Serum 25(OH)-vitamin D levels and bone metabolism in patients on maintenance hemodialysis

AIMS: An increasing amount of evidence suggests that 25-hydroxy vitamin D3 (25(OH)D3) may contribute to the bone health of patients with chronic kidney disease (CKD). The underlying vitamin D status of these patients, however, has often been neglected. In a cross-sectional study we assessed the association between vitamin D status and parathyroid function, bone turnover, bone mass and structure in patients on maintenance hemodialysis. METHODS: 69 patients on maintenance hemodialysis were assessed by bone densitometry (DEXA) and quantitative bone ultrasound (QUS). Serum 25-hydroxy vitamin D3 levels, serum markers of bone turnover and clinical data were tabulated. RESULTS: A high prevalence of potentially significant vitamin D3 deficiency was found in this patient group: 59% of the patients had a 25(OH)D3 level below 20 nmol/l. There was a significant negative correlation between serum 25(OH)D3 levels and serum intact parathyroid hormone (iPTH) (r = -0.231, p < 0.05), and this association remained significant after controlling for potential covariables. Furthermore, we show here that serum 25(OH)D3 concentration is positively correlated with bone mineral density (BMD) measured at the radius (r = 0.424, p < 0.01). Finally, we show for the first time that 25(OH)D3 levels are significantly and independently correlated with broadband ultrasound attenuation (beta = 0.262, p < 0.05) measured with calcaneal quantitative bone ultrasound (QUS) in patients with chronic renal failure. CONCLUSION: Vitamin D3 deficiency may contribute to the impaired bone health of patients on maintenance dialysis.     

Lack of seasonal variation in bone mass and biochemical estimates of bone turnover

Three previous studies have indicated a seasonal variation in bone mineral content, with values during the summer being 1.7% to 7.5% higher than during the winter. We have examined the seasonal influence on both bone mass, biochemical estimates of bone turnover and vitamin D metabolites in 86 healthy women, aged 29-53 years. All participants were followed up for 2 years with examinations every 6 weeks or 3 months. Bone mineral content in the proximal and distal part of the forearm (single photon absorptiometry) did not reveal any significant seasonal variation, whereas bone mineral density of the lumbar spine (dual photon absorptiometry) indicated that the highest values occurred in winter. None of the biochemical parameters showed any statistically significant cyclical changes. Serum concentrations of 25-hydroxyvitamin D and 24,25-dihydroxyvitamin D3 showed a highly significant seasonal variation, whereas the serum 1,25-dihydroxyvitamin D concentration was virtually unchanged. We conclude that seasonal variation in bone mineral content and bone turnover should not be taken into account when interpreting data from longitudinal studies of healthy pre- and postmenopausal women on a sufficient vitamin D nutriture.     

Relationship between vitamin D status, parathyroid hormone levels and bone mineral density in patients with chronic kidney disease stages 3 and 4

AIM: Low vitamin D status is associated with secondary hyperparathyroidism and increased bone turnover in the general population and can aggravate the hyperparathyroidism of chronic kidney disease (CKD) patients. It is also correlated to low bone mineral density (BMD), but this correlation is less clear in CKD patients. Aims of our study were to investigate these associations in CKD stages 3 and 4 patients, and to identify significant predictors of BMD in this population. METHODS: Serum 25-hydroxyvitamin D (25OHD) levels, BMD at the femur and radius, and bone mineral metabolism parameters were measured in 89 CKD stages 3 and 4 patients. Vitamin D status was defined according to the NKF/KDOQI guidelines. RESULTS: Mean 25OHD levels were 53.8+/-32.1 nmol/L and correlated to the severity of proteinuria. Thirty-five patients (39%) had vitamin D insufficiency, 29 (33%) had vitamin D deficiency and five (6%) had severe deficiency. Of the 89 patients, two had osteoporosis and 31 had osteopenia either at femur or radius. Independent predictors for the total femur BMD were the intact parathyroid hormone (iPTH) levels and the body mass index (BMI). For the total radius BMD, independent predictor was only the BMI. Serum 25OHD levels were not directly associated with BMD, but they were independent predictors of iPTH. CONCLUSION: Vitamin D insufficiency and deficiency are very common in CKD stages 3 and 4 population and may indirectly affect, via effects on iPTH, the BMD of these patients.     

Review article: Managing bone complications after kidney transplantation

Chronic kidney disease mineral and bone disorder (CKD-MBD) describes the laboratory, bone and vascular abnormalities that exist in patients with CKD stages 3–5D and that may persist after transplantation. Persisting abnormalities of bone turnover and abnormal mineralization, together with bone mineral density (BMD) loss from glucocorticoids, may all predispose to a loss of structural integrity and increased fracture risk in kidney and kidney pancreas recipients. Vitamin D, calcitriol, calcitonin and bisphosphonates have all been used to preserve BMD following transplantation, despite a lack of safety data and the potential for some of these drugs to cause harm. A limited number of post-transplant studies utilizing these drugs have not yet documented improved fracture prevention or fracture-related mortality and have not considered allocation based on risk factors for fracture or markers of bone turnover. Targeted allocation of the available therapies based on a stratification of risk appears warranted. This might be achieved using an algorithm incorporating BMD, X-ray evaluation, laboratory investigations including bone turnover markers and the assessment of standard fracture risk factors at the time of and soon after transplantation. This approach, which is similar to protocols used in the general population, may result in more effective management of patients and fewer adverse effects such as adynamic bone disease. Although BMD is a surrogate for fracture risk in the general population it is not validated in this transplant population. Consequently, such an approach should be confirmed by studies that include bone biopsy data and an evaluation of patient level outcomes.     

Bone mineral density and bone histomorphometry in children on long-term dialysis

Bone mineral density (BMD) at the lumbar vertebrae (L(1)-L(4)) was assessed by dual-energy X-ray absorptiometry (DXA) in 20 children with chronic kidney disease (CKD) on dialysis, and its results were compared with bone biopsy and biochemical parameters. Biopsy specimens provided evidence of hyperparathyroid bone disease in eight cases (40%), and low bone turnover in 12 (60%). For BMD, expressed as Z-scores relative to normal, median Z-scores were -1.05 (range -2.36 to 1.06) for hyperparathyroid patients and -1.05 (range -4.40 to -0.03) for low bone turnover patients, with no statistical differences between groups (P = 0.512). In relation to BMD, of the whole sample, five (25%) had a Z-score under -2.0. When it was corrected for height, BMD was in the normal range. Additionally, there were no significant differences in single samples of serum calcium, alkaline phosphatase, phosphorus and intact parathyroid hormone (PTH) between groups with high or low bone turnover. Assessment of nutritional status, through height/age, showed that ten patients had Z-scores below -2.0 (median -2.12, range -7.13 to 0.73). In conclusion, renal osteodystrophy (ROD) seems to have a high prevalence among CKD pediatric patients, although only approximately a quarter of them developed changes in BMD. In children with CKD, measurements of bone mineral density may not be used for classification of various forms of ROD.     

妊娠期糖尿病女性骨密度及骨代谢干预研究

目的 研究妊娠期糖尿病（gestational diabetes mellitus,GDM）女性骨密度、骨代谢变化及药物干预后的变化。方法 比较经骨化三醇干预后妊娠期GDM女性与未经骨化三醇干预的妊娠期GDM女性的骨代谢和骨密度改变,研究的骨代谢指标主要包括以下几项：双羟基维生素D[1, 25-（OH）2-VD3],甲状旁腺素（?parathyroid hormone,PTH）,骨钙素（bone gamma-carboxyglutamic-acid-containing proteins,BGP）,Ⅰ型前胶原羧基末端肽（procollagen type I carboxy-terminal peptide,PICP）,糖化血红蛋白（hemoglobin A1c,HbA1c）,血清钙（calcium,Ca）。骨密度指标为超声骨密度测量值。结果 补充骨化三醇的GDM女性与未补充的GDM女性在孕中期和孕晚期的1, 25-（OH）2-VD3、BGP与PICP均有统计学意义,孕晚期的骨密度有统计学意义。两组间的Ca及血糖水平无统计学意义。结论 给妊娠期GDM女性补充骨化三醇不会影响妊娠期血糖,且有助于改善妊娠期GDM女性骨密度。     

血清SM4D水平与绝经后骨质疏松症患者骨密度和骨代谢指标的相关性研究

目的探讨绝经后骨质疏松症(postmenopausal osteoporosis,POP)患者血清4D同型二聚体(SM4D)水平与骨密度(bone mineral density,BMD)和骨转换指标的关系。方法通过双能X线吸收测定法对257例POP患者和90例健康对照者进行BMD测量。通过酶联免疫吸附测定法测定受试者血清SM4D、BAP、BGP和TRACP-5b水平。使用自动电化学发光系统测量I型血清交联N端肽(NTX)、25-羟基维生素D[25(OH)D]和骨钙素的N-mid片段水平(N-MID-OT)。结果与健康对照组相比,POP妇女的SM4D水平显著升高[(1.40±0.33)μg/L vs.(0.58±0.18)μg/L,P=0.006]。SM4D水平与血清TRACP-5b和NTX水平呈正相关,与腰椎和股骨颈BMD、血清BAP和BGP水平呈负相关。SM4D水平与年龄、体质量指数以及血清25(OH)D和N-MID-OT水平之间无相关性。腰椎和股骨颈骨密度(β=-0.354,P<0.001;β=-31.234,P<0.001)和血清BAP水平(β=0.127,P=0.019)是POP患者血清SM4D水平的独立预测因子。结论绝经后骨质疏松症女性SM4D与骨密度和骨转换指标密切相关。     

Association of oral calcitriol with improved survival in nondialyzed CKD

Parenteral vitamin D is associated with improved survival among long-term hemodialysis patients. Among nondialyzed patients with chronic kidney disease (CKD), oral activated vitamin D reduces parathyroid hormone levels, but the impact on clinical outcomes is unknown. We evaluated associations of oral calcitriol use with mortality and dialysis dependence in 1418 nondialysis patients with CKD and hyperparathyroidism in the Veterans' Affairs Consumer Health Information and Performance Sets database. Incident calcitriol users and nonusers were selected on the basis of stages 3 to 4 CKD, hyperparathyroidism, and the absence of hypercalcemia before calcitriol use and then were matched by age and estimated kidney function. During a median follow-up of 1.9 yr, 408 (29%) patients died and 217 (16%) initiated long-term dialysis. After adjustment for demographics; comorbidities; estimated kidney function; medications; and baseline levels of parathyroid hormone, calcium, and phosphorous, oral calcitriol use was associated with a 26% lower risk for death (95% confidence interval 5 to 42% lower; P = 0.016) and a 20% lower risk for death or dialysis (95% confidence interval 1 to 35% lower; P = 0.038). The association of calcitriol with improved survival was not statistically different across baseline parathyroid hormone levels. Calcitriol use was associated with a greater risk for hypercalcemia. In conclusion, oral calcitriol use is associated with lower mortality in nondialysis patients with CKD.     

Fibroblast growth factor-23 mitigates hyperphosphatemia but accentuates calcitriol deficiency in chronic kidney disease

Hyperphosphatemia, calcitriol deficiency, and secondary hyperparathyroidism (SHPT) are common complications of chronic kidney disease (CKD). Fibroblast growth factor-23 (FGF-23) is a novel phosphaturic hormone that also inhibits renal 1alpha-hydroxylase activity and thus may be involved in the pathogenesis of SHPT. Several hypotheses were tested: that FGF-23 increases as renal function declines; is linearly associated with serum phosphate levels; is associated with increased phosphaturia independent of parathyroid hormone (PTH); and is associated with decreased calcitriol levels independent of renal function, hyperphosphatemia, and vitamin D stores. FGF-23, PTH, 25(OH)D3, calcitriol, calcium, phosphate, and urinary fractional excretion of phosphate (Fe(PO4)) were measured in 80 CKD patients. Multiple linear regression was used to test the hypotheses. FGF-23 and PTH were inversely associated with estimated GFR (eGFR), whereas calcitriol levels were linearly associated with eGFR. Hyperphosphatemia and hypocalcemia were present in only 12 and 6% of patients, respectively, all of whose eGFR was <30. Increased Fe(PO4) was associated with decreased eGFR, and both increased FGF-23 and PTH were independently associated with increased Fe(PO4). Increased FGF-23 and decreased 25(OH)D3 were independent predictors of decreased calcitriol, but the effects on calcitriol levels of renal function itself and hyperphosphatemia were completely extinguished by adjusting for FGF-23. It is concluded that FGF-23 levels increase early in CKD before the development of serum mineral abnormalities and are independently associated with serum phosphate, Fe(PO4), and calcitriol deficiency. Increased FGF-23 may contribute to maintaining normal serum phosphate levels in the face of advancing CKD but may worsen calcitriol deficiency and thus may be a central factor in the early pathogenesis of SHPT.     

Successful treatment of an adynamic bone disorder with bone morphogenetic protein-7 in a renal ablation model

An adynamic bone disorder (ABD) is an important complication of chronic kidney disease (CKD) of unknown etiology for which there is no adequate treatment. Reported is an animal model of ablative CKD complicated by an ABD characterized by the absence of secondary hyperparathyroidism and its successful treatment with a skeletal anabolic factor, bone morphogenetic protein-7 (BMP-7). Adult mice were subjected to electrocautery of the right kidney followed by left nephrectomy. Animals were randomized into groups fed normal chow or fed low-phosphate chow supplemented with calcitriol to maintain normophosphatemia in CKD. All groups were maintained on the regimens for 12 wk. Hyperphosphatemia, secondary hyperparathyroidism, and a mild osteodystrophy developed in the CKD/chow-fed group, as expected. When dietary phosphorus was restricted and calcitriol was administered in the CKD low-phosphate/calcitriol group (ABD), Ca, PO(4), and parathyroid hormone levels were maintained normal. A significant ABD developed in the ABD group characterized by significant depressions in osteoblast number, perimeters, bone formation rates, and mineral apposition rates when compared with the sham-operated, chow-fed group. The abnormal skeletal histomorphometry was reversed by BMP-7 therapy to normal values and significantly improved from the ABD group (P < 0.05). The sham-operated low-phosphate/calcitriol-fed control group and the CKD low-phosphate/calcitriol/BMP-7 groups had reduced phosphate levels compared with the other groups (P < 0.05). ABD produced in mice with CKD in the absence of hyperparathyroidism was successfully reversed with a bone anabolic, BMP-7, associated with a reduction in plasma phosphorus.     

Supplementation with oral vitamin D3 and calcium during winter prevents seasonal bone loss: a randomized controlled open-label prospective trial.

Bone metabolism follows a seasonal pattern with high bone turnover and bone loss during the winter. In a randomized, open-label 2-year sequential follow-up study of 55 healthy adults, we found that supplementation with oral vitamin D3 and calcium during winter abolished seasonal changes in calciotropic hormones and markers of bone turnover and led to an increase in BMD. Supplementation with oral vitamin D3 and calcium during the winter months seems to counteract the effects of seasonal changes in vitamin D and thus may be beneficial as a primary prevention strategy for age-related bone loss. INTRODUCTION: Bone metabolism follows a seasonal pattern characterized by high bone turnover and bone loss during winter. We investigated whether wintertime supplementation with oral vitamin D3 and calcium had beneficial effects on the circannual changes in bone turnover and bone mass. MATERIALS AND METHODS: This prospective study comprised an initial observation period of 12 months ("year 1"), followed by an intervention during parts of year 2. Fifty-five healthy subjects living in southwestern Germany (latitude, 49.5 degrees N) were randomized into two groups: 30 subjects were assigned to the treatment group and received oral cholecalciferol (500 IU/day) and calcium (500 mg/day) during the winter months of year 2 (October-April), while 25 subjects assigned to the control group obtained no supplements. Primary endpoints were changes in calciotropic hormones [serum 25(OH)D, 1,25(OH)2D, and parathyroid hormone], markers of bone formation (serum bone-specific alkaline phosphatase) and of bone resorption (urinary pyridinoline and deoxypyridinoline), and changes in lumbar spine and femoral neck BMD. RESULTS: Forty-three subjects completed the study. During year 1, calciotropic hormones, markers of bone turnover, and BMD varied by season in both groups. During the winter months of year 1, bone turnover was significantly accelerated, and lumbar spine and femoral BMD declined by 0.3-0.9%. In year 2, seasonal changes in calciotropic hormones and markers of bone turnover were either reversed or abolished in the intervention group while unchanged in the control cohort. In the subjects receiving oral vitamin D3 and calcium, lumbar and femoral BMD increased significantly (lumbar spine: +0.8%, p = 0.04 versus year 1; femoral neck: +0.1%, p = 0.05 versus year 1), whereas controls continued to lose bone (intervention group versus control group: lumbar spine, p = 0.03; femoral neck, p = 0.05). CONCLUSIONS: Supplementation with oral vitamin D3 and calcium during winter prevents seasonal changes in bone turnover and bone loss in healthy adults. It seems conceivable that annually recurring cycles of low vitamin D and mild secondary hyperparathyroidism during the winter months contributes, at least in part and over many years, to age-related bone loss. Supplementation with low-dose oral vitamin D3 and calcium during winter may be an efficient and inexpensive strategy for the primary prevention of bone loss in northern latitudes.     

Seasonal changes in calcium homeostasis affect the incidence of postoperative tetany in patients with Graves' disease

BACKGROUND: We have found that postoperative tetany occurs in patients with Graves' disease who have secondary hyperparathyroidism caused by a deficiency in calcium and vitamin D concomitant with transient hypoparathyroidism after surgery. There are seasonal variations in serum 25-hydroxyvitamin D (25[OH]D) concentrations. The purpose of this study was to investigate the effects of seasonal changes in calcium homeostasis on the incidence of postoperative tetany in patients with Graves' disease who undergo subtotal thyroidectomy. PATIENTS AND METHODS: A prospective study was carried out to investigate sequential changes in serum levels of intact parathyroid hormone (iPTH), calcium and other electrolytes, 25(OH)D, and 1,25-dihydroxyvitamin D (1,25[OH]2D) in female patients with Graves' disease who underwent subtotal thyroidectomy during the summer (n = 89) and during the winter (n = 89). RESULTS: The serum levels of calcium, magnesium, and 25(OH)D were significantly higher, but iPTH levels and 1,25(OH)2D levels were lower in summer than in winter. The percentage of vitamin D deficiency (25(OH)D < 25 nmol/L) was 23% in summer and 62% in winter (P < .001). iPTH was below the detection limit on the first postoperative day in 15 patients (13.8%) in summer and in 13 patients (11.4%) in winter. In summery, tetany developed in only 4 of 15 patients and in one patient whose iPTH level was below normal (incidence of tetany, 5.6%). In winter, however, tetany developed in 6 of 13 patients and in 4 patients whose iPTH level was below normal (incidence of tetany, 11.2%). CONCLUSIONS: Patients with Graves' disease are more susceptible to calcium and vitamin D deficiency during the winter than during the summer, resulting in the tendency toward a higher incidence of postoperative tetany in winter.     

Longitudinal Evaluation of Vitamin D Status in Healthy Subjects from Southern Italy: Seasonal and Gender Differences

Vitamin D status is currently considered among the relevant determinants of skeletal integrity. Since vitamin D levels present seasonal variations, we longitudinally studied young healthy men and women in order to investigate the related physiologic modifications of both calcium homeostasis and bone remodeling. Thirty-two men (mean age 39.4 ± 7.8 years) and 58 premenopausal women (aged 36.9 ± 6.4 years) from southern Italy were studied. In all subjects the following parameters were measured both in winter and in summer: serum calcium, phosphorus, creatinine, total alkaline phosphatase activity, 25-hydroxyvitamin D (25OHD), parathyroid hormone (PTH), osteocalcin (BGP), together with urinary calcium (Ca/Cr), total pyridinoline (Pyr/Cr) and deoxypyridinoline (d-Pyr/Cr), corrected for creatinine excretion. In both sexes 25OHD levels were significantly higher in summer, while PTH values were lower, than in winter. The prevalence of hypovitaminosis D, defined by concentrations of 25OHD lower than 30 nmol/l, was 17.8% in winter and 2.2% in summer in the whole sample, while it was 27.8% and 3.4%, respectively, among female subjects. Indeed male subjects did not display hypovitaminosis D, having throughout the year significantly higher calcium and 25OHD levels together with lower PTH values, than the women. Moreover, alkaline phosphatase total activity was more elevated in men both in winter and in summer. In women, during winter, bone remodeling markers levels were higher while urinary calcium levels were lower than in summer. In the whole sample serum 25OHD correlated positively with serum calcium and inversely with PTH. The seasonal percentage variations in PTH were inversely correlated with those of Ca/Cr. Our results show a relatively high prevalence of subclinical vitamin D deficiency among young healthy women from southern Italy. Significant gender-specific differences have been demonstrated in both calcium homeostasis and skeletal remodeling indexes; the seasonal fluctuations in the vitamin D–PTH axis are accompanied by cyclical variations of bone turnover rate, which were more pronounced in women. Received: 11 January 2001 / Accepted: 6 July 2001     

Effect of ergocalciferol supplementation on serum parathyroid hormone and serum 25-hydroxyvitamin D in chronic kidney disease

AIM: To assess the impact of the administration of ergocalciferol on serum parathyroid hormone levels at different stages of chronic kidney disease (CKD). METHODS: A continuous series of 85 patients with stages 3-5 CKD but excluding patients on dialysis referred to the Kaiser Kidney Program were followed. Baseline serum intact parathyroid hormone (iPTH) and serum 25(OH)D levels were measured. All patients were administered ergocalciferol in doses ranging from 800 iu/day to 100,000 iu/week. We obtained serum levels of iPTH and 25(OH)D for a post-treatment endpoint after a median treatment period of 90 days. RESULTS: Pre- and post-treatment serum iPTH levels displayed a mean difference of 2.8 pmol/L (95% CI 1.3-4.4, P < 0.001). Patients with stage 4 CKD had a mean difference of 3.6 pmol/L (95% CI 1.7-5.5, P < 0.001) between pre- and post-iPTH levels. Serum iPTH levels decreased among CKD stages 3 and 5, but were not statistically significant. All CKD groups analysed in the present study had significant increases in serum 25(OH)D levels. None of the study population required cessation of vitamin D therapy and no adverse outcomes were reported. CONCLUSION: Ergocalciferol supplementation appears a safe and effective treatment for CKD populations which may raise levels of serum 25(OH)D levels and decrease iPTH levels.     

Role of fibroblast growth factor 23 in phosphate homeostasis and pathogenesis of disordered mineral metabolism in chronic kidney disease

The discovery of fibroblast growth factor 23 (FGF23), a novel bone-derived hormone that inhibits phosphate reabsorption and calcitriol production by the kidney, has uncovered primary regulatory pathways and new systems biology governing bone mineralization, vitamin D metabolism, parathyroid gland function and renal phosphate handling. This phosphaturic hormone, which is made predominately by osteocytes in bone, appears to have a physiologic role as a counter-regulatory hormone for vitamin D. Evidence has also emerged to support the existence of a bone-kidney axis to coordinate the mineralization of bone with renal handling of phosphate. Pathologically, high circulating levels of FGF23 result in hypophosphatemia, decreased production of 1,25(OH)(2)D, elevated parathyroid hormone and rickets/osteomalacia in patients with functioning kidneys, whereas low levels are associated with tumoral calcinosis, hyperphosphatemia and elevated 1,25(OH)(2)D. In addition, patients with chronic kidney disease (CKD) exhibit marked elevations of circulating FGF23. While the significance of increased FGF23 levels in CKD remains to be defined, it might contribute to phosphate excretion and suppression of 1,25(OH)(2)D levels in CKD stages 3 and 4, as well as potentially contribute to secondary hyperparathyroidism through direct actions on the parathyroid gland in more advanced renal failure. As our knowledge expands regarding the regulation and functions of FGF23, the assessment of FGF23 will become an important diagnostic marker as well as a therapeutic target for management of disordered mineral metabolism in a variety of acquired and hereditary disorders.     

Gender- and Compartment-Specific Bone Loss in C57BL/6J Mice: Correlation to Season?

Seasonal variation in bone mineral density (BMD) has been documented in humans, and has been attributed to changes in 25-hydroxyvitamin D [25(OH)D] synthesis. To test the hypothesis that seasonal changes in bone mass occur in laboratory mice, we measured body composition, femoral bone phenotypes, and serum bone markers in 16-wk-old male and female C57BL/6 (B6) mice during the summer (June–August) and winter (December–February) months at The Jackson Laboratory in Bar Harbor, Maine. Both male and female B6 mice had higher volumetric BMD in the summer than winter. Females showed reduced trabecular bone, whereas males showed changes in bone volume. Males, but not females, had higher insulin-like growth factor 1 in summer than in winter, and only males showed an increase in body weight during the winter. No seasonal differences in serum TRAP5b, osteocalcin, or 25(OH)D were noted for either sex. We conclude that seasonal variation in skeletal and body composition parameters in B6 mice is significant and must be considered when performing longitudinal phenotyping of the skeleton. Further studies are needed to determine the environmental factors that cue seasonal changes in body composition and the mechanisms that produce these changes.     

Vitamin D treatment in chronic kidney disease

Activated vitamin D continues to be the major treatment for suppressing parathyroid hormone (PTH) levels in dialysis patients who have secondary hyperparathyroidism. Active vitamin D compounds are distinguished by their ability to bind with high affinity to vitamin D receptors (VDRs) not only in the parathyroid glands, but in cells throughout the body. Because of recent data showing that pulsatile, intravenous vitamin D treatment (calcitriol or paricalcitol) confers a survival advantage in the dialysis population, there is new interest in understanding the systemic effects of VDR activation, particularly in the predialysis stages of chronic kidney disease (CKD), where high mortality rates from cardiovascular disease have recently been documented. Previous underutilization of calcitriol treatment to control PTH levels in stages 3 and 4 CKD was often due to concerns about its potential for accelerating the progression of CKD as a consequence of hypercalcemia, hypercalciuria, or hyperphosphatemia. Vitamin D analogs with selective VDR activity (such as paricalcitol) have great potential for preventing parathyroid hyperplasia and bone loss in early CKD without adversely affecting kidney function. Whether they also reduce cardiovascular morbidity and mortality in early CKD, as they appear to do in dialysis patients, remains to be determined.     

Opinion: Which of the K/DOQI Guidelines for Bone Disease in Dialysis Patients Should be Changed?

The K‐DOQI guidelines for bone metabolism in chronic kidney disease recommend measuring 25(OH) vitamin D levels and correcting deficiencies in stages 3 and 4 but not in ESRD. Most nephrologists are not concerned with 25(OH) vitamin D deficiency, despite evidence in hemodialysis patients that deficient vitamin D status [as measured by 25(OH) vitamin D levels] plays a role in bone disease. PD patients are often deficient in 25(OH) vitamin D in part because of peritoneal effluent losses, and correction may decrease muscle and bone complaints. Data from other populations are indicative of the importance of vitamin D in cancer surveillance and immune functioning. Randomized controlled trials of correction of 25(OH) vitamin D deficiency in both hemodialysis and peritoneal dialysis patients are urgently needed. vitamin D).     

Vitamin D status in children with chronic kidney disease

Background

The role of vitamin D status in patients with renal insufficiency and its relation to dietary intake and parathyroid hormone (PTH) secretion is of utmost interest given the morbidity and mortality associated with the disordered mineral metabolism seen in chronic kidney disease (CKD).

Methods

We conducted a cross-sectional study of 100 pediatric patients with a diagnosis of CKD stage 1–5 at Children's Hospital Boston, measuring blood levels of 25-hydroxyvitamin D [25(OH)D], 1,25-dihydroxyvitamin D [1,25(OH)₂D], and parathyroid hormone and obtaining data on nutrient intake and other variables related to vitamin D status.

Results

Subjects ranged in age from 6 months to 18?years, and 60 were male, 40 female. Of the 100 patients, 16 % were deficient in 25(OH)D (≤20?ng/mL) and another 24 % were insufficient (≤30?ng/mL), with 40 % in the suboptimal range. Serum 25(OH)D and dietary vitamin D intake were not correlated.

Conclusions

We found a high prevalence of hyperparathyroidism in early-stage CKD and a significant relationship between 25(OH)D and PTH regardless of calcitriol level. Our study results support the suggestion that optimization of vitamin D levels may provide additional benefit in preventing or improving hyperparathyroidism in patients with early CKD and likely remains important as an adjunctive therapy in children with advanced CKD.     

Risk factors of bone density disorder and vascular calcification in non-dialysis chronic kidney disease patients

Objective To explore the risk factors of bone density disorder and vascular calcification in non-dialysis chronic kidney disease (CKD) patients. Methods Clinical data of non-dialysis CKD patients who were admitted to the First Affiliated Hospital of Fujian Medical University between January 2013 and June 2014 were retrospectively analyzed. Using dual energy X-ray absorptiometry to evaluate their bone mineral density (BMD) and T value. Patients were divided into normal BMD group (T≥-1), osteopenia group (-2.5＜T＜-1) and osteoporosis group (T≤-2.5). The vascular calcification was evaluated by pectoral computed tomography. Multi-factor stepwise logistic regression analysis was used to assess the risk factors for low bone density and vascular calcification in non-dialysis CKD patients. Results A total of 337 non-dialysis CKD patients were enrolled. There were 110 (32.6%) patients with normal BMD, and 146(43.3%) patients with osteopenia, and 81(24.0%) patients with osteoporosis. Gender, history of hypertension, 25-hydroxy vitamin D and N-terminal osteocalcin shown statistical differences among three groups (all P＜0.05). The incidence rate of 25-hydroxy vitamin D deficiency shown statistical difference among three groups (P=0.012). Further, the rates were increased with the decreased bone mass (χ2=7.100, P=0.008). The other mineral bone disorders, such as hypocalcemia, hyperphosphatemia, low intact parathyroid hormone (iPTH) and high iPTH had no statistical difference among three groups (all P＞0.05). Multi-factor stepwise logistic regression analysis revealed that increased iPTH (OR=1.938), and low bone density (OR=1.724) were independent risk factors for CKD patients with vascular calcification (all P＜0.05), while women (OR=3.312) and vascular calcification (OR=1.742) were independent risk factors for CKD patients with low bone density (all P＜0.05). Conclusion Increased iPTH and low bone density are independent risk factors for non-dialysis CKD patients with vascular calcification, while women and vascular calcification are independent risk factors for non-dialysis CKD patients with low bone density.