Who gets renal bone disease before beginning dialysis?

Cinacalcet studies in pediatric subjects with secondary hyperparathyroidism receiving dialysis

BACKGROUND

Secondary hyperparathyroidism (sHPT), a complication of chronic kidney disease (CKD) characterized by persistently elevated parathyroid hormone (PTH), alterations in calcium-phosphorus homeostasis, and vitamin D metabolism, affects 50% of children receiving dialysis. A significant proportion of these children develop CKD-mineral and bone disorder (CKD-MBD), associated with an increased risk of fractures and vascular calcification. The standard of care for sHPT in children includes vitamin D sterols, calcium supplementation, and phosphate binders. Several agents are approved for sHPT treatment in adults undergoing dialysis, including vitamin D analogs and calcimimetics, with limited information on their safety and efficacy in children. The calcimimetic cinacalcet is approved for use in adults with sHPT on dialysis, but is not approved for pediatric use outside Europe.

METHODS

This review provides dosing, safety, and efficacy information from Amgen-sponsored cinacalcet pediatric trials and data from non-Amgen sponsored clinical studies.

RESULTS

The Amgen cinacalcet pediatric clinical development program consisted of two Phase 3 randomized studies, one Phase 3 single arm extension study, one open-label Phase 2 study, and two open-label Phase 1 studies. Effects of cinacalcet on PTH varied across studies. Overall, 7.4 to 57.1% of subjects who received cinacalcet in an Amgen clinical trial attained PTH levels within recommended target ranges and 22.2 to 70.6% observed a ≥ 30% reduction in PTH. In addition, significant reductions in PTH were demonstrated in all non-Amgen-supported studies.

CONCLUSIONS

To help inform the pediatric nephrology community, this manuscript contains the most comprehensive review of cinacalcet usage in pediatric CKD patients to date.

Osteoporosis is a prevalent finding in patients with solid organ failure awaiting transplantation - a population based study

Post-transplant bone disease is common in solid organ recipients; however, there is limited information on their pre-transplant bone status. We aimed to compare bone mineral density (BMD) in different categories of patients with end-stage organ failure awaiting transplantation (Tx) in Norway. Overall 291 adult patients were enrolled, including 60, 84, 81 and 66 patients with end-stage lung, liver, kidney and heart failure, respectively. Mean age was 51 ± 12 yr with no significant differences between the groups. We measured BMD in lumbar spine, femur, proximal one third and ultra-distal radius by dual energy X-ray absorptiometry. Differences in T- and Z-scores between the groups were compared by ANOVA. Low bone mass was found in all four groups of patients. Both T- and Z-scores differed (p < 0.05) at all measured sites between the groups. Patients with lung failure had the highest prevalence of osteoporosis (67%) and lowest Z-scores, followed by patients with liver (31%), kidney (24%), and heart (23%) failure. Osteoporosis is prevalent in all groups of organ transplant candidates, and poor bone health is remarkably pronounced in patients with chronic lung disease. General practitioners and specialists who care for these patients before they are referred for transplantation should consider measures to prevent osteoporosis at an earlier stage.

Renal osteodystrophy in predialysis patients without stainable bone aluminum. A cross-sectional bone-histomorphometric study

Histomorphometry was performed on transiliac bone biopsies, double-labeled with tetracycline, from 60 consecutively admitted patients (20 women) at various stages of chronic renal failure (CRF). Eleven patients (1 woman) had normal bone resorption and formation indices. Bone resorption and osteoid formation increased with progression of renal failure, but abnormal values were seen even at slightly elevated creatinine levels. Mineralization lag time increased with CRF duration; prolonged values were only seen in patients with polycystic kidney disease or chronic pyelonephritis with advanced CRF. All patients with impaired mineralization also had increased bone resorption. Diabetes mellitus did not protect against skeletal lesions. The biochemical tests were too insensitive to predict type or severity of bone disease, and hand X-rays had no diagnostic value in early stages of renal osteodystrophy.

Evaluation of Cinacalcet Therapy to Lower Cardiovascular Events (EVOLVE): Rationale and Design Overview

BACKGROUND AND OBJECTIVES

The dramatically high rates of mortality and cardiovascular morbidity observed among dialysis patients highlights the importance of identifying and implementing strategies to lower cardiovascular risk in this population. Results from clinical trials undertaken thus far, including trials on lipid reduction, normalization of hematocrit, and increased dialysis dosage, have been unsuccessful. Available data indicate that abnormalities in calcium and phosphorus metabolism, as a result of either secondary hyperparathyroidism alone or the therapeutic measures used to manage secondary hyperparathyroidism, are associated with an increased risk for death and cardiovascular events. However, no prospective trials have evaluated whether interventions that modify these laboratory parameters result in a reduction in adverse cardiovascular outcomes.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Evaluation of Cinacalcet Therapy to Lower Cardiovascular Events is a global, phase 3, double-blind, randomized, placebo-controlled trial evaluating the effects of cinacalcet on mortality and cardiovascular events in hemodialysis patients with secondary hyperparathyroidism. Approximately 3800 patients from 22 countries will be randomly assigned to cinacalcet or placebo. Flexible use of traditional therapies will be permitted. The primary end point is the composite of time to all-cause mortality or first nonfatal cardiovascular event (myocardial infarction, hospitalization for unstable angina, heart failure, or peripheral vascular disease, including lower extremity revascularization and nontraumatic amputation).

RESULTS

The study will be event driven (terminated at 1882 events) with an anticipated duration of approximately 4 yr.

CONCLUSIONS

Evaluation of Cinacalcet Therapy to Lower Cardiovascular Events will determine whether management of secondary hyperparathyroidism with cinacalcet reduces the risk for mortality and cardiovascular events in hemodialysis patients.

Cinacalcet Hydrochloride Is an Effective Treatment for Secondary Hyperparathyroidism in Patients With CKD Not Receiving Dialysis

BACKGROUND

Secondary hyperparathyroidism develops early in patients with chronic kidney disease (CKD). Clinical guidelines from the National Kidney Foundation-Kidney/Disease Outcomes Quality Initiative emphasize the need to control parathyroid hormone (PTH), calcium, and phosphorus levels in patients with CKD not receiving dialysis to reduce poor outcomes. This phase 2 study evaluated the effects of the oral calcimimetic cinacalcet hydrochloride in patients with CKD not on dialysis therapy.

METHODS

A randomized, double-blind, placebo-controlled, 18-week study enrolled adults with an estimated glomerular filtration rate of 15 to 50 mL/min/1.73 m2 (0.25 to 0.83 mL/s/1.73 m2) and an intact PTH (iPTH) level greater than 130 pg/mL (ng/L). Cinacalcet (or placebo) was titrated from 30 to 180 mg once daily to obtain a 30% or greater reduction in iPTH levels from baseline.

RESULTS

Baseline mean iPTH levels were 243 pg/mL (ng/L) in the cinacalcet group (n = 27) and 236 pg/mL (ng/L) in the control group (n = 27). At baseline, 28% of subjects were being administered vitamin D sterols and 43% were being administered phosphate binders or calcium supplements. The addition of cinacalcet significantly decreased iPTH concentrations compared with controls during the efficacy-assessment phase: 56% versus 19% of subjects achieved a 30% or greater reduction in iPTH levels (P = 0.006), and mean iPTH levels decreased by 32% in the cinacalcet group, but increased by 6% in the control group (P < 0.001). Mean serum calcium and phosphorus levels remained within normal range throughout the study. Cinacalcet generally was well tolerated; the most frequent adverse events were gastrointestinal.

CONCLUSION

This preliminary study provides evidence that cinacalcet is efficacious for the treatment of secondary hyperparathyroidism in subjects with CKD not receiving dialysis.

The calcimimetic agent KRN 1493 lowers plasma parathyroid hormone and ionized calcium concentrations in patients with chronic renal failure on haemodialysis both on the day of haemodialysis and on the day without haemodialysis

AIMS

Treatment with vitamin D sterols can lower plasma parathyroid hormone (PTH) in patients with secondary hyperparathyroidism; however, hypercalcaemia, hyperphosphataemia, or both, often develop. Calcimimetic agents, employed in alternative therapeutic approaches, directly inhibit PTH secretion by activating the calcium-sensing receptor in the parathyroid glands.

METHODS

In this study, patients were given orally 25, 50, and 100 mg doses of the calcimimetic agent KRN 1493 each on two occasions, on the day of haemodialysis and on the day without haemodialysis.

RESULTS

In the pharmacokinetic results, because the clearance of KRN 1493 by haemodialysis was much smaller than the systemic clearance, the influence of haemodialysis was not remarkable. In the pharmacodynamic study, on both the days with or without haemodialysis, plasma PTH concentrations decreased in a dose-dependent manner. Serum calcium concentrations decreased in association with the decrease in plasma PTH concentrations. Mild dose-dependent adverse effects (mainly nausea) were seen after the administration of KRN 1493 on both the day of haemodialysis and the day without haemodialysis.

CONCLUSIONS

We conclude that the pharmacokinetics of KRN 1493 after a single administration were similar on the day of haemodialysis and the day without haemodialysis. KRN 1493 is safe and effective in suppressing PTH secretion and serum calcium concentrations on the day of haemodialysis and on the day without haemodialysis in patients with secondary hyperparathyroidism.

Proliferation in hyperplastic human and normal rat parathyroid glands: role of phosphate, calcitriol, and gender

BACKGROUND

Parathyroid gland hyperplasia develops in azotemic patients. A phosphate excess and calcitriol deficiency play critical roles in its development. Our goals were to determine whether differences in serum phosphate values at parathyroidectomy (PTX) in hemodialysis patients with refractory hyperparathyroidism: (1) correlated with parathyroid cell proliferation; and (2) affected the antiproliferative response to in vitro calcitriol. Studies were also performed to determine whether the phosphate concentration in the medium affected the antiproliferative response to calcitriol, and whether a high phosphate diet and calcitriol treatment affected parathyroid cell proliferation and parathyroid hormone (PTH) levels in normal rats.

METHODS

Forty-seven parathyroid glands from 19 hemodialysis patients were obtained at PTX. Flow cytometry was used to determine cell proliferation (percent cells in S phase) in excised parathyroid glands. Similarly, cell proliferation was determined in parathyroid tissue incubated for 24 hours in medium with or without 10(-7) mol/L calcitriol and with 1 or 4 mmol/L phosphate. In normal rats, the effect of 3 days of a high phosphate diet (1.2% P) and calcitriol treatment (100 pmol/kg) on PTH values and cell proliferation was evaluated.

RESULTS

In cells from freshly removed parathyroid glands obtained at PTX from hemodialysis patients, there were no significant correlations between the percent cells in S phase and age, gender, and serum phosphate, calcium, and PTH. While incubation of parathyroid tissue with 10(-7) mol/L calcitriol did reduce cell proliferation (P < 0.001), both the pre-PTX serum phosphate value (P= 0.003) and female gender (P=0.003) were associated with a decreased response to calcitriol. Incubation of parathyroid tissue in medium containing 4 mmol/L phosphate did not increase cell proliferation. In normal rats, a high phosphate diet for 3 days increased cell proliferation (P < 0.05) and PTH levels (P < 0.05), and calcitriol treatment was without effect.

CONCLUSION

Our findings suggest a high phosphate burden, as well as female gender, favor parathyroid cell proliferation and both may reduce the inhibition of parathyroid function by calcitriol.

Osteodystrophy in Indonesian haemodialysis patients

A preliminary study of the intact-parathyroid hormone (i-PTH) measurements from haemodialysis patients was conducted to determine the prevalence of renal bone diseases at the Dr Soetomo Hospital. The objective of this study is to evaluate the osteodystrophy renal pattern in haemodialysis patients using i-PTH and radiological parameters. The selected populations of 48 (32 males and 16 females), the mean age 48 +/- 10.3 years, was evaluated to conduct a cross-sectional study. The calorimetric method was applied to measure serum P and Ca, while a radioimmunoassay was used to assay the i-PTH level. Of those 48 patients receiving haemodialysis, with a duration ranging from 4 to 432 weeks, 61% had hypocalcaemia and 10% had hypercalcaemia. The i-PTH levels below 100 pg/mL (normal, 10-65 pg/mL) suggested 'aplastic' bone, and values of 100-200 pg/mL most commonly indicated 'normal' bone turnover. The i-PTH levels over 200 pg/mL suggested hyperparathyroidism. The results of this study demonstrated that 42% of those patients had <100 pg/mL (low turnover bone presumed, no biopsy), 23% had 100 - <200 pg/mL ('normal' bone turnover) and 35% of them had >200 pg/mL ('hyperparathyroidism'). In addition, the radiological study showed that 10% of those patients were positive for renal bone diseases. In conclusion, this study shows that the common type of renal osteodystrophy was of a low turnover type, which was different from the findings in other previous studies. It is postulated that this difference is likely to be caused by some factors such as the general health condition of the population those patients belong to and, in particular, the nutritional status of those patients.

CYP2D6, GST-M1 and GST-T1 enzymes: expression in parathyroid gland and association with the parathyroid hormone concentration during early renal replacement therapy

AIMS

The purpose of this research was to characterize CYP2D6, GST-M1 and GST-T1 enzyme expression in human parathyroid tissue, and to determine whether or not there is any association between deficiencies in these enzymes and serum parathyroid hormone concentrations in patients with end-stage renal disease.

METHODS

Surgical human parathyroid tissue was obtained and evaluated by immunohistochemistry for cellular localization of CYP2D6, GST-M1 and GST-T1 and colocalization of CYP2D6 with parathyroid hormone. Blood samples were collected from 328 Caucasian patients with end-stage renal disease for genetic testing of CYP2D6*3, *4, *5, *6, *7 and GST-M1*0 and GST-T1*0 alleles. Clinical chemistry data and serum intact parathyroid hormone (iPTH) concentrations were obtained from patient medical records. In 277 of the patients, the same laboratory performed all clinical tests.

RESULTS

CYP2D6, GST-M1 and GST-T1 were present in human parathyroid tissue. CYP2D6 was colocalized with parathyroid hormone in parathyroid chief cells. Within the end-stage renal disease population, a nonfunctional CYP2D6 genotype was present in 18.2%[95% confidence interval (CI) 8.0, 28.4] of patients in the 1st iPTH concentration quintile (iPTH < 64 pg x mL(-1)), in 0% (95% CI 0, 7.5) of those in the 2nd quintile, in 1.8% (95% CI 0, 9.3) of those in the 3rd quintile, in 9.1% (95% CI 1.5, 16.7) of those in the 4th quintile, and in 16.7% (95% CI 6.8, 26.5) of those in the 5th quintile (iPTH > 347 pg x mL(-1)) (P = 0.001). Out of 12 CYP2D6-deficient females, seven were in the 1st iPTH concentration quintile and the remaining five were in the 5th quintile. Patients deficient in the GST-M1 and GST-T1 enzymes displayed a far more uniform frequency distribution relative to serum iPTH concentrations.

CONCLUSIONS

The presence of CYP2D6, GST-M1 and GST-T1 in parathyroid cells was observed. An association is reported between a lack of CYP2D6 and iPTH concentrations in newly diagnosed end-stage renal disease patients. Gender and concomitant deficiency in GST-M1 and/or GST-T1 appear to define this association further. It remains to be established whether these associations reflect a cause-effect relationship between deficient expression of metabolizing enzymes and severity of secondary manifestation of renal failure.

Spectrum of renal bone disease in end-stage renal failure patients not yet on dialysis

BACKGROUND

During the last few years the spectrum of renal osteodystrophy (ROD) in dialysis patients has been studied thoroughly and the prevalence of the various types of ROD has changed considerably. Whereas until a decade ago most patients presented with secondary hyperparathyroidism (HPTH), adynamic bone (ABD) has become the most common lesion within the dialysis population over the last few years. Much less is known about the spectrum of ROD in end-stage renal failure (ESRF) patients not yet on dialysis.

METHODS

Transiliac bone biopsies were taken in an unselected group of 84 ESRF patients (44 male, age 54+/-12 years) before enrolment in a dialysis programme. All patients were recruited within a time period of 10 months from various centres (n=18) in Macedonia. Calcium carbonate was the only prescribed medication in patients followed up by the outpatient clinic.

RESULTS

HPTH was found in only 9% of the patients, whilst ABD appeared to be the most frequent renal bone disease as it was observed in 23% of the cases next to normal bone (38%). A relatively high number of patients (n=10; 12%) fulfilled the criteria of osteomalacia (OM). Mixed osteodystrophy (MX) was diagnosed in 18% of the subjects. There was no significant difference between groups in age, creatinine, or serum and bone strontium and aluminium levels. Patient characteristics associated with ABD included male gender and diabetes, whilst OM was associated with older age (>58 years).

CONCLUSIONS

In an unselected population of ESRF patients already, 62% of them have an abnormal bone histology. ABD is the most prevalent type of ROD in this population. In the absence of aluminium or strontium accumulation the relatively high prevalence of a low bone turnover as expressed by either normal bone or ABD and OM is striking.

The renal osteodystrophy pattern in Brazil and Uruguay: an overview

BACKGROUND

The prevalence of the types of renal osteodystrophy (ROD) has changed in the last two decades. This study evaluates the prevalence and determining factors of the types of ROD in two countries in South America.

METHODS

Symptomatic patients who underwent bone biopsies for diagnostic purposes (1985 through 2001) were included in the study. In Brazil, a total of 2340 patients were reviewed, 93.1% on hemodialysis (HD), and 6.9% on continuous ambulatory peritoneal dialysis (CAPD). In Uruguay, 167 patients on hemodialysis were included. Uncalcified bone samples were analyzed in order to diagnose the different types of ROD.

RESULTS

Comparing the 1980s to the 1990s, the prevalence of Brazilian patients with hyperparathyroid bone disease (HP) increased from 32.3% to 44.0%, while Al overload decreased from 61.3% to 42.4%. A logistic regression analysis showed that the main factors associated with HP included female gender, age of less than 40 years, black patients, longer time on dialysis, and absence of Al overload. In Uruguay, HP also increased over time from 31.8% to 70.5% (P < 0.05), while Al overload decreased from 42% to 27% (P < 0.05).

CONCLUSION

A better control of Al overload may lead to a change in histologic pattern, as evidenced by the increasing prevalence of HP.

The calcimimetic AMG 073 reduces parathyroid hormone and calcium x phosphorus in secondary hyperparathyroidism

BACKGROUND

A need exists for a therapy that lowers parathyroid hormone (PTH) without increasing calcium x phosphorus in patients with secondary hyperparathyroidism. The calcimimetic AMG 073 increases the sensitivity of the parathyroid calcium-sensing receptor to extracellular calcium, thereby reducing PTH secretion. Consequently, AMG 073 may provide a novel therapy for secondary hyperparathyroidism.

METHODS

Seventy-eight hemodialysis patients with secondary hyperparathyroidism were enrolled into this 18-week, double-blind, randomized, placebo-controlled, dose titration study. Daily oral AMG 073 doses were administered to determine the effect on PTH, serum calcium, phosphorus, and calcium x phosphorus.

RESULTS

The mean baseline PTH was similar in patients administered AMG 073 or placebo (632 +/- 280.1 pg/mL vs. 637 +/- 455.9 pg/mL, respectively). PTH decreased by 26.0% in the AMG 073-treated group, compared with an increase of 22.0% in the placebo group (P < 0.001). A greater proportion in the AMG 073 group (38%) had a decrease in PTH >or=30%, compared with the placebo group (8%) (P = 0.001). Decreases in PTH were independent of baseline vitamin D usage. Patients receiving AMG 073 had an 11.9% decrease in calcium x phosphorus compared with a 10.9% increase in the placebo group (P < 0.001). Use of vitamin D sterols, as well as both calcium and noncalcium-containing phosphate binders. were similar between treatment groups. Administration of AMG 073 was safe and well tolerated in this 18-week study.

CONCLUSIONS

The calcimimetic AMG 073 decreases both PTH and calcium x phosphorus levels in hemodialysis patients with secondary hyperparathyroidism.

Renal osteodystrophy in chronic renal failure

Bone disease develops relatively early in the development of chronic renal failure. Much of what is known about the evaluation and management of renal osteodystrophy in chronic renal failure is based on knowledge obtained in the dialysis population. The classic bone lesion found in the dialysis population is osteitis fibrosa, the high turnover lesion of secondary hyperparathyroidism. Clearly, hypocalcemia, hyperphosphatemia, and calcitriol deficiency play major roles in the development and maintenance of the high turnover disease. Interestingly, in both the dialysis and nondialysis patients, the incidence of adynamic bone disease, a low turnover lesion, is increasing. It is postulated that the aggressive use of calcium-containing phosphate binders and the use of calcitriol and other vitamin D analogs to treat secondary hyperparathyroidism may contribute to this shift in bone lesions. Treatment in the nondialysis kidney disease patient remains aggressive correction of hypocalcemia and hyperphosphatemia. The use of calcitriol and other agents to maintain serum calcium and to suppress elevated parathyroid hormone remains well supported. However, the increase in extraskeletal calcifications and incidence of adynamic bone disease in these patients raises concern about current management techniques.

Expression of 25-hydroxyvitamin D3-1alpha-hydroxylase in the human kidney

The secosteroid hormone 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) plays a vital role in calcium metabolism, tissue differentiation, and normal bone growth. Biosynthesis of 1,25(OH)2D3 is catalyzed by the mitochondrial cytochrome P450 enzyme 25-hydroxyvitamin D3 1alpha-hydroxylase (1alpha-hydroxylase). Although activity of this enzyme has been described in several tissues, the kidneys are recognized to be the principal site of 1,25(OH)2D3 production. To date, enzyme activity studies using vitamin D-deficient animals have suggested that 1alpha-hydroxylase is expressed exclusively in proximal convoluted tubules. With the recent cloning of 1alpha-hydroxylase, specific cRNA probes and in-house polyclonal antiserum have been used to determine the distribution of 1alpha-hydroxylase along the human nephron. Immunohistochemistry and in situ hybridization studies indicated strong expression of 1alpha-hydroxylase protein and mRNA in the distal convoluted tubule, the cortical and medullary part of the collecting ducts, and the papillary epithelia. Lower expression was observed along the thick ascending limb of the loop of Henle and Bowman's capsule. Weaker and more variable expression of 1alpha-hydroxylase protein and mRNA was seen in proximal convoluted tubules, and no expression was observed in glomeruli or vascular structures. These data show for the first time the distribution of alpha1-hydroxylase expression in normal human kidney. In contrast to earlier enzyme activity studies conducted in vitamin D-deficient animals, our data indicate that the distal nephron is the predominant site of 1alpha-hydroxylase expression under conditions of vitamin D sufficiency.

Vitamin D analogs: from renal bone disease to osteoporosis

The history of the use of vitamin D metabolites and analogs in clinical medicine began with their use in renal bone disease following the appreciation that the kidney is the major site of the 1 alpha-hydroxylase of vitamin D. In the presence of advanced renal failure, production of calcitriol is impaired and treatment is viewed conceptually as a hormone replacement therapy. Since then, there has been much interest in the rationale for the use of such compounds in osteoporosis. Arguments have been variously forwarded that osteoporosis is in part due to either a defective 1 alpha-hydroxylase occurring at menopause or in later life or to target tissue resistance to calcitriol; some argue that disturbances in vitamin D metabolism are irrelevant to osteoporosis, being either a consequence of aging or a result, not a cause, of osteoporosis itself. This paper reviews these various issues and explores the differences and similarities between the pathogenesis of renal bone disease and osteoporosis.

Bone mineral density and biochemical markers of bone turnover in patients with predialysis chronic renal failure

BACKGROUND

Metabolic bone disease might commence early in the course of renal failure. This study therefore examined the frequency and severity of the skeletal changes in predialysis chronic renal failure by measurements of bone mineral density (BMD), biochemical markers of bone turnover (osteocalcin, bone-specific alkaline phosphatase, carboxy terminal propeptide of type I collagen, and carboxy-terminal telopeptide of type I collagen), parathyroid hormone (PTH), ionized calcium (Ca++), phosphate (P), and vitamin D metabolites.

METHODS

The study was performed in 113 patients (male/female: 82/31) with chronic renal diseases [mean glomerular filtration rate (GFR) of 37 ml/min] and in 89 matched, normal control subjects.

RESULTS

The patients had significantly (P<0.05) reduced BMD in the spine (-6.3%), the femur (-12.1%), the forearm (-5.7%), and the total body (-4.2%) as compared with the control subjects. Dividing the patients into quartiles according to GFR revealed that BMD decreased with the gradual decline in renal function at all the measured skeletal sites, but was most pronounced in the femur: 0.63+/-0.03, 0.74+/-0.02, 0.77+/-0.02, and 0.82+/-0.03 g/cm2 in each quartile from lowest to highest GFR compared with 0.82+/-0.02 g/cm2 in the control group (P<0.0001). All of the measured bone markers showed increasing plasma levels with the more advanced stages of renal failure. Serum PTH and serum P levels increased, whereas serum Ca++ and 1,25-dihydroxyvitamin D decreased. BMD Z-scores of the femur and of the forearm correlated to the biochemical markers and to PTH (P<0.05 to P<0.0001). The biochemical markers all showed strong correlations to PTH, also when corrected for the effect of the decline in GFR (r = 0.40 to 0.92, P<0.01 to P< 0.0001).

CONCLUSION

Skeletal changes are initiated at an early stage of chronic renal failure, as estimated from reduced BMD and elevated levels of PTH and from the biochemical markers of both bone formation and bone resorption.

Effect of alfacalcidol on natural course of renal bone disease in mild to moderate renal failure

OBJECTIVE

To determine whether alfacalcidol--used in management of overt renal bone disease--may safely prevent renal bone disease when used earlier in course of renal failure.

DESIGN

Double blind, prospective, randomised, placebo controlled study.

SETTING

17 nephrology centres from Belgium, France, the Netherlands, and the United Kingdom.

SUBJECTS

176 patients aged 18-81 with mild to moderate chronic renal failure (creatinine clearance 15-50 ml/min) and with no clinical, biochemical, or radiographic evidence of bone disease.

INTERVENTIONS

Alfacalcidol 0.25 micrograms (titrated according to serum calcium concentration) or placebo given for two years.

MAIN OUTCOME MEASURES

Quantitative histology of bone to assess efficacy of treatment and renal function to assess safety.

RESULTS

132 patients had histological evidence of bone disease at start of study. Biochemical, radiographic, and histological indices of bone metabolism were similar for the 89 patients given alfacalcidol and the 87 controls given placebo. After treatment, mean serum alkaline phosphatase activity and intact parathyroid hormone concentration had increased by 13% and 126% respectively in controls but had not changed in patients given alfacalcidol (P < 0.001). Hypercalcaemic episodes occurred in 10 patients given alfacalcidol (but responded to decreases in drug dose) and in three controls. Histological indices of bone turnover significantly improved in patients given alfacalcidol and significantly deteriorated in controls: among patients with abnormal bone histology before treatment, bone disease resolved in 23 (42%) of those given alfacalcidol compared with two (4%) of the controls (P < 0.001). There was no difference in rate of progression of renal failure between the two groups.

CONCLUSION

Early administration of alfacalcidol can safely and beneficially alter the natural course of renal bone disease in patients with mild to moderate renal failure.

Renal osteodystrophy

Over the past decade important advances in our understanding of the pathophysiology and treatment of renal osteodystrophy have been made. In particular, the role of calcitriol deficiency in the genesis of hyperparathyroidism in early renal failure is now better understood. So too are the effects of aluminium on bone, and whereas the more florid aluminium related disease is now unusual the more subtle effects of aluminium are now being appreciated. There is still a major problem in the long-term treatment of hyperparathyroid bone disease. The reasons why parathyroid gland proliferation continues to occur on dialysis therapy require a better understanding of cellular events regulating hormone production and parathyroid cell replication. The case for early intervention with vitamin D is now strong but whether such an approach materially influences the long-term outcome is not yet established. Changes in the approach to treatment and in the modalities used for renal replacement therapy will continue to modify the nature of the bone disease.

Osteopenia and metatarsal fractures in diabetic neuropathy

Radiographs of the hands and feet of 19 diabetic patients with severe neuropathy were compared to those of 22 control patients without neuropathy. The two groups were matched for age, sex, and duration of diabetes. Cortical bone mass, measured by x-ray morphometry, was significantly lower in both the hands (p less than 0.002) and the feet (p less than 0.001) of those with neuropathy. The osteopenia was worse in the feet than the hands and also worse in women. Serum alkaline phosphatase levels were also significantly higher in the neuropathy group (p less than 0.005). Metatarsal fractures were a frequent finding in the neuropathic patients, but were not seen in controls. The presence of metatarsal fractures was strongly associated with the subsequent development of diabetic osteopathy (p less than 0.001). We conclude that cortical bone mass in the feet and hands is reduced in severe diabetic neuropathy. This may contribute to the predisposition to metatarsal fracture and diabetic osteopathy.

Hyperparathyroid bone disease in chronic renal failure

Much has been learnt over the past 80 years of the pathogenesis and management of hyperparathyroid bone disease in uraemia. Clinically it has changed from a rare disorder of childhood and adolescence to a common and difficult problem in patients maintained on dialysis programmes. Whereas effective treatments are now available for hyperparathyroid bone disease, these are not curative and there is clearly much more work to be done before a full understanding of its pathogenesis, and the best methods of treatment and prevention, can be reached.