Treatment of Persistent Hypercalcemia and Hyperparathyroidism With Cinacalcet After Successful Kidney Transplantation

Neurorescuing effect of Cinacalcet against hypercalcemia-induced nerve injury in chronic kidney disease via TRAF2/cIAP1/KLF2/SERPINA3 signal axis

Hypercalcemia is a common complication in chronic kidney disease (CKD) and unfortunately contributes to nerve injury. This study aims to investigate the potential role and underlying mechanisms of Cinacalcet (CIN) in hypercalcemia-driven nerve injury in CKD. A CKD mouse model was first established by adenine feeding to identify the therapeutic effects of CIN. Molecules related to CIN and CKD were predicted by bioinformatics analysis and their expression in the kidney tissues of CKD mice was measured by immunochemistry. Gain- and loss-of-functions assays were performed both in vitro and in vivo to evaluate their effects on nerve injury in CKD, as reflected by Scr and BUN, and brain calcium content as well as behavior tests. CIN ameliorated hypercalcemia-driven nerve injury in CKD mice. Interactions among TRAF2, an E3-ubiquitin ligase, KLF2, and SERPINA3 were bioinformatically predicted on CIN effect. CIN restricted the ubiquitin-mediated degradation of KLF2 by downregulating TRAF2. KLF2 targeted and inversely regulated SERPINA3 to repress hypercalcemia-driven nerve injury in CKD. CIN was substantiated in vivo to ameliorate hypercalcemia-driven nerve injury in CKD mice through the TRAF2/KLF2/SERPINA3 regulatory axis. Together, CIN suppresses SERPINA3 expression via TRAF2-mediated inhibition of the ubiquitin-dependent degradation of KLF2, thus repressing hypercalcemia-induced nerve injury in CKD mice.

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.

Therapy for persistent hypercalcemic hyperparathyroidism post-renal transplant: cinacalcet versus parathyroidectomy

Background:

Persistent hyperparathyroidism post-transplant is associated with increases in the incidence of cardiovascular events, fractures, and deaths. The aim of this study was to compare both therapeutic options available: parathyroidectomy (PTX) and the calcimimetic agent cinacalcet.

Methods:

A single center retrospective study including adult renal transplant recipients who developed hypercalcemia due to persistent hyperparathyroidism. Inclusion criteria: PTH > 65 pg/mL with serum calcium > 11.5 mg/dL at any time after transplant or serum calcium persistently higher than 10.2 mg/dL one year after transplant. Patients treated with cinacalcet (n=46) were compared to patients treated with parathyroidectomy (n=30). Follow-up period was one year. Clinical and laboratory data were analyzed to compare efficacy and safety of both therapeutic modalities.

Results:

PTX controlled calcemia faster (month 1 x month 6) and reached significantly lower levels at month 12 (9.1±1.2 vs 9.7±0.8 mg/dL, p < 0.05); PTX patients showed significantly higher levels of serum phosphate (3.8±1.0 vs 2.9±0.5 mg/dL, p < 0.05) and returned PTH to normal levels (45±51 pg/mL). Cinacalcet, despite controlling calcium and phosphate in the long term, decreased but did not correct PTH (197±97 pg/mL). The proportion of patients that remained with PTH above normal range was 95% in the cinacalcet group and 22% in the PTX group. Patients treated with cinacalcet had better renal function (creatinine 1.2±0.3 vs 1.7±0.7 mg/dL, p < 0.05).

Conclusions:

Surgical treatment was superior to cinacalcet to correct the metabolic disorders of hyperparathyroidism despite being associated with worse renal function in the long term. Cinacalcet proved to be a safe and well tolerated drug.

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.

Parathyroid hormone

Parathyroid hormone is an essential regulator of extracellular calcium and phosphate. PTH enhances calcium reabsorption while inhibiting phosphate reabsorption in the kidneys, increases the synthesis of 1,25-dihydroxyvitamin D, which then increases gastrointestinal absorption of calcium, and increases bone resorption to increase calcium and phosphate. Parathyroid disease can be an isolated endocrine disorder or part of a complex syndrome. Genetic mutations can account for diseases of parathyroid gland formulation, dysregulation of parathyroid hormone synthesis or secretion, and destruction of the parathyroid glands. Over the years, a number of different options are available for the treatment of different types of parathyroid disease. Therapeutic options include surgical removal of hypersecreting parathyroid tissue, administration of parathyroid hormone, vitamin D, activated vitamin D, calcium, phosphate binders, calcium-sensing receptor, and vitamin D receptor activators to name a few. The accurate assessment of parathyroid hormone also provides essential biochemical information to properly diagnose parathyroid disease. Currently available immunoassays may overestimate or underestimate bioactive parathyroid hormone because of interferences from truncated parathyroid hormone fragments, phosphorylation of parathyroid hormone, and oxidation of amino acids of parathyroid hormone.

Safety and Efficacy of a 3-Year Therapy With Cinacalcet in Persistent Hyperparathyroidism After Renal Transplant

BACKGROUND

Persistent post-transplant hyperparathyroidism (PPTHP) can occur in 20% to 50% of renal transplant recipients. The aim of this study was to analyze safety and efficacy of long-term cinacalcet therapy in a group of renal transplant recipients with PPTHP.

METHODS

A single center retrospective cohort study including renal transplant recipients, adults (>18 years old) with PPTHP and hypercalcemia. Inclusion criteria for cinacalcet therapy was increased parathormone levels (PTH > 65 pg/mL) associated with serum calcium >11.5 mg/dL any time after transplant or calcium >10.2 mg/dL within the first year after transplant. The follow-up period was 3 years. Demographic, laboratory data and adverse events were assessed.

RESULTS

Forty-six patients were included, mean age of 50 ± 11 years old, majority of white race (60%), male (58%), with a pretransplant length on dialysis of 67 ± 34 months. Cinacalcet therapy was started 37 ± 40 months after transplant, and normal calcium levels were achieved after 6 months of therapy. PTH levels presented a steady reduction over time, reaching levels near normal after 36 months (317 ± 242 vs 145 ± 72 pg/mL, baseline × month 36, P < .05). Renal function remained stable over time (GFR > 60 mL/min/1.73 m²) and no acute rejection episodes were observed. Most common adverse events were mild gastrointestinal symptoms. In 6 patients (12.5%) treatment was interrupted due to adverse events. Only 1 case (2%) was classified as treatment failure.

CONCLUSION

Cinacalcet therapy proved to be efficient for PPTHP and safe for graft and patient. Long-term treatment reduced PTH levels to near normal range.

Secondary and Tertiary Hyperparathyroidism in Chronic Kidney Disease: An Endocrine and Renal Perspective

Secondary Hyperparathyroidism (SHP) seen as a frequent complication in Chronic Kidney Disease (CKD) has many pathogenetic peculiarities that are still incompletely defined and understood. During the long course of chronic renal failure, SHP can also transform sometimes into the hypercalcemic state characterized by quasi-autonomous production of Parathyroid Hormone from the parathyroid glands: a disorder that is termed Tertiary Hyperparathyroidism. The clinical consequences of SHP in CKD are protean, encompassing bone and mineral abnormalities but as recently identified, also several metabolic and cardiovascular problems, the most important of which is vascular calcification. There have been several advances in the therapeutic armamentarium available for the treatment of SHP, though clear demonstration of a benefit regarding major clinical outcomes with any of the new agents is still lacking. This narrative review summarizes the current understanding about this disorder and highlights some of the recent research on the subject.

Surgical Treatment of Hyperparathyroidism After Kidney Transplant

Chronic renal impairment is often associated with complex bone disorders. Improvement of secondary hyperparathyroidism (HPT) is expected after kidney transplant (KT) if the glomerular filtration rate is normalized.

PATIENTS AND METHODS

There were 888 KTs performed between 1996 and 2017 at our department. A total of 558 general patients have been operated on for HPT during the same period. The 2 populations had a common part: out of the 558, a total of 69 (12.4%) were in end-stage renal failure when operated on because of secondary HPT. That also means that 7.8% of all KTs were associated with HPT. Retrospective, single-center analysis was performed using the patients' medical records. The aim of our study was to analyze the results of parathyroidectomies after KT.

RESULTS

Parathyroid surgery was performed on 19 patients (2.14%) because of HPT after KT. The applied surgical technique was total parathyroidectomy with autotransplant in 6 cases, subtotal parathyroidectomy in 3 cases, and selective parathyroidectomy in 10 cases. In all cases, histology revealed benign disease. Complications were observed in 10 cases (52%); there were 6 cases of postoperative hypocalcaemia (31.58%), 1 case of transient laryngeal recurrent nerve paresis (5.26%), and 6 cases of recurrent HPT (31.58%).

SUMMARY

The first step of HPT management is calcimimetic drug treatment. It is essential to prevent possible complications with regular laboratory monitoring. If the proper conservative therapy is refractory or severe in complications, surgery should be chosen. If the patient is already waiting for a KT, it is worth performing the parathyroid surgery before KT. Close collaboration with endocrinologists and nephrologists is needed to achieve successful therapy.

Pathogenesis and treatment of electrolyte problems post transplant

PURPOSE OF REVIEW

Electrolyte abnormalities posttransplant are common occurrences that can have significant short-term and long-term effects on graft outcome and patient quality of life. Understanding the pathophysiology of these electrolyte derangements can help guide management to optimize bone health and minimize cardiovascular disease. This review explores the pathogenesis of the most common postrenal transplant electrolytes abnormalities as well as current treatment options.

RECENT FINDINGS

Clarifications of the role of FGF-23 has improved our understanding of posttransplant bone disease in addition to the known roles of hyperparathyroidism and vitamin D. The mechanisms of renal electrolyte wasting by immunosuppressive agents give insight into potential treatment options for hyperkalemia and hypomagnesemia.

SUMMARY

Understanding the pathogenesis of the common electrolyte abnormalities found post renal transplant may lead to targeted treatment options that in turn may improve transplant complications. Further studies are required to evaluate the effects on long-term outcomes of renal allografts.

Risk factors for persistent hyperparathyroidism in children with stable renal function after kidney transplantation

This study aimed to investigate the risk factors for PHPT in children with stable renal function who received KT. We retrospectively analyzed the clinical findings and laboratory results of patients who underwent KT below 19 years of age, between 1996 and 2016 at our hospital. Patients were followed up for more than 1 year after KT. We calculated the mean ± standard deviation or median [minimum - maximum] for each parameter. We included a total of 46 patients (male:female = 26:20). Twelve patients (26.1%) were included in the PHPT group, and 34 (73.9%) were in the nPTH group. The dialysis duration was 57.1 ± 49.9, 44 [0-145] months in the PHPT group and 23.5 ± 25.8, 15 [1-121] months in the nPTH group (P = .040). The post-KT total CO2 level was significantly higher in the PHPT group (P = .022). The pre- (P = .021) and post-KT (P = .005) and 3-month average (P = .018) iPTH levels were also significantly higher in PHPT group. The height z-score showed a negative correlation, and the pre-KT, 3-month average phosphorus and alkaline phosphate levels showed positive correlations with iPTH levels, at 1 year after KT. Patients who undergo prolonged durations of dialysis, have increased iPTH levels before and after KT, and have low bicarbonate levels after KT are at risk of PHPT and should be monitored carefully.