The rationale for intermittent administration of PTH in the management of mineral and bone disorder of chronic kidney disease

A major complication of chronic kidney disease is the derangement of mineral metabolism, leading to increased risk of fractures and cardiovascular mortality. Current therapeutic regimens are focused on reducing parathyroid hormone levels caused by secondary hyperparathyroidism, and the active vitamin D metabolite l,25(OH)2D, with limited success. It may be a more effective approach, however, if we could target the delayed response of parathyroid hormone in the early retention of phosphate following loss of renal function.We propose intermittent administration (even in stage 2 chronic kidney disease) of parathyroid hormone, known for its bone anabolic effects compared to the catabolic effects of the continuously elevated parathyroid hormone associated with the hyperparathyroid state, to mitigate the retention of phosphate. This approach may prevent the compensatory responses of the other two major calcium- and phosphate-regulating hormones (FGF-23 and l,25(OH)2D) that lead to further worsening of the derangement of mineral metabolism.In addition to its strong theoretical basis, there are data supporting the need for further research focused on the use of intermittent parathyroid hormone in the management of chronic kidney disease-mineral bone disorder.

Effect of Early and Delayed Commencement of Paricalcitol in Combination with Enalapril on the Progression of Experimental Polycystic Kidney Disease

Vitamin D secosteroids are intranuclear regulators of cellular growth and suppress the renin-angiotensin system. The aim of this study was to test the hypothesis that the vitamin D receptor agonist, paricalcitol (PC), either alone or with enalapril (E) (an angiotensin-converting enzyme inhibitor), reduces the progression of polycystic kidney disease. Preventative treatment of Lewis polycystic kidney (LPK) and Lewis control rats with PC (0.2 μg/kg i.p. 5 days/week) or vehicle from postnatal weeks 3 to 10 did not alter kidney enlargement. To evaluate the efficacy in established disease, LPK rats received either PC (0.8 μg/kg i.p; 3 days/week), vehicle, E (50 mg/L in water) or the combination of PC + E from weeks 10 to 20. In established disease, PC also did not alter the progression of kidney enlargement, kidney cyst growth or decline in renal function in LPK rats. Moreover, the higher dose of PC was associated with increased serum calcium and weight loss. However, in established disease, the combination of PC + E reduced systolic blood pressure and heart-body weight ratio compared to vehicle and E alone (p < 0.05). In conclusion, the combination of PC + E attenuated cardiovascular disease but caused hypercalcaemia and did not alter kidney cyst growth in LPK rats.

Extended-release calcifediol in stage 3-4 chronic kidney disease: a new therapy for the treatment of secondary hyperparathyroidism associated with hypovitaminosis D

A high percentage of patients with chronic kidney disease have hypovitaminosis D, which is a driver of secondary hyperparathyroidism and an important factor in chronic kidney disease-mineral and bone disorder. Vitamin D deficiency (serum total 25-OH vitamin D levels < 30 ng/mL) occurs early in the course of chronic kidney disease and treatment guidelines recommend early intervention to restore 25-OH vitamin D levels as a first step to prevent/delay the onset/progression of secondary hyperparathyroidism. The vitamin D forms administered to replace 25-OH vitamin D include cholecalciferol, ergocalciferol, and immediate- or extended-release formulations of calcifediol. Most patients with intermediate-stage chronic kidney disease will develop secondary hyperparathyroidism before dialysis is required. Control of parathyroid hormone levels becomes a major focus of therapy in these patients. This article focuses on the position of extended-release calcifediol in the treatment of patients with stage 3–4 chronic kidney disease and secondary hyperparathyroidism with hypovitaminosis D. Several characteristics of extended-release calcifediol support its use in the intermediate stages of chronic kidney disease. The pharmacokinetics of extended-release calcifediol make it effective for replenishing 25-OH vitamin D levels, with minimal impact on vitamin D catabolism from fibroblast-growth factor-23 and CYP24A1 upregulation. Extended-release calcifediol increases circulating 25-OH vitamin D levels in a dose-dependent manner and lowers parathyroid hormone levels by a clinically relevant extent, comparable to what can be achieved by administering active vitamin D analogues, though with a lower risk of hypercalcaemia and hyperphosphataemia. Active vitamin D analogues are reserved for patients undergoing dialysis or pre-dialysis patients with severe progressive secondary hyperparathyroidism.

Bone Quality in Chronic Kidney Disease Patients: Current Concepts and Future Directions - Part II

Background

Patients with chronic kidney disease (CKD) have an increased risk of osteoporotic fractures, which is due not only to low bone volume and mass but also poor microarchitecture and tissue quality. The pharmacological and nonpharmacological interventions detailed, herein, are potential approaches to improve bone health in CKD patients. Various medications build up bone mass but also affect bone tissue quality. Antiresorptive therapies strikingly reduce bone turnover; however, they can impair bone mineralization and negatively affect the ability to repair bone microdamage and cause an increase in bone brittleness. On the other hand, some osteoporosis therapies may cause a redistribution of bone structure that may improve bone strength without noticeable effect on BMD. This may explain why some drugs can affect fracture risk disproportionately to changes in BMD.

Summary

An accurate detection of the underlying bone abnormalities in CKD patients, including bone quantity and quality abnormalities, helps in institution of appropriate management strategies. Here in this part II, we are focusing on advancements in bone therapeutics that are anticipated to improve bone health and decrease mortality in CKD patients.

Key Messages

Therapeutic interventions to improve bone health can potentially advance life span. Emphasis should be given to the impact of various therapeutic interventions on bone quality.

The Role of Vitamin D in Small Animal Bone Metabolism

Dogs and cats have differences in vitamin D metabolism compared to other mammalian species, as they are unable to perform vitamin D cutaneous synthesis through sun exposure. Therefore, they are dependent on the dietary intake of this nutrient. The classic functions of vitamin D are to stimulate intestinal calcium and phosphate absorption, renal calcium and phosphate reabsorption and regulate bone mineral metabolism. Thus, it is an important nutrient for calcium and phosphorus homeostasis. This review highlights the evidence of the direct and indirect actions of vitamin D on bone mineral metabolism, the consequences of nutritional imbalances of this nutrient in small animals, as well as differences in vitamin D metabolism between different size dogs.

Efficacy and safety of microwave ablation treatment for secondary hyperparathyroidism: systematic review and meta-analysis

Purpose: The present systematic review and meta-analysis was designed to evaluate the efficacy and safety of microwave ablation (MWA) treatment for secondary hyperparathyroidism (SHPT).Materials and methods: The study authors systematically searched the Web of Science, Cochrane Library, PubMed, Embase and Ovid databases for studies published in English prior to 7October 2019. All studies included in the meta-analysis measured levels of parathyroid hormone (PTH), calcium and phosphorus, and included data related to complications following MWA treatment for SHPT.Results: The meta-analysis ultimately included 233 patients from two retrospective cohort studies and six retrospective self-control studies. Compared to PTH level measurements obtained after MWA, measurements obtained at one day (weighted mean differences (WMD): 890.314, 95% confidence interval (CI): 767.121-1013.506, p < 0.01) , one week (WMD: 860.298, 95% CI: 759.401-961.194, p < 0.01), one month (WMD: 800.846, 95% CI: 687.709-913.983, p < 0.01) and six months (WMD: 860.847, 95% CI: 745.214-976.480, p < 0.01) after MWA were significantly lower. Calcium and phosphorus levels at one day and one week after MWA were also significantly lower than those measured before MWA. After MWA, the incidence of nerve injury was 1.2% (3/233; effect size (ES): 0.022, 95% CI: -0.003-0.048, p < 0.01). After MWA, the incidence of hypocalcemia was 15.8% (37/233; ES: 0.449, 95% CI: 0.341-0.556, p < 0.01).Conclusion: The preliminary results of this meta-analysis indicate that MWA may be effective and safe in treating patients with SHPT, and that future prospective research and randomized controlled trials (RCT) are necessary.

Current Understanding of Mineral and Bone Disorders of Chronic Kidney Disease and the Scientific Grounds on the Use of Exogenous Parathyroid Hormone in Its Management

Chronic Kidney disease (CKD) disturbs mineral homeostasis leading to mineral and bone disorders (MBD). Serum calcium and phosphate (Pi) remain normal until the late stages of CKD at the expense of elevate fibroblast growth factor-23 (FGF-23), a phosphaturic hormone, followed by reduced 1,25-dihydroxy-vitamin D (1,25[OH]₂D) and finally elevated parathyroid hormone (PTH). Pi retention is thought to be the initial cause of CKD-MBD. The management of MBD is a huge clinical challenge because the effectiveness of current therapeutic regimens to prevent and treat MBD is limited. An intermittent regimen of PTH, when administered at the early stages of CKD, through its phosphaturic action, could prevent FGF-23 increases, the drop of 1,25(OH)₂D, and the development of renal osteodystrophy, including secondary hyperparathyroidism (HPT) and its catabolic effects on the skeleton. Even in more advanced stages of CKD that have not progressed to tertiary HPT, could be beneficial. Therapeutic effects could be achieved in vascular calcification as well. Limited experimental/clinical data support the effectiveness of PTH in CKD-MBD. Its safety, has been established only when it is used for the treatment of osteoporosis, including patients with CKD. The proposed intermittent PTH administration is biologically plausible but its effectiveness and safety has to be critically assessed in long term prospective studies in patients with CKD-MBD.

Effectiveness of Native Vitamin D Therapy in Patients with Chronic Kidney Disease Stage 3 and Hypovitaminosis D in Colombia, South America

Introduction: In a high percentage of patients with chronic kidney disease (CKD) low levels of vitamin D are detected. The purpose of this study was to evaluate if the native vitamin D therapy (cholecalciferol) in the patients with stage 3 and hypovitaminosis D allows to modify markers of bone and mineral metabolism once normal serum levels have been achieved.

MATERIALS AND METHODS

From an initial base of 297 patients with CKD and hypovitaminosis D, those with normal or high levels of PTH were chosen for therapy with native vitamin D. The initial administered dose was 1000 IU/day, with adjustments every 4 months of 1000 IU (maximum 4000 IU/day, according to RDA and IOM), until achieving serum levels of 25 hydroxyvitamin D greater than 30 ng/mL and lower than 80 ng/mL. The variables calcium, phosphorus, intact parathormone (iPTH), creatinine and glomerular filtration rate (GFR) were also evaluated every 4 months.

RESULTS

The total number of patients included in this study was 170. Seventy-three patients were excluded along the follow-up: 17 non-responders (never achieved the projected serum levels of vitamin D), and 56 for not completing one year of follow-up. A total of 97 patients were finally included. In 82 patients, follow-up was achieved for 12 months (G1) and in 38 patients for 24 months (G2). In 15 patients despite achieving satisfactory levels of vitamin D at 12 months, it was not possible to obtain adequate levels of iPTH for their GFR according to K/DOQI 2003 guidelines and they were called refractory to therapy (G3). In both groups 1 and 2, a non-significant tendency to increase calcium and serum phosphorus was observed. iPTH decreased significantly at 12 and 24 months follow-up. In group 3, we opted at 12 months for conversion to calcitriol, with a significant reduction in iPTH values. In this group, the initial value of GFR was close to 30 mL/min, and its fall in time more significant than the other two groups to CKD stage 4.

CONCLUSION

Cholecalciferol with adjustment in its dose, and obtaining normal serum levels is an excellent therapeutic alternative for the treatment of patients with CKD stage 3, and hypovitaminosis D. In the group of patients with GFR close to 30 mL/min, or lower values (stage 4), and with the presence of secondary hyperparathyroidism, the use of active form of vitamin D (calcitriol, paricalcitol) is recommended as the first therapeutic alternative.

Active Vitamin D in Chronic Kidney Disease: Getting Right Back Where We Started from?

BACKGROUND

The vitamin D system is essential for optimal health in humans. Circulating calcitriol, a key metabolite in maintaining calcium and phosphorus homeostasis, is produced in the kidney. In kidney failure, calcitriol levels progressively decrease, contributing to the development of renal secondary hyperparathyroidism (SHPT).

SUMMARY

For years, SHPT had a central role in the disturbed mineral metabolism of renal patients. As calcitriol deficiency contributes to SHPT development, treatment with calcitriol or other compounds able to activate the vitamin D receptor (VDR) was one of the mainstays of therapy for renal patients in the last 40 years. In this review, we discuss how the treatment with VDR activators (VDRA) evolved during this time in the United States, as well as the main factors responsible for these changes.

KEY MESSAGES

Management of SHPT with VDRA in renal patients has undergone a few paradigm shifts over the last 40 years. When treating SHPT, the newly developed therapies as well as VDRA need to be carefully considered and used appropriately. Nephrologists need to use an integrated approach that avoids excessive use of VDRA, ensures replenishment of vitamin D stores, and avoids hypercalcemia and hyperphosphatemia.

Medication Safety Principles and Practice in CKD

Ensuring patient safety is a priority of medical care because iatrogenic injury has been a primary concern. Medications are an important source of medical errors, and kidney disease is a thoroughfare of factors threatening safe administration of medicines. Principal among these is reduced kidney function because almost half of all medications used are eliminated via the kidney. Additionally, kidney patients often suffer from multimorbidity, including diabetes, hypertension, and heart failure, with a range of prescribers who often do not coordinate treatments. Patients with kidney disease are also susceptible to further kidney injury and metabolic derangements from medications, which can worsen the disease. In this review, we will present the key issues and threats to safe medication use in kidney disease, with a focus on predialysis CKD, as the scope of medication safety in ESKD and transplantation are unique and deserve their own consideration. We discuss drugs that need to be avoided or dose modified, and review the complications of a range of medications routinely administered in CKD, as these also call for cautious use.

Impact of Vitamin D on the Cardiovascular System in Advanced Chronic Kidney Disease (CKD) and Dialysis Patients

In patients suffering from chronic kidney disease (CKD), the prevalence of cardiovascular disease is much more common than in the general population. The role of vitamin D deficiency had been underestimated until a significant association was found between vitamin D therapy and survival benefit in haemodialysis patients. Vitamin D deficiency is present even in the early stages of chronic kidney disease. The results of experimental studies have revealed the relationship between vitamin D deficiency and impairment of cardiac contractile function, higher cardiac mass and increased myocardial collagen content. Experimental models propose that intermediate end points for the relationship between vitamin D deficiency and higher risk of cardiovascular disease comprise diminished left ventricular hypertrophy (LVH), enhanced left ventricular diastolic function, and decreased frequency of heart failure. Multiple observational studies have demonstrated an association between the use of active vitamin D therapy in patients on dialysis and with CKD and improved survival. However, there are also many studies indicating important adverse effects of such treatment. Therefore, large randomized trials are required to analyze whether supplementation of vitamin D may affect outcomes and whether it is safe to be used in CKD patients.