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

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.

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.

Understanding Bone Damage After Kidney Transplantation: A Retrospective Monocentric Cross Sectional Analysis

BACKGROUND

Kidney transplantation (KT) immunosuppression may induce bone tissue damage with bone mineral density (BMD) loss increasing bone fractures risk. Steroid therapy is considered the major player, but others factors are still under review.

PATIENTS AND METHODS

We designed an observational retrospective cohort study to evaluate bone damage after KT. The prevalence of osteopenia, osteoporosis, bone fractures, and the associated risk factors were investigated. The following parameters were recorded before transplantation and at the last follow-up: demographic indexes, cumulative steroid dose (CSD), dialytic and transplantologic age, previous nephropathy, femoral and lumbar BMD, fractures, immunosuppressors, calcemia, phosphoremia, rejection episodes, estimated glomerular filtration rate, and parathyroid hormone and vitamin D levels. Stata software (Stata Corporation, College Station, Texas, United States) was used for the statistical analysis, to perform the Fisher's exact test, Kruskal-Wallis test, Student t test, as well as univariate and multivariate analyses.

RESULTS

The analyzed cohort was composed of 297 patients (65.3% males and 34.7% females). Sixty percent of KT patients had normal BMD, 24% had osteopenia, and 15% had osteoporosis. Twelve percent were victims of bone fractures (8.4% minor, 2% femoral, and 1.7% vertebral). A significant correlation (P <.05) was observed for both osteopenia and osteoporosis with menopause, transplantologic age, CSD, previous glomerulonephritis, and mammalian target of rapamycin (mTOR) inhibitors treatment (imTOR).

CONCLUSION

This study confirms the correlation between CSD (both before and after transplantation) and post-transplantation bone damage. It also shows that a large fraction of these patients had normal BMD related with a low steroid dose in our protocols. This correlation between imTOR assumption and osteoporosis deserves attention and warrants further in vitro analyses to be performed.

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.

Alendronate as an effective treatment for bone loss and vascular calcification in kidney transplant recipients

Kidney transplant recipients develop secondary osteoporosis induced by immunosuppressive medication, with a high risk of fracture, and abdominal aortic calcification (AC) is a known predictor of cardiovascular mortality. In this study of 12 stable kidney recipients, we estimated the preventive effect of bisphosphonate treatment on bone loss and progression of AC. We randomly divided the subjects into a treatment group with alendronate (group A: 5 subjects) and a control group (group C: 7 subjects). Group A patients received 35 mg/week of alendronate over 24 months, while group C patients were not administered with any bisphosphonates. Two major endpoints were established: (1) the time-dependent change in bone mineral density (BMD) estimated with DEXA and (2) progression of abdominal AC, calculated twice as an index (ACI) using computed tomography data. Over the 2-year study period, group A patients showed significantly increased BMD of 1.86 ± 0.85% (P = 0.015 versus baseline), and almost complete inhibition of ACI progression (38.2 ± 24.2% to 39.6 ± 24.3%), but group C patients showed a decrease in BMD decline with bone loss and progression of ACI (32.8 ± 25.0% to 37.8 ± 29.2%, P = 0.061). In conclusion, alendronate therapy was an effective treatment in kidney transplant recipients for secondary osteoporosis and vascular calcification as ectopic calcification. This clinical trial is registered with number JMA-IIA00155 of JMACCT CTR.