Posttransplant bone disease: evidence for a high bone resorption state

Prevalence and treatment of decreased bone density in renal transplant recipients: a randomized prospective trial of calcitriol versus alendronate

BACKGROUND

Reduced bone mineral density (BMD) is common in long-term renal transplant recipients and results in a high incidence of fractures. The optimal therapy for these patients is not known.

METHODS

Baseline BMD determinations were obtained in 211 long-term adult renal transplant recipients. One hundred and seventeen patients with a reduced BMD (T score < or = -1) were randomly assigned to treatment with alendronate and calcium (n=60) versus calcitriol and calcium (n=57). Of these, 46 and 51 patients, respectively, completed 1 year of treatment. Forty-nine patients who were not eligible or did not consent to the trial were followed prospectively.

RESULTS

Reduced baseline BMD (T score < or = -1) was present in 159 (78.7%) of patients at the lumbar spine or femur. There was no significant loss of BMD in the prospectively followed patients during 2.7 years. The average lumbar BMD increased from 0.984+/-0.149 to 1.025+/-0.143 g/cm2 (P<0.001) with alendronate and from 1.014+/-0.15 to 1.034+/-0.146 g/cm2 (P=0.002) with calcitriol. BMD at the femur increased from 0.809+/-0.092 to 0.836+/-0.107 g/cm2 (P<0.001) with alendronate and from 0.830+/-0.144 to 0.857+/-0.125 g/cm2 (P=0.023) with calcitriol.

CONCLUSIONS

One year of treatment with alendronate or calcitriol, both with calcium supplementation, resulted in significant increases in BMD at the lumbar spine and femur, with a trend toward alendronate being more effective at the spine (P=0.082). Further studies are needed to determine whether BMDs continue to increase after 1 year and whether there is any additional benefit to combining vitamin D and alendronate. Larger studies are needed to determine whether treatment decreases fracture rates.

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.

Osteoarticular pain and bone mineral density in renal transplantation

INTRODUCTION

The reduction of bone mineral density (BMD) levels is an important complication after renal transplantation. The prevalence of nontraumatic lesions may reach 22%. Patients with lower osseous mass suffer the highest number of lesions.

OBJECTIVE

Evaluate BMD in patients over 30-years old who have undergone renal transplantation more than 1 year prior, who attend a medical facility complaining of osteoarticular pain and were prescribed rest or any analgesia.

PATIENTS AND METHODS

One hundred twenty-three patients who received a renal transplant from a cadaveric donor from 1980 through 2000 were included in the present study to measure BMD levels in the hips and the vertebral column using a densitometer (Hologic 4500 QDR). Our study complied with WHO recommendations, which define normal values as a T score >-1 SD osteopenia as a (T score between <-1 and >-2.5 SD), and osteoporosis as a T score <-2.5 SD. Patients were divided into three groups according to gender and hormonal status. The following clinical and analytic data were collected: age, gender, race, age at onset of menopause, diabetes mellitus (DM), weight, size, retransplantation, period of evolution after transplantation, and parathormone (PTH), creatinine, and renal clearance values.

RESULTS

There were 51 men (41.1%) included. Forty postmenopausal (32.5%) and premenopausal women (26%) were also included. In all patients we observed a correlation between a reduction in BMD values and age, duration post-transplantation, and body weight (P<.05). Reduced BMD levels in premenopausal women were related with lower body weight, (P<.05) and elevated PTH levels (P<.024).

CONCLUSIONS

We observed that patients who had undergone transplantation displayed a moderately higher risk of suffering a fracture. Such risk increased in the case of women with more frequent fractures in the vertebral column. In 23.8% of patients reporting osseous pain, there was no reduction in BMD levels. Therefore, we must look for other disorder, responsible for the pain and prescribe adequate treatment.

Influence of cyclosporin A therapy on bone healing around titanium implants: a histometric and biomechanic study in rabbits

BACKGROUND

Immunosuppressive agents may induce severe changes on bone metabolism. The purpose of the present study was to evaluate the influence of the administration of cyclosporin A (CsA) on the bone tissue around titanium implants.

METHODS

Eighteen New Zealand rabbits were randomly divided into 2 groups of 9 each. The test group (CsA) received daily subcutaneous injection of CsA (10 mg/kg body weight) and the control group (CTL) received saline solution by the same administration route. Three days after therapy began, 2 implants (7.0 mm long and 3.75 mm in diameter) were inserted bilaterally at the region of the tibial methaphysis. After 4, 8, and 12 weeks the animals were sacrificed and biomechanical tests and histometrical procedures, consisting of the determination of the percentages of bone-implant contact and bone area within the limits of the implant threads, were performed.

RESULTS

Intergroup analysis showed that the removal torque and the percentage of bone contact with the implant surface for CsA group were significantly lower than those of the CTL group at 12 weeks (28.5 and 39.2 N cm, P = 0.01; 7.76% and 18.52%, P = 0.02, respectively).

CONCLUSION

The data from the present study suggest that long-term administration of cyclosporin A may negatively influence bone healing around dental implants.

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.

Clinical evaluation for osteoporosis

The clinical evaluation of the osteoporotic patient should include a careful assessment of risk factors for low bone mass, falls, and fractures; quantitation of BMD; a thorough medical history and physical examination; and a targeted set of laboratory, radiographic, and other diagnostic studies as indicated. Among the elderly, vitamin D deficiency ranks high as one of the most underdiagnosed and yet reversible causes of osteoporosis. Regardless of age, every patient with low bone mass or fractures deserves an evaluation to uncover reversible, treatable disorders and to detect serious underlying illnesses.

Bone disease after renal transplantation

Bone disease is common after renal transplantation. The main syndromes are bone loss with a consequent fracture rate of 3% per year, osteonecrosis of the hip, and bone pain. The causes of disease include preexisting uremic osteodystrophy (hyperparathyroidism, aluminum osteomalacia, beta2-associated amyloidosis, and diabetic osteopathy), postoperative glucocorticoid therapy, poor renal function, and ongoing hyperparathyroidism, as the result of either autonomous transformation of the parathyroid gland or ongoing physiologic stimuli. Cyclosporine A treatment, hyperphosphaturia, and a pathogenic vitamin D allele have also been implicated. Bone loss is particularly pronounced during the first year after operation, amounting to up to 9% of bone mass. The clinical and biochemical picture is consistent with a high turnover bone disease, but histomorphometric studies do not completely support this. Principal prophylactic options include preoperative osteodystrophy prophylaxis; postoperative calcium, vitamin D, or calcitriol therapy; estrogen therapy for postmenopausal women; and parathyroidectomy for medically intractable hyperparathyroidism. Recently, prophylactic biphosphonate treatment has shown promise, but the exact indications for treatment remain to be determined.

Calcium-phosphorus-magnesium homeostasis in pregnant women after renal transplantation

OBJECTIVE

The aim of the study was the assessment of calcium-phosphorus-magnesium homeostasis in pregnant women after renal transplantation.

METHODS

The study covered 64 pregnant women in the third trimester of gestation including: 33 women after renal transplantation (the study group) and 31 healthy pregnant women (the control group). Women from both groups were at the similar age: 30.8+/-4.7 vs. 31.3+/-5.0 years (NS) and at the same gestational age 34.8+/-2.4 vs. 35.3+/-2.6 weeks (NS). The mean body mass index (BMI) in the women from the study group before pregnancy was 21.49+/-2.81 vs. 22.1+/-3.02 in the control group (NS), BMI before delivery was 25.43+/-3.05 vs. 26.0+/-3.35 (NS), the percentage of the BMI increase during pregnancy was 18.7+/-7.68 vs. 17.65+/-7.13 (NS) and BMI increase during gestation was 3.93+/-1.56 vs. 3.90+/-1.54, respectively (NS). Arterial blood pressure at the time of blood samples collection for biochemical tests was 151.4+/-26.8/92.5+/-16.9 in women from the study group comparing to 115.0+/-6.0/68.0+/-7.0 mmHg (P<0.001) in the patients from the control group. The maximal blood pressure during pregnancy was 169.2+/-20.7/102.7+/-14.0 vs. 118.0+/-7.0/70.0+/-8.0 mmHg (P<0.001), respectively. We estimated serum levels of: total Ca, ionized Ca(2+), inorganic phosphorus (P(i)), Mg, total protein, albumin and blood morphology. Moreover, urine levels of Ca, P(i), Mg and protein were assessed.

RESULTS

The pregnant women after renal transplantation presented increases in serum concentrations of total Ca (2.54+/-0.20 vs. 2.16+/-0.10 mmol/l; P<0.001) and ionized Ca(2+) (1.322+/-0.104 vs. 1.12+/-0.07 mmol/l; P<0.001) and the decrease in P(i) level (1.013+/-0.211 vs. 1.10+/-0.16 mmol/l; P<0.05), total protein (59.3+/-7.0 vs. 65+/-5 g/l; P<0.001) and albumin (461.6+/-65.65 vs. 493.2+/-59 micromol/l; P<0.05). Moreover, in the study group drop in red blood cells count to 3.71+/-0.56 vs. 4.01+/-0.35 x 10(12)/l (P<0.02) in the control group was detected. Despite increased volume of 24-h urine collection in the kidney recipients we observed significantly decreased urine 24-h calcium excretion 2.47+/-0.92 vs. 6.72+/-3.49 mmol (P<0.001) and simultaneous increase in urine Mg excretion 3.422+/-1.025 vs. 2.18+/-0.52 mmol/24 h (P<0.001). There was no difference in urine 24-h P(i) excretion between the study and the control group. The pregnant renal transplant recipients presented proteinuria of 1.19+/-1.9 g/24 h.

CONCLUSIONS

Women after kidney grafting present vital aberrations in calcium-phosphorus-magnesium homeostasis during pregnancy. The most significant changes are associated with calcium metabolism (high increase in serum Ca levels and impairment of renal elimination of calcium). The observed changes may be influenced by the doses of immunosuppressive agents and disturbed renal function.

Bone mineral density changes within six months of renal transplantation

BACKGROUND

The effective use of new steroid-sparing immunosuppressive regimens may lower cumulative glucocorticoid use among renal transplant recipients. However, it is unknown what effect this therapeutic trend has had on bone disease.

METHODS

Unselected newly transplanted inpatients (n=45) were identified and comprehensively evaluated for metabolic bone disease at a median of 16 days (range 9-33) posttransplant. A follow-up evaluation was conducted a median of 5.7 months (range 4.8-9.3) later. Follow-up values for bone mineral density (BMD) and select laboratories were compared with baseline values using nonparametric statistics. Odds ratios (ORs) and 95% confidence intervals (CIs) were used to describe the associations of baseline characteristics, select laboratory values, and cumulative prednisone and cyclosporine use with spinal BMD loss and were calculated using logistic regression.

RESULTS

A significant decrease in intact parathyroid hormone (P<0.001) and a significant increase in calcitriol (P=0.02) were noted postengraftment. At follow-up, subjects had lost a mean of 2.4% BMD at the lumbar spine (P=0.003) but did not experience significant declines at the femoral neck. The highest tertiles of cumulative prednisone (OR=28.4; 95% CI 2.5-329 and OR=15.8; 95% CI 1.4-179, respectively) and past alcohol use (OR=9.3; 95% CI 1.46-58.5) were significantly associated with spinal BMD loss.

CONCLUSIONS

Significant loss in lumbar BMD occurred within 6 months of transplantation in more than one third of a prospective cohort of renal transplant recipients. Lumbar bone loss seemed to be mediated primarily by glucocorticoid dose and a history of alcohol use.

Cyclosporine A-induced hypercalciuria in calbindin-D28k knockout and wild-type mice

BACKGROUND

It is known that cyclosporine A (CsA) treatment induces high bone-turnover osteopenia and hypercalciuria. It has been proposed that down-regulation of renal calbindin-D28k by CsA results in renal calcium wasting. We investigated the role of the kidney and bone in CsA-induced hypercalciuria in calbindin-D28k knockout (KO) and wild-type (WT) mice.

METHODS

Two sets of experiments were performed. In experiment 1, KO and WT mice were treated with CsA 20 mg/kg/day intraperitoneally (IP) for 7 days. In experiment 2, to eliminate the CsA effect on bone resorption, pamidronate (APD) 2.5 mg/kg IP was given every 4 days with the first dose given 4 days prior to the 7-day course of CsA. Serum levels of creatinine, calcium, and osteocalcin, as well as renal calcium excretion were measured to assess CsA's effects on calcium homeostasis. Effects of CsA on the expression of calbindin-D28k, and two calcium channels in the apical membrane of the distal tubule, epithelial calcium channel (ECaC) and alpha1G-subunit of a voltage-dependent Ca channel (alpha1G), in the kidney were examined by semiquantitative reverse transcription polymerase chain reaction (RT-PCR).

RESULTS

KO mice had a threefold increase in renal calcium excretion when compared with WT mice at the baseline. This difference disappeared when calcium load was reduced by overnight fasting. After the CsA treatment, both WT and KO mice had a significant increase of renal calcium excretion (urine Ca/Cr ratio in WT, 0.11 +/- 0.01 to 1.29 +/- 0.17; in KO, 0.39 +/- 0.04 to 1.18 +/- 0.13; both P < 0.01). CsA treatment decreased renal calbindin-D28k mRNA by 61%, but did not affect the expression of ECaC and alpha1G. Baseline serum osteocalcin level of KO mice was significantly lower than that of WT mice. After CsA treatment, both groups had a 50% increase in the serum osteocalcin level, indicating increased bone turnover. When mice were treated with both CsA and APD, the increase in serum osteocalcin level was prevented, and renal calcium excretion was significantly lower than that in mice treated with CsA alone. However, there was still a significant increase in the urine Ca/Cr ratio in WT and KO mice compared with pretreatment levels (urine Ca/Cr in WT, 0.11 +/- 0.01 to 0.76 +/- 0.05, P < 0.01; in KO, 0.39 +/- 0.05 to 0.79 +/- 0.06; P < 0.01).

CONCLUSION

Calbindin-D28k KO mice have diet-dependent hypercalciuria and a lower bone turnover rate. CsA treatment suppresses the expression of calbindin-D28k in mice, but has no effects on ECaC and alpha1G gene expression at the mRNA level. The pathogenesis of CsA-induced hypercalciuria involves both down-regulation of calbindin-D28k with subsequent impaired renal calcium reabsorption and CsA-induced high turnover bone disease. Additionally, our results suggest that mechanism(s) independent of calbindin-D28k within the kidney also may contribute to the CsA-induced calcium leak.

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.

The effects of vitamin D receptor polymorphism on secondary hyperparathyroidism and bone density after renal transplantation

Immunosuppresive treatment and secondary hyperparathyroidism (SHPT) are considered among the most important pathogenetic factors for postrenal transplant bone disease. The aim of this study was to investigate the relationships among vitamin D receptor (VDR) gene polymorphism, parathyroid hormone (PTH) levels, and bone density in renal transplant recipients. We enrolled 69 patients (47 men and 22 women; mean age, 47 +/- 11 years) who had undergone kidney transplantation 51 +/- 5 months before. All patients underwent an evaluation of the main biochemical parameters of bone metabolism as well as bone densitometry. VDR alleles were typed by a polymerase chain reaction (PCR) assay based on a polymorphic BsmI restriction site. When the patients were categorized according to the VDR genotype (BB, Bb, and bb), serum creatinine, and the cumulative doses of immunosuppressive drugs were similar across the groups. PTH levels higher than 80 pg/ml were found in 53.6% of the patients, with the highest values being detected in the bb VDR genotype (p < 0.05). PTH was significantly correlated to urinary type I collagen cross-linked N-telopeptide (NTx) values. Bone density was low in the whole population; however, spinal bone density was lower in the bb subgroup (p < 0.02). In the whole population, only PTH (p < 0.05) and body mass index (BMI; p < 0.01) were independent predictors of spinal bone density. When grouping the patients by the VDR gene polymorphism, only PTH continued to be an independent predictor of spinal bone density in the bb allele subgroup (R2 adj. = 0.17). We can conclude that the VDR genotype polymorphism affects bone density of renal transplant recipients via its effects on the severity of SHPT.

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.

Bone disease after liver transplantation

1. Bone disease is a common problem in patients with chronic liver disease and liver transplants. 2. The cause of bone disease in these patients is multifactorial. 3. Bone disease worsens initially after liver transplantation, with subsequent improvement over time. However, bone disease in liver transplant recipients is common with long-term follow-up. 4. Evaluation of these patients should include metabolic and hormonal evaluations in conjunction with dual energy x-ray absorptiometry or bone mineral density evaluation. 5. Treatment with calcium, vitamin D, and hormonal supplements should be considered when appropriate for patients awaiting and after liver transplantation. The use of bisphosphanates and calcitonin also should be considered, although published studies in these populations are few in number.

Bisphosphonates in renal osteodystrophy

The present review considers the role that bisphosphonates might have in patients with renal failure. Although bisphosphonates are widely used to reduce fracture risk in patients with osteoporosis, few studies have documented their effect in patients with renal osteodystrophy. The pathogenesis of bone loss after renal transplantation and the role of the recently identified osteoprotegerin/receptor activating nuclear factor-kappaB system is described. Inhibition of bone resorption may prove beneficial when high bone turnover is present, but there are potential drawbacks to widespread use of bisphosphonates. These issues are discussed, with emphasis placed on reports published within the past 18 months.

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

BACKGROUND

Osteoporosis is a serious complication of kidney transplantation. Various factors have been postulated to contribute to posttransplant bone loss, among them treatment with corticosteroids, the use of cyclosporine and cyclosporine-like agents, and persistent hyperparathyroidism. In a previous cross-sectional study of long-term renal transplant recipients, we observed that osteoporosis or osteopenia was present in 88% of patients. Because biochemical markers of bone formation (serum osteocalcin) and bone resorption (urine pyridinoline, PYD, and deoxypyridinoline, DPD) were elevated in the majority of study subjects, we hypothesized that elevated rates of bone-turnover contribute to posttransplant bone loss in long-term renal transplant patients. This study was performed to examine this hypothesis.

METHODS

The study population was composed of 62 patients who were more than 1-year postrenal transplantation and who had preserved renal function. They were followed prospectively for 1 year. Biochemical markers of bone-turnover were measured at study entry, and patients were classified as having high bone-turnover based on elevated urinary levels of at least one marker of bone resorption (i.e., PYD or DPD) and/or serum osteocalcin (group 1). If none of these were present, they were classified as having normal bone-turnover (group 2). Bone mineral density (BMD) was measured by dual energy x-ray absorptiometry (DEXA) at time of entry into the study and again after 1 year of follow-up. The changes in BMD at the lumbar spine, hip, and wrist over the period of the study were compared between the high and normal bone-turnover groups.

RESULTS

Forty-three patients (69%) were classified as having high bone-turnover (Group 1), and 19 patients (31%) were classified as having normal bone-turnover (Group 2). There was a statistically significant difference in change in BMD between the two groups at the lumbar spine (-1.11+/-0.42%, high bone-turnover, vs. 0.64+/-0.54%, normal bone-turnover; P=0.02) and the hip (-0.69+/-0.38%, high bone-turnover, vs. 1.36+/-0.66%, normal bone-turnover; P=0.006). Whereas group 2 had stable bone mass, group 1 exhibited bone loss at these skeletal sites.

CONCLUSIONS

Our results indicate that bone loss is greater in renal transplant recipients with elevated biochemical markers of bone-turnover, suggesting that these markers may be useful in identifying patients at risk for continued bone loss. These data support the hypothesis that continued bone loss in long-term renal transplant recipients is associated with high bone-turnover. If accelerated bone resorption does play a role in posttransplant bone loss, this would provide a strong rationale for use of antiresorptive therapy for the prevention and treatment of this complication.