RENAL OSTEODYSTROPHY continues to

Transcription

1 Variant of Adynamic Bone Disease in Hemodialysis Patients: Fact or Fiction? Lillian A. Rocha, MD, Andrea Higa, MD, Fellype C. Barreto, MD, Luciene M. dos Reis, PhD, Vanda Jorgetti, MD, PhD, Sérgio A. Draibe, MD, PhD, and Aluizio B. Carvalho, MD, PhD Background: Adynamic bone disease is a type of renal osteodystrophy characterized by low bone turnover and paucity of bone cells. It was proposed that a new type of this disease featuring high osteoclastic resorption without parathyroid hormone stimulus and designated adynamic bone disease variant occurs in hemodialysis patients. The present study is designed to evaluate the frequency and characteristics of both diseases in a large series of bone biopsy specimens. Methods: We reviewed 1,160 bone biopsy specimens from hemodialysis patients. Specimens in which adynamic bone disease was diagnosed were selected and categorized as classic or variant based on osteoclastic surface. Results: In 218 bone biopsy specimens (18.8%), adynamic bone disease was identified, whereas the variant form was identified in 35 specimens (38.8%). Biopsy specimens categorized as the variant form were from patients who were younger and had greater phosphorus and parathyroid hormone levels. Histologically, the variant form presented greater osteoid volume, fibrosis volume, osteoid surface, osteoblast surface, and eroded surface. Similarly, values for all dynamic parameters were greater in the variant group. Osteoclastic surface correlated with phosphorus level, parathyroid hormone level, and osteoblast surface. Age and osteoblast surface were identified as independent determinants of the variant form. Conclusion: Adynamic bone disease variant seems to occur in younger hemodialysis patients with greater levels of parathyroid hormone, which acts on cell-covered bone surfaces. It probably is a transitional phase from low- to high-turnover status, rather than a true entity within the spectrum of renal osteodystrophy. Am J Kidney Dis 48: by the National Kidney Foundation, Inc. INDEX WORDS: Adynamic bone disease; bone biopsy; bone histomorphometry; hemodialysis; renal osteodystrophy. From the Nephrology Department, Federal University of São Paulo School of Medicine; and Nephrology Department, University of São Paulo School of Medicine, São Paulo, Brazil. Study conducted at Federal University of São Paulo School of Medicine, São Paulo, Brazil. Received January 30, 2006; accepted in revised form May 30, Originally published online as doi: /j.ajkd on July 24, Support: This study received financial support from the Brazilian Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq, Council for Scientific and Technological Development) and from the Oswaldo Ramos Foundation. Potential conflicts of interest: None. Address reprint requests to Lillian A. Rocha, MD, Rua Borges Lagoa, 960, São Paulo SP, Brazil lillianrocha@yahoo.com.br 2006 by the National Kidney Foundation, Inc /06/ $32.00/0 doi: /j.ajkd RENAL OSTEODYSTROPHY continues to be a therapeutic dilemma for practicing nephrologists. Abnormalities in mineral and bone metabolism are responsible for considerable morbidity and mortality in patients with chronic kidney disease (CKD). Mechanisms involved in the development of renal osteodystrophy are multifactorial and controversial. The adult skeleton is not a static tissue and maintains nonstop removal of bone and apposition of new mineralized matrix. This dynamic process is caused by the action of bone cells modulated by hormones and cytokines. 1,2 Renal osteodystrophy can be subdivided into 3 major histological groups: predominant hyperparathyroidism, low-turnover bone disease (osteomalacia and adynamic bone disease [ABD]), and mixed uremic osteodystrophy, consisting of mild to moderate hyperparathyroidism and mineralization defect. Aluminum deposits on bone surface are seen in varying degrees in all 3 groups. These groups are not fixed entities, and transformation from one form to another can occur. 1 A new type of low bone turnover condition related to aluminum deposition was first described in patients with CKD in Initially designated aplastic bone disease, it was later named ABD. 4 In 1989, emergence of an idiopathic adynamic disease unrelated to aluminum was described in dialysis patients. 5 Since then, an increase in its prevalence was reported in patients in all stages of CKD In addition, in an elegant study analyzing calcium kinetics in longterm hemodialysis patients, Kurz et al 11 found that ABD was characterized by very low capacity of bone to buffer calcium and consequent inability to handle extra calcium loads. Recently, ABD also was found to correlate with vascular calcifi- 430 American Journal of Kidney Diseases, Vol 48, No 3 (September), 2006: pp

2 ADYNAMIC BONE DISEASE IN HEMODIALYSIS 431 cation, 12 as well as increased risk for fractures and mortality. 13 The histological hallmark of ABD is a profound decrease in number of active remodeling sites, evidenced by a dramatic decrease in the number of bone-forming (osteoblasts) and boneresorbing cells (osteoclasts), together with decreased bone formation and mineralization. The bone structure seen in patients with ABD is predominantly lamellar, peritrabecular fibrosis rarely is seen, and mineralizing surfaces are decreased markedly, shown by means of tetracycline labeling. 1 The physiopathologic process of ABD is multifactorial. Typically found in patients with lower parathyroid hormone (PTH) levels, ABD is more common in older patients, patients with diabetes, and peritoneal dialysis patients. Overtreatment with vitamin D, aluminum intoxication, and use of corticosteroids, as well as low sexual and thyroid hormone levels, are important causes to be considered. In addition, cytokines and other related factors were implicated in this form of renal osteodystrophy. 6,10,13,14 In a study involving hemodialysis patients, Gal-Moscovici and Popovtzer 15 recently described a new type of ABD, the so-called ABD variant (ABD-V), characterized by high osteoclastic resorption. The investigators found that 26% of hemodialysis patients with ABD had ABD-V. All patients with ABD-V had a history of parathyroidectomy. Based on histomorphometric analysis, the investigators found that ABD-V resulted in a 2-fold increase in osteoclastic number and osteoclastic surface area compared with healthy control subjects. In addition, in patients with ABD-V, intact PTH (ipth) levels were as low as those in patients with classic ABD, duration of hemodialysis treatment was significantly longer, and 2 -microglobulin ( 2M) levels were significantly greater. The investigators suggested that 2M, modified by advanced glycation end products and acting as a stimulator of osteoclasts and inhibitor of osteoblasts, might be involved in this new pattern of ABD. The present study was performed to evaluate the frequency and characteristics of ABD in a large sample of hemodialysis patients, identifying ABD-V and its correlated factors. METHODS Patients We reviewed 1,160 biopsy specimens of undecalcified transiliac bone, obtained from patients undergoing treatment at various hemodialysis units throughout Brazil. All bone biopsies were performed between July 1993 and July Most specimens had been collected by our group, although some were collected by other medical centers and sent to our group for further analysis and diagnosis. Our laboratory currently maintains the bone samples and stained sections, and we compiled a database of information for all patients. The protocol for acceptance of a bone biopsy specimen by the Bone Disease Unit of the Federal University of São Paulo Hospital do Rim e Hipertensão (Kidney and Hypertension Hospital) requires that a blood sample be sent with the bone sample to perform biochemical and hormonal laboratory tests (for calcium, phosphorus, alkaline phosphatase, and ipth). Samples consistent with a diagnosis of ABD were identified and selected for study. Only samples from patients older than 18 years and undergoing hemodialysis treatment for at least 6 months were included. Exclusion criteria were no tetracycline labeling before bone biopsy, use of corticosteroids in the 6 months preceding the bone biopsy, and lack of a concomitant blood sample for laboratory tests. Samples inappropriate for histomorphometric analysis also were excluded. Data regarding age, sex, ethnic group, cause of kidney disease, duration of dialysis therapy, diabetes mellitus, use of calcitriol, and previous parathyroidectomy were collected. The study protocol was reviewed and approved by the ethics committee of the local institution. Biochemistry Total serum calcium, phosphorus, and alkaline phosphatase were measured by using standard laboratory techniques. Reference values for alkaline phosphatase are less than 270 U/L for males and less than 240 U/L for females. For most patients, ipth level was determined by means of chemiluminescence immunoassay (DPC Medlab, Los Angeles, CA; 15 to 65 ng/l). For the rest, ipth level was determined by means of immunoradiometric assay from the Nichols Institute, San Juan Capistrano, CA. Bone Biopsies and Bone Histomorphometry Tetracycline double labeling (20 mg/kg/d) was conducted on 3 days, with a 12-day interval between each administration. At 2 to 5 days after the second tetracycline administration, bone samples were obtained. Core biopsies of transiliac bone were performed by using either a manual or electric drill Bordier trephine. Biopsy samples were fixed in 70% ethanol. At a later stage, samples were dehydrated and embedded in methyl methacrylate, as previously described. 16 Sections (5- m thick) were cut with a microtome (Polycut-S; Leica, Wetzlar, Germany) and stained with toluidine blue (ph 6.4) for histomorphometric analysis, solochrome azurine for aluminum, and Perls reaction for iron staining. Unstained (10- m) sections were reserved for tetracycline examination under fluorescence microscopy. Histomorphometric analysis was performed using a Sony video camera (Tokyo, Japan) coupled to a Nikon E-600

3 432 microscope (Tokyo, Japan), and images were analyzed by using a semiautomatic system (OsteoMeasure Advanced Bone Histomorphometry Video-System; OsteoMetrics, Atlanta, GA). For each biopsy specimen, all trabecular bone fields between the 2 cortices were measured. Various quantitative measurements of static and dynamic parameters were performed on trabecular bone. Static parameters. The static parameters assessed were as follows: trabecular bone volume (BV/TV) as percentage of trabecular bone, including mineralized bone and osteoid, in relation to overall bone volume; osteoid volume (OV/BV) as percentage of bone volume represented by osteoid; osteoid surface (OS/BS) as percentage of trabecular surface covered by osteoid; osteoid thickness in micrometers; eroded surface (ES/BS) as percentage of total bone surface; osteoblast surface (Ob.S/BS) as percentage of total bone surface presenting active osteoblasts; osteoclast surface (Oc.S/BS) as percentage of total bone surface presenting osteoclasts; fibrosis volume (Fb.V/TV) as percentage of trabecular bone presenting marrow fibrosis; trabecular thickness as width of trabeculae in micrometers; trabecular separation as distance between midpoints of trabeculae in micrometers; trabecular number as density of trabeculae (n/mm); aluminum surface (Al.S/BS) as percentage of bone surface covered by aluminum; and iron surface (Ir.S/BS) as percentage of bone surface covered by iron. Dynamic parameters. We also assessed the following dynamic parameters: mineralized surface (MS/BS) as percentage of bone surface presenting tetracycline labeling; mineral apposition rate (MAR) as distance in micrometers per day between midpoints of 2 consecutive labels, divided by the time between the 2 labels; bone formation rate (BFR/BS) as volumetric amount of new mineralized bone per unit of trabecular bone surface per day ( m 3 / m 2 /d), calculated by using the formula MS/BS.MAR; adjusted apposition rate (Aj.AR) as mineral apposition rate in micrometers per day averaged over the entire osteoid perimeter, calculated by using the formula MS/BS.MAR/OS/BS; and mineralization lag time as mean interval in days between deposition and mineralization of osteoid matrix, calculated by using the formula osteoid thickness/aj.ar. All parameters were evaluated in accordance with recommendations made by the Histomorphometry Nomenclature Committee of the American Society of Bone and Mineral Research. 17 Histomorphometric Classification of ABD Reference values for static parameters were determined from autopsy bone samples obtained from 100 (50 men, 50 women) previously healthy adult Brazilians who experienced violent deaths. Mean age at time of death was years (range, 18 to 90 years). Dynamic parameters for healthy subjects were those established by Melsen and Mosekilde. 18 Bone biopsy specimens were classified histologically as ABD according to the following criteria: decreased OV/BV ( 15%), little or no fibrous tissue volume ( 0.5%), and decreased BFR/BS ( 0.04 m 3 / m 2 /d for females and 0.06 m 3 / m 2 /d for males). Cutoff values for BFR/BS were arrived at by subtracting 1 SD from the mean value of healthy subjects. ROCHA ET AL A diagnosis of ABD-V was made when, in addition to meeting criteria for classic ABD, Oc.S/BS was more than 2 SDs greater than that of healthy sex-matched controls. Bone aluminum intoxication is defined as Al.S/BS of 30% or greater. In addition, Ir.S/BS was measured in all samples. Statistical Analysis Data are expressed as percentage or mean SD. Mann- Whitney U test was used to elucidate differences between classic ABD and ABD-V. Differences between categorical variables were analyzed by using chi-square test. Correlations between histomorphometric indices and biochemical parameters were analyzed by using Spearman correlation coefficient. Multiple regression analysis was performed to identify determinants of increased Oc.S/BS. Because Oc.S/BS is not a Gaussian variable, it was considered a categorical variable in the logistic regression model. P of 0.05 or less is considered statistically significant. All statistical analyses were carried out using the SPSS program, version 13.0 (SPSS Inc, Chicago, IL). RESULTS Of 1,160 bone biopsy specimens evaluated, 218 specimens (18.8%) showed overt ABD and were selected. Of those 218 biopsy specimens, 128 specimens were rejected for the following reasons: patient time on hemodialysis therapy less than 6 months (4 patients); patient use of corticosteroids in the 6 months preceding the bone biopsy (7 patients); lack of patient medical history, demographic data, or blood sample to perform laboratory tests (38 patients); and bone samples containing fewer than 50 fields, with no previous tetracycline labeling, or presenting breaks, therefore inappropriate for histomorphometric analysis (79 patients). Consequently, 90 biopsy specimens met the criteria and were included in analysis. For those patients, mean age was years, 62.2% were men, 53.3% were white, and mean time on hemodialysis therapy was months. Principal causes of CKD were hypertensive disease (37.8%) and chronic glomerulonephritis (21.1%). Only 8.9% of patients had diabetes. Most patients (84.4%) were not administered calcitriol at the time of bone biopsy. A diagnosis of ABD-V was made in 35 of 90 ABD bone biopsy specimens (38.8%). Table 1 shows the comparison between patients with classic ABD and ABD-V according to demographic and clinical characteristics. No difference was observed between groups regarding sex, race, time on dialysis therapy, frequency of diabetes, or use of vitamin D. Patients with ABD-V were younger than those with classic

4 ADYNAMIC BONE DISEASE IN HEMODIALYSIS 433 Table 1. Comparison Between Classic ABD and ABD-V According to Patient Demographic and Clinical Characteristics Classic ABD (n 55) ABD-V (n 35) P Age (y) Sex (men/women) 33/22 23/12 NS Race (white/nonwhite) 28/27 20/15 NS Time on hemodialysis (mo) NS Diabetes (%) NS Total calcium (mg/dl) NS Phosphorus (mg/dl) Alkaline phosphatase (U/L) NS ipth (pg/ml) NOTE. Values expressed as mean SD, number of patients, or percent. To convert total calcium in mg/dl to mmol/l, multiply by ; phosphorus in mg/dl to mmol/l, multiply by ; ipth in pg/ml to ng/dl, multiply by 1. Abbreviation: NS, not significant. ABD, although the difference was less than statistically significant. In addition, no difference was found between the 2 groups in relation to distribution of CKD causes. Laboratory tests showed that phosphorus and ipth levels were significantly greater in patients with ABD-V than those with classic ABD. Alkaline phosphatase levels were greater in the ABD-V group, although the difference was less than statistically significant. Of note, total calcium levels were similar between the 2 groups. Table 2 shows the comparison between patients with classic ABD and ABD-V according to static histomorphometric parameters. We found BV/TV to be lower in the ABD-V group, although the difference was less than statistically significant. However, OV/BV, OS/BS, ES/BS, Ob.S/BS, and Fb.V/TV were significantly greater in the ABD-V group than the classic ABD group. No differences were observed between groups in Al.S/BS or Ir.S/BS. Aluminum intoxication was greater than 30% of the mineralizing surface in 51.4% of ABD-V samples and 52.7% of ABD samples. Table 3 shows the comparison between patients with classic ABD and ABD-V according to dynamic histomorphometric parameters, which were significantly greater in the ABD-V group (MS/BS, MAR, BFR/BS, Aj.AR, and mineralization lag time). In univariate analysis, Ob.S/BS correlated with ipth level (r 0.31; P 0.002). In addition, Oc.S/BS correlated with age (r 0.19; P 0.06), phosphorus level (r 0.24; P 0.02), ipth level (r 0.29; P 0.005), and Ob.S/BS (r 0.46; P ). The same variables were analyzed in a multiple logistic regression model to identify determinants of increased Oc.S/BS and, consequently, ABD-V. The final model indicated that age (coefficient 0.051; odds ratio, 0.950; 95% confidence interval, to 0.992; Table 2. Comparison Between Classic ABD and ABD-V According to Static Histomorphometric Parameters Classic ABD (n 55) ABD-V (n 35) P BV/TV (%) NS OV/BV (%) OS/BS (%) O.Th ( ) NS ES/BS (%) Ob.S/BS (%) Oc.S/BS (%) NA Fb.V/TV (%) Tb.Th ( m) NS Tb.Sp ( m) NS Tb.N (n/mm) NS Al.S/BS (%) NS Ir.S/BS (%) NS NOTE. Results expressed as mean SD. Abbreviations: ABD, adynamic bone disease; ABD-V, adynamic bone disease-variant; NS, non-significant; NA, not applicable; BV/TV, trabecular bone volume; OS/BS, osteoid surface; OV/BV, osteoid volume; O.Th, osteoid thickness; ES/BS, eroded surface; Ob.S/BS, osteoblast surface; Oc.S/BS, osteoclast surface; Fb.V/TV, fibrosis volume; Tb.Th, trabecular thickness; Tb.Sp, trabecular separation; Tb.N, trabecular number; Al.S/BS, aluminum bone surface; Ir.S/BS, iron bone surface.

5 434 Table 3. Comparison Between Classic ABD and ABD-V According to Dynamic Histomorphometric Parameters Classic ABV (n 55) ABD-V (n 35) P MS/BS (%) MAR ( m/d) BFR/BS ( m 3 / m 2 /d) Aj.AR ( m/d) MLT (d) NOTE. Results expressed as mean SD. Abbreviations: MS/BS, mineralized surface; MAR, mineral appositional rate; BFR/BS, bone formation rate; Aj.AR, adjusted appositional rate; MLT, mineralization lag time. P 0.01) and Ob.S/BS (coefficient 1.113; odds ratio, 3.045; 95% confidence interval, to 5.661; P ) were independent determinants of ABD-V. DISCUSSION The increase in survival of patients with CKD has reinforced the importance of comorbidities seen in this population. Special attention was given to renal osteodystrophy, the spectrum of which is dynamic, changing from year to year in individual patients and in cross-sectional studies as therapy is modified. 6,8,10 Because ABD as a particular pattern of renal osteodystrophy is characterized by low bone turnover together with decreased ability of the skeleton to take up calcium, 11 leading to increased risk for extraosseous calcification, 12,14 prompt prevention and early treatment are essential. Although various investigators attempted to clarify physiopathologic mechanisms of ABD, they remain unclear and controversial. As for ABD-V, it was characterized as presenting increased osteoclastic bone resorption in the absence of parathyroid hyperactivity and correlated with longer time on hemodialysis therapy, greater serum 2M levels, and parathyroidectomy. 15 In the present study, the finding that 18.8% of patients had ABD is in accordance with those of previous studies conducted by our group and other investigators. 8,9,10,15 In addition, findings of previous studies of risk factors for ABD support our findings that most patients with ABD ROCHA ET AL were male, white, on dialysis therapy for a short time, and of more advanced age. 6,10,14 Of the ABD bone biopsy specimens selected, we found that, based on the classification system proposed by Gal-Moscovici and Popovtzer, 15 the frequency of ABD-V in the present study (38.8%) was greater than that reported by those investigators. Because our study was performed in a much larger population and histomorphometric data were compared with local healthy control subjects, our results could be considered more accurate. When bone biopsy specimens were divided into 2 groups (Table 1), patients with ABD-V tended to be younger than those with classic ABD, a finding also divergent from results of the study by Gal-Moscovici and Popovtzer. 15 Bone turnover decreases with age and may be an independent factor in the pathogenesis of low bone remodeling, a hallmark of classic ABD. In addition, parathyroid cells, bone cells, and their receptors are assumed to have diminished response capacity or decreased sensitivity in older patients. 14 In the present study, a borderline negative correlation (P 0.06) was observed between Oc.S/BS (the bone parameter that defines ABD-V) and age, indicating greater resorptive cell activity in younger subjects. The importance of this is emphasized by results of multiple regression analysis, which showed that age was one of the independent determinants of ABD-V. In addition to greater osteoclastic resorption (higher Oc.S/BS and ES/BS), our patients with ABD-V also had greater osteoblastic bone formation (higher OV/BV, OS/BS, Ob.S/BS, and BFR/ BS). Furthermore, the well-known coupling property between bone cells, evidenced by the positive correlation between Ob.S/BS and Oc.S/BS, 19 was present in our sample. Moreover, fibrosis volume was greater, albeit discretely so, in the ABD-V group than the classic ABD group. Confirming the participation of bone cells in the pathogenesis of ABD-V, we found Ob.S/BS to be an independent determinant of ABD-V, identified through multiple regression analysis. Currently, PTH level continues to be a useful predictor of bone turnover, exerting its effect through cell receptors. 1,20 In addition, N-terminally truncated PTH fragments, mainly PTH 7-84, could interfere with the biological activity of PTH 1-84, modulating its effect on bone. 21,22 In the present retrospective study, only ipth was

6 ADYNAMIC BONE DISEASE IN HEMODIALYSIS 435 available for analysis. PTH level correlated positively with Oc.S/BS and Ob.S/BS. Therefore, we can conclude that compared with patients with classic ABD, our patients with ABD-V had greater bone turnover, triggered by osteoblastic activity and very likely a consequence of PTH stimulation. As listed in Table 1, patients with ABD-V had significantly greater serum phosphorus and PTH levels than patients with classic ABD. In addition, there was a tendency toward lower serum calcium levels and higher alkaline phosphatase levels. Altogether, the scenario presented by ABD-V resembles the earliest phase of secondary hyperparathyroidism in patients with CKD. Because there is no doubt that ABD-V truly is a nonosteomalacic low-turnover bone disease, we could speculate that this newly proposed type of bone disease represents a transitional state from lower to higher bone turnover, rather than a new entity within the spectrum of renal osteodystrophy. In contrast to our findings, Gal-Moscovici and Popovtzer 15 observed no differences between patients with classic ABD and those with ABD-V for PTH levels or bone formation. Because their patients with ABD-V had greater serum 2M levels than patients with classic ABD or osteitis fibrosa, the investigators suggested that 2M, modified by advanced glycation end products, acts as an osteoclast stimulator and osteoblast inhibitor. Because the present study was conducted retrospectively, data regarding serum 2M levels are unavailable. However, greater levels of 2M in patients with ABD-V evaluated in the study by Gal-Moscovici and Popovtzer 15 could be a confounding factor. First, it is well known that serum 2M levels increase in parallel with longer time on dialysis therapy. 23 Second, serum 2M levels did not correlate with tissue deposition of the same. 24 In addition, results of an elegant study conducted by Onishi et al 25 suggested that bone deposition of 2M is associated with osteitis fibrosa, not with ABD. In the study by Gal-Moscovici and Popovtzer, 15 patients with ABD-V had been on hemodialysis therapy for a longer time than patients with classic ABD, and all patients with ABD-V had undergone parathyroidectomy. In our study, only 2 patients (1 patient in each group) had undergone parathyroidectomy. Therefore, greater osteoclastic resorption seen in patients with ABD-V studied by Gal-Moscovici and Popovtzer 15 might simply be a sequela of previous hyperparathyroid bone disease. The trend toward lower BV/TV values in our ABD-V group is noteworthy. Similarly, we observed a correlation between low BV/TV and low bone turnover in another study recently conducted by our group. 26 Because patients with ABD-V evaluated in the present study presented a 2-fold increase in osteoclastic resorption in the presence of low bone formation rate, such patients should be monitored closely to avoid further bone loss. In summary, we suggest that the so-called ABD-V is a transitional phase between the lowturnover state of ABD and the high-turnover state of hyperparathyroid bone disease. This change most likely occurs because of the effect of greater PTH levels on a cell-covered bone surface. Disregarding that ABD-V could be either a transitional bone-turnover state or a true entity of renal osteodystrophy, attention should be given to the bone structure derangement to which this special group of patients with CKD is prone. Undoubtedly, further studies of ABD are warranted. Such studies might delineate the roles that such factors as osteocalcin, cross-laps, PTH 7-84, cytokines, and even deposition of 2M in bone have in bone remodeling. ACKNOWLEDGMENT The authors thank Marcos Messias for lending his expertise and assistance to the performance of the bone histology procedures. REFERENCES 1. Malluche HH, Faugere MC: Renal bone disease 1990: An unmet challenge for the nephrologists. Kidney Int 38: , Canalis E, McCarthy T, Centrella M: Growth factors and the regulation of bone remodeling. J Clin Invest 81: , Ott SM, Maloney NA, Coburn JW, Alfrey AC, Sherrard DJ: The prevalence of bone aluminum deposition in renal osteodystrophy and its relation to the response to calcitriol therapy. N Engl J Med 307: , Goodman WG: Bone disease and aluminum: Pathogenic considerations. Am J Kidney Dis 6: , Moriniere P, Cohen-Solal M, Belbrik S, et al: Disappearance of aluminic bone disease in a long term asymptomatic dialysis population restricting Al(OH)3 intake: Emergence of an idiopathic adynamic bone disease not related to aluminum. Nephron 53:93-101, 1989

7 Sherrard DJ, Hercz G, Pei Y, et al: The spectrum of bone disease in end-stage renal failure An evolving disorder. Kidney Int 43: , Spasovski GB, Bervoets ARJ, Behets GJS, et al: Spectrum of renal bone disease in end-stage renal failure patients not yet on dialysis. Nephrol Dial Transplant 18: , Araujo SMHA, Ambrosoni P, Lobão RRS, et al: The renal osteodystrophy pattern in Brazil and Uruguay: An overview. Kidney Int Suppl 85:S54-S56, Monier-Faugere MC, Malluche HH: Trends in renal osteodystrophy: A survey from 1983 to 1995 in a total of 2248 patients. Nephrol Dial Transplant 11:S111-S120, 1996 (suppl 3) 10. Malluche HH, Monier-Faugere MC: Risk of adynamic bone disease in dialyzed patients. Kidney Int Suppl 38:S62-S67, Kurz P, Monier-Faugere MC, Bognar B, et al: Evidence for abnormal calcium homeostasis in patients with adynamic bone disease. Kidney Int 46: , London GM, Marty C, Marchais SJ, Guerin AP, Metivier F, Vernejoul MC: Arterial calcifications and bone histomorphometry in end-stage renal disease. J Am Soc Nephol 15: , Heaf J: Causes and consequences of adynamic bone disease. Nephron 88:97-106, Cannata-Andía JB: Adynamic bone and chronic renal failure: An overview. Am J Med Sci 320:81-84, Gal-Moscovici A, Popovtzer MM: Parathyroid hormone-independent osteoclastic resorptive bone disease: A new variant of adynamic bone disease in haemodialysis patients. Nephrol Dial Transplant 17: , Malluche HH, Faugere M-C: Technique of mineralized bone histology, in Malluche HH, Faugere M-C: Atlas of Mineralized Bone Histology (ed 1). New York, NY, Karger, 1986, pp ROCHA ET AL 17. Parfitt AM, Drezner MK, Glorieux FH, et al: Bone histomorphometry: Standardization of nomenclature, symbols, and units. Report of theasbmr Histomorphometry Nomenclature Committee. J Bone Miner Res 2: , Melsen FD, Mosekilde L: Tetracycline double labeling of iliac bone in 41 normal adults. Calcif Tissue Res 26:99-102, Suda T, Takahashi N, Udagawa N, Jimi E, Gillespie MT, Martin TJ: Modulation of osteoclast differentiation and function by the new members of the tumor necrosis factor receptor and ligand families. Endocr Rev 20: , National Kidney Foundation: K/DOQI Clinical Practice Guidelines for Bone Metabolism and Disease in Chronic Kidney Disease. Am J Kidney Dis 42:S123-S124, 2003 (suppl 3) 21. Monier-Faugere MC, Geng Z, Mawad Friedler RM, Gao P, Cantor TL, Malluche HH: Improved assessment of bone turnover by the PTH-(1-84)/large C-PTH fragments ratio in ESRD patients. Kidney Int 60: , Coen G, Bonucci E, Ballanti P, et al: PTH 1-84 and PTH 7-84 in the noninvasive diagnosis of renal bone disease. Am J Kidney Dis 40: , Gejyo F, Homma N, Arakawa M: Carpal tunnel syndrome and beta 2-microglobulin-related amyloidosis in chronic hemodialysis patients. Blood Purif 6: , Gejyo F, Homma M, Suzuki Y, Arakawa M: Serum levels of beta 2-microglobulin as a new form of amyloid protein in patients undergoing long-term hemodialysis. N Engl J Med 314: , Onishi S, Andress DL, Maloney NA, Coburn JW, Sherrard DJ: Beta 2 microglobulin deposition in bone in chronic renal failure. Kidney Int 39: , Barreto FC, Barreto DV, Moyses RMA, et al: Osteoporosis in hemodialysis patients revisited by histomorphometry. A new insight into an old problem. Kidney Int 69: , 2006