Evolution of Bone Disease at 2 Years After Transplantation: A Single-Center Study

Relation of testosterone level and other factors with bone mineral density in male kidney transplant recipients: a cross-sectional study

BACKGROUND

Although testosterone has a pivotal role in bone health, its correlation with bone mineral density (BMD) is understudied in kidney transplant recipients who are at high risk of osteoporosis. This study aimed to elucidate if there is any correlation between serum free testosterone and BMD in this population.

PATIENTS AND METHODS

Sixty male kidney transplant recipients were enrolled in this cross-sectional study, and they were subjected to history taking, clinical examination, and laboratory investigations (including total and free testosterone). BMD was assessed in three regions (forearm, hip, and lumbar spine) using DEXA scan.

RESULTS

The mean age of the included patients was 45.55 ± 13.58 years. Serum total and free testosterone had mean values of 5.17 ± 1.4 ng/ml and 95.46 ± 28.24 pg/ml, respectively, with all levels within the normal range. DEXA scan detected osteoporosis and osteopenia in 9 (15%) and 30 (50%) patients in the lumbar region, 3 (5%) and 36 (60%) in the hip region, as well as 21 (35%) and 33 (55%) in the forearm region, respectively. BMD of the lumbar region had a significant positive correlation with free testosterone, phosphorus, and eGFR, while it had a significant negative correlation with platelets and patient age. BMD of the hip region was positively correlated with serum phosphorus, parathyroid hormone, and duration since the transplant, whereas it was negatively correlated with platelets and total testosterone level. BMD of the forearm had a significant positive correlation with eGFR, whereas it had a significant negative correlation with age and duration since transplantation. In addition, forearm BMD was significantly lower in patients with a radiocephalic AVF.

CONCLUSION

Even within the normal range, free testosterone has a significant positive correlation with lumbar spine BMD with no significant association with the forearm or hip BMD.

Clinical predictors of incipient vertebral fractures and bone mineral density in kidney transplant patients

PURPOSE

Kidney transplant recipients are prone to metabolic bone diseases and consequent fractures. This study aimed to evaluate the incidence of incipient vertebral fractures, osteopenia, osteoporosis, and the clinical factors associated with incipient vertebral fractures in a group of kidney transplant patients.

METHODS

Two hundred sixty-four patients (F/M 124/140, 45.3 ± 13 years) who had undergone kidney transplantation in tertiary care centers were included. Vertebral fractures were assessed semiquantitatively using conventional thoracolumbar lateral radiography in 202 of the patients.

RESULTS

Vertebral fractures were observed in 56.4% (n = 114) of the study group. The frequency of osteoporosis was 20.0% (53 of 264 patients), and osteopenia was 35.6% (94 of 264 patients). Bone mineral density (BMD) levels were in the normal range in 40.3% (n = 46) of the subjects with vertebral fractures. It was in the osteoporotic range in 20.1% (n = 23) and the osteopenic range in 40.3% (n = 46). Vertebral fractures were associated with age, duration of hemodialysis, BMI, and femoral neck Z score (R² 37.8%, p = 0.027).

CONCLUSION

As incipient vertebral fractures can be observed in patients with normal BMD levels in kidney transplant recipients, conventional X-ray screening for vertebral fractures may be beneficial for a proper therapy decision of metabolic bone disease in kidney transplant recipients.

Vitamin K Dependent Proteins in Kidney Disease

Patients with chronic kidney disease (CKD) have an increased risk of developing vascular calcifications, as well as bone dynamics impairment, leading to a poor quality of life and increased mortality. Certain vitamin K dependent proteins (VKDPs) act mainly as calcification inhibitors, but their involvement in the onset and progression of CKD are not completely elucidated. This review is an update of the current state of knowledge about the relationship between CKD and four extrahepatic VKDPs: matrix Gla protein, osteocalcin, growth-arrest specific protein 6 and Gla-rich protein. Based on published literature in the last ten years, the purpose of this review is to address fundamental aspects about the link between CKD and circulating VKDPs levels as well as to raise new topics about how the interplay between molecular weight and charge could influence the modifications of circulating VKDPs at the glomerular level, or whether distinct renal etiologies have effect on VKDPs. This review is the output of a systematic literature search and may open future research avenues in this niche domain.

Systematic review of surgical and medical treatment for tertiary hyperparathyroidism

BACKGROUND

A significant proportion of patients with chronic kidney disease and secondary hyperparathyroidism (HPT) remain hyperparathyroid after kidney transplantation, a state known as tertiary HPT. Without treatment, tertiary HPT can lead to diminished kidney allograft and patient survival. Parathyroidectomy was commonly performed to treat tertiary HPT until the introduction of the calcimimetic drug, cinacalcet. It is not known whether surgery or medical treatment is superior for tertiary HPT.

METHODS

A systematic review was performed and medical literature databases were searched for studies on the treatment of tertiary HPT that were published after the approval of cinacalcet.

RESULTS

A total of 1669 articles were identified, of which 47 were included in the review. Following subtotal and total parathyroidectomy, initial cure rates were 98·7 and 100 per cent respectively, but in 7·6 and 4 per cent of patients tertiary HPT recurred. After treatment with cinacalcet, 80·8 per cent of the patients achieved normocalcaemia. Owing to side-effects, 6·4 per cent of patients discontinued cinacalcet treatment. The literature regarding graft function and survival is limited; however, renal graft survival after surgical treatment appears comparable to that obtained with cinacalcet therapy.

CONCLUSION

Side-effects and complications of both treatment modalities were mild and occurred in a minority of patients. Surgical treatment for tertiary HPT has higher cure rates than medical therapy.

Current Status of Research on Osteoporosis after Solid Organ Transplantation: Pathogenesis and Management

Improved survival following organ transplantation has brought to the forefront some long-term complications, among which osteoporosis and associated fractures are the major ones that adversely affect the quality of life in recipients. The pathogenesis of osteoporosis in transplant recipients is complex and multifactorial which may be related to increased bone resorption, decreased bone formation, or both. Studies have shown that the preexisting underlying metabolic bone disorders and the use of immunosuppressive agents are the major risk factors for osteoporosis and fractures after organ transplantation. And rapid bone loss usually occurs in the first 6–12 months with a significant increase in fracture risk. This paper will provide an updated review on the possible pathogenesis of posttransplant osteoporosis and fractures, the natural history, and the current prevention and treatment strategies concerning different types of organ transplantation.

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.

Bone metabolism and arterial stiffness after renal transplantation

BACKGROUND/AIMS

To assess the relationship between bone and vascular disease and its changes over time after renal transplantation. Metabolic bone disease (MBD) is common in chronic kidney disease (CKD) and is associated with cardiovascular (CV) disease. Following transplantation (Tx), improvement in CV disease has been reported; however, data regarding changes in bone disease remain controversial.

METHODS

Bone turnover and arterial stiffness (pulse wave velocity (PWV)) were assessed in 47 Tx patients (38 (3-191) months after Tx).

RESULTS

Bone alkaline phosphatase (BALP), osteocalcin (OC) and beta-crosslaps were significantly higher in Tx patients, and decreased significantly after one year. There was a negative correlation between BALP, OC and steroid administered (r = -0.35; r = -0.36 respectively). PWV increased in the Tx group (1.15 SD). In patients with a follow up of <24 months, PWV was correlated with BALP and beta-crosslaps (r=0.53; r = 0.69 respectively) while in the ≥24 months group, PWV was correlated with cholesterol (r=0.38).

CONCLUSIONS

Increased bone turnover and arterial stiffness are present following kidney transplantation. While bone turnover decreases with time, arterial stiffness correlates initially with bone turnover, after which the influence of cholesterol becomes significant. Non-invasive estimation of bone metabolism and arterial stiffness may help to assess CKD-MBD following renal transplantation.

Persistence of bone and mineral disorders 2 years after successful kidney transplantation

BACKGROUND

Studies that have conducted bone biopsies after kidney transplantation are scarce, and the results are conflicting.

METHODS

We evaluate the bone histomorphometry, in vitro proliferation, and alkaline phosphatase expression in osteoblasts isolated from bone biopsies from 27 kidney transplant patients. The patients had preserved renal function and were treated with the same immunosuppressive therapy, receiving a minimum dose of corticosteroids.

RESULTS

The biochemical analysis revealed that 41% of the patients presented with hypercalcemia, 26% presented with hypophosphatemia, and hypovitaminosis D was detected in 63%. The histomorphometric analysis showed a reduced trabecular number and increased trabecular separation, mineral apposition rate, and mineralization lag time, as well as higher osteoid surface, osteoblastic surface, resorption surface, and osteoclastic surface and a lower mineralizing surface, compared with the controls. Based on the TMV classification, bone turnover was normal in 48%, high in 26%, and low in 26% of patients. Bone mineralization was delayed in 48% of the patients, and 58% of the patients with hypovitaminosis D presented with delayed bone mineralization. Bone volume was low in 37% of the patients. The osteoblasts from patients exhibited a higher degree of proliferation compared with those from controls.

CONCLUSION

Eight-two percent of our patients presented with alterations in at least one of the TMV parameters. Persistence of hyperparathyroidism, hypovitaminosis D, and immunosuppressive drugs may have influenced osteoblast function, which would explain many of the bone alterations found in these patients.

Low graft function and ongoing hyperparathyroidism are closely related to post-transplantation osteoporosis

INTRODUCTION

Renal transplantation (RT) is the gold standard therapy for chronic renal failure. Immunosuppressive drug choice, malnutrition, adynamic bone disease and hyperparathyroidism are important factors impacting the development of posttransplant osteoporosis. Body composition analysis with bioimpedance devices (BIA) is a useful noninvasive tool to detect malnutrition among the RT population. We investigated the effects of graft function, immunosuppressive drug regimens and biochemical characteristics on bone mineral density of RT patients as well as the reliability of BIA measurements to diagnose osteoporosis.

METHODS

One hundred three recipients with a minimum of 12 months post-RT follow-up underwent body composition analysis using the Tanita Analyzer. The last 6 months of monthly biochemical parameters and glomerular filtration rates (GFR) as well as drug regimens were collected retrospectively from patient charts. Patients were divided into 2 groups, according to their femoral neck and lumbal T scores, as osteoporosis (n = 42) and control groups (n = 61).

RESULTS

The mean GFR of osteoporotic patients was significantly lower (P = .04) and parathyroid hormone (PTH) levels significantly higher (P = .002). According to BIA, osteoporotic patients showed lower bone mass, fat mass, visceral fat ratio, muscle mass, waist-hip ratios, and body mass index values (P < .05). Correlation analysis revealed GFR to negatively correlate with PTH (r = -0.231, P = .010) and positively with femur t scores (r = 0.389, P = .0001) as well as with BIA findings (P = .0001). In contrast, PTH levels in negatively correlated with lumbar and femoral neck t scores (r = -0.22, -0.4 and P = .026, .0001, respectively) but not with BIA findings including bone mass.

CONCLUSION

Changes in bone density after RT were affected by graft function. The rapid loss of bone mineral density emphasizes the need for prevention started in the early posttransplant period. BMD measurements provided a guide for treatment and for subsequent evaluation.

[Effect of cinacalcet on parathyroid hormone level in hypercalcemic hyperparathyroidism of patients with renal transplantation]

BACKGROUND AND OBJECTIVES

Cinacalcet reduces parathyroid hormone (PTH) levels in uremic hyperparathyroidism (HPT), and in renal transplantation it is useful in the management of HPT with hypercalcemia. Our main aim is to evaluate if cinacalcet administered once daily, reduces and maintains reduced PTH levels for 24 hours in renal transplant recipients with HPT and hypercalcemia.

PATIENTS AND METHOD

We studied PTH levels and other bone biomarkers in two groups of renal transplant recipients: one with HPT and hypercalcemia (Group 1), another without alteration of mineral metabolism (Group 2), and a third group of healthy volunteers (Group 3): 35 subjets. Group 1 received a single dose of 60 mg of cinacalcet at 9 am. In all the groups we withdrew blood samples at 8, 10, 11, 12, 13, 19 hours (day 1) and 9 am the following day (day 2), determining levels of PTH and bone biomarkers.

RESULTS

In Group 1, basal PTH levels decreased shortly after dispensing cinacalcet (basal PTH level 237 [86.7] versus 10 hour level 113 [54.7] p<0.05), objectifying a progressive increase to a similar level to baseline after 24 hours of the administration (day 2 9h PTH level 241 [117.4] ns). In Group 2, comparisons among PTH mean levels were not different at any time. In Group 3, the mean baseline PTH level was higher than that observed at 10h (47 [22.7] versus 28 [11.2] p<0.05) and other comparisons were not significant. Beta-ctx was higher at baseline in the three groups in comparison with levels at 11, 12, 13 and 19 hour, and similar to that at 10 am on day 1 and 9 am on day 2. With respect to other bone biomarkers, no differences were observed.

CONCLUSION

Cinacalcet administered once daily reduces PTH in renal transplant recipients with HPT and hypercalcemia, without holding it for 24 hours.

Prevalence and patterns of bone loss in the first year after renal transplant in South East Asian patients

BACKGROUND

Limited data are available regarding patterns of bone loss in South East Asian renal transplant patients. We aimed to determine the prevalence of low bone density and factors contributing to bone loss in Singaporean patients in the first year after renal transplant.

METHODS

Seventy-nine consecutive patients who underwent renal transplant were evaluated. Bone mineral density (BMD) was evaluated at 0 (baseline), and at 6 and 12 months after transplant. Baseline parathyroid hormone and vitamin D levels were also assessed. Multivariate regression models were used to investigate the relationship between the different variables and BMD.

RESULTS

Thirty-six patients (45.6%) had low BMD at baseline. Factors correlating with the low BMD were older age, postmenopausal status, and tertiary hyperparathyroidism (P<0.0005, 0.009, and 0.027, respectively). There was a linear decrease in total hip and lumbar spine BMD from baseline to 12 months, the decrease from baseline to 6 months being significant (P=0.019 for total hip and P<0.0005 for lumbar spine). Patients with tertiary hyperparathyroidism had a greater risk of decrease in BMD at 6 months compared with patients with secondary hyperparathyroidism (odds ratio=13.5, confidence interval: 1.3, 144.4) and with those who had parathyroidectomy (odds ratio=34.9; confidence interval: 2.0, 598.8).

CONCLUSIONS

The prevalence of low BMD in this population of renal transplant recipients was high. Parathyroid status was the only independent factor that correlated with low BMD at baseline and subsequent bone loss highlighting the critical role of this hormone in bone metabolism after renal transplant.