Parathyroid hormone levels in long-term renal transplant children and adolescents

Hyperparathyroidism Is an Independent Risk Factor for Allograft Dysfunction in Pediatric Kidney Transplantation

Introduction

Little is known about the consequences of deranged chronic kidney disease-mineral and bone disorder (CKD-MBD) parameters on kidney allograft function in children. We examined a relationship between these parameters over time and allograft outcome.

Methods

This registry study from the Cooperative European Paediatric Renal Transplant Initiative (CERTAIN) collected data at baseline, months 1, 3, 6, 9, and 12 after transplant; and every 6 months thereafter up to 5 years. Survival analysis for a composite end point of graft loss or estimated glomerular filtration rate (eGFR) ≤30 ml/min per 1.73 m² or a ≥50% decline from eGFR at month 1 posttransplant was performed. Associations of parathyroid hormone (PTH), calcium, phosphate, and 25-hydroxyvitamin D (25(OH)D) with allograft outcome were investigated using conventional stratified Cox proportional hazards models and further verified with marginal structural models with time-varying covariates.

Results

We report on 1210 patients (61% boys) from 16 European countries. The composite end point was reached in 250 grafts (21%), of which 11 (4%) were allograft losses. In the conventional Cox proportional hazards models adjusted for potential confounders, only hyperparathyroidism (hazard ratio [HR], 2.94; 95% confidence interval [CI], 1.82-4.74) and hyperphosphatemia (HR, 1.94; 95% CI, 1.28-2.92) were associated with the composite end point. Marginal structural models showed similar results for hyperparathyroidism (HR, 2.74; 95% CI, 1.71-4.38), whereas hyperphosphatemia was no longer significant (HR, 1.35; 95% CI, 0.87-2.09), suggesting that its association with graft dysfunction can be ascribed to a decline in eGFR.

Conclusion

Hyperparathyroidism is a potential independent risk factor for allograft dysfunction in children.

Body mass index is associated with hyperparathyroidism in pediatric kidney transplant recipients

BACKGROUND

Hyperparathyroidism persists in up to 50% of pediatric kidney transplant recipients. The aims of this study were to describe the evolution of parathyroid hormone (PTH) in the first year after transplantation and to identify factors associated with hyperparathyroidism.

METHODS

This retrospective study included children who underwent kidney transplantation at the University Hospitals of Ghent, Leuven, Rotterdam, or Amsterdam. Data from 149 patients were collected before and up to 12 months after transplantation. Severe hyperparathyroidism was defined as PTH 2-fold above the reference value. Factors associated with hyperparathyroidism and severe hyperparathyroidism were identified using multivariate logistic regression analysis.

RESULTS

Before transplantation, 97 out of 137 patients (71%) had hyperparathyroidism. The probability of hyperparathyroidism and severe hyperparathyroidism declined from 0.49 and 0.17 to 0.29 and 0.09 at 3 and 12 months after transplantation, respectively. BMI SDS (β: 0.509; p = 0.011; 95% CI: 1.122-2.468), eGFR (β: - 0.227; p = 0.030; 95% CI: 0.649-0.978), and pre-transplant hyperparathyroidism (β: 1.149; p = 0.039; 95% CI: 1.062-9.369) were associated with hyperparathyroidism 12 months after transplantation. Pre-transplant hyperparathyroidism (β: 2.115; p = 0.044; 95% CI: 1.055-65.084), defined as intact parathormone (iPTH) levels > 65 ng/l (6.9 pmol/l) or 1-84 PTH > 58 ng/l (6.2 pmol/l), was associated with severe hyperparathyroidism at 3 months. Only eGFR (β: - 0.488; p = 0.010; 95% CI: 0.425-0.888) was inversely associated with severe hyperparathyroidism at 9 months after transplantation.

CONCLUSIONS

Allograft function remains the main determinant of severe hyperparathyroidism after transplantation. Our findings emphasize the importance of BMI and pre-transplant PTH control.

Left ventricular stiffness in paediatric patients with end-stage kidney disease

BACKGROUND

We tested the hypothesis that myocardial stiffness is altered in paediatric patients with end-stage kidney disease (ESKD) and explored its association with clinical parameters of chronic kidney disease (CKD).

METHODS

Thirty-five patients with ESKD (16 males) aged 17.5 ± 3 years old, 18/35 of whom were receiving dialysis and 17 post kidney transplant, were studied. Left ventricular (LV) myocardial stiffness was determined by measurement of diastolic wall strain (DWS) and stiffness index (SI), while LV diastolic function was interrogated by pulsed-wave and tissue Doppler echocardiography.

RESULTS

Compared with available literature data, both dialysis and transplanted patients had significantly lower DWS and greater SI, reduced transmitral early (E) to late diastolic velocity ratio and septal and lateral mitral annular early (e') diastolic velocities, and greater septal and lateral E/e' ratios (all p < 0.05). Multivariate analysis revealed that z score of diastolic blood pressure (β = 0.43, p = 0.004) and the duration of renal replacement therapy (β = 0.55, p < 0.001) were significant determinants of LV SI. Subgroup analysis in post-transplant patients showed z score of diastolic blood pressure (β = 0.54, p = 0.025) remained as a significant determinant of LV SI.

CONCLUSION

Increased LV myocardial stiffness is evident in paediatric dialysis and transplanted patients with ESKD, and is associated with blood pressure and duration of renal replacement 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.

Association of calcium, phosphate and parathyroid hormone with renal allograft function: a retrospective cohort study

BACKGROUND

Significant variations in postoperative levels of parathyroid hormone (PTH), calcium and phosphate exist after renal transplantation, but whether they affect allograft function is unknown. We investigated the association between early post-transplant levels of PTH, calcium and phosphate and graft function.

METHODS

We performed a single-centre cohort study of renal transplant recipients from Addenbrooke's Hospital, Cambridge, between April 1997 and March 2007, evaluating the association between plasma calcium, phosphate and PTH 1 month after transplantation and change in epidermal growth factor receptor (eGFR) in the first 12 months after transplantation (estimated using the Modification of Diet in Renal Disease Study equation). Differences in eGFR between 26 and 52 weeks after transplantation were computed using mixed effects linear regression models for repeated measures of eGFR, while adjusting for sociodemographic and biochemical variables.

RESULTS

Three hundred and forty-three patients were eligible for study. The mean age (standard deviation) at transplant was 43 years (13 years). Between 30 and 90 days after transplantation, the median (25th-75th percentile) eGFR was 33 (26-50) ml/min/1.73 m(2), the mean calcium level was 2.4 (0.17) mmol/l and the mean phosphate level was 0.78 (0.23) mmol/l. There was a significant interaction between calcium and phosphate levels (p = 0.006). In patients with low levels of phosphate, higher levels of calcium were associated with declining eGFR over time. However, in patients with a high phosphate level, higher calcium was associated with improved eGFR.

CONCLUSIONS

Higher serum calcium in patients with low serum phosphate after transplantation is associated with a decline in graft function during the first year after transplantation. Disorders of mineral metabolism after transplant may represent an important therapeutic target to preserve allograft function.

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.