Parameters of high bone-turnover predict bone loss in renal transplant patients: a longitudinal study

The effect of a previous created distal arteriovenous-fistula on radial bone DXA measurements in prevalent renal transplant recipients

Background

Accelerated bone loss occurs rapidly following renal transplantation due to intensive immunosuppression and persistent hyperparathyroidism. In renal transplant recipients (RTRs) due to the hyperparathyroidism the non-dominant forearm is often utilized as a peripheral measurement site for dual-energy x-ray absorptiometry (DXA) measurements. The forearm is also the site of previous created distal arteriovenous fistulas (AVF). Although AVF remain patent long after successful transplantation, there are no data available concerning their impact on radial bone DXA measurements.

Methods

In this cross-sectional study we performed DXA in 40 RTRs with preexisting distal AVF (RTRs-AVF) to assess areal bone mineral density (aBMD) differences between both forearms (three areas) and compared our findings to patients with chronic kidney disease (CKD, n = 40), pre-emptive RTRs (RTRs-pre, n = 15) and healthy volunteers (n = 20). In addition, we assessed relevant demographic, biochemical and clinical aspects.

Results

We found a marked radial asymmetry between the forearms in RTRs with preexisting AVF. The radial aBMD at the distal AVF forearm was lower compared to the contralateral forearm, resulting in significant differences for all three areas analyzed: the Rad-1/3: median (interquartile range) in g/cm², Rad-1/3: 0.760 (0.641–0.804) vs. 0.742 (0.642, 0.794), p = 0.016; ultradistal radius, Rad-UD: 0.433 (0.392–0.507) vs. 0.420 (0.356, 0.475), p = 0.004; and total radius, Rad-total: 0.603 (0.518, 0.655) vs. 0.599 (0.504, 0.642), p = 0.001). No such asymmetries were observed in any other groups. Lower aBMD in AVF forearm subregions resulted in misclassification of osteoporosis.

Conclusions

In renal transplant recipients, a previously created distal fistula may exert a negative impact on the radial bone leading to significant site-to-site aBMD differences, which can result in diagnostic misclassifications.

Ibandronate in stable renal transplant recipients with low bone mineral density on long-term follow-up

BACKGROUND

Bone mineral density (BMD) has been reported to increase without specific treatment in long-term renal transplant recipients. The aim of this study was to evaluate the effect of ibandronate on BMD and kidney function in long-term renal transplant recipients as compared to a control group. Furthermore, we searched for a gender-specific treatment effect of ibandronate on BMD.

METHODS

In a retrospective, matched case-control study 60 stable renal transplant recipients were included on long-term follow-up. The patient cohort was divided into two groups. The control group (n = 30) comprised patients with close-to-normal bone mineral density who did not receive ibandronate treatment and the treatment group (n = 30) comprised patients with reduced bone mineral density who received ibandronate treatment. The groups were matched for sex, age at the time of renal transplantation, use of steroids, renal transplant function and time lag between the dual-energy X-ray absorptiometry (DEXA) measurements and renal transplantation. Patients of the treatment group were treated with 12.0 ± 6.7 g ibandronate. Treatment cycles lasted 19.3 ± 11.0 months. The first bone mineral density testing was performed 55.3 ± 60.2 months after renal transplantation followed by a second measurement 26.8 ± 12.1 months later.

RESULTS

Both groups did not differ in absolute (g/cm(2)) or relative (%) changes in BMD at the lumbar spine (0.033 ± 0.079 vs. 0.055 ± 0.066 g/cm(2), p = 0.217 and 3.6 ± 7.8 vs. 6.4 ± 8.1 %, p = 0.124) or femoral neck (0.013 ± 0.106 vs. 0.025 ± 0.077 g/cm(2), p = 0.647 and 3.2 ± 13.6 vs. 5.0 ± 13.1 %, p = 0.544) over the study period. There was no correlation of ibandronate dosages with changes in BMD (LS: r = -0.089; p = 0.639 and FN: r =+0.288; p = 0.445). We could neither determine a negative effect of ibandronate on renal transplant function over the study period, estimated via the CKD-EPI formula (-2.9 ± 7.6 vs. -2.7 ± 10.6 mL/min/1.73 m(2), p = 0.900) nor a gender-specific action of ibandronate on bone mass changes.

CONCLUSIONS

Ibandronate treatment was safe with respect to renal transplant function but did not result in a significant additive improvement in bone mineral density as compared to the untreated control group. A gender-specific action of ibandronate on BMD at the LS or FN could not be determined either.

Osteoporosis after renal transplantation

Bone loss and fracture are serious sequelae of kidney transplantation, associated with morbidity, mortality and high economic costs. The pathogenesis of post-transplantation bone loss is multifactorial and complex. Pre-existing bone mineral disease is responsible for a significant part, but it is aggravated by risk factors emerging after renal transplantation with immunosuppressive agents being one of the key contributors. The decrease in bone mass is particularly prominent during the first 6-12 months after transplantation, continuing at a lower rate thereafter. Bone mineral density measurements do not predict bone histology and bone biopsy findings reveal heterogeneous lesions, which vary according to time after transplantation. Currently, vitamin D and bisphosphonates are the most extensively tested therapeutic agents against this accelerated bone loss in renal transplant recipients. Both of these agents have proven effective, but there is no evidence that they decrease fracture risk. More studies are needed to examine the complex pathophysiologic mechanisms implicated in this population, as well as the effects of different therapeutic interventions on bone disorders after kidney transplantation.

Bone and mineral disorders after kidney transplantation: therapeutic strategies

Mineral and bone diseases (MBD) are common in patients with chronic kidney disease who undergo kidney transplantation. The incidence, types and severity of MBD vary according to the duration of chronic kidney disease, presence of comorbid conditions and intake of certain medications. Moreover, multiple types of pathology may be responsible for MBD. After successful reversal of uremia by kidney transplantation, many bone and mineral disorders improve, while immunosuppression, other medications, and new and existing comorbidities may result in new or worsening MBD. Chronic kidney disease is also common after kidney transplantation and may impact bone and mineral disease. In this article, we reviewed the prevalence, pathophysiology, and impact of MBD on post-transplant outcomes. We also discussed the diagnostic approach; immunosuppression management and potential treatment of MBD in kidney transplant recipients.

Oral alendronate can suppress bone turnover but not fracture in kidney transplantation recipients with hyperparathyroidism and chronic kidney disease

Post-transplantation bone diseases negatively affect the quality of life of solid organ recipients. Secondary or tertiary hyperparathyroidism is a frequent complication in kidney transplantation (KTx) recipients. Treatment with immunosuppressive agents including glucocorticoids can lead to deterioration in bone metabolism in these patients. In the present study, we explored the effects of a three-year treatment period with oral alendronate (ALN) in long-term KTx recipients. Post-KTx recipients were recruited (n = 24, M/F = 12/12, mean age 52.0 ± 7.8 years) into this study. All patients were prescribed methylprednisolone (4.07 ± 0.86 mg/day) with various immunosuppressive agents. Before treatment with oral ALN (35 mg/week), the mean concentrations of intact parathyroid hormone (iPTH) and 25-hydroxyvitamin D were 139.2 ± 71.4 pg/mL and 20.8 ± 4.1 ng/mL, respectively. After 36 months of ALN treatment, mean iPTH levels increased slightly (+20.9 %). Treatment with ALN reduced bone-specific alkaline phosphatase (-35.4 %), serum type I collagen N-terminal telopeptide (-31.2 %) and osteocalcin (-55.6 %) levels. ALN did not increase bone mass after 24 months. Four patients with the highest baseline iPTH levels suffered a clinical osteoporotic fracture during the 36-month ALN treatment period. Higher iPTH levels with chronic kidney disease (CKD) at baseline were associated with the incidence of new clinical fractures during ALN treatment. In conclusion, anti-resorptive therapy with ALN can suppress bone turnover even when iPTH concentration is elevated in long-term KTx recipients. However, hyperparathyroidism with CKD seems to be associated with new clinical fractures during ALN treatment.

Management of mineral and bone disorder after kidney transplantation

PURPOSE OF REVIEW

Mineral and bone disorders (MBDs), inherent complications of moderate and advanced chronic kidney disease, occur frequently in kidney transplant recipients. However, much confusion exists about the clinical application of diagnostic tools and preventive or treatment strategies to correct bone loss or mineral disarrays in transplanted patients. We have reviewed the recent evidence about prevalence and consequences of MBD in kidney transplant recipients and examined diagnostic, preventive and therapeutic options to this end.

RECENT FINDINGS

Low turnover bone disease occurs more frequently after kidney transplantation according to bone biopsy studies. The risk of fracture is high, especially in the first several months after kidney transplantation. Alterations in minerals (calcium, phosphorus and magnesium) and biomarkers of bone metabolism (parathyroid hormone, alkaline phosphatase, vitamin D and FGF-23) are observed with varying impact on posttransplant outcomes. Calcineurin inhibitors are linked to osteoporosis, whereas steroid therapy may lead to both osteoporosis and varying degrees of osteonecrosis. Sirolimus and everolimus might have a bearing on osteoblast proliferation and differentiation or decreasing osteoclast-mediated bone resorption. Selected pharmacologic interventions for the treatment of MBD in transplant patients include steroid withdrawal, and the use of bisphosphonates, vitamin D derivatives, calcimimetics, teriparatide, calcitonin and denosumab.

SUMMARY

MBD following kidney transplantation is common and characterized by loss of bone volume and mineralization abnormalities, often leading to low turnover bone disease. Although there are no well established therapeutic approaches for management of MBD in renal transplant recipients, clinicians should continue individualizing therapy as needed.

Osteoporosis following organ transplantation: pathogenesis, diagnosis and management

Organ transplantation has become popular for the management of various chronic illnesses. With the advent of modern immunosuppressive treatments, the longevity of transplant recipients has increased. Consequently, morbid complications such as osteoporosis and bone fractures are seen at an increasing frequency in this population. In most transplant recipients, bone mineral density (BMD) falls shortly after transplantation. However, bone fracture rate plateaus in all except for post-renal transplant patients. Although the underlying pathophysiologic mechanism for this difference is not fully understood, potential mechanisms for sustained bone loss in renal transplant recipients may be persistent phosphorus wasting and defective bone mineralization. Current treatment regimens are based on studies in a small numbers of subjects with BMD as the primary outcome. Although BMD is recognized as a gold standard in the assessment of bone fracture risk, to date, its association with bone fracture risk in the general post-transplant population is not robust. Therefore, randomized controlled trials with bone fracture as the primary end point are crucial. The development of noninvasive bone markers in distinguishing bone turnover and bone mineralization status is also pivotal since skeletal lesions are heterogeneous in various organ transplantations. The elucidation of these underlying skeletal lesions is necessary for the consideration of selective treatment in this population.

Bone disease after renal transplantation

In light of greatly improved long-term patient and graft survival after renal transplantation, improving other clinical outcomes such as risk of fracture and cardiovascular disease is of paramount importance. After renal transplantation, a large percentage of patients lose bone. This loss of bone results from a combination of factors that include pre-existing renal osteodystrophy, immunosuppressive therapy, and the effects of chronically reduced renal function after transplantation. In addition to low bone volume, histological abnormalities include decreased bone turnover and defective mineralization. Low bone volume and low bone turnover were recently shown to be associated with cardiovascular calcifications, highlighting specific challenges for medical therapy and the need to prevent low bone turnover in the pretransplant patient. This Review discusses changes in bone histology and mineral metabolism that are associated with renal transplantation and the effects of these changes on clinical outcomes such as fractures and cardiovascular calcifications. Therapeutic modalities are evaluated based on our understanding of bone histology.

The effect of low-dose cholecalciferol and calcium treatment on posttransplant bone loss in renal transplant patients: a prospective study

BACKGROUND/AIM

Posttransplant steroid doses have been reduced with the use of new and potent immunosuppressive agents. However, posttransplant osteoporosis is still a serious problem. Our aim in this study was to investigate the effect of low-dose cholecalciferol and calcium supplementation on bone loss after transplantation in renal transplant patients.

METHODS

Fifty-eight renal transplantation patients were included in the study. Fourteen newly transplanted patients (group 1) and 44 renal transplantation patients with a graft age of at least six months (group 2) were involved. All patients received 400 IU/day orally cholecalciferol (vitamin D3) and 600 mg/day orally calcium replacement starting from the second day posttransplantation. All patients baseline serum and urine biochemistry, serum 25-hydroxy vitamin D3 (25 (OH)D3), and bone mineral density (BMD) tests were performed. Also, the same measurements were performed at the 12th month in group 1.

RESULTS

After one year of treatment, BMDs were improved in group 1. Patients in group 1 had a nonsignificant increase of lumbar spine (8.12 +/- 18.64% of baseline BMD) and femoral total (7.10 +/- 13.48% of baseline BMD) BMD at the end of the first year. On the other hand, there was a significant increase in femoral neck (10.06 +/- 15.70% of baseline BMD, p < 0.05) measurements. The baseline results of group 2 were similar to group 1. In group 1, 25 (OH)D3 levels were increased while PTH levels were decreased at the end of the year.

CONCLUSION

In renal transplant patients who use low-dose metilprednisolon and new immunosuppressive agents together, low doses of vitamin D3 and calcium replacement for one year provides a reduction in lumbar spine, femoral neck, and femoral total bone loss and prevents bone loss in group 2. In addition, it contributed to the normalization of PTH levels.

Evaluation and management of bone disease and fractures post transplant

Bone disease is common in recipients of kidney, liver, heart, and lung transplants and results in fractures in 20-40% of patients, a rate much higher than expected for age. Fractures occur because of the presence of bone disease as well as other factors such as neuropathy, poor balance, inactivity, and low body or muscle mass. Major contributors to bone disease include both preexisting bone disease and bone loss post transplant, which is greatest in the first 6-12 months when steroid doses are highest. Bone disease in kidney transplant recipients should be considered different from that which occurs in other solid organ transplant recipients for several reasons including the presence of renal osteodystrophy, which contributes to low bone mineral density in these patients; the location of fractures (more common in the legs and feet in these patients than in spine and hips as in other solid organ recipients); and the potential danger in using bisphosphonate therapy, which may cause more harm than good in kidney transplant recipients with low bone turnover. Evaluation in all patients should preferably occur in the pretransplant period or early post transplant and should include assessment of fracture risk as well as metabolic factors that can contribute to bone disease. Bone mineral density measurement is recommended in all patients even if its predictive value for fracture risk in the transplant population is unproven. Management of bone disease should be directed toward decreasing fracture risk as well as improving bone density. Pharmacologic and nonpharmacologic treatment strategies are discussed in this review. Although there have been many studies describing a beneficial effect of bisphosphonates and vitamin D analogues on bone density, none have been powered to detect a decrease in fracture rate.

Renal osteodystrophy after successful renal transplantation: a histomorphometric analysis in 57 patients

Renal transplantation is the treatment of choice for patients with end-stage renal disease. It corrects most of the metabolic abnormalities that cause renal osteodystrophy. Nevertheless, renal osteodystrophy persists in many transplant recipients. The aim of this study was to investigate frequency and histomorphometric pattern of bone disease after renal transplantation. Bone biopsy specimens were taken from the iliac crest of 57 patients, including 28 women (26-70 years old) and 29 men (27-67 years old). Indications for biopsy were hypercalcemia, elevation of parathyroid hormone, and, in 19 cases, without suspected bone abnormalities based on laboratory parameters. The mean time of dialysis prior to renal transplantation was 43 months (range, 6-91 months in women and 10-111 months in men) and the mean interval between transplantation and bone biopsy was 53.5 months (range, 4-191 months in women and 5-90 months in men). Fourteen patients were treated with either 25-hydroxyvitamin D3 and/or 1-alpha hydroxyvitamin D3 or 1,25 dihydroxyvitamin D3, 3 with phosphate-binding agents. The immunosuppression consisted of cyclosporine, azathioprine, and prednisolone. The cumulative dosage of corticosteroids was 5569+/-5305 mg. For static and dynamic histomorphometry, we used American Society of Bone and Mineral Research nomenclature. Mild osteitis fibrosa and osteitis fibrosa, the most frequent forms of renal osteodystrophy, were observed in 13. (22.8%) and 14 patients (24.6%), respectively. Mixed uremic osteodystrophy was found in 7 patients (12.3%), adynamic renal bone disease in 3 patients (5.3%), and osteomalacia in 2 patients (3.5%). In 13 patients (22.8%), reduced bone mass and structural damage without typical signs of renal osteodystrophy, such as endosteal fibrosis or osteoclasia, were detected, and 5 patients (8.7%) showed normal histomorphometric parameters. We concluded that renal osteodystrophy, especially forms with high bone turnover, persisted in many patients after successful renal transplantation. This finding may be due to preexisting conditions, such as duration of dialysis and degree of hyperparathyroidism. Bone disease is increased by corticosteroid and immunosuppressive therapy after renal transplantation and requires close monitoring.

Abnormal bone and mineral metabolism in kidney transplant patients--a review

BACKGROUND/AIMS

Abnormal bone and mineral metabolism is common in patients with kidney failure and often persists after successful kidney transplant.

METHODS

To better understand the natural history of this disease in transplant patients, we reviewed the literature by searching MEDLINE for English language articles published between January 1990 and October 2006 that contained Medical Subject Headings and key words related to secondary or persistent hyperparathyroidism and kidney transplant.

RESULTS

Parathyroid hormone levels decreased significantly during the first 3 months after transplant but typically stabilized at elevated values after 1 year. Calcium tended to increase after transplant and then stabilize at the higher end of the normal range within 2 months. Phosphorus decreased rapidly to within or below normal levels after surgery and hypophosphatemia, if present, resolved within 2 months. Low levels of 1,25(OH)2 vitamin D typically did not reach normal values until almost 18 months after transplant.

CONCLUSION

This review provides evidence demonstrating that abnormal bone and mineral metabolism exists in patients after kidney transplant and suggests the need for treatment of this condition. However, better observational and interventional research is needed before advocating such a treatment guideline.

Transplantation osteoporosis

In the past two decades, there has been a rapid increase in the number of organ transplanted worldwide, including Brazil, along with an improvement in survival and quality of life of the transplant recipients. Osteoporosis and a high incidence of fragility fractures have emerged as a complication of organ transplantation. Many factors contribute to the pathogenesis of osteoporosis following organ transplantation. In addition, most patients have some form of bone disease prior to transplantation, which is usually related to adverse effects of end-stage organ failure on the skeleton. This chapter reviews the mechanisms of bone loss that occur both in the early and late post-transplant periods, as well as the features specific to bone loss after kidney, lung, liver, cardiac and bone marrow transplantation. Prevention and treatment for osteoporosis should be instituted prior and in the early and late phase after transplantation, and will also be addressed in this article.

Bone mineral content and mineral metabolism during cyclosporine treatment of nephrotic Syndrome

OBJECTIVE

Although cyclosporine (Cy) has been associated with bone loss following transplantation, its effects on bone in growing children are largely unknown.

STUDY DESIGN

Thirty-seven patients (2-16 years of age) with remitting nephrotic syndrome (NS), n = 16 receiving Cy for 39 +/- 27 months and n = 21 without Cy, underwent mineral metabolism and bone turnover assessment. In 28 of 37 patients, bone mineral density (BMD) was obtained while off corticosteroid therapy (Rx).

RESULTS

Urinary calcium (Ca), phosphate (PO(4)), and magnesium (Mg) excretion was normal, but serum Mg was lower in patients receiving Cy (1.8 +/- 0.1 v 1.95 +/- 0.2 mg/dL, P < .05). BMD Z scores were similar at the spine (-0.45 +/- 0.74 v 0.04 +/- 0.9) and femur (-0.17 +/- 0.52 v 0.38 +/- 1.28) with no Z score <-2. Serum bone-specific alkaline phosphatase was normal, and N-telopeptide of type I collagen also normal, was higher on Cy (P < .05). Cumulative prednisone exposure was similar and had no significant effect on height and BMD Z scores. Length of Cy-Rx and time elapsed from onset of NS did not correlate with BMD, height Z score, or markers of bone turnover.

CONCLUSIONS

In growing children with NS, during long-term Cy-Rx urinary wasting of Ca and Mg was absent and bone density was preserved.

Bone disease after kidney transplantation

Advances in immunosuppressive therapy have allowed for enhanced allograft survival in kidney transplantation. With this increasing success of transplantation, however, has come a greater appreciation of subsequent complications, such as bone and mineral disease. In patients with chronic kidney disease who are awaiting transplantation, disorders in mineral metabolism and renal osteodystrophy are an essentially universal finding, and several different pathophysiologic mechanisms are believed to contribute to the development of these disorders.

Lumbar bone mineral density in very long-term renal transplant recipients: impact of circulating sex hormones

The influence of circulating sex hormones and gender on the bone mineral density (BMD) in long-term renal transplant recipients needs further investigation. We performed a retrospective analysis of lumbar BMD between 6 years and 20 years after renal transplantation. In 67 patients (47+/-12 years, 38 male) with a minimum interval of 72 months after transplantation, lumbar BMD measurements (dual energy X-ray absorptiometry) were performed (=complete cohort). Thirty-one patients (=longitudinal cohort) underwent at least three serial BMD measurements (mean follow-up 39+/-18 months, start at 86+/-22 months). All patients received prednisolone. In the complete cohort, BMD was significantly reduced in comparison to young healthy (mean T-score -1.33+/-1.40) and age-matched controls (mean Z-score -0.91+/-1.45) at 88+/-31 months (p<0.05). Osteopenia or osteoporosis were present in two-thirds of patients. In the longitudinal cohort, a mean annual lumbar BMD loss of -0.6+/-1.9% was detectable equivalent to a -0.03+/-0.15 reduction of Z-scores per year (regression analysis). Impact of hormonal status: In the complete cohort, postmenopausal status was associated with significantly lower BMD levels compared to men (p=0.0441). Women and men within the lowest tertile of sex hormone levels (LH, FSH, DHEAS, testosterone, progesterone, estradiol) did not exhibit significant differences in terms of lumbar BMD compared to those in the highest tertile. The mean annual bone loss was statistically indistinguishable between men and women. There was no significant correlation of sex hormone levels and BMD in men and premenopausal women. In postmenopausal women, however, low estradiol and high LH levels correlated with the extent of annual BMD loss (p<0.05). Our data confirm significantly reduced lumbar T-scores in the very late period after renal transplantation. The lumbar BMD decreased by -0.6+/-1.9% per year. In postmenopausal long-term renal transplant recipients, low estradiol levels were associated with accelerated bone loss.

Bone mineral density and bone turnover in patients with Bartter syndrome

The aim of this investigation was to evaluate bone mineral density (BMD), by use of DXA, and bone turnover, in patients with Bartter syndrome (BS). Ten patients (2 with BS type II and 8 with BS type III) were included in the procedure. Age at study varied between 2 and 30 years. During the studies usual treatment with indomethacin, spironolactone, and potassium chloride was maintained. Results were compared with those obtained in the 20 asymptomatic parents. Height of the patients at the time of the study did not differ from reference values (Z-score -1.2 to +0.8). Three patients (1 with BS type II and 2 with BS type III) presented reduced lumbar spine BMD or overt osteopenia (BMD Z-scores: -2.3, -1.3, and -1.1). BMD did not correlate significantly with age. Paternal and maternal femoral neck BMD values correlated significantly with lumbar spine BMD of the patients (r=0.65, P<0.05, and r=0.80, P<0.01). Lumbar spine BMD Z-scores correlated negatively with urinary Ca excretion when values both from patients and parents were jointly analyzed (r=-0.43, P<0.05). Plasma calcium concentration was significantly higher (P<0.001) and plasma phosphate Z-score was significantly lower (P<0.05) in the patients than in the parents. However, no significant differences were observed in values for intact PTH, 1,25 (OH)(2)D(3) and 25 (OH)D(3). Intact PTH values correlated positively with BMD Z-scores at lumbar spine (r=0.45, P<0.05) and at femoral neck (r=0.63, P<0.01). Age-corrected biochemical markers of bone formation (plasma alkaline phosphatase and osteocalcin concentrations) were normal whereas age-corrected markers of bone reabsorption (urinary PYD and DPD excretion) were significantly higher than parental values (P<0.01 and <0.05, respectively). We conclude that: (1) reduced BMD is not an exclusive feature of neonatal BS and it can be also observed in classic BS; (2) the loss of bone mineral is not progressive, probably because of the hypocalciuric effect of indomethacin therapy; and (3) this study did not determine whether loss of bone mass is the cause or the consequence of hypercalciuria although the beneficial effect of indomethacin therapy implies the latter.

Long-term follow-up study on bone mineral density and fractures after simultaneous pancreas-kidney transplantation

BACKGROUND

In type 1 diabetic patients with end-stage renal failure, low bone mass is prevalent and the incidence of fractures high after simultaneous pancreas kidney transplantation (SPK). Data are scarce on preexisting skeletal morbidity or the long-term effects of SPK on bone mass and risk of fractures.

METHODS

We conducted a prospective study addressing these issues in 19 consecutive SPK recipients before and at 3, 6, and 12 months, and 2.5 to 4 years after establishment of graft function.

RESULTS

Prior to transplantation, 13 patients (68%) had hyperparathyroidism, 7 of whom had osteoporosis. Mean bone mineral density (BMD) was significantly lower at the femoral neck than at the lumbar spine (T-scores -2.0 +/- 0.89 vs. -0.66 +/- 0.84). There was a significant decrease in BMD at both lumbar spine and femoral neck at 6 months post-transplantation (-6.0 +/- 5.4% and -6.9 +/- 4.3%, respectively). No further loss was observed in the following 6 months. At 1 year post-transplantation, 9 patients had osteoporosis associated with hyperparathyroidism in 8, and none had sustained a clinical fracture. A significant albeit small increase in BMD was observed 6 months after start of alfacalcidol 0.25 microg/day. At end-evaluation, osteoporosis and hyperparathyroidism persisted in the patients in whom it was documented at 1 year. Five patients who had lower BMD at the femoral neck pretransplantation sustained a clinical fracture.

CONCLUSION

Cortical osteoporosis is prevalent in SPK recipients at the time of transplantation, progresses early post-transplantation, and is associated with relatively high incidence of fractures. Reversal of persistent hyperparathyroidism with the use of alfacalcidol may contribute to a decrease in skeletal morbidity.

Reduced bone mineral density in male renal transplant recipients: evidence for persisting hyperparathyroidism

BACKGROUND

Osteoporosis is increasingly recognized as a major source of morbidity following renal transplantation. The aim of this cross-sectional study was to determine the prevalence of osteoporosis in a cohort of male transplant recipients and examine factors that may influence their bone loss.

METHODS

Bone mineral density (BMD) and biochemical markers of bone metabolism were measured in 134 out of 154 male renal allograft recipients in our center.

RESULTS

The mean age of the patients was 49.7 years (range 26-76) with a median of 6 years post-transplant. Only 17% had normal BMD, 30% were osteoporotic at either hip or spine, and this proportion rose to 41% if the ultradistal radius was included. Parathyroid hormone (PTH) was negatively correlated with BMD at all skeletal sites. In a multiple regression model, independent predictors of femoral neck BMD included body mass index (p=0.004), diabetes (p=0.025), and PTH (p=0.049). The only independent predictor of BMD at the ultradistal radius was PTH (p<0.001). Nineteen men sustained a total of 25 appendicular fractures after transplantation (median time to fracture was 3 years). Prevalent vertebral fractures were only identified in five men. PTH was elevated in 72.4% of patients (mean PTH 142 +/- 118 pg/ml). Bone resorption markers were increased in 48% of patients. PTH was positively correlated with serum carboxyterminal telopeptide of type 1 collagen (r=0.473, p<0.001) and procollagen type 1 amino terminal propeptide (r=0.419, p<0.001).

CONCLUSIONS

Osteopenia and osteoporosis are common in male transplant recipients, and the hip and radius are the most severely affected sites. Elevated rates of bone resorption driven by hyperparathyroidism appear to be the most important contributing factor.

Osteoporosis in chronically ill children

Gains in bone mass are very rapid during adolescence and peak bone mass, the most important determinant of osteoporosis, is attained by early adulthood. Glucocorticoids, widely used in children with chronic illness, are known to impact bone mass and quality. In addition, disease and treatment-related factors, nutrient and hormone deficiencies and decreased physical activity may all negatively affect bone mass accrual. Although decreased bone density is increasingly recognized in chronically ill children, current knowledge of the epidemiology, diagnosis and optimal treatment of pediatric secondary osteoporosis is limited. In addition to bone densitometry, biochemical and radiographic tests should be used in the diagnosis of osteoporosis. Bone histomorphometry may be needed in selected situations. At risk children should be advised to ensure sufficient calcium and vitamin D intake and weight bearing physical activity. Growth and pubertal development require careful assessment because of their close correlation with bone formation. Given limited experience with bisphosphonates, it seems prudent to target antiresorptive therapy to those children who have developed symptomatic disease. Ideally this should be done in controlled settings. Early identification and adequate intervention, in selected cases with bisphosphonates, is needed in order to prevent deleterious skeletal complications of osteoporosis in chronically ill children.

Early rapid loss followed by long-term consolidation characterizes the development of lumbar bone mineral density after kidney transplantation

BACKGROUND

Bone mineral density (BMD) decreases significantly early after renal transplantation. This prospective study was designed to evaluate the long-term lumbar BMD development.

METHODS

Sixty-three renal-transplant recipients (mean age 44 +/- 12 years, 37 [59%] male) underwent serial yearly posttransplant laboratory parameter and BMD measurements of the lumbar spine (dual energy x-ray absorptiometry). Combined maintenance immunosuppression included prednisolone in 95% of patients. The minimum number of consecutive scans was three; the maximum number seven (n = 15). Examinations were performed between 3 +/- 2 and 68 +/- 4 months posttransplant.

RESULTS

BMD was significantly lower compared with healthy controls at all times after transplantation. t scores were below -1. BMD development revealed a biphasic pattern: between 3 +/- 2 and 10 +/- 2 months, a significant BMD decrease of -0.016 +/- 0.055 g/cm2 (-1.6%, P = 0.024) occurred. Later, a moderate increase resulting in BMD stability until the sixth year posttransplant was detected. Within the first year, posttransplant osteocalcin (from 19 +/- 15 to 32 +/- 23 microg/L) and calcitriol (from 24 +/- 15 to 43 +/- 24 ng/L) displayed a significant increase. Compared with patients with a pronounced decrease, patients with a substantial increase in early posttransplant BMD had a lower baseline BMD (0.989 +/- 0.131 vs. 1.149 +/- 0.202 g/cm2 [P = 0.0122]) and lower creatinine levels (105 +/- 23 vs. 141 +/- 53 mmol/L [P = 0.0227]).

CONCLUSION

Our study confirms a significant decrease of lumbar BMD early after renal transplantation. Bone loss was less pronounced than previously described. The longitudinal follow-up verifies a previously assumed biphasic lumbar BMD development: after the first year, no further significant bone loss occurred, and bone density remained relatively stable at significantly lower levels compared with healthy controls.

Interleukin-6, transforming growth factor-beta 1, and bone markers after kidney transplantation

The aim of this study was to investigate the relationship between interleukin 6 (IL-6), transforming growth factor (TGF)-beta 1, IL-6 soluble receptors, and biochemical parameters of bone turnover after kidney transplantation. Of 64 patients enrolled in the study, 19 received the kidney transplant 2 to 12 months before the study, and 45 within the previous 15 to 175 months. We measured IL-6, TGF-beta 1, intact parathyroid hormone (PTH) bone alkaline phosphatase (BALP), osteocalcin (OC), and procollagen type I propeptide (P1CP) concentrations in the serum, and deoxypyridinoline crosslinks (DPD) in the urine of the patients. In 16 patients in the first posttransplantation year, the concentrations of IL-6 (P = 0.02), TGF-beta 1 (P = 0.01), BALP (P = 0.0002), OC (P = 0.001), and DPD (P = 0.01) were significantly higher than in patients with longer posttranslation period. Statistically significant negative correlation was found between post-transplantation time and IL-6 (P = 0.04), BALP (P = 0.003), OC (P = 0.0009), P1CP (P = 0.03), and DPD (P = 0.01) concentrations. Repeated measurements of the investigated parameters in the first post-transplantation year showed a significant decrease only in TGF-beta I level. In all patients, IL-6 correlated positively with PTH (P = 0.0009) and DPD (P = 0.03), and IL-6 soluble receptor (IL-6 sR) with DPD (P = 0.03). A decrease in IL-6 and TGF-beta 1 concentrations that paralleled the decrease in bone turnover markers in the posttransplantation period indicated that IL-6 and TGF-beta 1 were probably involved in the bone turnover after kidney transplantation.

Local biochemical markers of bone turnover: relationship to subsequent density of healing alveolar bone defects

OBJECTIVES

This pilot study was designed to test whether biochemical markers of bone turnover in washes of periosteal or trabecular alveolar bone surfaces could be correlated with increases in bone density of an adjacent healing implant socket.

METHODS

Ten subjects had a canula inserted into the alveolar crest and sterile phosphate-buffered saline was washed over the periosteal and trabecular surfaces and collected. Surgical flaps were reflected, 5 mm diameter bone cores were removed from the bone wash site, and standardized radiographs were taken. The sites were allowed to heal for 12 weeks, and radiographs were repeated. Bone washes of the healing sites were also collected after 2 and 12 weeks. Washes were analysed for bone turnover markers osteocalcin (OC; radioimmunoassay) and C-terminal telopeptide of Type 1 collagen (ICTP; enzyme-linked immunosorbent assay (ELISA)), and blood component albumin (ALB; ELISA). Changes in bone density during healing were determined by radiographic absorptiometry.

RESULTS

OC/ALB and ICTP/ALB ratios were higher for trabecular than periosteal washes at baseline (p<or=0.01). Trabecular OC/ALB and ICTP/ALB were inversely correlated with increasing bone density of the healing bone core socket (r=-0.72, p=0.03; Pearson's correlation coefficient).

CONCLUSIONS

Biochemical markers of bone turnover in bone washes of specific alveolar bone sites may prove helpful in predicting how the bone density will increase around healing dental implants.

Bone disease after kidney transplantation

Kidney transplantation is the optimal form of renal replacement therapy for many with end-stage kidney disease. However, kidney transplantation comes with a unique set of medical complications, important among them is bone disease. Posttransplant bone disorders are manifestations of pathologic processes occurring posttransplant that are superimposed on preexisting disorders of bone and mineral metabolism secondary to kidney failure and/or diabetes mellitus. As a consequence of early rapid bone loss, which is seen commonly within the first 3 to 6 months of transplant, the fracture risk posttransplant increases and has been reported as high as 5% to 44%. Posttransplant fractures occur more commonly at peripheral than central sites. Patients with a history of diabetes mellitus are at particular risk for fracture. Parathyroid hormone (PTH) and osteocalcin levels generally decrease after transplantation. Alkaline phosphatase and urinary collagen cross-links are unpredictable. Bone histology varies. No single biomarker unequivocally distinguishes between the various bone disorders found on biopsy examination. Immunosuppression is a major cause of posttransplant bone disorders. Glucocorticoids lead to decreased bone formation whereas the calcineurin inhibitors appear to cause increased bone turnover. Evaluating and managing posttransplant bone disease is an integral part of posttransplant medical care.

Correlations of new markers of bone formation and resorption in kidney transplant recipients

Renal osteodystrophy is a common complication of chronic renal failure and renal replacement therapy. Successful kidney transplantation reverses many of these abnormalities, but the improvement is often incomplete. The evaluation of renal osteodystrophy in everyday practice is based on noninvasive measurements. Taking this into consideration the aim of the present study was to assess new markers of bone metabolism: serum CrossLaps degradation products of C-terminal telopeptides of type I collagen tartrate-resistant acid phosphatase (TRAP) and bone-specific alkaline phosphatase (bALP), as well as their correlations with bone mineral disease (BMD) in kidney transplant recipients. Twenty-six patients (aged 26 to 54 years) receiving a triple immunosuppressive regimen with stable graft function were enrolled in the study. Serum parathormone (PTH) osteocalcin type collagen C-terminal peptides (ICTP), and procollagen type I carboxyterminal extension peptide (PICP) concentrations were measured by radioimmunoassay (RIA), Serum CrossLaps, bALP, beta2-microglobulin, TRAP 5b by enzyme-linked immunoassay (ELISA), and deoxypyridinoline (DPD) in urine immunochemiluminescence. BMD, as measured by dual-energy X-ray absorptiometry (DEXA), correlated negatively with markers of bone formation (bALP, osteoclacin, and PICP) and resorption (TRAP, ICTP, and beta2-microglobulin). The only positive correlation was between urine DPD and BMD at the femoral neck. Interestingly, BMD correlated negatively with CsA concentration. TRAP 5b correlated positively with serum creatinine, ALP, bALP, osteocalcin, iPTH, ICTP, and serum beta2-microglobulin, and negatively with CsA concentration, and azathioprine and prednisone dose. DPD did not correlate with any parameters. Serum CrossLaps correlated with markers of both bone formation and resorption. Because TRAP and serum CrossLaps correlated with markers of both bone formation and or resorption, additional studies are needed to establish the value of these markers of bone resorption to assess renal osteodystrophy.

Development of lumbar bone mineral density in the late course after kidney transplantation

BACKGROUND

Rapid bone loss is a frequent finding early after kidney transplantation. Only limited data are available on the bone mineral density (BMD) in long-term kidney transplant recipients.

METHODS

In 26 kidney transplant recipients (13 men and 13 women, age 45.3 +/- 12.3 years), serum biochemical markers of bone metabolism and BMD at the lumbar vertebrae L2-4 were evaluated prospectively in three serial examinations (E1, E2, E3; method: dual-energy X-ray absorptiometry). Examinations were performed at 47 +/- 2 months, 59 +/- 2 months, and 71 +/- 2 months after transplantation. All patients received standard dual or triple immunosuppression including prednisolone.

RESULTS

The mean BMD was significantly lower (P < 0.001) than in sex-matched young controls: T-score was -1.43 +/- 1.49 (E1), -1.39 +/- 1.40 (E2), and -1.44 +/- 1.30 (E3). The BMD did not change significantly (Delta BMD, -0.5 +/- 5.9%) from E1 to E3. Regression analysis did not show significant associations between Delta BMD and biochemical parameters or prednisolone dosage. No clinically apparent new lumbar vertebral fracture occurred. The mean intact parathyroid hormone was 110.1 +/- 97.5 pg/mL (E1), 121 +/- 102.7 pg/mL (E2), and 134.5 +/- 128.6 pg/mL (E3). Serum creatinine was 1.44 +/- 0.45 (128 +/- 40) mg/dL (micromol/L) (E1), 1.44 +/- 0.47 (127 +/- 42) mg/dL (micromol/L) (E2), and 1.45 +/- 0.70 (128 +/- 62) mg/dL (micromol/L) (E3). Ten patients (38.5%) showed an increase of BMD (+5.7 +/- 3.2%) and 15 patients (57.7%) showed a decrease of -4.7 +/- 3.2% (P < 0.0001). Both groups were different in T-scores at E1 (-2.29 +/- 1 versus -0.88 +/- 1.5); intact parathyroid hormone, creatinine, vitamin D levels, and prednisolone dosage were not significantly different.

CONCLUSION

This study shows that lumbar BMD is reduced in long-term kidney transplant recipients. During our 24-month observation period, overall lumbar BMD remained stable.

Treatment of osteoporosis and osteopenia in long-term renal transplant patients with alendronate

Bone mineral density (BMD) and biochemical markers of bone-turnover were evaluated in a 2-year study in 58 long-term renal transplant recipients with good renal function. In the first year of study, data were collected and patients with osteoporosis and parameters of high bone turnover were classified as being at high risk for on-going bone loss (Group A; n = 29). Patients with lesser degrees of bone loss or without biochemical parameters of high bone turnover were followed longitudinally (Group B; n = 29). Group A patients were then placed on alendronate 10mg/day and both groups were followed for an additional year. Changes in regional BMD and bone-turnover markers between the first and second year within each group were analyzed using paired tests. BMD in Group A, which had declined at the lumbar spine (- 1.6 +/- 0.5%) and total femur (-1.5 +/- 0.4%) during the first year of the study, increased on alendronate therapy at both the lumbar spine (+3.4 +/- 0.6%, p = 0.001) and total femur (+1.6 +/- 0.6%, p <0.001). These patients also experienced a significant decline in levels of serum alkaline phosphatase, osteocalcin, urinary levels of deoxypyridinoline and pyridinoline. In contrast, neither BMD nor biochemical markers changed significantly over 2 years in Group B. The current results demonstrate that renal transplant patients with osteoporosis and biochemical parameters of high bone turnover are at continued risk for bone loss. Therapy with a bisphosphonate can reverse this bone loss and even increase bone mass in these patients. Whether patients with lesser degrees of bone loss and/or patients without parameters of high bone turnover can also benefit from bisphosphonate therapy deserves further study.