Effect of parathyroidectomy on bone aluminum accumulation in chronic renal failure

Aluminum overload in the reverse osmosis dialysis era: does it exist?

Background

Aluminum accumulation is a well-described complication in dialysis patients. Improvements in hemodialysis technology have possibly eliminated the occurrence of aluminum overload. Limited evidence suggests that aluminum overload may decline in the era of aluminum removal from dialysis fluids, even with the use of aluminum binders.

Methods

We examined the data from January 2014 to June 1, 2020, identified through our electronic records, to evaluate the desferrioxamine (DFO) test results for aluminum overload. The presentation and treatment of aluminum overload were recorded.

Results

Ninety-nine dialysis patients were enrolled for the DFO test. Forty-seven patients (47.5%) were identified as DFO test positive for aluminum overload, of which 14 (14/47) patients had symptoms, including one patient with an unexplained fracture, eight patients with unexplained anemia despite high-dose erythropoiesis-stimulating agents, and five patients with hypercalcemia (serum calcium >11 mg dL^-1). None of the patients with aluminum overload developed encephalopathy. Only four of the 47 patients had microcytic anemia. Patients requiring longer treatments (>10 months versus <10 months) had similar basal serum aluminum (p = 0.219) but had an increase in serum aluminum after DFO (p = 0.041). Furthermore, the treatments decreased erythropoietin doses in the aluminum overload group, with serum total alkaline phosphatase levels <60 U L^-1 (p = 0.028).

Conclusion

We concluded that aluminum overload existed in the reverse osmosis dialysis era. In light of non-obvious symptoms, such as anemia and bone turnover change, serum aluminum in dialysis patients should be monitored in countries using aluminum-based phosphate binders, despite reverse osmosis dialysis.

The Role of Bone Biopsy in the Management of CKD-MBD

A bone biopsy is still considered the gold standard for diagnosis of renal osteodystrophy. It allows to measure both static and dynamic parameters of bone remodeling and is the only method able to evaluate mineralization and allows analysis of both cortical and trabecular bone. Although bone volume can be measured indirectly by dual-energy X-ray absorptiometry, mineralization defects, bone metal deposits, cellular number/activity, and even turnover abnormalities are difficult to determine by techniques other than qualitative bone histomorphometry. In this review, we evaluate the role of bone biopsy in the clinical practice.

Aluminum overload hampers symptom improvement following parathyroidectomy for secondary hyperparathyroidism

BACKGROUND

Aluminum overload and accumulation in tissues may lead to skeletal, hematological, and neurological toxicity. The aim of this study was to assess the effects of serum aluminum levels on presentations, postoperative recovery, and symptom improvement in patients undergoing parathyroidectomy for secondary hyperparathyroidism.

METHODS

From 2008 to 2013, all patients with end-stage renal disease undergoing initial parathyroidectomy were included in the study. Serum aluminum level was measured preoperatively and/or within 1 week after surgery. Preoperative and postoperative biochemical profile and symptoms were compared between the low and high aluminum groups.

RESULTS

A total of 176 patients were included in the study. Of these, 38 (22 %) patients had serum aluminum levels higher than 20 μg/L. A higher percentage of patients in the high aluminum group were on peritoneal dialysis than in the low aluminum group (24 vs. 4 %, p = 0.001). Both groups had similar bone mineral density and changes in biochemical profiles. The preoperative parathyroidectomy assessment of symptoms (PAS) score was not associated with serum aluminum levels (p = 0.349), whereas the postoperative PAS score showed positive association (p = 0.005). There was a negative association between serum aluminum levels and the improvement of total PAS scores (p = 0.001). The high aluminum group had more residual symptoms in three aspects: bone pain (p = 0.038), difficulty getting out of a chair or car (p = 0.045), and pruritus (p = 0.041).

CONCLUSIONS

A high serum aluminum level was associated with reduced symptom improvement in patients undergoing parathyroidectomy for secondary hyperparathyroidism.

IL-1beta, TNF-alpha, TGF-beta, and bFGF expression in bone biopsies before and after parathyroidectomy

BACKGROUND

There is growing evidence pointing to an involvement of cytokines and growth factors in renal osteodystrophy. In this study, the expression of interleukin-l beta (IL-1 beta), tumor necrosis factor-alpha (TNF-alpha), transforming growth factor-beta (TGF-beta), and basic fibroblast growth factor (bFGF) in bone biopsies taken from uremic patients before and 1 year after parathyroidectomy (PTX) was evaluated. Biochemical features and histomorphometric outcome were also studied.

METHODS

Iliac bone biopsies were taken before and 1 year after PTX in nine uremic patients with severe hyperparathyroidism (HPT). Immunohistochemical techniques were used to identify the expression of IL-1 beta, TNF-alpha, TGF-beta, and bFGF in these bone samples.

RESULTS

At the time of the second bone biopsy, the mean serum total alkaline phosphatase activity was normal, whereas mean serum intact parathyroid hormone (iPTH) level was slightly above the upper limit of normal values. Histomorphometric analysis showed a decrease in resorption parameters and static bone formation parameters after PTX. Dynamically, mineral apposition rate (MAR) and mineralization surface (MS/BS) decreased significantly. There was a marked local expression of IL-1beta, TNF-alpha, TGF-beta, and bFGF in bone biopsies before PTX, particularly in fibrous tissue and resorption areas. One year after PTX, IL-1beta decreased from 23.6 +/- 7.5% to 9.9 +/- 3.1%, TNF-alpha from 4.5 +/- 1.5% to 0.7 +/- 0.8%, TGF-beta from 49.6 +/- 9.8% to 15.2 +/- 4.6%, and bFGF from 50.9 +/- 12.7% to 12.9 +/- 7.9% (P < 0.001). A significant correlation was documented between cytokines and growth factors expression in bone with iPTH levels before and after PTX (P < 0.05).

CONCLUSIONS

Based on these results, we suggest that IL-1beta, TNF-alpha, TGF-beta, and bFGF are involved in bone remodeling regulation, acting as local effectors, possibly under the control of PTH.

Clinical course after total parathyroidectomy without autotransplantation in patients with end-stage renal failure

In patients with chronic renal failure, hyperparathyroidism is a common problem and surgical parathyroidectomy (PTX) is frequently required. The three different surgical approaches are subtotal PTX, total PTX with autotransplantation, and total PTX without autotransplantation. Recurrence of hyperparathyroidism varies from 5% to 80% in different studies for the first two surgical approaches. To minimize the risk for recurrence, and because we fear severe relapses with calciphylaxia, we perform total PTX without autotransplantation. From October 1993 to October 1997, 20 patients (9 men and 11 women) underwent total PTX without autotransplantation (median age, 52 years; range, 23 to 74 years; median dialysis time before PTX, 6.5 years; range, 1 to 22 years). All patients were supplemented with vitamin D analogues postoperatively. Patients were followed up for 1 to 48 months (median, 20 months). Bone pain, when present, disappeared within the first week after total PTX. Postoperatively, most patients had temporary hypocalcemia. In the long term, five patients had asymptomatic hypocalcemia. One patient, however, repeatedly had hypocalcemic seizures. Five patients developed asymptomatic hypercalcemia when supplemented with calcitriol. At the end of the individual's observation time, parathyroid hormone (PTH) levels were less than normal in six patients, normal in seven patients, and increased in seven patients despite total PTX. We conclude that total PTX should be reconsidered an option for the treatment of hyperparathyroidism secondary to renal failure. There was no evidence of clinical bone disease after total PTX. Apparently, remaining ectopic parathyroid tissue accounts for PTH levels after total PTX.

Long-term follow-up after subtotal parathyroidectomy in patients with renal failure

OBJECTIVES/HYPOTHESIS

The most appropriate type of surgery for hyperparathyroidism secondary to renal failure remains controversial. We report a 5-year experience of patients with hyperparathyroidism secondary to end-stage renal disease who underwent subtotal parathyroidectomy. We believe that this is the procedure of choice, offering several advantages over total parathyroidectomy with and without reimplantation.

STUDY DESIGN

Retrospective review.

METHODS

Review of 14 consecutive renal failure patients who underwent subtotal parathyroidectomy by one surgeon (A.K.) was performed. Follow-up ranged from 4 to 54 months. All patients were receiving chronic maintenance dialysis. All patients came to surgery with clinical symptoms of parathyroid bone disease, elevated serum calcium levels (10.1-12.4 mg/dL), and intact parathyroid hormone levels (619-4160 pg/mL), despite maximal medical therapy. At exploration four glands were identified in all patients and three and a half were removed.

RESULTS

All patients experienced symptomatic relief postoperatively with normalization or near-normalization of serum calcium concentration and intact parathyroid hormone concentrations. One patient developed recurrent disease 4 months after surgery, and on re-exploration a supernumerary substernal gland was identified. A second patient developed recurrent symptoms 4 years after surgery and at the time of this writing was awaiting re-exploration.

CONCLUSIONS

All patients had either resolution of or marked improvement in their subjective complaints. There have been no cases of permanent hypoparathyroidism. We believe that subtotal parathyroidectomy is the best procedure for patients with refractory symptoms of secondary hyperparathyroidism.

Renal osteodystrophy

Renal osteodystrophy is a general complication of chronic renal failure and end-stage renal disease. The nature of renal osteodystrophy has changed since osteomalacia due to aluminum intoxication has become less prevalent. Osteomalacia has been replaced by the adynamic bone disorder. Suppression of osteitis fibrosa, calcitrol and control of secondary hyperparathyroidism has been shown to produce the adynamic bone disorder. Thus, many other factors besides secondary hyperparathyroidism and calcitrol deficiency contribute to the pathogenesis of renal osteodystrophy. Some of these factors, according to our current state of knowledge, are discussed in this chapter along with the presentation and treatment of renal osteodystrophy.

Chronic effect of aluminium ingestion on bone in calcium-deficient rats

In order to elucidate the relationship of osteogenesis with aluminum and iron deposition, we investigated the histopathological findings of bone in calcium and/or aluminium-deficient rats, together with levels of calcium, aluminium and iron in sera and bone tissues, and also the level of serum parathyroid hormone. Four week old male STD-Wistar rats were divided into four groups to examine the effects of four kinds of diets for ten weeks. The rats on normal diet (Group I) and normal diet+aluminum (Group II) did not show any pathological changes of the bones, but in both calcium-deficient diet group (Group III) and calcium deficient diet added aluminium (Group IV), the compact bone converted into spongy bone in varying degrees, particularly in Group IV. Aluminium deposition was demonstrated at the calcification fronts and the cement lines only in Group IV as red or violet-red lines with aluminium stain, together with iron deposition as revealed with Berlin blue stain, showing similar distribution pattern as aluminum. It was clearly indicated that aluminium and iron, instead of calcium, deposited on the calcification front of the bone under the condition of calcium deficiency, inhibiting the normal osteogenesis.

Experimental osteodystrophy of chronic renal failure induced by aluminum- and ferric-nitrilotriacetate in Wistar rats

The aluminum (AI) and iron (Fe) chelate complexes of nitrilotriacetate (NTA) cause renal insufficiency when they are administered intraperitoneally to rats. Their effects on bone metabolism were studied in 4 week old Wistar rats. Daily intraperitoneal administration of AI-NTA (3mg AI/kg for 11 weeks) induced osteomalacia, impaired bone growth, decreased bone mineral density, lower serum PTH levels than normal as well as renal insufficiency. Al staining showed diffuse deposition in the trabecula and a strong linear band of aluminum deposited at the mineralization front and along the cement line. The osteoid seen markedly within the trabecula was probably the decalcified portion of the bone, the calcium apatite of which was defectively fabricated because of diffuse Al deposition in the trabecula. Al deposition along the cement line would make it much more susceptible to external shear stress than normal. Although daily intraperitoneal administration of Fe-NTA (6 mg Fe/kg for 11 weeks) caused impaired bone growth, decreased bone mineral content and renal insufficiency, the osteoid volume did not increase. Fe staining showed that Fe was deposited diffusely in the cytoplasm of osteoblasts. The results of this study demonstrated that during renal insufficiency, different minerals exhibit different modes of action on bone metabolism, and that Al-NTA is useful for experimental animal models of Al-induced osteomalacia in renal insufficiency.

Risk factors for renal osteodystrophy: a multivariant analysis

To assess the risk factors associated with renal osteodystrophy, we examined the database of 256 patients who were prospectively studied in three Toronto dialysis centers between October of 1987 and 1989. The potential risk factors examined included age, sex, type and duration of dialysis, type and dose of phosphate binders, vitamin D treatment, and history of diabetes mellitus, renal allograft failure, parathyroidectomy, and bilateral nephrectomy. All patients had undergone a bone biopsy and were categorized into one of four disease groupings: (1) osteitis fibrosa and mixed bone disease, (2) aluminum bone disease, (3) mild bone disorder, and (4) aplastic bone disorder. The mean (+/- SD) age of the patients at bone biopsy was 57 +/- 15 years, and 62% were men. Forty-five percent of patients were treated by hemodialysis and 55% by peritoneal dialysis. The mean duration of dialysis was 4 +/- 4 years. Twenty-five percent were also diabetic. The most common disorder was the aplastic (or "adynamic") bone disorder, found in 34% of patients. Aluminum bone disease was found in 27%, osteitis fibrosa or mixed bone disease in 27%, and mild bone disorder in 12% of patients. Cumulative intake of aluminum gels was associated with aluminum bone disease, whereas peritoneal dialysis with supraphysiologic calcium concentrations, ingestion of calcium carbonate, and diabetes mellitus were associated with both mild bone disorder and aplastic bone disorder. These three latter risk factors may be important in predisposing patients to a low bone turnover state through modulation of parathyroid hormone secretion.(ABSTRACT TRUNCATED AT 250 WORDS)

Evidence of healing of secondary hyperparathyroidism in chronically hemodialyzed uremic patients treated with long-term intravenous calcitriol

The aim of this study was to assess the effect of a long-term course of high-dose i.v. pulses of calcitriol (CLT) on hyperparathyroid bone disease (HBD) and functional mass of parathyroid glands of chronically hemodialyzed uremic (CHU) patients. We prospectively studied nine CHU patients treated with CLT, 30 ng/kg/body wt, i.v., thrice weekly over a period of eight months. Plasma concentrations of intact parathyroid hormone (iPTH), bone GLA protein (bGLA) and bone isoenzyme of alkaline phosphatase (biALP) were sampled throughout. Transiliac bone biopsies were made before and after the start of CLT therapy. Double scanning scintigraphy of the neck with 201Tl-99Tc was made before, during and eight months after the start of the treatment. All patients but one, who later responded to higher than planned CLT doses, had significant decreases of plasma iPTH (F = 76; P < 0.0001; ANOVA). The mean pretreatment value of PTH was 966 +/- 160 (mean +/- SE) pg/ml and it had decreased significantly by the first week (T = 2.4, P < 0.04), and had fallen an average of 80% by the 35th week. Ionized plasma calcium concentration was 1.19 +/- .01 mmol/liter which rose significantly (F = 13.5; P < 0.0001) by the 14th week to maximal peak levels, averaging 1.34 +/- .02 mmol/liter. Changes in biALP were parallel to those of iPTH, while bGLA tended to increase immediately after the start of the therapy and to significantly decrease thereafter (T = 3.2; P < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Aplastic osteodystrophy without aluminum: the role of "suppressed" parathyroid function

We evaluated 259 dialysis patients using serum parathyroid hormone (PTH, IRMA; normal range 1 to 5.5 pM or 10 to 55 pg/ml), the deferoxamine infusion test and iliac crest bone biopsy to determine the various forms of renal osteodystrophy and their risk factors. Although half of the biopsied patients had low turnover osteodystrophy, evidence of aluminum toxicity was present in only 1/3 of them. Additional risk factors for this bone lesion included treatment with peritoneal dialysis, ingestion of calcium carbonate, diabetes mellitus and advanced age. The PTH levels in patients with the aplastic lesion were significantly lower than in patients with normal or high bone turnover lesions [7.7 +/- 6.1 vs. 36.9 +/- 3.2 pM (77 +/- 61 vs. 369 +/- 32 pg/ml), P < 0.0001]. Aside from hypercalcemia, these patients were relatively asymptomatic. In a second study, 10 patients on peritoneal dialysis with the aplastic lesion had their dialysate calcium lowered from 1.62 to 1.0 mM. This resulted in a significant increase in PTH levels, from [3.7 +/- 0.8 to 10.6 +/- 1.9 pM (37 +/- 8 to 106 +/- 19 pg/ml), P < 0.001] which persisted over the nine-month observation period. In conclusion, the aplastic lesion is the most common form of renal osteodystrophy, with aluminum intoxication implicated in only 1/3 of the cases. In the remainder, factors identified include therapy with peritoneal dialysis using supraphysiological dialysate calcium, oral CaCO3 intake and diabetes mellitus.(ABSTRACT TRUNCATED AT 250 WORDS)

Southwestern Internal Medicine Conference: bone disease in kidney failure: diagnosis and management

Recent technologic and therapeutic advances have improved the life of the patient with end-stage renal disease. High efficiency and high-flux hemodialyzer membranes have shortened the time required to dialyze, and recombinant erythropoietin has all but eliminated anemia as a major cause of morbidity, but the problem of renal osteodystrophy remains. The following discussion examines the spectrum of bone and joint disease in the patient with end-stage renal disease. The diagnostic and therapeutic strategies currently being tried in the management of these disorders are discussed.

Aluminum and renal osteodystrophy A diminishing clinical problem

Aluminum-associated osteomalacia is a serious complication of advanced renal disease. Sources o f aluminum include the water used for hemodialysis and the gastrointestinal absorption o f aluminum from the antacids used to bind dietary phosphorus in an effort to prevent hyperparathyroidism. Definitive diagnosis is made by bone biopsy and staining for aluminum. Noninvasive testing using the deferoxamine challenge test together with serum PTH levels is also of value in many instances. The goal for the future is to eliminate aluminum-related osteodystrophy by the avoidance of aluminum, control of phosphorus with non-aluminum-containing binders, and development of novel approaches to facilitate phosphorus removal by dialysis.

Low-dose intravenous calcitriol treatment of secondary hyperparathyroidism in hemodialysis patients. Italian Group for the Study of Intravenous Calcitriol

Intravenous calcitriol is known to directly suppress PTH secretion and release. We evaluated the effect of four months of treatment with low-dose intravenous calcitriol on PTH levels in 83 hemodialysis patients. The criteria for including patients in the study were a serum PTH levels at least four times the normal limit, a serum total calcium less than 10 mg/dl and good control of the serum phosphorus level. All patients underwent standard bicarbonate or acetate dialysis; dialysate calcium level was maintained at the usual 3.5 mEq/liter concentration. Initial calcitriol dose was 0.87 +/- 0.02 (SEM) micrograms (0.015 micrograms/kg body wt) thrice weekly at the end of dialysis, and it was reduced in case of hypercalcemia or elevated calcium-phosphate product. Seven out of 83 patients dropped out during treatment. Among the 76 patients who completed the study, 58 (76%) showed a highly significant decrease of intact PTH levels (average reduction 48%) and of alkaline phosphatase levels after four months of therapy. Total serum calcium increased slightly but significantly in the responder group but remained unchanged in the non-responders. No significant changes in ionized calcium levels could be detected, even in responders. Treatment was well tolerated by patients, but 60% of them had transient episodes of hyperphosphatemia. Mean serum phosphate was 4.95 mg/dl at the beginning of the study. It increased significantly after four months of treatment in patients who showed a decrease of PTH levels, although it remained within acceptable limits, below 5.5 mg/dl. Twenty-eight of 76 patients (37%) reduced the dose of calcitriol because their calcium-phosphate products exceeded 60.(ABSTRACT TRUNCATED AT 250 WORDS)

Safety and efficacy of long-term treatment of secondary hyperparathyroidism by low-dose intravenous calcitriol

To assess the safety and efficacy of low-dose intravenous (IV) calcitriol therapy for the treatment of secondary hyperparathyroidism, 21 hemodialysis patients with amino-terminal parathyroid hormone (N-PTH) levels greater than 4 times normal were treated for 12 to 24 months in a prospective trial. The initial dose was 0.50 microgram, which was titrated every 3 months thereafter, as dictated by predialysis calcium, phosphorus, and N-PTH concentration. Dialysate calcium concentration was 1.5 mmol/L. Low-dose IV calcitriol decreased the N-PTH concentration to 48 +/- 6% and 29 +/- 5% of baseline following 12 and 24 months of therapy, respectively. The maximum dose of calcitriol was 0.92 +/- 0.11 microgram (0.50 to 2.25 micrograms). After 12 months of therapy, serum calcium increased from 2.22 +/- 0.04 to 2.41 +/- 0.03 mmol/L (8.9 +/- 0.2 to 9.7 +/- 0.1 mg/dL) without change thereafter. Baseline serum phosphorus was 1.44 +/- 0.09 mmol/L (4.5 +/- 0.3 mg/dL), and was unaltered by calcitriol therapy. Control of serum phosphorus was achieved with calcium-containing phosphate binders, except in three patients who were subsequently withdrawn from the study after 12 months because of persistent hyperphosphatemia due to noncompliance. We conclude that long-term, low-dose IV calcitriol is a safe and effective therapy for most hemodialysis patients with secondary hyperparathyroidism. In contrast to conventional dosing regimens, low-dose IV therapy does not necessitate the use of aluminum-containing phosphate binders and/or a low-calcium dialysate bath.

Hyperphosphatemia: its consequences and treatment in patients with chronic renal disease

Control of phosphorus accumulation in chronic renal insufficiency is crucial to the prevention of secondary hyperparathyroidism and metastatic calcification. In early renal failure, calcitriol levels are normal and parathyroid hormone levels are elevated. The phosphorus levels are maintained in the normal range by the phosphaturia induced by hyperparathyroidism. In this situation, dietary phosphorus restriction increases calcitriol levels and suppresses parathyroid hormone secretion. As renal failure progresses into late stages, hyperphosphatemia is evident along with low levels of calcitriol and worsening hyperparathyroidism. Phosphorus restriction will not affect calcitriol concentrations, yet parathyroid levels may decline. During long-term dialysis, urinary excretion of phosphorus is usually minimal. Therefore, phosphorus balance is determined primarily by the net amount absorbed by the bowel and the quantity removed during dialytic therapy. Given an adequate diet, no form of conventional dialysis is able to fully compensate for the gastrointestinal absorption of phosphorus. Hence, compounds that bind phosphorus in the bowel are often necessary. With the realization that the use of phosphorus binders containing aluminum leads to aluminum accumulation and its sequelae: osteomalacia, dementia, myopathy, and anemia, other phosphorus binders have been evaluated. Calcium carbonate has been investigated the most thoroughly and is in wide use. It is inexpensive and contains a high percent of elemental calcium. However, it is only modestly potent in the binding of phosphorus, and large doses are often necessary to attain satisfactory control of phosphorus. This may lead to hypercalcemia. One approach to this problem is to decrease the concentration of calcium in the dialysate. Alternatively, a more effective phosphorus binder may be used. Calcium acetate has been shown in acute studies to have twice the binding capacity of phosphorus per calcium absorbed than calcium carbonate. Whether use of this compound decreases the incidence of hypercalcemia is unproven. Calcium citrate increases the gastrointestinal absorption of aluminum and offers no advantage over calcium carbonate. Other compounds, such as calcium ketoacids and calcium alginate, have not been extensively studied and are not generally available. The use of phosphorus binders containing magnesium in conjunction with a dialysate low in magnesium may be efficacious. Large doses of magnesium will cause diarrhea and thus limit its use as a single agent. Reasons for failure to control hyperphosphatemia include poor compliance, improper prescription of binders, poor dissolution rates seen with some generic brands of calcium carbonate, and the presence of severe hyperparathyroidism. Optimal control of serum phosphorus in dialysis patients should always be viewed in the context of adequate nutrition and protein intake.

Pretransplant parathyroidectomy in renal failure: effects on bone histology and aluminum deposits during dialysis and after kidney transplantation

Using repeat bone biopsies, we studied whether 1) subtotal parathyroidectomy (PTX) enhances aluminum (Al) deposition in bone and 2) whether pretransplant PTX affects Al removal from bone after kidney transplantation. Twenty-four kidney graft recipients, 10 subjected to PTX 9-44 months prior to transplantation and 14 controls matched for dialysis duration, had bone biopsies taken at transplantation. Serum calcium and parathyroid hormone levels had decreased after PTX in all 10. At transplantation, eroded bone surface was lower in PTX-recipients, while extent of Al-stained bone surface and prevalence of symptomatic Al-related bone disease were similar in both groups (PTX: 2/10; non-PTX: 4/14). Hence, PTX did not enhance accumulation of stainable bone Al nor increase prevalence of clinical bone disease during dialysis. Fourteen (7 PTX) recipients with functioning grafts had a second biopsy 12 months after transplantation. Symptomatic Al-related bone disease was cured regardless of pretransplant PTX, and Al-stained surface had decreased in all but one (PTX) recipient.

Scintigraphy in the clinical evaluation of disorders of mineral and skeletal metabolism in renal failure

In patients with renal bone disease skeletal and extra-skeletal abnormalities can be visualised using conventional bone scintigraphy. Some of these abnormalities are associated with characteristic scintigraphic appearances, which are reviewed in detail, and the possible mechanisms involved are discussed. Specific imaging with iodine 123 serum amyloid P component and iodine 131 beta 2-microglobulin is also discussed in the diagnosis of beta 2-microglobulin amyloidosis specific to patients on dialysis. In the light of available evidence, it appears that bone scintigraphy plays, so far, a limited role in the clinical evaluation of skeletal and extra-skeletal abnormalities in chronic renal failure. The potential role of bone scintigraphy in identifying patients with aluminium-related bone disease needs to be investigated further, and in this respect special attention must be given to the problem of high soft-tissue activity associated with impaired renal function. Timing haemodialysis sessions before scintigraphic imaging deserves wider recognition as it reduces high soft-tissue activity, thereby allowing bone uptake to be assessed more accurately. Specific imaging of amyloidosis resulting from beta 2-microglobulin deposition is a promising technique, but the relative value of the two proposed radiopharmaceuticals needs further clarification.

Calcium carbonate as a phosphate binder in dialysis patients: evaluation of an enteric-coated preparation and effect of additional aluminium hydroxide on hyperaluminaemia

Calcium carbonate has been successfully used as a phosphate binder in patients with chronic renal failure; however, a high frequency of hypercalcaemia has been reported. To study the effects of calcium carbonate preparations with different dissolution characteristics on the incidence of this side effect, we conducted a double-blind, crossover trial in 21 patients undergoing chronic haemodialysis. Aluminum hydroxide therapy was replaced with calcium carbonate. The subjects then randomly received either an enteric-coated or a gastric-coated preparation. Calcium carbonate (3.1-3.6 g/d) controlled serum phosphate concentrations as effectively as aluminium hydroxide (2.9 g/d). Concurrently, there was a significant rise in mean serum calcium and a fall in serum concentrations of both parathyroid hormone and osteocalcin, the latter suggesting a decrease in bone turnover. Overall, hypercalcaemic episodes developed in 9 patients (43%) and occurred at a considerable frequency (33 episodes per 100 patient-months) during treatment with the gastric-coated formulation. Following conversion to enteric-coated calcium carbonate (3.6 g/d) patients had fewer occurrences of hypercalcaemia (12 episodes per 100 patient-months, P less than 0.05) and, as compared to the gastric-coated preparation, increases in serum calcium greater than 3.00 mmol/l were not observed at all. Hyperaluminaemia was regressive during therapy with calcium carbonate, but addition of small doses of aluminium hydroxide caused a large rise in serum aluminium concentrations after infusion of desferrioxamine, indicating an enhanced rate of absorption or aberrant compartmentalization of aluminium. We conclude that calcium carbonate can control hyperphosphataemia in dialysis patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Impairment of bone formation with aluminum and ferric nitrilotriacetate complexes

The deleterious effects of aluminum(AL) and iron(Fe) on bone formation were studied in the presence of nitrilotriacetate (NTA) as a chelator. Both Al-NTA (1.0-1.5 mg Al/kg/day, n = 12)- and ferric nitrilotriacetate (Fe-NTA) (2.0 mg/kg/day, n = 4)-treated Wistar rats showed renal insufficiency blood urea nitrogen [BUN] levels of 25 +/- 8.8-20 +/- 0.7 compared to 12 +/- 0.7-11 +/- 0.4 mg/dl), osteomalacia with a relative osteoid volume of 31.5 +/- 5.6-13.2 +/- 2.4 compared to 4.6 +/- 1.8-0.83 +/- 0.12%, and bone growth retardation (3.1 +/- 0-3.0 +/- 0.2 compared to 3.4 +/- 0-3.3 +/- 0.1 cm) in 24 control rats. Dietary vitamin E(VE) supplementation prevented the Fe-NTA-induced impairment, but not the Al-NTA toxicity. Aluminum was deposited at the interface between osteoid and mineralized bone, while Fe was deposited in the osteoblasts and osteoclasts. There seems to be a positive correlation between hypophosphatemia and osteomalacia but carboxy-terminal parathyroid hormone (C-PTH) and calcium (Ca) levels in the serum were not related to the degree of osteomalacia. Administration of Al-NTA results in more bone Al deposition than that of aluminum chloride (AlCl3) (450 +/- 40 compared to 211 +/- 18 mg/kg fat-free dry weight). The Fe-NTA bone change is related to VE-preventable cellular injury, being consistent with the notion that Fe-NTA toxicity is caused by lipid peroxidation. Al-NTA can be used as an animal model of renal osteodystrophy. Osteodystrophy by Al in chronic renal failure may be mediated by the intrinsic chelator or chelating substance(s) retained in the body fluid due to renal insufficiency.

Results of surgical treatment for hyperparathyroidism associated with renal disease

Recently, the role and timing of surgery for treating secondary and tertiary hyperparathyroidism (HPT) have been questioned. In order to delineate the indications for surgery in these patients, a retrospective analysis of 53 consecutive patients treated with parathyroidectomy was conducted. Subtotal thyroidectomy was done in 37 of 45 patients undergoing their initial operations for HPT. Eight additional patients were referred after failed operations. Of 33 patients with preoperative bone pain, 70% improved. Joint pain improved in 87% of 30 patients, pruritus improved in 81% of 27 patients, and preoperative malaise improved in 73% of 33 patients after parathyroidectomy. Abdominal pain and irritated eyes were unlikely to improve. The best predictors of a successful outcome were a markedly elevated preoperative immunoreactive parathyroid hormone (mid-region) level and an elevated alkaline phosphatase level. There were no perioperative deaths. One patient (1.6%) had a recurrent laryngeal nerve injury, and one patient required reoperation for a neck hematoma. No patient had permanent hypoparathyroidism, but transient hypocalcemia (less than 7 mg/dL) occurred in 22%. Postoperative hypocalcemia correlated with elevated preoperative alkaline phosphatase levels (r2 = 0.247).

Attenuated bone aluminum deposition in nonuremic beagles with reduced bone remodeling

Excess bone aluminum accumulates in uremic subjects after parathyroidectomy. To evaluate whether decreased bone remodeling caused by parathyroidectomy augments bone aluminum deposition, we administered aluminum chloride (0.75 mg/kg iv 3 times/wk) or vehicle to thyroparathyroidectomized (TPTX) and sham-operated (Sham) nonuremic beagles for 8 wk. TPTX alone effectively lowered plasma parathyroid hormone concentrations (8.2 +/- 2.8 vs. 27 +/- 2.2 pg/ml) and consequently suppressed bone remodeling, as evidenced by the diminished resorptive surface (0.8 +/- 0.3 vs. 4.0 +/- 0.5%), osteoid surface (0.5 +/- 0.2 vs. 13.3 +/- 2.3%), and bone formation rate (1.8 +/- 0.6 vs. 15.5 +/- 2.2%/yr) compared with untreated Shams. Aluminum treatment resulted in no further suppression of bone remodeling in TPTX dogs and did not cause osteomalacia. Aluminum-treated TPTX dogs, however, accumulated much less total bone (28.1 +/- 4.5 micrograms/g) and surface aluminum (3.8 +2- 1.4%) than similarly treated Shams (61.4 +/- 5.6 micrograms/g; 12.2 +/- 2.7%, respectively) despite displaying higher plasma aluminum concentrations (1,209 +/- 330 vs. 181 +/- 18 micrograms/l). These observations illustrate that diminished bone turnover retards rather than augments bone aluminum accumulation. Thus bone aluminum deposition after parathyroidectomy in uremic subjects is not likely to be the result of passive aluminum accumulation on inactive bone surfaces. Further studies are needed to determine whether factors, such as prior bone aluminum accumulation and/or the degree of preexistent hyperosteoidosis, modulate aluminum accumulation after parathyroidectomy.

Aluminum administration in the rat separately affects the osteoblast and bone mineralization

Aluminum administration in the experimental animal results in osteomalacia as characterized by osteoid accumulation and decreased mineralization. Previous in vivo and in vitro studies have indicated that either aluminum directly inhibits mineralization or is toxic to the osteoblast. In the present study, PTH was continuously infused in rats with aluminum-induced osteomalacia to evaluate whether aluminum administration decreased mineralization without a concomitant decrease in osteoblasts. Four groups of rats were studied: chronic renal failure (CRF); CRF + aluminum (AL); CRF + PTH; and CRF + PTH + AL. Rats were sacrificed 5 and 12 days after aluminum or diluent administration; in the PTH groups, bovine PTH (1-34) was administered at 2 units/h via a subcutaneously implanted Alzet pump. Aluminum administration decreased osteoblast surface, increased osteoid accumulation, and produced a cessation of bone formation. The infusion of PTH alone increased osteoblast surface and bone formation. The simultaneous administration of aluminum and PTH resulted in an osteoblast surface intermediate between aluminum and PTH alone; however, despite a PTH-induced restoration of osteoblast surface, bone formation did not increase. These findings indicate (1) aluminum is toxic to osteoblasts and also directly inhibits mineralization even when osteoblasts are not decreased; (2) PTH is capable of increasing osteoblasts even in the presence of aluminum; and (3) despite a PTH-induced increase in osteoblast surface, mineralization of osteoid was not improved.

[Aluminum toxicity]

In view of the increasing pollution of our environment and forest decline, growing interest has been focused on aluminum toxicity. Aluminum is one of the most abundant metals and commonly present in tap water, beverages, food, cosmetics, and pharmaceutical preparations. Thus everybody is exposed to aluminum to a greater or lesser extent. It is now beyond any doubt that aluminum intoxication may cause encephalopathy, fracturing vitamin D resistant osteomalacia, and microcytic anemia in patients with chronic renal insufficiency as well as in experimental animals. The risk of aluminum intoxication has also to be considered in several other groups. These include elderly individuals with physiologically impaired excretory renal function who are treated with aluminum-containing antacids, patients with chronic liver disease, infants who are fed highly aluminum-contaminated formula at a time when their excretory renal function has not jet fully developed, patients on total parenteral nutrition, and, possibly, patients with Alzheimer's disease.

Intravenous calcitriol in the treatment of refractory osteitis fibrosa of chronic renal failure

Osteitis fibrosa, a frequent complication of chronic renal failure, is characterized by increased rates of bone formation and bone resorption due to increased secretion of parathyroid hormone (PTH). Effective treatment with oral calcitriol is often impossible in patients with osteitis fibrosa, because low doses may cause hypercalcemia. Because short-term infusions of intravenous calcitriol are capable of suppressing the secretion of parathyroid hormone in patients with uremia without causing hypercalcemia, we evaluated the effectiveness of long-term intermittent calcitriol infusions (1.0 to 2.5 micrograms three times weekly, during dialysis) in treating severe osteitis fibrosa in 12 consecutive patients on hemodialysis whose disease was refractory to conventional therapy. After a mean (+/- SE) treatment period of 11.5 +/- 1.4 months, the mean bone-formation rate declined from 1642 +/- 277 to 676 +/- 106 microns 2 per square millimeter per day (P less than 0.01) in the 11 patients who successfully completed the study. Similar reductions occurred in the osteoblastic osteoid (18 +/- 3 to 9 +/- 2 percent; P less than 0.01) and the degree of marrow fibrosis (6.2 +/- 1.7 to 3.5 +/- 1.3 percent; P = 0.01). Concomitant serum biochemical changes included increased calcium levels (2.55 +/- 0.03 to 2.67 +/- 0.05 mmol per liter; P less than 0.01), decreased alkaline phosphatase levels (489 +/- 77 to 184 +/- 32 U per liter; P less than 0.001), and decreased levels of PTH (amino-terminal, 172 +/- 34 to 69 +/- 16 ng per liter in five patients, P less than 0.03; and carboxy-terminal, 1468 +/- 467 to 1083 +/- 402 ml-eq per liter in six patients, P not significant). Although the majority of the patients had transient episodes of asymptomatic hypercalcemia, this complication could be quickly reversed by temporarily halting treatment or decreasing the dose of calcitriol. We conclude that long-term intermittent infusions of intravenous calcitriol are effective in ameliorating osteitis fibrosa in patients on dialysis. Patients whose osteitis fibrosa is refractory to oral calcitriol and who are candidates for parathyroidectomy should be considered first for intravenous calcitriol therapy.

Deferoxamine test and bone disease in dialysis patients with mild aluminum accumulation

Aluminum bone disease is a frequent complication of dialysis patients. The deferoxamine (DFO) test has been advocated as a noninvasive procedure for the diagnosis of AI bone lesion. However most of these studies have been performed in symptomatic patients with significant AI bone disease. Whether this test may provide similar data at an earlier stage of AI toxicity is not known. The present study evaluates prospectively 28 patients with mild AI load. Patients studied ranged in age from 21 to 65 years; duration of dialysis was 5.6 +/- 3.2 years; deferoxamine, 40 mg/kg body weight, was infused at the end of dialysis. Serum AI was measured before DFO administration and before the next dialysis treatment. Bone biopsies were performed in all patients. Cortical bone AI was determined biochemically; trabecular and cortical bone AI were also determined histochemically. Mean basal serum AI (43.2 +/- 30.8 micrograms/L) and cortical bone AI (25.7 +/- 35.2 micrograms/g) were moderately increased. Basal serum AI correlated (r = 0.77) with the increment in serum AI after DFO infusion. After DFO, stainable trabecular and cortical bone AI correlated in a similar manner with both basal serum AI and increment in serum AI. Only biochemically determined cortical bone AI was not significantly related to basal serum AI. Nineteen of the 28 patients had evidence of osteitis fibrosa on bone biopsy. Stained AI surfaces but not trabecular AI were different in patients with low and patients with high bone formation rates. The bone findings, assessed as bone formation rates and resorption surfaces, did not correlate with biochemically or histochemically determined bone AI.(ABSTRACT TRUNCATED AT 250 WORDS)