The effect of cinacalcet on bone remodeling and renal function in transplant patients with persistent hyperparathyroidism

Role of Calcimimetics in Treating Bone and Mineral Disorders Related to Chronic Kidney Disease

Renal osteodystrophy is common in patients with chronic kidney disease and end-stage renal disease and leads to the risks of fracture and extraosseous vascular calcification. Secondary hyperparathyroidism (SHPT) is characterized by a compensatory increase in parathyroid hormone (PTH) secretion in response to decreased renal phosphate excretion, resulting in potentiating bone resorption and decreased bone quantity and quality. Calcium-sensing receptors (CaSRs) are group C G-proteins and negatively regulate the parathyroid glands through (1) increasing CaSR insertion within the plasma membrane, (2) increasing 1,25-dihydroxy vitamin D3 within the kidney and parathyroid glands, (3) inhibiting fibroblast growth factor 23 (FGF23) in osteocytes, and (4) attenuating intestinal calcium absorption through Transient Receptor Potential Vanilloid subfamily member 6 (TRPV6). Calcimimetics (CaMs) decrease PTH concentrations without elevating the serum calcium levels or extraosseous calcification through direct interaction with cell membrane CaSRs. CaMs reduce osteoclast activity by reducing stress-induced oxidative autophagy and improving Wnt-10b release, which promotes the growth of osteoblasts and subsequent mineralization. CaMs also directly promote osteoblast proliferation and survival. Consequently, bone quality may improve due to decreased bone resorption and improved bone formation. CaMs modulate cardiovascular fibrosis, calcification, and renal fibrosis through different mechanisms. Therefore, CaMs assist in treating SHPT. This narrative review focuses on the role of CaMs in renal osteodystrophy, including their mechanisms and clinical efficacy.

The American Association of Endocrine Surgeons Guidelines for the Definitive Surgical Management of Secondary and Tertiary Renal Hyperparathyroidism

OBJECTIVE

To develop evidence-based recommendations for safe, effective, and appropriate treatment of secondary (SHPT) and tertiary (THPT) renal hyperparathyroidism.

BACKGROUND

Hyperparathyroidism is common among patients with chronic kidney disease, end-stage kidney disease, and kidney transplant. The surgical management of SHPT and THPT is nuanced and requires a multidisciplinary approach. There are currently no clinical practice guidelines that address the surgical treatment of SHPT and THPT.

METHODS

Medical literature was reviewed from January 1, 1985 to present January 1, 2021 by a panel of 10 experts in SHPT and THPT. Recommendations using the best available evidence was constructed. The American College of Physicians grading system was used to determine levels of evidence. Recommendations were discussed to consensus. The American Association of Endocrine Surgeons membership reviewed and commented on preliminary drafts of the content.

RESULTS

These clinical guidelines present the epidemiology and pathophysiology of SHPT and THPT and provide recommendations for work-up and management of SHPT and THPT for all involved clinicians. It outlines the preoperative, intraoperative, and postoperative management of SHPT and THPT, as well as related definitions, operative techniques, morbidity, and outcomes. Specific topics include Pathogenesis and Epidemiology, Initial Evaluation, Imaging, Preoperative and Perioperative Care, Surgical Planning and Parathyroidectomy, Adjuncts and Approaches, Outcomes, and Reoperation.

CONCLUSIONS

Evidence-based guidelines were created to assist clinicians in the optimal management of secondary and tertiary renal hyperparathyroidism.

Alkaline Phosphatase: An Old Friend as Treatment Target for Cardiovascular and Mineral Bone Disorders in Chronic Kidney Disease

Alkaline phosphatase (ALP) is an evolutionary conserved enzyme and widely used biomarker in clinical practice. Tissue-nonspecific alkaline phosphatase (TNALP) is one of four human isozymes that are expressed as distinct TNALP isoforms after posttranslational modifications, mainly in bone, liver, and kidney tissues. Beyond the well-known effects on bone mineralization, the bone ALP (BALP) isoforms (B/I, B1, B1x, and B2) are also involved in the pathogenesis of ectopic calcification. This narrative review summarizes the recent clinical investigations and mechanisms that link ALP and BALP to inflammation, metabolic syndrome, vascular calcification, endothelial dysfunction, fibrosis, cardiovascular disease, and mortality. The association between ALP, vitamin K, bone metabolism, and fracture risk in patients with chronic kidney disease (CKD) is also discussed. Recent advances in different pharmacological strategies are highlighted, with the potential to modulate the expression of ALP directly and indirectly in CKD–mineral and bone disorder (CKD-MBD), e.g., epigenetic modulation, phosphate binders, calcimimetics, vitamin D, and other anti-fracture treatments. We conclude that the significant evidence for ALP as a pathogenic factor and risk marker in CKD-MBD supports the inclusion of concrete treatment targets for ALP in clinical guidelines. While a target value below 120 U/L is associated with improved survival, further experimental and clinical research should explore interventional strategies with optimal risk–benefit profiles. The future holds great promise for novel drug therapies modulating ALP.

Bone and Mineral Disease in Kidney Transplant Recipients

After kidney transplantation, mineral and bone disorders are associated with higher risk of fractures and consequent morbidity and mortality. Disorders of calcium and phosphorus, vitamin D deficiency, and hyperparathyroidism are also common. The epidemiology of bone disease has evolved over the past several decades due to changes in immunosuppressive regimens, mainly glucocorticoid minimization or avoidance. The assessment of bone disease in kidney transplant recipients relies on risk factor recognition and bone mineral density assessment. Several drugs have been trialed for the treatment of post-transplant mineral and bone disorders. This review will focus on the epidemiology, effect, and treatment of metabolic and skeletal derangements in the transplant recipient.

Parathyroidectomy or cinacalcet: Do we still not know the best option for graft function in kidney-transplanted patients? A meta-analysis

BACKGROUND

Tertiary hyperparathyroidism occurs in 25% to 50% of kidney-transplanted patients. Indication of parathyroidectomy is now discussed, since the calcimimetic agent, cinacalcet, is an alternate option. The effects of either of these treatments on graft function remain controversial, studied only in small cohorts showing either decrease or absence of modification. We performed a meta-analysis to evaluate the evolution of graft function after surgical or medical treatment.

METHODS

Studies assessing graft function in tertiary hyperparathyroidism after parathyroidectomy or cinacalcet introduction were enrolled into quantitative analysis using Pubmed, Embase, and Cochrane databases following the Preferred Reporting Items for Systematic Reviews and Meta-Analysis reporting guidelines. Among 68 screened studies, 18 had no missing data and were included for statistical analyses. We performed random effect meta-analysis to determine changes in serum creatinine and estimated glomerular filtration rate.

RESULTS

Seven studies assessing the evolution of graft function 6 and/or 12 months after parathyroidectomy and 13 after administration of cinacalcet were included. Meta-analysis found no significant variations after parathyroidectomy in serum creatinine (6 studies, 314 patients) and estimated glomerular filtration rate (2 studies, 105 patients). No significant variation was found after administration of cinacalcet in serum creatinine (10 studies, 404 patients) and estimated glomerular filtration rate (6 studies, 149 patients). A significant heterogeneity between the studies (P < .01, Cochran's Q) was found.

CONCLUSION

Meta-analysis shows that parathyroidectomy and cinacalcet do not significantly impair graft function in patients with tertiary hyperparathyroidism. However, the significant heterogeneity between selected studies, partially explained by the lack of consensual definition of tertiary hyperparathyroidism, limits the conclusions of all previously published series.

Tertiary Hyperparathyroidism: Why the Delay?

OBJECTIVE

To evaluate the reason for delay of surgical referral in tertiary hyperparathyroidism (THPT) and its impact on renal allograft function.

BACKGROUND

Persistent hyperparathyroidism after renal transplant has been shown to negatively impact allograft function, yet referral for definitive treatment of THPT is often delayed.

METHODS

A retrospective review was performed of patients undergoing parathyroidectomy for THPT (n = 38) at a single institution from May 2016 to June 2018. The first elevated serum calcium after transplant and time to referral for parathyroid surgery were recorded. Baseline creatinine post-transplant and the most recent creatinine level were used to assess allograft function.

RESULTS

Thirty-eight patients were included, with mean age 53 ± 2 years and 66% male. Mean preoperative calcium and parathyroid hormone were 10.8 ± 0.1 mg/dL and 328 ± 48 pg/mL, respectively. THPT after renal transplant was diagnosed at a median of 15 days (range of 1-4892 days). Median time to parathyroidectomy referral was 320 days (range 16-6281 days). In over 50% of patients, the cited reason for referral to an endocrine surgeon was difficulty with cinacalcet - either cost, poor calcium control, and poor compliance or tolerance. In comparing renal function between patients referred early (<278 days, n = 19) versus later (>278 days, n = 19) for parathyroidectomy, those referred early had an improvement in creatinine (27.6% vs -5%, P = 0.007).

CONCLUSIONS

Patients with THPT wait approximately a year, on average, before referral to an endocrine surgeon for curative parathyroidectomy; earlier referral was associated with improvement in serum creatinine.

The use of cinacalcet after pediatric renal transplantation: an international CERTAIN Registry analysis

BACKGROUND

Secondary hyperparathyroidism (SHPT) may persist after renal transplantation (RTx), inducing hypophosphatemia and hypercalcemia that precludes the use of vitamin D analogs. The calcimimetic cinacalcet improved plasma calcium and parathyroid hormone (PTH) levels in randomized controlled trials in adults after RTx, but pediatric data are scarce.

METHODS

In this retrospective study, we analyzed 20 pediatric patients from the Cooperative European Paediatric Renal TransplAnt Initiative (CERTAIN) Registry who received cinacalcet after RTx. The results are presented as median and interquartile range (25th-75th percentile).

RESULTS

At 13.7 (11.0-16.5) years of age, 20 pediatric patients received a renal allograft. Cinacalcet was introduced at 0.4 (0.3-2.7) years post-transplant at an estimated glomerular filtration rate (eGFR) of 50 (34-66) mL/min/1.73 m², plasma calcium of 2.58 (2.39-2.71) mmol/L, age-standardized (z score) phosphate of - 1.7 (- 2.7-- 0.4), and PTH of 136 (95-236) ng/L. The starting dose of cinacalcet was 0.5 (0.3-0.8) mg/kg per day, with a maximum dose of 1.1 (0.5-1.3) mg/kg per day. With a follow-up of 3.0 (1.5-3.6) years on cinacalcet therapy, eGFR remained stable; PTH levels decreased to 66 (56-124) ng/L at the last follow-up (p = 0.015). One patient displayed hypocalcemia (1.8 mmol/L). Cinacalcet was withdrawn in three patients (hypocalcemia, parathyroidectomy, incompliance). Nephrocalcinosis of the graft was not reported.

CONCLUSIONS

This pilot study suggests that cinacalcet as off-label therapy for SHPT after pediatric RTx is efficacious in controlling post-transplant SHPT with acceptable tolerability. Continuing cinacalcet even with normal PTH can lead to dangerous life-threatening hypocalcemia. Therefore, at each subsequent visit, the need to continue cinacalcet must be assessed.

Management of Post-transplant Hyperparathyroidism and Bone Disease

Significant advances in immunosuppressive therapies have been made in renal transplantation, leading to increased allograft and patient survival. Despite improvement in overall patient survival, patients continue to require management of persistent post-transplant hyperparathyroidism. Medications that treat persistent hyperparathyroidism include vitamin D, vitamin D analogues, and calcimimetics. Medication side effects such as hypocalcemia or hypercalcemia, and adynamic bone disease, may lead to a decrease in the drugs. When medical management fails to control persistent post-transplant hyperparathyroidism, treatment is a parathyroidectomy. Surgical techniques are not uniform between centers and surgeons. Undergoing the surgery may include a subtotal technique or a technique including total parathyroid gland resection with partial heterotopic gland reimplantation. In addition, there are possible post-surgical complications. The ideal treatment for persistent post-transplant hyperparathyroidism is the treatment and prevention of the condition while patients are being managed for their late-stage chronic kidney disease and end-stage renal disease.

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.

Long-Term Use of Cinacalcet in Kidney Transplant Recipients With Hypercalcemic Secondary Hyperparathyroidism: A Single-Center Prospective Study

OBJECTIVES

Persistent secondary hyperparathyroidism is common after successful kidney transplant, with concomitant hypercalcemia and hypophosphatemia potentially leading to reduced graft survival and increased cardiovascular risk. Cinacalcet, a calcimimetic agent that activates the calcium-sensing receptors in parathyroid glands, is a therapeutic option. In this study, we assessed the long-term treatment effects of cinacalcet for a period of up to 5 years in a cohort of kidney transplant recipients.

MATERIALS AND METHODS

Forty-seven patients with secondary hyperparathyroidism (intact parathyroid hormone level > 70 pg/mL or 7.43 pmol/L) and hypercalcemia (corrected calcium > 10.4 mg/dL or 2.6 mmol/L) were considered eligible for treatment with cinacalcet and were included in the analysis. Data were recorded at initiation of treatment and every 6 months up to a maximum follow-up of 60 months. A control group of patients treated with placebo, conventional treatment, or surgical treatment was not available for this study.

RESULTS

Mean follow-up time was 45 ± 16 months. Treatment with cinacalcet was initiated at a median of 25 months after renal transplant. Serum calcium decreased by 0.21 mmol/L (2.69 vs 2.48 mmol/L; 95% confidence interval, 0.08-0.345; P < .001) during the first 6 months, and this reduction was sustained during follow-up. Intact parathyroid hormone level decreased by 7.68 pmol/L (32.96 ± 36.4 vs 25.28 ± 19.5 pmol/L; 95% confidence interval, -6.42 to 21.75; P = not significant) at 6 months, whereas at the end of follow-up intact parathyroid hormone level decreased further by 20.07 pmol/L (32.96 ± 36.4 vs 12.89 ± 5.73 pmol/L; 95% confidence interval, 2.02-38.1; P < .01). Mean starting dose of cinacalcet was 33.5 ± 10 mg/day. According to the therapeutic response, cinacalcet dose increased steadily and reached 51.1 ± 33 mg/day at the end of the observation period. Mean serum phosphorus increased significantly, whereas estimated glomerular filtration rate remained virtually stable throughout follow-up. Adverse reactions were observed in 4 patients, comprising mild gastro-intestinal complaints.

CONCLUSIONS

Long-term treatment with cinacalcet in kidney transplant recipients with secondary hyperparathyroidism is effective in controlling hypercalcemia and correcting hypophosphatemia, without affecting graft function while being well-tolerated.

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.

Long-term clinical practice experience with cinacalcet for treatment of hypercalcemic hyperparathyroidism after kidney transplantation

Within this prospective, open-label, self-controlled study, we evaluated the long-term effects of the calcimimetic cinacalcet on calcium and phosphate homeostasis in 44 kidney transplant recipients (KTRs) with hypercalcemic hyperparathyroidism by comparing biochemical parameters of mineral metabolism between pre- and posttreatment periods. Results are described as mean differences (95% CIs) between pre- and posttreatment medians that summarize all repeated measurements of a parameter of interest between the date of initial hypercalcemia and cinacalcet initiation (median of 1.6 (IQR: 0.6-3.8) years) and up to four years after treatment start, respectively. Cinacalcet was initiated after 1.8 (0.8-4.7) years posttransplant and maintained for 6.2 (3.9-7.6) years. It significantly decreased total serum calcium (-0.30 (-0.34 to -0.26) mmol/L, P < 0.001) and parathyroid hormone levels (-79 (-103 to -55) pg/mL, P < 0.001). Serum levels of inorganic phosphate (Pi) and renal tubular reabsorption of phosphate to glomerular filtration rate (TmP/GFR) increased simultaneously (Pi: 0.19 (0.15-0.23) mmol/L, P < 0.001, TmP/GFR: 0.20 (0.16-0.23) mmol/L, P < 0.001). In summary, cinacalcet effectively controlled hypercalcemic hyperparathyroidism in KTRs in the long-term and increased low Pi levels without causing hyperphosphatemia, pointing towards a novel indication for the use of cinacalcet in KTRs.

Vitamin D and cinacalcet administration pre-transplantation predict hypercalcaemic hyperparathyroidism post-transplantation: a case-control study of 355 deceased-donor renal transplant recipients over 3 years

BACKGROUND

The effects of pre-transplantation medication for secondary hyperparathyroidism on post-transplantation parathyroid hormone (PTH) and calcium levels have not yet been conclusively determined. Therefore, this study sought to determine the level of off-label use of cinacalcet and to determine predictors of its administration during the long-term follow-up of a cohort of individuals who received deceased-donor renal transplants. Furthermore, safety considerations concerning the off-label use of cinacalcet are addressed.

METHODS

This was a case-control study of 355 stable renal transplant recipients. The patient cohort was divided into two groups. Transplant group A comprised patients who did not receive cinacalcet treatment, and transplant group B comprised patients who received cinacalcet treatment during follow-up after renal transplantation. The characteristics of the patients were evaluated to determine predictors of cinacalcet use after successful renal transplantation.

RESULTS

Compared with the control individuals (n = 300), the cinacalcet-treated individuals (n = 55) had significantly higher PTH levels at 4 weeks post-transplantation (20.3 ± 1.6 versus 40.7 ± 4.0 pmol/L, p = 0.0000) when they were drug naive. At 3.2 years post-transplantation, cinacalcet-treated patients showed higher PTH (26.2 ± 2.3 versus 18.4 ± 2.3 pmol/L, p = 0.0000), higher calcium (2.42 ± 0.03 versus 2.33 ± 0.01 mmol/L, p = 0.0045) and lower phosphate (0.95 ± 0.04 versus 1.06 ± 0.17 mmol/L, p = 0.0021) levels. Individuals in the verum group were more likely to receive cinacalcet therapy (45.5% versus 14.3%, p = 0.0000), and they had higher pill burdens for the treatment of hyperparathyroidism (1.40 ± 0.08 versus 0.72 ± 0.03 pills per patient, p = 0.0000) whilst they were on the waiting list for transplantation. Regression analysis confirmed the associations between hypercalcaemic hyperparathyroidism and PTH levels at 4 weeks post-transplantation (p = 0.0001), cinacalcet use (p = 0.0000) and the preoperative total pill burden (p = 0.0000). Renal function was the same in both groups.

CONCLUSIONS

Parathyroid gland dysfunction pre-transplantation translates into clinically relevant hyperparathyroidism post-transplantation, despite patients being administered more intensive treatment whilst on dialysis. PTH levels at 4 weeks post-transplantation might serve as a marker for the occurrence of hypercalcaemic hyperparathyroidism during follow-up.

Cinacalcet for hypercalcaemic secondary hyperparathyroidism after renal transplantation: a multicentre, retrospective, 3-year study

AIMS

Our aim was to evaluate the long-term effect of cinacalcet in patients with hypercalcaemic secondary hyperparathyroidism (SHPT) after renal transplantation (RT) in order to expand real-world data in this population.

METHODS

We performed a multicentre, observational, retrospective study in 17 renal transplant units from Spain. We collected data from renal recipients with hypercalcaemic (calcium >10.2 mg/dL) SHPT (intact parathyroid hormone (iPTH) > 120 pg/mL) who initiated cinacalcet in the clinical practice.

RESULTS

We included 193 patients with a mean (standard deviation (SD)) age of 52 (12) years, 58% men. Cinacalcet treatment was initiated at a median of 20 months after RT (median dose 30 mg/day). Mean calcium levels decreased from a mean (SD) of 11.1 (0.6) at baseline to 10.1 (0.8) at 6 months (9.0% reduction, P < 0.0001). Median iPTH was reduced by 23.0% at 6 months (P = 0.0005) and mean phosphorus levels increased by 11.1% (P < 0.0001). The effects were maintained up to 3-years. No changes were observed in renal function or anticalcineurin drug levels. Only 4.1% of patients discontinued cinacalcet due to intolerance and 1.0% due to lack of efficacy.

CONCLUSIONS

In renal transplant patients with hypercalcaemic SHPT, cinacalcet controlled serum calcium, iPTH and phosphorus levels up to 3 years. Tolerability was good.

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.

[Mineral and bone disorders in renal transplantation]

The deregulation of bone and mineral metabolism during chronic kidney disease (CKD) is a daily challenge for physicians, its management aiming at decreasing the risk of both fractures and vascular calcifications. Renal transplantation in the context of CKD, with pre-existing renal osteodystrophy as well as nutritional impairment, chronic inflammation, hypogonadism and corticosteroids exposure, represents a major risk factor for bone impairment in the post-transplant period. The aim of this review is therefore to provide an update on the pathophysiology of mineral and bone disorders after renal transplantation.

Recovery versus persistence of disordered mineral metabolism in kidney transplant recipients

In patients with end-stage renal disease, successful renal transplantation improves the quality of life and increases survival, as compared with long-term dialysis treatment. Although it long has been believed that successful kidney transplantation to a large extent solves the problem of chronic kidney disease-mineral and bone disorders (CKD-MBD), increasing evidence indicates that it only changes the phenotype of CKD-MBD. Posttransplant CKD-MBD reflects the effects of immunosuppression, previous CKD-MBD persisting after transplantation, and de novo CKD-MBD. A major and often-underestimated problem after successful renal transplantation is persistent hyperparathyroidism. Besides contributing to posttransplant hypercalcemia and hypophosphatemia, persistent hyperparathyroidism may be involved in the pathogenesis of allograft dysfunction (nephrocalcinosis), progression of vascular calcification, and bone disease (uncoupling of bone formation and bone resorption and bone mineral density loss) in renal transplant recipients. Similar to nontransplanted patients, CKD-MBD has a detrimental impact on (cardiovascular) mortality and morbidity. Additional studies urgently are needed to get more insights into the pathophysiology of posttransplant CKD-MBD. These new insights will allow for a more targeted and causal therapeutic approach.

Cinacalcet for the treatment of hyperparathyroidism in kidney transplant recipients: a systematic review and meta-analysis

BACKGROUND

Hyperparathyroidism is present in up to 50% of transplant recipients 1 year after transplant, often despite good graft function. Posttransplant patients frequently have hypercalcemia-associated hyperparathyroidism, limiting the role of vitamin D analogues and sometimes requiring parathyroidectomy. Multiple observational studies have investigated treatment of posttransplant hyperparathyroidism with the calcimimetic agent cinacalcet.

METHODS

We performed a systematic review and meta-analysis of prospective and retrospective studies from 2004 through January 26, 2012, using MEDLINE. We identified studies evaluating treatment with cinacalcet in renal transplant recipients with hyperparathyroidism. We performed random effects meta-analysis to determine changes in calcium, phosphorus, parathyroid hormone, and serum creatinine.

RESULTS

Twenty-one studies with 411 kidney transplant recipients treated with cinacalcet for hyperparathyroidism met inclusion criteria. Patients were treated for 3 to 24 months. By meta-analysis, calcium decreased by 1.14 mg/dL (95% confidence interval, -1.00 to -1.28), phosphorus increased by 0.46 mg/dL (95% confidence interval, 0.28-0.64), parathyroid hormone decreased by 102 pg/mL (95% confidence interval, -69 to -134), and there was no significant change in creatinine (0.02 mg/dL decrease; 95% confidence interval, -0.09 to 0.06). Cinacalcet resulted in hypocalcemia in seven patients. The most common side effect was gastrointestinal intolerance.

CONCLUSIONS

From nonrandomized studies, cinacalcet appears to be safe and effective for the treatment of posttransplant hyperparathyroidism. Larger observational studies and randomized controlled trials, performed over longer follow-up times and looking at clinical outcomes, are needed to corroborate these findings.

Impact of post-kidney transplant parathyroidectomy on allograft function

BACKGROUND

The impact of parathyroidectomy on allograft function in kidney transplant patients is unclear.

METHODS

We conducted a retrospective, observational study of all kidney transplant recipients from 1988 to 2008 who underwent parathyroidectomy for uncontrolled hyperparathyroidism (n = 32). Post-parathyroidectomy, changes in estimated glomerular filtration rate (eGFR) and graft loss were recorded. Cross-sectional associations at baseline between eGFR and serum calcium, phosphate, and parathyroid hormone (PTH), and associations between their changes within subjects during the first two months post-parathyroidectomy were assessed.

RESULTS

Post-parathyroidectomy, the mean eGFR declined from 51.19 mL/min/1.73 m(2) at parathyroidectomy to 44.78 mL/min/1.73 m(2) at two months (p < 0.0001). Subsequently, graft function improved, and by 12 months, mean eGFR recovered to 49.76 mL/min/1.73 m(2) (p = 0.035). Decrease in serum PTH was accompanied by a decrease in eGFR (p = 0.0127) in the first two months post-parathyroidectomy. Patients whose eGFR declined by ≥20% (group 1) in the first two months post-parathyroidectomy were distinguished from the patients whose eGFR declined by <20% (group 2). The two groups were similar except that group 1 had a higher baseline mean serum PTH compared with group 2, although not significant (1046.7 ± 1034.2 vs. 476.6 ± 444.9, p = 0.14). In group 1, eGFR declined at an average rate of 32% (p < 0.0001) during the first month post-parathyroidectomy compared with 7% (p = 0.1399) in group 2, and the difference between these two groups was significant (p = 0.0003). The graft function recovered in both groups by one yr. During median follow-up of 66.00 ± 49.45 months, 6 (18%) patients lost their graft with a mean time to graft loss from parathyroidectomy of 37.2 ± 21.6 months. The causes of graft loss were rejection (n = 2), pyelonephritis (n = 1) and chronic allograft nephropathy (n = 3). No graft loss occurred during the first-year post-surgery.

CONCLUSION

Parathyroidectomy may lead to transient kidney allograft dysfunction with eventual recovery of graft function by 12 months post-parathyroidectomy. Higher level of serum PTH pre-parathyoidectomy is associated with a more profound decrease in eGFR post-parathyroidectomy.

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.

Impact of parathyroidectomy on allograft outcomes in kidney transplantation

We performed retrospective, multi-center study of the impacts of parathyroidectomy (PTX) after or before kidney transplantation on allograft outcomes. A total of 63 patients who underwent PTX after kidney transplantation were identified. Deterioration in eGFR by more than 25% at 1 month after PTX occurred in 20% of the patients. The baseline eGFR was significantly lower in impairment group than nonimpairment group [adjusted odds ratio (OR) 0.87, 95% confidence interval (CI) 0.77-0.99, P = 0.033]. Low iPTH concentration after PTX was also a significant risk factor for the renal impairment (OR 0.96, CI 0.94-0.99, P = 0.009). A total of 37 patients who underwent PTX before transplantation were identified. Thirty-six percent of the patients had persistent hyperparathyroidism by 1 year after transplantation. A high iPTH level before PTX was a significant risk factor for persistent post-transplant hyperparathyroidism (adjusted OR 1.002, CI 1.000-1.005, P = 0.039). Finally, eGFR values during the first 5 years after transplantation were significantly lower in the patients who underwent PTX at less than 1 year after transplantation, than the pretransplant PTX patients (P = 0.032). As PTX after kidney transplantation has a risk of deterioration of allograft function, pretransplant PTX should be considered for patients with severe hyperparathyroidism, who could undergo post-transplant PTX.

Pharmacotherapy of chronic kidney disease and mineral bone disorder

INTRODUCTION

Disturbances of the bone and mineral metabolism are a common complication of chronic kidney disease (CKD); these disturbances are known as CKD-mineral bone disorder (CKD-MBD). A better understanding of the pathophysiological mechanisms of CKD-MBD, along with its negative impact on other organs and systems, as well as on survival, has led to a shift in the treatment paradigm of this disorder. The use of phosphate binders changed dramatically over the last decade when noncalcium-containing phosphate binders, such as sevelamer and lanthanum carbonate, became possible alternative treatments to avoid calcium overload. Vitamin D receptor activators, such as paricalcitol and doxercalciferol, with fewer calcemic and phosphatemic effects, have also been introduced to control parathormone production and the interest in native vitamin D supplementation has grown. Furthermore, a new drug class, the calcimimetics, has recently been introduced into the therapeutic arsenal for treating secondary hyperparathyroidism.

AREAS COVERED

This review discusses the advantages and disadvantages of the above pharmacological options to treat CKD-MBD.

EXPERT OPINION

The individual-based use of phosphate binders, vitamin D and calcimimetics, separately or in combination, constitute a reasonable approach to treat CKD-MBD. These treatments aim to achieve a rigorous control of phosphorus and parathormone levels, while avoiding calcium overload.

[Cinacalcet impact on calcium homeostasis and bone remodeling in 13 renal transplanted patients with hyperparathyroidism and hypercalcaemia]

The purpose of the study is to assess the impact of cinacalcet on calcium and bone remodeling, in post-renal transplanted patients with persistent hypercalcaemia secondary to hyperparathyroidism. Thirteen renal-transplanted adult recipients with a glomerular filtration rate over 30 ml/min/1.73 m(2), a total serum calcium>2.60 mmol/l with ionized calcium>1.31 mmol/l and a parathyroid hormone serum level over 70 pg/ml, were treated with cinacalcet for 4 months followed by a 15-day wash out. The results show that cinacalcet lowers significantly total and ionized calcium respectively from 2,73 (2,67-2,86) to 2,31 (2,26-2,37) mmol/l (P<0.05) and from 1,39 (1,37-1,47) to 1,21 (1,15-1,22) mmol/l (P<0.05) with no alteration of the 24-hour urine calcium/creatinine ratio and no significant expected PTH serum level suppression (153 [115-214,9] and 166 [122-174] pg/ml). On the other hand, fasting urine calcium was significantly decreased from 0,61 (0,27-1,02) to 0,22 (0,15-0,37) (P<0.05) and bone-specific alkaline phosphatases increased from 20,5 (13-46,6) to 33,8 (12-58,9) ng/ml, upon cinacalcet treatment. After its discontinuation, all these effects were reversible. In conclusion, cinacalcet normalizes total and ionized calcium in renal-transplanted recipients with hypercalcemia secondary to hyperparathyroidism through a mechanism that could be independent of PTH serum level suppression. The increase in bone-specific alkaline phosphatases, biochemical markers of bone accretion and the significant decrease in fasting urine calcium suggest the possibility of a beneficial impact of cinacalcet on bone remodeling.