phosphate, and total alkaline phosphatase (AP) activity were analyzed over the first year of dialysis using multivariate linear mixed models.

RESULTS

African-American race predicted 23% higher serum PTH (95% CI, 4.7-41.3%) when compared to Caucasian patients, while Hispanic ethnicity predicted 17.5% higher PTH (95% CI, 2.3-38%). Upon gender stratification, the differences in PTH were magnified in African-American and Hispanic females: 38% (95% CI, 14.8-69.8%) and 28.8% (95% CI, 4.7-54.9%) higher PTH compared to Caucasian females. Despite higher PTH values, African-American females persistently demonstrated up to 10.9% lower serum AP activity (95% CI, - 20.6-- 0.7%).

CONCLUSIONS

There are racial-ethnic differences in the markers of MBM. Higher PTH is seen in African-American and Hispanic children and young adults on dialysis with a magnification of this difference amongst the female population. There is a need to consider how factors like race, ethnicity, and gender impact the goal-targeted treatment of MBM disorders.

Prevalence of CKD-MBD in pre-dialysis patients using biochemical markers in Enugu, South-East Nigeria

BACKGROUND

As kidney function declines, there is a progressive deterioration in mineral homeostasis with disruption of normal serum and tissue concentration of phosphorus and calcium, and changes in circulating levels of hormones-parathyroid hormone (PTH), calcitriol (1,25(OH)2 D), and Fibroblast growth factor-23 (FGF-23).

OBJECTIVE

This study was aimed at determining the prevalence of markers of CKD-MBD in pre-dialysis patients.

METHODS

We evaluated consecutively 168 subjects made up of 85 CKD patients and 83 healthy controls, who were attending the renal clinics and medical outpatient of University of Nigeria Teaching Hospital, Enugu. GFR was estimated and serum calcium, phosphorus, alkaline phosphatase, PTH, and 25(OH) D levels assayed.

RESULTS

The prevalence of various mineral bone disease abnormalities were 70% hyper-phosphatemia, 85% hyper-parathyroidism, and 100% low levels of 25 (OH) D among the patients. Estimated GFR correlated negatively with both serum phosphorus, and PTH. Age of the patients ranged from18-76 years with a male to female ratio of 1.7:1. Chronic Glomerulonephritis (CGN), hypertension and diabetes mellitus caused CKD in 75% of the patients. There was no significant decrease in serum calcium levels of patients compared to controls. The patients did not have pathologically raised alkaline phosphatase, although their mean level was significantly higher than that of the control group.

CONCLUSION

Low 25 (OH) D levels (insufficiency/deficiency), hyperparathyroidism, and hyper-phosphatemia were the obvious markers of CKD-MBD in our pre-dialysis patients. These should be evaluated at presentation in these patients.

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.

Mineralocorticoid receptor antagonism confers cardioprotection in heart failure

The symptoms and signs constituting the congestive heart failure (CHF) syndrome have their pathophysiologic origins rooted in a salt-avid renal state mediated by effector hormones of the renin-angiotensin-aldosterone and adrenergic nervous systems. Controlled clinical trials, conducted over the past decade in patients having minimally to markedly severe symptomatic heart failure, have demonstrated the efficacy of a pharmacologic regimen that interferes with these hormones, including aldosterone receptor binding with either spironolactone or eplerenone. Potential pathophysiologic mechanisms, which have not hitherto been considered involved for the salutary responses and cardioprotection provided by these mineralocorticoid receptor antagonists, are reviewed herein. In particular, we focus on the less well-recognized impact of catecholamines and aldosterone on monovalent and divalent cation dyshomeostasis, which leads to hypokalemia, hypomagnesemia, ionized hypocalcemia with secondary hyperparathyroidism and hypozincemia. Attendant adverse cardiac consequences include a delay in myocardial repolarization with increased propensity for supraventricular and ventricular arrhythmias, and compromised antioxidant defenses with increased susceptibility to nonischemic cardiomyocyte necrosis.

[Ethnicity and vitamin D]

Cohort studies, mainly US, show that vitamin D deficiency is more common in African-American population. Social and environmental factors play a role but the difference in skin color is essential. Despite low 25-hydroxyvitamin D concentrations, a lower risk of fragility or fracture exists in these populations. Vitamin D deficiency is a contributing factor in many chronic diseases. There is a relationship between vitamin D deficiencies, progression of chronic kidney disease and increased relative risk of mortality. If the ethnicity of patients is now taken into account to estimate renal function, probably specific recommendations for vitamin D deficiency are needed.

Disturbances in calcium metabolism and cardiomyocyte necrosis: the role of calcitropic hormones

A synchronized dyshomeostasis of extra- and intracellular Ca(2+), expressed as plasma ionized hypocalcemia and excessive intracellular Ca(2+) accumulation, respectively, represents a common pathophysiologic scenario that accompanies several diverse disorders. These include low-renin and salt-sensitive hypertension, primary aldosteronism and hyperparathyroidism, congestive heart failure, acute and chronic hyperadrenergic stressor states, high dietary Na(+), and low dietary Ca(2+) with hypovitaminosis D. Homeostatic responses are invoked to restore normal extracellular [Ca(2+)](o), including increased plasma levels of parathyroid hormone and 1,25(OH)(2)D(3). However, in cardiomyocytes these calcitropic hormones concurrently promote cytosolic free [Ca(2+)](i) and mitochondrial [Ca(2+)](m) overloading. The latter sets into motion organellar-based oxidative stress, in which the rate of reactive oxygen species generation overwhelms their detoxification by endogenous antioxidant defenses, including those related to intrinsically coupled increments in intracellular Zn(2+). In turn, the opening potential of the mitochondrial permeability transition pore increases, allowing for osmotic swelling and ensuing organellar degeneration. Collectively, these pathophysiologic events represent the major components to a mitochondriocentric signal-transducer-effector pathway to cardiomyocyte necrosis. From necrotic cells, there follows a spillage of intracellular contents, including troponins, and a subsequent wound healing response with reparative fibrosis or scarring. Taken together, the loss of terminally differentiated cardiomyocytes from this postmitotic organ and the ensuing replacement fibrosis each contribute to the adverse structural remodeling of myocardium and progressive nature of heart failure. In conclusion, hormone-induced ionized hypocalcemia and intracellular Ca(2+) overloading comprise a pathophysiologic cascade common to diverse disorders and that initiates a mitochondriocentric pathway to nonischemic cardiomyocyte necrosis.

Stressor states and the cation crossroads

Neurohormonal activation involving the hypothalamic-pituitary-adrenal axis and adrenergic nervous and renin-angiotensin-aldosterone systems is integral to stressor state-mediated homeostatic responses. The levels of effector hormones, depending upon the degree of stress, orchestrate the concordant appearance of hypokalemia, ionized hypocalcemia and hypomagnesemia, hypozincemia, and hyposelenemia. Seemingly contradictory to homeostatic responses wherein the constancy of extracellular fluid would be preserved, upregulation of cognate-binding proteins promotes coordinated translocation of cations to injured tissues, where they participate in wound healing. Associated catecholamine-mediated intracellular cation shifts regulate the equilibrium between pro-oxidants and antioxidant defenses, a critical determinant of cell survival. These acute and chronic stressor-induced iterations in extracellular and intracellular cations are collectively referred to as the cation crossroads. Intracellular cation shifts, particularly excessive accumulation of Ca2+, converge on mitochondria to induce oxidative stress and raise the opening potential of their inner membrane permeability transition pores (mPTPs). The ensuing loss of cationic homeostasis and adenosine triphosphate (ATP) production, together with osmotic swelling, leads to organellar degeneration and cellular necrosis. The overall impact of iterations in extracellular and intracellular cations and their influence on cardiac redox state, cardiomyocyte survival, and myocardial structure and function are addressed herein.

Renal osteodystrophy in the first decade of the new millennium: analysis of 630 bone biopsies in black and white patients

Renal osteodystrophy occurs early during loss of kidney function. There are 26 million American patients with chronic kidney disease (CKD), and almost all patients with CKD stage 5 have abnormal bone histology. Six hundred and thirty bone biopsies from adult CKD-5 patients on dialysis were evaluated by histomorphometry and analyzed using the turnover (T), mineralization (M), and volume (V) classification. There were racial differences; whites exhibited predominantly low turnover (62%), whereas blacks showed mostly normal or high turnover (68%). A mineralization defect was observed in only 3% of patients. In whites, cancellous bone volume was low, normal, or high in approximately the same number of patients, whereas in blacks, cancellous bone volume was high in two-thirds of the patients. More than 80% of blacks and whites with low cancellous bone volume had thin trabeculae owing to low bone formation. Cortical thickness was low in half the whites, whereas it was normal in three-quarters of blacks. Cortical porosity was high in 50% of whites, whereas three-quarters of blacks had high porosity. In summary, the TMV system gives relevant information. It should be expanded to include the architecture of cancellous and cortical bone. There are racial differences. Low bone volume and low bone turnover are more frequent than heretofore appreciated, whereas mineralization defects nowadays are observed rarely in adults. These findings call for an adjustment of the current therapeutic paradigm that takes into consideration race and risk of low bone volume and turnover. The latter have been shown to be associated with increased vascular calcifications.

Cellular and molecular pathways to myocardial necrosis and replacement fibrosis

Fibrosis is a fundamental component of the adverse structural remodeling of myocardium present in the failing heart. Replacement fibrosis appears at sites of previous cardiomyocyte necrosis to preserve the structural integrity of the myocardium, but not without adverse functional consequences. The extensive nature of this microscopic scarring suggests cardiomyocyte necrosis is widespread and the loss of these contractile elements, combined with fibrous tissue deposition in the form of a stiff in-series and in-parallel elastic elements, contributes to the progressive failure of this normally efficient muscular pump. Cellular and molecular studies into the signal-transducer-effector pathway involved in cardiomyocyte necrosis have identified the crucial pathogenic role of intracellular Ca2+ overloading and subsequent induction of oxidative stress, predominantly confined within its mitochondria, to be followed by the opening of the mitochondrial permeability transition pore that leads to the destruction of these organelles and cells. It is now further recognized that Ca2+ overloading of cardiac myocytes and mitochondria serves as a prooxidant and which is counterbalanced by an intrinsically coupled Zn2+ entry serving as antioxidant. The prospect of raising antioxidant defenses by increasing intracellular Zn2+ with adjuvant nutriceuticals can, therefore, be preferentially exploited to uncouple this intrinsically coupled Ca2+ - Zn2+ dyshomeostasis. Hence, novel yet simple cardioprotective strategies may be at hand that deserve to be further explored.

Cation dyshomeostasis and cardiomyocyte necrosis: the Fleckenstein hypothesis revisited

An ongoing loss of cardiomyocytes to apoptotic and necrotic cell death pathways contributes to the progressive nature of heart failure. The pathophysiological origins of necrotic cell loss relate to the neurohormonal activation that accompanies acute and chronic stressor states and which includes effector hormones of the adrenergic nervous system. Fifty years ago, Albrecht Fleckenstein and coworkers hypothesized the hyperadrenergic state, which accompanies such stressors, causes cardiomyocyte necrosis based on catecholamine-initiated excessive intracellular Ca(2+) accumulation (EICA), and mitochondrial Ca(2+) overloading in particular, in which the ensuing dysfunction and structural degeneration of these organelles leads to necrosis. In recent years, two downstream factors have been identified which, together with EICA, constitute a signal-transducer-effector pathway: (i) mitochondria-based induction of oxidative stress, in which the rate of reactive oxygen metabolite generation exceeds their rate of detoxification by endogenous antioxidant defences; and (ii) the opening of the mitochondrial inner membrane permeability transition pore (mPTP) followed by organellar swelling and degeneration. The pathogenesis of stress-related cardiomyopathy syndromes is likely related to this pathway. Other factors which can account for cytotoxicity in stressor states include: hypokalaemia; ionized hypocalcaemia and hypomagnesaemia with resultant elevations in parathyroid hormone serving as a potent mediator of EICA; and hypozincaemia with hyposelenaemia, which compromise antioxidant defences. Herein, we revisit the Fleckenstein hypothesis of EICA in leading to cardiomyocyte necrosis and the central role played by mitochondria.

Fibrosis in hypertensive heart disease: molecular pathways and cardioprotective strategies

Fibrosis is a fundamental component of the adverse structural remodelling of myocardium found in hypertensive heart disease (HHD). A replacement fibrosis appears at sites of previous cardiomyocyte necrosis to preserve the structural integrity of the myocardium. Such scarring has adverse functional consequences. The extensive distribution of fibrosis involving the right and left heart suggests cardiomyocyte necrosis is widespread. Together, the loss of these contractile elements and fibrous tissue deposition in the form of stiff in-series and in-parallel elastic elements contribute to the progressive failure of this normally efficient muscular pump. Pathogenic mechanisms modulating fibrous tissue formation at sites of repair include auto/paracrine properties of locally generated angiotensin II and endothelin-1. This study focuses on the signal-transducer-effector pathway involved in cardiomyocyte necrosis and the crucial pathogenic role of intracellular calcium overloading, and the subsequent induction of oxidative stress originating within its mitochondria that dictates the opening of the mitochondrial permeability transition pore. The ensuing osmotic destruction of these organelles is followed by necrotic cell death. It is now further recognized that calcium overloading of cardiac myocytes and mitochondria functioning as pro-oxidant is pathophysiologically counterbalanced by an intrinsically coupled zinc entry, which serves as an antioxidant. The prospect of raising intracellular zinc by adjuvant nutriceutical supplementation can, therefore, be preferentially exploited to uncouple this intrinsically coupled calcium-zinc dyshomeostasis in favour of endogenous antioxidant defences. Novel cardioprotective strategies may thus be at hand and deserve to be explored further in the overall management of patients with HHD.

Efavirenz is associated with severe vitamin D deficiency and increased alkaline phosphatase

OBJECTIVE(S)

To identify factors (including exposure to specific antiretroviral drugs) associated with severe vitamin D deficiency (VDD) in HIV-infected individuals and to explore the effects of severe VDD and antiretroviral drug exposure on serum alkaline phosphatase (ALP) as surrogate marker of bone turnover.

DESIGN

Cross-sectional survey of vitamin D status among HIV-infected patients attending for routine clinical care at a large London HIV clinic.

METHODS

Severe VDD was defined as 25(OH)D levels of less than 10 microg/l (<25 nmol/l). Multivariate logistic regression analysis was used to identify factors associated with severe VDD and upper quartile ALP levels.

RESULTS

Vitamin D levels were measured in 1077 patients and found to be suboptimal in 91%. One-third of patients had severe VDD. Black ethnicity, sampling in winter, nadir CD4 cell count less than 200 cells/microl, and exposure to combination antiretroviral therapy were associated with severe VDD. In analyses restricted to patients on combination antiretroviral therapy, current efavirenz use was significantly associated with severe VDD [adjusted odds ratio 2.0 (95% confidence interval 1.5-2.7)]. Current tenofovir [adjusted odds ratio 3.5 (95% confidence interval 2.3-5.2)] and efavirenz use [adjusted odds ratio 1.6 (95% confidence interval 1.02-2.4)], but not severe VDD [odds ratio 1.1 (0.8-1.5)], were associated with increased bone turnover (upper quartile ALP).

CONCLUSION

Efavirenz was associated with severe VDD, a condition associated with multiple adverse health outcomes, and efavirenz and tenofovir with increased ALP. The clinical significance of these findings requires further investigation, given the widespread use of efavirenz and tenofovir in first-line combination antiretroviral therapy.

Myocardial remodeling in low-renin hypertension: molecular pathways to cellular injury in relative aldosteronism

The pathologic hypertrophy of hypertensive heart disease is related to the quality, not the quantity, of myocardium; the presence of fibrosis is inevitably linked to structural and functional insufficiencies with increased cardiovascular risk. Elevations in plasma aldosterone that are inappropriate relative to dietary sodium, or relative aldosteronism, are accompanied by suppressed plasma renin activity, elevation in arterial pressure, and dyshomeostasis of divalent cations. The accompanying hypocalcemia, hypomagnesemia, and hypozincemia of aldosteronism contribute to the appearance of secondary hyperparathyroidism. Parathyroid hormone-mediated intracellular calcium overloading of cardiac myocytes and mitochondria leads to the induction of oxidative stress and molecular pathways associated with cardiomyocyte necrosis and scarring of myocardium, whereas the dyshomeostasis of zinc compromises antioxidant defenses. This dys-homeostasis of calcium and zinc, intrinsically coupling prooxidant calcium and antioxidant zinc, raises the prospect for therapeutic strategies designed to mitigate intracellular calcium overloading while enhancing zinc-mediated antioxidant defenses, thus preventing adverse myocardial remodeling with fibrosis, associated diastolic dysfunction, and cardiac arrhythmias.

Ethnicity, socioeconomic status, and attainment of clinical practice guideline standards in dialysis patients in the United kingdom

BACKGROUND AND OBJECTIVES

The role of socioeconomic status (SES) and its contribution to ethnic differences in standards attainment among dialysis patients is not known.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

We examined associations between area- level SES (Townsend index) and ethnicity (white, black, South Asian) and standards attainment in 14,117 incident dialysis patients (1997-2004) in the UK.

RESULTS

Deprived patients were less likely to achieve hemoglobin (Hb) > or = 10 g/dl (trend P < 0.001) but not after controlling for patient and center characteristics (trend P = 0.1). There was no association with hemodialysis dose and parathyroid hormone (PTH) standard but deprived patients had better attainment of phosphate (PO4) <5.6 mg/dl, calcium (Ca) and Calcium-phosphate (CaPO4) standard (e.g., most deprived versus least deprived adjusted odds ratio [OR] 1.25, 95% confidence intervals [CI] 1.12, 1.38). There was no association with SES using a lower limit for PO4 (3.5 - 5.5 mg/dl). Compared with Whites, Blacks had lower attainment of Hb (adjusted OR 0.57, 95% CI 0.45, 0.71) and PTH standards (adjusted OR 0.27, 95% CI 0.22, 0.33) but better attainment of PO4 and CaPO4, while South Asians experienced better or comparable outcomes for most standards except Ca and PTH.

CONCLUSIONS

There was no evidence of socioeconomic inequity in standards attainment or a consistent pattern of inequity by ethnic group. The lower attainment of some standards in ethnic minorities may reflect biologic differences rather than ethnicity-related inequity of care.

Prostate cancer, serum parathyroid hormone, and the progression of skeletal metastases

Bony metastases from prostate cancer are a significant cause of morbidity and mortality. These metastases are predominantly blastic (bone-forming) and commonly cause increased serum levels of parathyroid hormone (PTH) as calcium ions are transferred from serum into blastic bone. The epidemiologic and clinical significance of secondary hyperparathyroidism in advanced prostate cancer have not been widely appreciated. Prostate cancer bony metastases show increased expression of the PTH receptor (PTH-IR) and PTH promotes the growth and invasiveness of prostate cancer cells in bone. Thus, blastic metastases appear to induce a "vicious cycle" in which PTH resorbs normal bone to support the growth of blastic bone. Recognition of the potential role of PTH in the progression of skeletal metastases suggests novel opportunities for prostate cancer secondary prevention. In particular, we propose that suppressing serum PTH in advanced prostate cancer may reduce morbidity by decreasing fractures and pain caused by bone resorption and may reduce mortality by retarding the progression of metastatic disease.

Hypovitaminosis D in African Americans residing in Memphis, Tennessee with and without heart failure

BACKGROUND

Factors contributing to heart failure (HF) in African Americans (AA) are under investigation. Reduced 25(OH)D confers increased cardiovascular risk, including HF.

METHODS

We monitored serum 25(OH)D, 1,25(OH)2D3, parathyroid hormone (PTH), and creatinine clearance in 102 AA residing in Memphis: 58 hospitalized with decompensated HF of >or=4 weeks in 34 (21 men; 53.3 +/- 1.8 years) or of 1 to 2 weeks in 24 (17 men; 49.6 +/- 2.4 years) and associated with a dilated cardiomyopathy and reduced ejection fraction (<35%); 19 outpatients with compensated HF (14 men; 52.6 +/- 2.7 years) with comparable ejection fraction; 16 outpatients (9 men; 55.4 +/- 2.9 years) with heart disease, but without HF; and 9 healthy volunteers (3 men; 35.8 +/- 3.5 years).

RESULTS

Serum 25(OH)D <or=30 ng/mL was found in 96% and 90% with protracted or short-term decompensated HF, where it was of moderate to marked severity (<20 ng/mL) in 83% and 76%, respectively. In patients with either compensated or no HF, 25(OH)D <30 ng/mL was found in 95% and 100%, respectively, and in 30% of volunteers. Normal serum 1,25(OH)2D3 did not differ between patients. Serum PTH >65 pg/mL was found in all AA with decompensated HF of >or=4 weeks (132.4 +/- 12.0 pg/mL) and 67% with 1 to 2 weeks duration (82.3 +/- 7.9 pg/mL), but only 11% with compensated HF (45.8 +/- 6.1 pg/mL), 12% without HF (29.6 +/- 5.4 pg/mL), and none of the volunteers (31.1 +/- 3.9 pg/mL). Creatinine clearance did not differ between patient groups.

CONCLUSIONS

Hypovitaminosis D is prevalent amongst AA residing in Memphis, with or without HF. Elevations in serum PTH in keeping with secondary hyperparathyroidism are only found in AA with decompensated HF, where hypovitaminosis D and other factors are contributory.

Clinical epidemiology of parathyroidectomy in hemodialysis patients: The USRDS waves 1, 3, and 4 study

Despite advances in the medical management of secondary hyperparathyroidism, parathyroidectomy remains necessary in some end-stage renal disease patients. Observational studies may help with the design of intervention trials. We linked the retrospective Waves 1, 3, and 4 Dialysis Morbidity and Mortality Study datasets to Medicare claims data to identify incident parathyroidectomy in 10,588 Medicare patients receiving hemodialysis in the United States on December 31, 1993. The mean age was 60.0 years, and the mean follow-up 3.6 years. De novo parathyroidectomy incidence was 14.2/1000 patient-years. Considered as quintiles (Q), higher levels of standard bone metabolism variables were associated (p<0.0001) with parathyroidectomy stepwise, such that adjusted hazards ratios (AHR) for Q5 (vs. Q1) were, for calcium (>10.3 mg/dL), 5.09 (3.64-7.10); for phosphorus (>7.5 mg/dL), 2.92 (2.06-4.15); for calcium-phosphorus product (>71 mg2/dL2), 3.32 (2.27-4.85); and for parathyroid hormone (PTH; >480 pg/mL), 13.81 (7.47-25.55). Other antecedent associations included younger age, lower hemoglobin, and longer dialysis vintage, while transplantation, as a time-dependent covariate, was associated with lower hazards ratios. Using interval Poisson analysis, parathyroidectomy was associated with higher mortality risk ratios in the first year, and progressively lower risk ratios subsequently. Demographic variables may modify the risk of parathyroidectomy. Younger patients on long-term hemodialysis may be at a special risk. Parathyroidectomy risk increases stepwise with alterations in bone metabolism variables, suggesting that a single-threshold management approach may not be ideal.

Macro- and micronutrients in African-Americans with heart failure

An emerging body of evidence suggests secondary hyperparathyroidism (SHPT) may be an important covariant of congestive heart failure (CHF), especially in African-Americans (AA) where hypovitaminosis D is prevalent given that melanin, a natural sunscreen, mandates prolonged exposure of skin to sunlight and where a housebound lifestyle imposed by symptomatic CHF limits outdoor activities and hence sunlight exposure. In addition to the role of hypovitaminosis D in contributing to SHPT is the increased urinary and fecal losses of macronutrients Ca(2+) and Mg(2+) associated with the aldosteronism of CHF and their heightened urinary losses with furosemide treatment of CHF. Thus, a precarious Ca(2+) balance seen with reduced serum 25(OH)D is further compromised when AA develop CHF with circulating RAAS activation and are then treated with a loop diuretic. SHPT accounts for a paradoxical Ca(2+) overloading of diverse tissues and the induction of oxidative stress at these sites which spills over to the systemic circulation. In addition to SHPT, hypozincemia and hyposelenemia have been found in AA with compensated and decompensated heart failure and where an insufficiency of these micronutrients may have its origins in inadequate dietary intake, altered rates of absorption or excretion and/or tissue redistribution, and treatment with an ACE inhibitor or AT(1) receptor antagonist. Zn and Se deficiencies, which compromise the activity of several endogenous antioxidant defenses, could prove contributory to the severity of heart failure and its progressive nature. These findings call into question the need for nutriceutical treatment of heart failure and which is complementary to today's pharmaceuticals, especially in AA.

Secondary hyperparathyroidism and hypovitaminosis D in African-Americans with decompensated heart failure

OBJECTIVE

We previously noted secondary hyperparathyroidism (SHPT) in African-American patients hospitalized during February, 2005 with either untreated or treated congestive heart failure (CHF) due to ischemic or idiopathic cardiomyopathy. Herein, we hypothesized that housebound African-American patients hospitalized during the period of June 1 through August 31, 2005, with CHF would have SHPT and hypovitaminosis D.

METHODS

Twenty-five African-American patients with an ejection fraction (EF) less than 35% due to ischemic or dilated (idiopathic) cardiomyopathy were monitored: 20 were hospitalized with CHF, stratified on historical grounds as of 4 weeks' or longer duration or of 1 to 2 weeks' duration in 11 and 9 patients, respectively, despite medical care that included furosemide; serum parathyroid hormone (PTH) and 25(OH)D at the time of admission in these patients were compared to five asymptomatic outpatients seen during the summer with stable, compensated failure.

RESULTS

Serum PTH was elevated (127 +/- 13; 82-243 pg/mL) in all patients with CHF of 4 weeks' or longer duration (normal, 12-65 pg/mL) and was elevated in three of nine patients (59 +/- 8; 18-99 pg/mL) with CHF of 1 to 2 weeks' duration. Ionized hypocalcemia (1.09 +/- 0.03 and 1.08 +/- 0.02 mmol/L; normal, 1.12-1.30) and hypomagnesemia (0.47 +/- 0.02 and 0.46 +/- 0.03 mmol/L; normal, 0.53-0.67) were respectively found in long- or short-duration CHF. No compensated patient had elevated PTH (42 +/- 5; 17-53). Hypovitaminosis D (< or =30 ng/mL) was universally present in patients with CHF of 4 weeks' or longer duration (15.1 +/- 1.4; 7.0-23.8 ng/mL) and was also prevalent in the other groups (20.3 +/- 5.1, 7.0-54.1 ng/mL in CHF of 1 to 2 weeks' duration and 23.1 +/- 4.9; 17.2-42.7 ng/mL in compensated failure).

CONCLUSIONS

In African-American patients with CHF, hypovitaminosis D, aldosteronism, and loop diuretic treatment each exaggerate Ca and Mg losses to stress a fragile Ca balance leading to ionized hypocalcemia and hypomagnesemia with SHPT.

Race and sex: predictors of the severity of hyperparathyroidism in peritoneal dialysis patients

BACKGROUND

Uraemic hyperparathyroidism remains a common clinical problem. Conversely, oversuppression of parathyroid hormone (PTH), particularly in diabetic patients on peritoneal dialysis, has been implicated in low bone turnover disease. Race may also be an important factor determining susceptibility to hyperparathyroidism and the different forms of renal osteodystrophy. These compounding factors that might influence the severity of hyperparathyroidism have been studied in US dialysis and predialysis populations. Dialysis-dependant Africans and Afro-Caribbeans (AC) are known to have higher circulating PTH concentrations than comparable Caucasians (C) but Indo-Asians (IA) living in temperate climates have not been studied.

METHODS

We performed a cross-sectional study of all patients undergoing peritoneal dialysis at St Bartholomew's and The Royal London Hospital on 1 May 2000. The highest historical recorded PTH was recorded with concurrent biochemical and demographic details. Regression models were used for the analysis of covariance and separate manova was performed incorporating the factors that were shown on univariate analysis to be significant.

RESULTS

The current study confirmed that in 50 AC patients on peritoneal dialysis, the mean (+/- SEM) peak PTH concentration (93.9 +/- 9.3 pmol/L) was higher than in 148 C (56.7 +/- 4.3 pmol/L) and 67 IA (60.2 +/- 5.7 pmol/L), P < 0.0001 and P < 0.002, respectively. This is despite there being no significant difference in serum calcium concentrations and AC having a lower serum phosphate concentration at the time of peak hyperparathyroidism. There was no significant difference in mean peak PTH concentration between C and IA. Females were also found to have higher peak PTH concentrations, but the presence of diabetes did not influence the peak PTH concentration in this study.

CONCLUSION

Although we have demonstrated that patients of African (but not Asian) descent undergoing peritoneal dialysis have more severe hyperparathyroidism than Caucasians, other studies suggest that Afro-Americans develop low bone turnover at higher PTH. This would suggest that PTH values should be interpreted with care and that bone biopsies to determine histology remain important. It may emerge that there are different optimal PTH concentrations according to race.

Secondary hyperparathyroidism in patients with untreated and treated congestive heart failure

BACKGROUND

The congestive heart failure syndrome includes a systemic illness with wasting of soft tissues and bone. We hypothesized secondary hyperparathyroidism (HPT) would be found in hospitalized patients with decompensated congestive heart failure (CHF), where secondary aldosteronism is expected, and who were either untreated or treated medically.

METHODS

In 9 consecutive patients (7 males, 2 females; 8 African-American, 1 Caucasian; 33-60 yrs) admitted to the Regional Medical Center during a 28-day period with chronic left ventricular systolic dysfunction (EF<35%) and decompensated CHF (5 untreated; 4 treated with an angiotensin converting enzyme inhibitor, furosemide, and small-dose spironolactone), we measured: plasma parathyroid hormone (PTH); serum calcium corrected for albumin, magnesium, and phosphorus; serum creatinine and calculated creatinine clearance.

RESULTS

Plasma PTH was elevated above the normal range (6-65 pg/mL) in both untreated and treated patients with CHF (204+/-60 and 134+/-14 pg/mL, respectively). Serum corrected calcium was normal (8.4-10.2 mg/dL) in both untreated and treated CHF (9.7+/-0.l and 9.1+/-0.2 mg/dL, respectively) as were serum magnesium and phosphorus. Calculated creatinine clearance did not differ between untreated and treated patients (74+/-15 and 83+/-21 mL/min, respectively).

CONCLUSIONS

Secondary HPT was found in 5 untreated and 4 treated patients consecutively hospitalized over a 28-day period with decompensated CHF. Corrected serum calcium was normal. Plasmaionized calcium, a determinant of PTH secretion, was not measured. Although vitamin D levels were not assessed, the presence of hypovitaminosis D in these housebound patients with symptomatic CHF cannot be discounted. HPT may contribute to the systemic illness that accompanies CHF, including bone wasting.

Predictors and consequences of altered mineral metabolism: the Dialysis Outcomes and Practice Patterns Study

BACKGROUND

Altered mineral metabolism contributes to bone disease, cardiovascular disease, and other clinical problems in patients with end-stage renal disease.

METHODS

This study describes the recent status, significant predictors, and potential consequences of abnormal mineral metabolism in representative groups of hemodialysis facilities (N= 307) and patients (N= 17,236) participating in the Dialysis Outcomes and Practice Patterns Study (DOPPS) in the United States, Europe, and Japan from 1996 to 2001.

RESULTS

Many patients fell out of the recommended guideline range for serum concentrations of phosphorus (8% of patients below lower target range, 52% of patients above upper target range), albumin-corrected calcium (9% below, 50% above), calcium-phosphorus product (44% above), and intact PTH (51% below, 27% above). All-cause mortality was significantly and independently associated with serum concentrations of phosphorus (RR 1.04 per 1 mg/dL, P= 0.0003), calcium (RR 1.10 per 1 mg/dL, P < 0.0001), calcium-phosphorus product (RR 1.02 per 5 mg(2)/dL(2), P= 0.0001), PTH (1.01 per 100 pg/dL, P= 0.04), and dialysate calcium (RR 1.13 per 1 mEq/L, P= 0.01). Cardiovascular mortality was significantly associated with the serum concentrations of phosphorus (RR 1.09, P < 0.0001), calcium (RR 1.14, P < 0.0001), calcium-phosphorus product (RR 1.05, P < 0.0001), and PTH (RR 1.02, P= 0.03). The adjusted rate of parathyroidectomy varied 4-fold across the DOPPS countries, and was significantly associated with baseline concentrations of phosphorus (RR 1.17, P < 0.0001), calcium (RR 1.58, P < 0.0001), calcium-phosphorus product (RR 1.11, P < 0.0001), PTH (RR 1.07, P < 0.0001), and dialysate calcium concentration (RR 0.57, P= 0.03). Overall, 52% of patients received some form of vitamin D therapy, with parenteral forms almost exclusively restricted to the United States. Vitamin D was potentially underused in up to 34% of patients with high PTH, and overused in up to 46% of patients with low PTH. Phosphorus binders (mostly calcium salts during the study period) were used by 81% of patients, with potential overuse in up to 77% patients with low serum phosphorus concentration, and potential underuse in up to 18% of patients with a high serum phosphorus concentration.

CONCLUSION

This study expands our understanding of the relationship between altered mineral metabolism and outcomes and identifies several potential opportunities for improved practice in this area.

Differences in bone turnover and intact PTH levels between African American and Caucasian patients with end-stage renal disease

BACKGROUND

Evidence derived from healthy subjects suggests that African Americans have higher serum parathyroid hormone (PTH) levels and decreased bone responsiveness to PTH than Caucasians. African American patients with end-stage renal disease (ESRD) also have higher serum PTH than Caucasians. Studies that correlate intact PTH (iPTH) levels with bone turnover in ESRD patients were performed in a predominantly Caucasian population.

METHODS

In this study, serum iPTH and bone histomorphometric data were analyzed for racial differences in 76 ESRD patients (Caucasian = 48, African Americans = 28). Bone turnover was determined by histomorphometric measurement of activation frequency in all patients.

RESULTS

Age, duration of dialysis, and calcium and phosphorus levels were similar between the two groups. iPTH levels (pg/mL; mean +/- SE) were significantly higher in the African American group (534 +/- 79 vs. 270 +/- 46, P < 0.01). Also, alkaline phosphatase levels (IU/L) were significantly higher in the African American group (162 +/- 31 vs. 144 +/- 43, P < 0.01). Correlations between PTH levels and activation frequency were r = 0.60, P < 0.01 in Caucasians and r = 0.22, P = NS in African Americans. The mean PTH level in African American patients with histologic findings of low bone turnover was 460 +/- 115 vs. 168 +/- 41 in Caucasian patients with similar bone turnover (P < 0.01). In patients with low bone turnover, African Americans had significantly higher osteoid volume and thickness, number of osteoblasts and osteoclasts, erosion surface, peritrabecular fibrosis, and single-label surface than Caucasians. However, erosion depth, bone formation rate per osteoblast and mineralization apposition rate were similar between the two groups.

CONCLUSION

There is no correlation between iPTH and bone turnover in African Americans with ESRD. A substantial number of African American patients with low bone turnover have very high serum PTH levels. Bone histomorphometric results reveal differences in remodeling dynamics and responses to PTH between African American and Caucasian patients. Further studies utilizing newer PTH measurement assays are needed to better delineate the correlation between PTH and bone turnover in the various racial groups.