A Proposed Test for Determining Physical Working Capacity at the Oxygen Consumption Threshold (PWC&Vdot;O2)

The purpose of this study was 3-fold: (a) to determine if the mathematical model used to estimate the electromyographic fatigue threshold (EMGFT) and physical working capacity at the heart rate threshold (PWCHRT) could be applied to VO2 measurements, (b) to propose a new fatigue threshold called the physical working capacity at the oxygen consumption threshold (PWCVO2), and (c) to compare the power output at the PWCVO2 to those of the EMGFT, PWCHRT, and ventilatory threshold (VT). Fifteen adult volunteers (mean age +/- SD = 22 +/- 2 years) performed a maximal cycle ergometer test to determine VO2peak and VT as well as 4 8-minute submaximal work bouts for the determination of PWCHRT, EMGFT, and PWCVO2. A 1-way repeated measures analysis of variance (ANOVA) with Tukey post hoc comparison indicated that PWCHRT (84 +/- 36) was significantly (p < 0.05) less than EMGFT (126 +/- 51), but there were no differences for PWCVO2 (111 +/- 44) and VT (111 +/- 60) versus PWCHRT or EMGFT. The results of this study indicated that (a) the mathematical model used to determine the PWCHRT and EMGFT was applicable to the measurement of VO2 and could be used to estimate the PWCVO2 during cycle ergometry, (b) there was a difference in the mean power outputs that corresponded to the fatigue thresholds determined from EMG and heart rate measurements, and (c) the PWCVO2 test may provide a useful submaximal technique for estimating the VT.

Importance of health science education for personal fitness trainers

Using a questionnaire developed for the current study, the Fitness Instructors Knowledge Assessment (FIKA(Copyright )), we examined relations between commonly used indicators of knowledge (training and experience) and actual knowledge in the five areas of (a) nutrition, (b) health screening, (c) testing protocols, (d) exercise prescription, and (e) general training knowledge regarding special populations. FIKA provided reliable measures of knowledge in these areas, which are of critical importance in developing an optimal fitness program for the client and for avoiding unnecessary injuries. A survey of 115 health fitness professionals revealed that a bachelor's degree in the field of exercise science and possession of American College of Sports Medicine or the National Strength and Conditioning Association certifications as opposed to other certifications were strong predictors of a personal trainer's knowledge, whereas years of experience was not related to knowledge. These findings suggest that personal fitness trainers should have licensing requirements, such as a bachelor's degree in exercise science and certification by an organization whose criteria are extensive and widely accepted, before being allowed to practice their craft.

Efficacy and side effects of intermittent intravenous and oral doxercalciferol (1alpha-hydroxyvitamin D(2)) in dialysis patients with secondary hyperparathyroidism: a sequential comparison

Most reports on the effectiveness and side effects of oral versus parenteral calcitriol or alfacalcidol in hemodialysis patients with secondary hyperparathyroidism show no advantage of parenteral treatment. The efficacy and safety of intravenous doxercalciferol (1alphaD(2)) were studied in hemodialysis patients with secondary hyperparathyroidism (plasma intact parathyroid hormone [iPTH]: range, 266 to 3,644 pg/mL; median, 707 pg/mL). These results were compared with those of a previous trial using intermittent oral 1alphaD(2); the same 70 patients were entered onto both trials, and 64 patients completed both trials per protocol. Twelve weeks of open-label treatment in both trials were preceded by identical 8-week washout periods. Degrees of iPTH suppression from baseline were similar in the two trials, with iPTH level reductions less than 50% in 89% and 78% of patients during oral and intravenous treatment, respectively. Grouping patients according to entry iPTH levels (<750 and >/=750 pg/mL) showed similar but more rapid iPTH suppression in the low-iPTH groups, whereas longer treatment and larger doses were required by the high-iPTH groups. Highest serum calcium levels averaged 9.82 +/- 0.14 and 9.67 +/- 0.11 mg/dL during oral and intravenous 1alphaD(2) treatment, respectively (P: = not significant [NS]). Prevalences of serum calcium levels greater than 11.2 mg/dL during oral and intravenous treatment were 3.62% and 0.86% of calcium measurements, respectively (P: < 0.001). Highest serum phosphorus levels during oral and intravenous treatment averaged 5.82 +/- 0.21 and 5.60 +/- 0.21 mg/dL, respectively (P: = NS). The percentage of increments in serum phosphorus levels during oral treatment exceeded that during intravenous treatment during 5 of 12 treatment weeks. Thus, intermittent oral and intravenous therapy with 1alphaD(2) reduced iPTH levels effectively and similarly, hypercalcemia was less frequent, and serum phosphorus levels increased less during intravenous than oral 1alphaD(2) therapy, suggesting that intravenous 1alphaD(2) therapy may be advantageous in patients prone to hypercalcemia or hyperphosphatemia.

Effect of intensive glycemic control on microalbuminuria in type 2 diabetes. Veterans Affairs Cooperative Study on Glycemic Control and Complications in Type 2 Diabetes Feasibility Trial Investigators

OBJECTIVE

Microalbuminuria can reflect the progress of microvascular complications and may be predictive of macrovascular disease in type 2 diabetes. The effect of intensive glycemic control on microalbuminuria in patients in the U.S. who have had type 2 diabetes for several years has not previously been evaluated.

RESEARCH DESIGN AND METHODS

We randomly assigned 153 male patients to either intensive treatment (INT) (goal HbA(1c) 7.1%) or to standard treatment (ST) (goal HbA(1c) 9.1%; P = 0.001), and data were obtained during a 2-year period. Mean duration of known diabetes was 8 years, mean age of the patients was 60 years, and patients were well matched at baseline. We obtained 3-h urine samples for each patient at baseline and annually and defined microalbuminuria as an albumin:creatinine ratio of 0.03-0.30. All patients were treated with insulin and received instructions regarding diet and exercise. Hypertension and dyslipidemia were treated with similar goals in each group.

RESULTS

A total of 38% of patients had microalbuminuria at entry and were evenly assigned to both treatment groups. INT retarded the progression of microalbuminuria during the 2-year period: the changes in albumin:creatinine ratio from baseline to 2 years of INT versus ST were 0.045 vs. 0.141, respectively (P = 0.046). Retardation of progressive urinary albumin excretion was most pronounced in those patients who entered the study with microalbuminuria and were randomized to INT. Patients entering with microalbuminuria had a deterioration in creatinine clearance at 2 years regardless of the intensity of glycemic control. In the group entering without microalbuminuria, the subgroup receiving ST had a lower percentage of patients with a macrovascular event (17%) than the subgroup receiving INT (36%) (P = 0.03). Use of ACE inhibitors or calcium-channel blockers was similarly distributed among the groups.

CONCLUSIONS

Intensive glycemic control retards microalbuminuria in patients who have had type 2 diabetes for several years but may not lessen the progressive deterioration of glomerular function. Increases in macrovascular event rates in the subgroup entering without albuminuria who received INT remain unexplained but could reflect early worsening, as observed with microvascular disease in the Diabetes Control and Complications Trial.

Intermittent doxercalciferol (1alpha-hydroxyvitamin D(2)) therapy for secondary hyperparathyroidism

Hypercalcemia and hyperphosphatemia frequently necessitate vitamin D withdrawal in hemodialysis patients with secondary hyperparathyroidism. In short-term trials, doxercalciferol (1alpha-hydroxyvitamin D(2) [1alphaD(2)]) suppressed intact parathyroid hormone (iPTH) effectively with minimal increases in serum calcium and phosphorus (P) levels. This modified, double-blinded, controlled trial examined the efficacy and safety of 1alphaD(2) use in 138 hemodialysis patients with moderate to severe secondary hyperparathyroidism by using novel dose titration; 99 patients completed the study. Hemodialysis patients with secondary hyperparathyroidism were enrolled onto this study, consisting of washout (8 weeks), open-label 1alphaD(2) treatment (16 weeks), and randomized, double-blinded treatment with 1alphaD(2) or placebo (8 weeks). Oral 1alphaD(2) was administered at each hemodialysis session, with doses titrated to achieve target iPTH levels of 150 to 300 pg/mL. Baseline iPTH levels (897 +/- 52 [SE] pg/mL) decreased by 20% +/- 3.4% by week 1 (P: < 0.001) and by 55% +/- 2.9% at week 16; iPTH levels returned to baseline during placebo treatment but remained suppressed with 1alphaD(2) treatment. In 80% of the patients, iPTH level decreased by 70%, reaching the target level in 83% of the patients. Grouping patients by entry iPTH level (<600, 600 to 1,200, and >1,200 pg/mL) showed rapid iPTH suppression in the group with the lowest level; greater doses and longer treatment were required in the group with the highest level. During open-label treatment, serum calcium and P levels were 9.2 +/- 0.84 (SD) to 9.7 +/- 1.05 mg/dL and 5.4 +/- 1.10 to 5.9 +/- 1.55 mg/dL, respectively. During double-blinded treatment, serum calcium levels were slightly greater with 1alphaD(2) than placebo, but P levels did not differ. During double-blinded treatment, 3.26% and 0.46% of serum calcium measurements exceeded 11.2 mg/dL with 1alphaD(2) and placebo, respectively (P: < 0.01); median level was 11.6 mg/dL during hypercalcemia. Intermittent oral 1alphaD(2) therapy effectively suppresses iPTH in hemodialysis patients with secondary hyperparathyroidism, with acceptable mild hypercalcemia and hyperphosphatemia.

A calcimimetic agent lowers plasma parathyroid hormone levels in patients with secondary hyperparathyroidism

BACKGROUND

The calcimimetic agent R-568 lowers plasma parathyroid hormone (PTH) levels in hemodialysis patients with mild secondary hyperparathyroidism, but its efficacy in those with more severe secondary hyperparathyroidism has not been studied.

METHODS

Twenty-one patients undergoing hemodialysis three times per week with plasma PTH levels between 300 and 1200 pg/mL were randomly assigned to 15 days of treatment with either 100 mg of R-568 (N = 16) or placebo (N = 5). Plasma PTH and blood ionized calcium levels were measured at intervals of up to 24 hours after oral doses on days 1, 2, 3, 5, 8, 11, 12, and 15.

RESULTS

Pretreatment PTH levels were 599 +/- 105 (mean +/- SE) and 600 +/- 90 pg/mL in subjects given R-568 or placebo, respectively, and values on the first day of treatment did not change in those given placebo. In contrast, PTH levels fell by 66 +/- 5%, 78 +/- 3%, and 70 +/- 3% at one, two, and four hours, respectively, after initial doses of R-568, remaining below pretreatment values for 24 hours. Blood ionized calcium levels also decreased after the first dose of R-568 but did not change in patients given placebo. Despite lower ionized calcium concentrations on both the second and third days of treatment, predose PTH levels were 422 +/- 70 and 443 +/- 105 pg/mL, respectively, in patients given R-568, and values fell each day by more than 50% two hours after drug administration. Predose PTH levels declined progressively over the first nine days of treatment with R-568 and remained below pretreatment levels for the duration of study. Serum total and blood ionized calcium concentrations decreased from pretreatment levels in patients given R-568, whereas values were unchanged in those given placebo. Blood ionized calcium levels fell below 1.0 mmol/L in 7 of 16 patients receiving R-568; five patients withdrew from study after developing symptoms of hypocalcemia, whereas three completed treatment after the dose of R-568 was reduced.

CONCLUSIONS

The calcimimetic R-568 rapidly and markedly lowers plasma PTH levels in patients with secondary hyperparathyroidism caused by end-stage renal disease.

Calcimimetic agents and the calcium-sensing receptor

Blood ionized extracellular calcium is closely regulated. To accomplish this, a hormone-like receptor that is responsive to extracellular ionized calcium regulates both the secretion of parathyroid hormone and the excretion of urinary calcium (as well as other cellular processes). Several hereditary disorders have mutations that cause either loss or gain of function of the calcium-sensing receptor, and alterations of the calcium-sensing receptor may play a role in both primary and secondary hyperparathyroidism. Calcimimetics are agents that act to make the calcium-sensing receptor more sensitive to extracellular ionized calcium; thereby they suppress the secretion of parathyroid hormone. Early trials in animal models of secondary hyperparathyroidism and in patients with primary hyperparathyroidism or with uremic secondary hyperparathyroidism have shown that the first generation calcimimetic, R-568, effectively lowers parathyroid hormone levels and is well tolerated.

Calcium-sensing receptor and calcimimetic agents

Recognizing the role of the extracellular calcium-sensing receptor (CaR) in mineral metabolism greatly improves our understanding of calcium homeostasis. The biology of the low affinity, G-protein-coupled CaR and the effects of its activation in various tissues are reviewed. Physiological roles include regulation of parathyroid hormone (PTH) secretion by small changes in ionized calcium (Ca2+) and control of urinary calcium excretion with small changes in blood Ca2+. The CaR also affects the renal handling of sodium, magnesium and water. Mutations affecting the CaR that make it either less or more sensitive to Ca2+ cause various clinical disorders; heterozygotes of mutations causing the CaR to be less sensitive to extracellular Ca2+ cause familial hypocalciuric hypercalcemia, while the homozygous form results in severe infantile hyperparathyroidism. Mutations causing increased sensitivity of the CaR to extracellular Ca2+ produce hereditary forms of hypoparathyroidism. Disorders, such as primary and secondary hyperparathyroidism, may exhibit acquired abnormalities of the CaR. Calcimimetic drugs, which amplify the sensitivity of the CaR to Ca2+, can suppress PTH levels, leading to a fall in blood Ca2+. Experiences with this agent in patients with secondary and primary hyperparathyroidism and parathyroid carcinoma are summarized. In animals and humans with hyperparathyroidism, this agent produces a dose-dependent fall in PTH and blood Ca2+, with larger doses causing more sustained effects. The treatment has been short-term except for one patient followed for more than 600 days for parathyroid carcinoma; nonetheless the drug did not cause major side-effects and appears to be safe. Further long-term controlled studies are needed with calcimimetic agents of this type.

Prevention of metabolic bone disease in the pre-end-stage renal disease setting

The methods for preventing hyperparathyroid bone disease, the major variety of renal osteodystrophy, from developing in patients with renal impairment are reviewed. With far-advanced chronic renal failure (creatinine clearance [CCr] < 15 to 20 ml/min), when many of these patients are seen by nephrologists, the use of diets very low in protein, and hence also very low in phosphorus content, combined with calcium-containing phosphate binders, have been shown to lower serum intact PTH levels and improve the osseous pathology. However, the degree of dietary restriction required to achieve success may be quite difficult to follow by most patients encountered in clinical practice. In less-advanced renal insufficiency (CCr, 25 to 60 ml/min), the active vitamin D sterols calcitriol or alfacalcidol [1 alpha-hydroxyvitamin D3] have been shown to ameliorate the skeletal lesions of renal osteodystrophy. The results of six double-blind, placebo-controlled studies and five major open-labeled studies with calcitriol or alfacalcidol are reviewed. Skeletal biopsies were improved and sometimes normalized by using calcitriol or alfacalcidol in daily doses of 0.25 to 0.5 microgram/d, and the incidence of hypercalcemia was quite low with these doses. When the dosage was increased in one study, there was a higher incidence of hypercalcemia. Improved bone mineral density of the spine and hip was reported after 1 yr in calcitriol-treated patients compared with results in the placebo group. Another report documented more favorable intact PTH suppression with intermittent dosing of 2.0 micrograms given either once or three times weekly compared with daily dosing (0.5 microgram/d); there was no rise of serum Ca over the 3-mo trial with any protcol. Other data support the greater likelihood of having normal bone if treatment is initiated when CCr exceeds 25 ml/min. There was no risk of more rapid progression of renal insufficiency in any of the studies reviewed, which include 242 patients who were given an active vitamin D sterol. One trial that used a calcitriol dose of 0.5 microgram/d noted a fall in CCr and a rise in serum creatinine, but true GFR (inulin clearance) did not change. A calcitriol-induced reduction of tubular creatinine secretion is suggested. The risk of inducing low bone turnover (adynamic bone) seems to be quite low with 10.4% of alfacalcidol-treated patients versus 6.5% of placebo developing this "lesion" after 2 yr. Despite the lack of Food and Drug Administration approval for use of these sterols in the predialysis state, evidence is compelling that: there are benefits in retarding the development or progression of metabolic bone disease; there is minimal risk, providing that low doses are used; and there is close monitoring of serum Ca, P, and creatinine. The optimal benefits may be obtained if this treatment is started early in the course of renal insufficiency (CCr in the range of 25 to 60 ml/min).

Intermittent oral 1alpha-hydroxyvitamin D2 is effective and safe for the suppression of secondary hyperparathyroidism in haemodialysis patients. 1alphaD2 Study Group

Calcitriol and alfacalcidol are useful in suppressing parathyroid hormone (PTH) in haemodialysis patients, but hypercalcaemia and hyperphosphataemia are frequent. The vitamin D analogue, 1alpha-hydroxyvitamin D2 (1alphaD2), has a higher therapeutic index in animal models. Previously, 1alphaD2, 4 microg/day or 4 microg/haemodialysis, lowered iPTH to the target range in 87.5% of 24 haemodialysis patients with moderate to severe secondary hyperparathyroidism (plasma iPTH, 359-1521 pg/ml). The incidences of hypercalcaemia (serum Ca>2.8 mM) or hyperphosphataemia (serum P>2.23 mM) were low. Later, 10 of these patients were re-treated with 1alphaD2, initial dose, 10 microg, thrice weekly with haemodialysis. The iPTH was suppressed as readily, and there was no greater incidence of hypercalcaemia and hyperphosphataemia. Based on these data, a large, multicentre study is ongoing in California and Tennessee/Mississippi, using 1alphaD2 in haemodialysis patients with iPTH >400 pg/ml. In this and the earlier studies, only calcium-based phosphate binders were used to control serum phosphorus. The initial dose, 10 microg thrice weekly with haemodialysis, is adjusted to maintain a target iPTH within the range of 150-300 microg/ml; the final dose range is 2.5-20 microg per haemodialysis. The protocol includes 8 weeks of wash-out with no vitamin D, 16 weeks of open label treatment period with 1alphaD2, and finally 8 weeks of randomized double blinded treatment with either continued 1alphaD2 or placebo. Forty two patients from California and 38 from Tennessee/Mississippi have completed 16 weeks of open label treatment. In California, iPTH declined from 832+/-95 pg/ml at baseline to 222+/-71 pg/ml at the nadir and to 477+/-117 pg/ml at week 16 of the treatment. In Tennessee/Mississippi, the iPTH declined from 977+/-65 pg/ml to 286+/-42 pg/ml at the lowest point and to 493+/-79 at the end of the treatment. Plasma iPTH reached or fell below the target range in 84% of the 80 patients completing open treatment. Asymptomatic hypercalcaemia (serum Ca>2.8 mM) increased from 0.3 episodes/100 weeks during wash-out to 3.6 episodes/100 treated weeks in California and from 0 to 3.7 episodes in Tennessee/Mississippi. In California and Tennessee, the episodes of hyperphosphataemia (serum P>2.2 mM) increased from 5.0 and 5.0 episodes per 100 patient/week during wash-out to 10.1 and 10.9 episodes/100 treatment weeks, respectively, with 1alphaD2 treatment. There were no adverse events in association with 1alphaD2 treatment. Thus, oral 1alphaD2 is safe and highly effective for the treatment of secondary hyperparathyroidism.

Effective suppression of parathyroid hormone by 1 alpha-hydroxy-vitamin D2 in hemodialysis patients with moderate to severe secondary hyperparathyroidism

Calcitriol, as used for treating secondary hyperparathyroidism, has a low therapeutic index. The safety and efficacy of the vitamin D analog, 1 alpha (OH)-vitamin D2, (1 alpha D2), which has less toxicity in animals than 1 alpha (OH)-vitamin D3, was tested in a multicenter study of 24 hemodialysis patients with secondary hyperparathyroidism [serum intact (i) PTH > 400 pg/ml]. Calcium-based phosphate binders alone were used to maintain serum phosphorus < or = 6.9 mg/dl. After eight weeks without calcitriol (washout), oral 1 alpha D2, 4 micrograms/day or 4 micrograms thrice weekly, was started, with the dose adjusted over 12 weeks to maintain serum iPTH between 130 and 250 pg/ml. Pre-treatment serum iPTH fell from 672 +/- 70 pg/ml (SEM) to 289 +/- 36 after treatment (P < 0.05). The maximal decrease in serum iPTH was 48 to 96%, with 87.5% of patients reaching target iPTH levels. The final dose of 1 alpha D2 average 14.2 micrograms/week. Pre-treatment serum calcium rose modestly from 8.8 +/- 0.2 mg/dl to 9.5 +/0 0.2 after treatment (P < 0.001). Only once did modest hypercalcemia (serum Ca > 11.2 mg/dl) necessitate stopping treatment. Neither the average serum P level, the incidence of hyperphosphatemia, nor the dose of phosphate binders changed from washout to treatment. Thus, oral 1 alpha D2 is highly efficacious in suppressing secondary hyperparathyroidism in hemodialysis patients and is safe despite exclusive use of calcium-based phosphate-binders. Future studies should clarify the optimal dosage regimen.

1 alpha-Hydroxy-vitamin D2: a new look at an 'old' compound

Calcitriol is effective in suppressing PTH levels in haemodialysis patients with hyperparathyroidism but has a low therapeutic index. There is a search for other vitamin D sterols that suppress PTH but cause less hypercalcaemia. We review evidence that 1 alpha-hydroxy-vitamin D2 (1 alpha-D2) may be an effective and safer alternative to calcitriol. In vitamin D-deficient rats, 1 alpha-D2 is equipotent to 1 alpha-D3, which is converted to calcitriol before it acts; but, in normal rats, 1 alpha-D2 is much less toxic at high doses. In osteopenia models, either steroid-induced or following ovariectomy, 1 alpha-D2 is equal to or more effective than 1 alpha-D3 in preventing bone loss but causes less hypercalciuria. Studies in osteoporotic women reveal minimal hypercalciuria with 1 alpha-D2 at doses up to 4 micrograms/day, data suggesting greater safety than reported with calcitriol or 1 alpha-D3. Preliminary data in haemodialysis patients with secondary hyperparathyroidism demonstrate the efficacy of 1 alpha-D2 in suppressing PTH levels with minimal untoward effects on serum Ca and no effects on serum P. Taken together, these observations suggest that 1 alpha-D2 deserves strong consideration as a therapeutic agent for secondary hyperparathyroidism associated with end-stage renal disease.

Symptomatic hypercalcemia in a diabetic patient undergoing continuous ambulatory peritoneal dialysis: value of bone biopsy in the diagnosis and management

An elderly man with diabetes mellitus and end-stage renal disease managed with continuous ambulatory peritoneal dialysis (CAPD) was hospitalized with peripheral vascular insufficiency; he developed hypercalcemia and became mentally obtunded. Lowering dialysate Ca from 3.5 mEq/L to 2.5 mEq/L, stopping calcium acetate, and ultimately hemodialysis with calcium-free dialysate did not lead to reversal of the hypercalcemia or improvement of his symptoms. The intact parathyroid hormone PTH level was 187 pg/mL, a value rarely associated with significant osteitis fibrosa. A search for other causes of hypercalcemia was unrevealing, and a iliac crest bone biopsy was done. The latter showed osteitis fibrosa, and the patient underwent parathyroidectomy. The hypercalcemia reversed quickly, and his mental symptoms slowly improved. The discussion reviews the probable causes of hypercalcemia in diabetic patient undergoing CAPD with 3.5 mEq/L dialysate calcium and using calcium-containing phosphate binders, with hyperparathyroidism certainly not the usual cause. The reason for the occurrence of significant hyperparathyroidism in the face of only modest elevation of PTH is considered. The value of bone biopsy in resolution of this problem is apparent.

Effects of sucralfate and ranitidine on aluminum concentrations in elderly volunteers

Elevated aluminum concentrations have been implicated in several disease states in the elderly. We examined the effects of sucralfate, a basic aluminum salt of sucrose sulfate, and ranitidine, administered individually and in combination, on plasma and urine aluminum concentrations in the elderly in a prospective, randomized, three-arm crossover study. Subjects were 20 healthy volunteers over age 65 years, with no clinically significant comorbidities or recent use of aluminum-containing drugs or histamine (H)2-antagonists. The three regimens were ranitidine 300 mg at bedtime, sucralfate 1 g 4 times/day, and ranitidine 300 mg at bedtime plus sucralfate 1 g 4 times/day, administered for 4 weeks, with a washout period of at least 1 week between regimens. Plasma and urine aluminum concentrations were measured on days 0, 1, 7, 14, and 28 of each regimen. After 28 days, mean plasma aluminum concentrations were significantly higher in subjects receiving sucralfate alone (8.5 +/- 1.8 micrograms/L) and sucralfate plus ranitidine (5.1 +/- 1.3 micrograms/L) compared with those receiving ranitidine alone (2.4 +/- 0.7 micrograms/L). Urine aluminum concentrations were significantly higher in subjects receiving sucralfate alone (133.2 +/- 32.8 micrograms/g creatinine) and sucralfate plus ranitidine (148.1 +/- 51.9 micrograms/g creatinine) compared with those receiving ranitidine alone (11.0 +/- 3.7 micrograms/g creatinine). There was no significant difference in plasma or urine aluminum concentrations between subjects who received sucralfate alone versus those who received sucralfate plus ranitidine. Sucralfate 4 g/day in elderly subjects produces a significant increase in both plasma and urine aluminum concentrations, compared with ranitidine 300 mg/day. This increase most likely is secondary to gastrointestinal absorption of aluminum in the sucralfate formulation. The clinical relevance of this increase requires further evaluation.

Total parenteral nutrition and its effects on bone metabolism

Total parenteral nutrition (TPN) may affect bone metabolism in a variety of ways. These may include potential indirect effects such as on gastrointestinal hormone secretion, liver function, especially cytochrome P450 isoenzymes, metabolic biorhythms where established, and the continuous compared with the intermittent supply of nutrients. More substantial evidence exists for the reduction of bone formation, parathyroid hormone secretion, and calcitriol production in TPN patients along with high urinary calcium excretion. This review considers both aluminum loading and vitamin D sensitivity as etiologic factors and suggests that aluminum may have played a primary role in the pathogenesis of these abnormalities in bone and mineral metabolism, but that vitamin D may have potentiated the deleterious actions of aluminum. While the sources of aluminum contamination of TPN solutions have been identified and efforts are under way to reduce its contamination of TPN solutions, the persistence of low bone mass measurement in TPN patients is a problem that has been identified repeatedly, does not have a current explanation, and requires further study.

Bone disease in burn patients

Burn patients are at risk for bone disease due to aluminum (Al) exposure from use of antacids and albumin, partial immobilization, and increased production of endogenous glucocorticoids. Moreover, severely burned children are growth impaired up to 3 years after the burn. To determine the extent of bone disease, we studied nine men and three women, ages 18-41 years, with greater than 50% body surface area burn. Seven patients underwent iliac crest bone biopsy following double tetracycline labeling, one additional patient expired after a single label, and three others had postmortem specimens obtained for quantitative Al only. Serial serum and urine samples were obtained weekly until biopsy or death. All biopsied patients had reduced bone formation and osteoid area, surface, and width, with mineral apposition rate, osteoblast surface, and osteoclast number with normal eroded surfaces compared to age- and sex-matched normal ambulatory volunteers. Burn patients also had reduced bone formation, mineral apposition rate, osteoid area, and surface compared to age-matched volunteers at short-term bed rest. Serum levels of osteocalcin were low. Most patients had mild hypercalcemia but only a third had hypercalciuria. All patients had elevated Al in blood or urine; urine Al correlated inversely with serum osteocalcin. In 60% significant bone Al was detectable by stain or quantitation. Our data are compatible with burn patients having markedly reduced bone turnover. Al loading, partial immobilization, endogenous corticosteroids, and cytokine production may be among the etiologic factors.

The use of 1,25-dihydroxyvitamin D3 in early renal failure

Alterations in renal calcitriol synthesis are important in the pathogenesis of secondary hyperparathyroidism in patients with progressive renal failure. Many of the manifestations of secondary hyperparathyroidism can be reversed by treatment with 1 alpha-hydroxylated vitamin D sterols, such as calcitriol and 1 alpha-hydroxyvitamin D3, but some studies suggest that such treatment accelerates the rate of progression of renal disease in patients with mild to moderate renal failure. Thus, calcitriol and 1 alpha-hydroxyvitamin D3 have been used infrequently in this group of patients. A review of more than 20 clinical reports indicates that the use of calcitriol or 1 alpha-hydroxyvitamin D3, in daily doses of 0.25-0.5 microgram, is rarely associated with hypercalcemia, hyperphosphatemia, or impairment in renal function. If such complications arise, they are usually reversible when treatment with vitamin D sterols is withdrawn and serum calcium levels return to pretreatment values. There is evidence that calcitriol impairs creatinine secretion by the renal tubule; thus, serum creatinine levels may increase and measurements of creatinine clearance may fall during calcitriol therapy in patients with mild to moderate renal failure without any change in true glomerular filtration rate. Daily oral doses of 0.25-0.50 microgram of calcitriol or 1 alpha-hydroxyvitamin D3 are well tolerated, and they can reverse the biochemical and histologic features of secondary hyperparathyroidism. Calcitriol therapy may be particularly valuable in patients recognized to be at higher risk of developing progressive secondary hyperparathyroidism as their renal failure slowly advances.

Deferoxamine therapy and mucormycosis in dialysis patients: report of an international registry

Fifty-nine cases of mucormycosis in dialysis patients have been reported to the registry (25 new cases and 34 previously reported cases). The presenting forms of mucormycosis included disseminated in 44%, rhinocerebral in 31%, and other forms in 25%. The diagnosis was made during life in only 39%, while the diagnosis was discovered at autopsy in 61% of the cases. The fungus, cultured in only 36%, was always Rhizopus. The infection was fatal in 86% of cases. No known risk factors for fungal infections, eg, diabetes mellitus, liver disease, splenectomy, neutropenia, steroid therapy, or other immunosuppressive therapy, were present in 70% of patients, but 78% of patients were being treated with deferoxamine. The role played by this drug and more particularly by its iron chelate, feroxamine, in the pathogenesis of mucormycosis in these patients is underscored. Because of this risk, deferoxamine therapy in dialysis patients should be limited to severe aluminum toxicity, the deferoxamine should be given at the lowest possible dose, and dialytic methods to augment the removal of feroxamine should be studied.

Calcium citrate markedly enhances aluminum absorption from aluminum hydroxide

The effect of calcium citrate on intestinal aluminum absorption, assessed by the increment in urinary aluminum excretion, was evaluated in eight normal men. Baseline urinary aluminum excretion was determined for 2 days; thereafter, subjects ingested aluminum hydroxide for 3 days. In a cross-over study, subjects were given either calcium citrate, 950 mg four times a day, or placebo during the 3 days of aluminum hydroxide ingestion (2.4 g/d). Plasma aluminum levels were measured on the second control day and the third day of aluminum hydroxide ingestion. Baseline urinary aluminum excretion was 0.02 +/- 0.004 (6.5 +/- 1.1 micrograms/g creatinine) and 0.03 +/- 0.005 mumol/mmol creatinine (7.4 +/- 1.3 micrograms/g creatinine). These values increased during aluminum hydroxide therapy, but values were much greater when calcium citrate was ingested with aluminum hydroxide. On 3 consecutive days, urinary aluminum excretion levels were 11.1 +/- 3.23, 8.8 +/- 2.9, and 5.3 +/- 0.7 times greater during the administration of calcium citrate with aluminum hydroxide than with aluminum hydroxide alone. Plasma aluminum levels did not differ in the two treatment groups. Thus, calcium citrate markedly enhances the absorption of aluminum from aluminum hydroxide and the two must not be prescribed together in patients with renal failure.

Beta 2-microglobulin deposition in bone in chronic renal failure

Recently, there have been reports of beta 2-microglobulin (beta 2 m) related amyloid deposition in perineural and periarticular tissues in patients receiving long-term hemodialysis, but it has been rarely described in bone. We, therefore, examined previously obtained bone biopsy specimens in patients receiving long-term hemodialysis to determine the prevalence of beta 2 m deposition in bone and to assess the relationship between beta 2 m deposits and bone histomorphometry. We found beta 2 m deposits in bone in 8% of 224 patients examined. Bone deposition of beta 2 m was absent in patients who were on dialysis for less than six years, but was present in 19% who dialyzed longer than 10 years. beta 2 m deposits were found in specimens from the iliac crest, femoral bone, tibia, vertebra and rib. In the iliac crest beta 2 m deposition was localized predominantly to the periosteum. Among these patients with beta 2 m in iliac crest periosteum, 62% had suffered a femoral neck fracture compared to only 4% of matched patients who had negative staining for beta 2 m in the iliac crest (P less than 0.001). Histologically, osteitis fibrosa seemed more common in patients positive for beta 2m than in patients negative for beta 2m deposition. We conclude that beta 2m deposition in bone is common in uremic patients who have received hemodialysis longer than 10 years. The high prevalence of femoral neck fracture in patients with beta 2m localized to the periosteum of the iliac crest suggests that this involvement may be useful to predict susceptibility to femoral fracture.

Pharmacokinetics of calcitriol in continuous ambulatory and cycling peritoneal dialysis patients

Oral calcitriol is commonly used for the treatment of secondary hyperparathyroidism in patients undergoing long-term dialysis, but it has been suggested that intravenous (IV) or intraperitoneal (IP) administration enhances the therapeutic efficacy of the sterol. To examine potential mechanisms for this difference, the bioavailability of calcitriol was evaluated after single oral (PO), IV, and IP doses of 60 ng/kg in each of six adolescent patients with osteitis fibrosa undergoing continuous ambulatory peritoneal dialysis (CAPD) or continuous cycling peritoneal dialysis (CCPD). Serum calcitriol levels were 3.6 +/- 4.3, 8.2 +/- 7.5, and 2.5 +/- 3.0 pg/mL, respectively, before IV, PO, and IP doses of the sterol; these values increased to similar levels at 24 hours: 55.6 +/- 14.6 pg/mL after PO, 56.4 +/- 17.6 pg/mL after IV, and 53.8 +/- 20.1 pg/mL after IP. Serum calcitriol levels were higher 1, 3, and 6 hours after IV injections than after PO or IP doses; values thereafter did not differ among groups. The bioavailability of calcitriol, determined from the 24-hour area under the curve (AUC0-24) for the increase in serum calcitriol concentration above baseline values was 50% to 60% greater after IV, 2,340 +/- 523 pg.mL-1.h-1, than after PO, 1,442 +/- 467 pg.mL-1.h-1, or IP, 1,562 +/- 477 pg.mL-1.h1, dosages, P less than 0.05. These differences were due to higher values for AUC during the first 6 hours after calcitriol administration. Although IP calcitriol did not increase sterol bioavailability, radioisotope tracer studies indicated that 35% to 40% of the hormone adheres to plastic components of the peritoneal dialysate delivery system.(ABSTRACT TRUNCATED AT 250 WORDS)

Prospective evaluation of aluminum loading from formula in infants with uremia

Assessment of potential aluminum loading from regular ingestion of a commercial infant formula (Similac PM 60/40), as the only milk substitute, was made in 14 infants aged 9.6 +/- 4.4 months who were also undergoing continuous cycling peritoneal dialysis. Tissue aluminum accumulation was assessed by serial measurements of plasma aluminum levels, from the increment in plasma aluminum after a standardized deferoxamine infusion, and from quantitative histomorphometry of bone and measurements of total bone aluminum content. Initial mean plasma aluminum levels were 0.61 +/- 0.32 mumol/L, (normal 0.30 +/- 0.04 mumol/L), and values were less than 0.92 mumol/L during the follow-up of 20 +/- 8 months. Plasma aluminum levels increased from 0.59 +/- 0.18 to 0.88 +/- 0.22 mumol/L after a single dose of deferoxamine. The histochemical stain for bone aluminum was negative for all patients, and the bone aluminum content was 0.27 +/- 0.22 mmol/kg dry weight (normal 0.08 +/- 0.04 mmol/kg dry weight). Thus the infant formula Similac PM 60/40 can be safely used in infants with chronic renal failure.

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.

Amyloid syndromes associated with hemodialysis

A historical review and current clinical findings relating a new type of amyloid material to long term hemodialysis are presented, followed by a review of the biochemistry, metabolism and involvement of beta 2-M and theories for the pathogenesis of HRA. The syndromes develop several years after replacement of renal function by dialysis, and seem to be progressive over time. Preliminary clinical studies utilizing more permeable artificial kidney membranes suggest their potential usefulness in the prevention of HRA syndromes, specifically those attributable to persistent elevation of serum beta 2-M; however, caution in their employment is advised. The development of effective treatment for long-term hemodialysis patients afflicted with CTS, arthritic symptoms and skeletal manifestations of HRA is unfortunately constrained by deficiencies in our knowledge. Renal transplantation has been demonstrated to reduce the elevated serum beta 2-M levels in hemodialysis patients to normal; however, the effectiveness of this modality to treat clinical manifestations of HRA has not been reported. Thus, efficacious treatment strategies have lagged considerable behind diagnostic techniques. Intensive research is needed as the story of this new form of renal osteodystrophy unfolds.

Metabolic bone disease of total parenteral nutrition: course after changing from casein to amino acids in parenteral solutions with reduced aluminum content

Bone disease with total parenteral nutrition (TPN) has been attributed to aluminum loading or vitamin D therapy. We studied 17 patients who first received TPN containing casein hydrolysate with high Al and ergocalciferol (25 micrograms/d) for 6-72 mo followed by TPN containing amino acids with reduced Al and ergocalciferol (5 micrograms/d) for 9-58 mo. We also did a cross-sectional study of 22 patients receiving casein and ergocalciferol (25 micrograms/d) compared with 46 patients receiving amino acids and ergocalciferol (5 micrograms/d) for 6-58 mo. Bone formation was higher and osteoid area, bone-surface stainable Al and total bone Al were lower with amino acid TPN than with casein TPN. Bone formation varied inversely with both plasma Al and bone-surface Al, suggesting that plasma or bone-surface Al, acquired during TPN, can reduce bone formation and lead to patchy osteomalacia. Serum levels of iPTH and 1,25-dihydroxyvitamin D were higher with amino acid TPN.

Renal osteodystrophy: some new questions on an old disorder

The two major lesions of renal osteodystrophy are osteitis fibrosa cystica (OFC) and osteomalacia (OM). OFC is the characteristic bone lesion of uremic hyperparathyroidism. Although renal failure causes predictable parathyroid hyperplasia, the precise pathogenetic mechanism is still not defined. The "hyperphosphatemia-hypocalcemia-parathyroid hormone (PTH) hypersecretion" sequence of events is no longer an adequate model for the pathogenesis of uremic hyperparathyroidism. Other abnormalities associated with uremia include reduced 1,25-dihydroxyvitamin D (1,25D) synthesis, changes in intracellular phosphorus content or transcellular phosphate fluxes, or alteration in PTH metabolism, eg, change in set-point for PTH secretion. Each abnormality interacts with others and contributes to PTH hypersecretion, but none can completely account for the development and persistence of hyperparathyroidism in renal failure. The possibility that uremia may directly cause parathyroid hyperplasia remains open. It is also possible that factor(s) that initiate hyperparathyroidism may turn out to be quite different from that which sustains the hyperparathyroid state. Although both vitamin D-deficient and vitamin D-resistant OM may develop in patients with renal failure, the majority of uremic OM seen currently is "vitamin D-refractory." Although now there is persuasive evidence implicating aluminum (Al) accumulation as the major pathogenetic cause for the mineralization defect seen in this disorder, additional disturbances may play important contributory roles. Such factors would include extraskeletal effects of Al, differences in host-susceptibility to this element, the localization of Al within bone, uremia per se, and the participation of other metals and toxins. Finally, possible interactions between hyperparathyroidism and OM of uremia are speculated on.

Bone disease in pediatric patients undergoing dialysis with CAPD or CCPD

The histologic features of renal osteodystrophy and the prevalence of bone aluminum deposition in children receiving regular dialysis have not been described. Forty-four pediatric patients undergoing continuous ambulatory (CAPD) or cycling (CCPD) peritoneal dialysis had bone biopsies and deferoxamine (DFO) infusion tests; all were receiving oral calcitriol. Osteitis fibrosa (OF) was found in 39%, mild lesions (M) in 25%, normal histology (NH) in 16%, aplastic lesions (AP) in 11%, and osteomalacia (OM) in 9%. Bone surface aluminum (SA) was present by histochemical staining in 10 out of 20 given aluminum-containing phosphate-binding agents and in 0 of 24 treated with calcium carbonate; chi 2 = 15.5, P less than 0.0001. Serum biochemistries and DFO infusion tests failed to predict bone histology, but plasma aluminum levels were markedly elevated and bone aluminum content was highest in patients with OM. Bone formation rate (BFR) correlated with serum parathyroid hormone (PTH), r = 0.55, P less than 0.001; BFR was inversely related to bone aluminum content (r = -0.42, P less than 0.01), even in patients with OF (r = -0.66, P less than 0.05). All patients with SA greater than 30% had normal or reduced BFR when compared to those with SA less than 30%; chi 2 = 12.2, P less than 0.005. Based on SA greater than 30%, six patients were classified as aluminum-related bone disease: three OM, one AP, and two NH. Two-thirds of pediatric patients undergoing CAPD/CCPD have persistent hyperparathyroidism despite treatment with calcitriol, but aluminum can adversely affect BFR when SA exceeds 30% regardless of histologic lesion or serum PTH level.

Reversal of aluminum-related bone disease after substituting calcium carbonate for aluminum hydroxide

Aluminum-related osteodystrophy, a crippling disease in patients with renal failure, can develop from the long-term ingestion of aluminum hydroxide gels. We present a diabetic patient treated with continuous ambulatory peritoneal dialysis (CAPD) who developed markedly elevated plasma aluminum levels but no musculoskeletal symptoms. Bone biopsy revealed features of the aplastic form of aluminum-related disease with significant aluminum staining, decreased osteoblastic osteoid, and decreased bone formation by double tetracycline labeling, but no excess accumulation of unmineralized osteoid. Aluminum hydroxide gels were discontinued and the patient received calcium carbonate to control hyperphosphatemia; 9 months later, a bone biopsy showed marked improvement of the aluminum-related bone disease, and at 2 to 10 months, plasma aluminum had decreased from 208.7 +/- 10.3 (SE) to 55.7 +/- 3.9 micrograms/L.

Bone histomorphometry of renal osteodystrophy in diabetic patients

Bone biopsies and plasma parathyroid hormone (PTH) from 27 diabetic dialysis patients were compared to biopsies and PTH levels from matched patients without diabetes to determine if PTH has a role in preserving bone mass in diabetic renal osteodystrophy. Significantly lower values were present in the diabetic group for mineralized bone area (p less than 0.003), osteoblastic osteoid (p less than 0.01), resorptive surface (p less than 0.001), fibrosis (p less than 0.005), bone apposition rate (p less than 0.01), bone formation rate (BMU level) (p less than 0.04), and plasma PTH (p less than 0.05). Bone-surface aluminum was higher in the diabetic group (44 +/- 5% vs. 20 +/- 5%, p less than 0.005). Linear regression analysis revealed significant positive correlations of mineralized bone area with time on dialysis, bone formation rate, bone resorption, and PTH only in the group without diabetes. While both groups had significant positive correlations of PTH with osteoblastic osteoid and bone resorption, only in the nondiabetic group was there a positive correlation of PTH with bone apposition and bone formation rate (BMU level), observations suggesting that the lower bone formation in the diabetic patients may have arisen in part from a failure of PTH to promote bone mineralization. We conclude that relatively low PTH levels and high bone aluminum in diabetic patients with chronic renal failure may be responsible in part for low bone mass when compared to uremic patients without diabetes.

Effects of a magnesium-free dialysate on magnesium metabolism during continuous ambulatory peritoneal dialysis

While the use of magnesium-containing compounds is usually contraindicated in dialysis patients, the risk of toxicity from hypermagnesemia can be reduced by lowering the magnesium concentration in dialysate. We examined the effects of a magnesium-free dialysate on both serum magnesium level and the peritoneal removal rate of magnesium over 12 weeks in 25 stable patients undergoing continuous ambulatory peritoneal dialysis (CAPD). After 2 weeks, the serum magnesium level decreased from 2.2 to 1.9 mg/dL (0.9 to 0.8 mmol/L) (P less than .02) and the peritoneal removal rate increased from 66 to 83 mg/d (2.8 to 3.5 mmol/d) (P less than .05), with both values remaining stable thereafter. There was a strong association between these parameters (r = -0.62, P less than .05), suggesting that the serum magnesium level decreased as a result of the initial increased peritoneal removal rate. For an additional 4-week period, a subgroup of nine patients received magnesium-containing, phosphate binding agents instead of those containing only aluminum. During this phase, serum inorganic phosphorus was well controlled. The serum magnesium level increased only from 1.8 to 2.5 mg/dL (0.7 to 1.0 mmol/L) (P less than .05), due in great part to the concomitant 41% rise in peritoneal magnesium removal from 91 to 128 mg/d (3.8 to 5.3 mmol/d) (P less than .05). No toxicity was noted during the entire 16-week study period, nor did serum calcium change. Thus, serum magnesium levels remained within an acceptable range as magnesium-containing phosphate binders were given through the use of magnesium-free peritoneal dialysate.(ABSTRACT TRUNCATED AT 250 WORDS)

Osteomalacia and aplastic bone disease in aluminum-related osteodystrophy

The bone histology in patients with chronic renal failure and aluminum-related bone disease does not always show the excess accumulation of unmineralized osteoid (matrix) characteristic of osteomalacia. Frequently, bone aluminum accumulation is associated with normal or reduced amounts of unmineralized osteoid and low bone formation and is referred to as aplastic bone disease. In this study, we compared static and dynamic bone histomorphometric parameters and plasma PTH and aluminum levels in 12 patients with osteomalacia and 18 patients with aplastic bone disease who had been receiving dialysis for the same duration to determine if the difference in osteoid accumulation in these 2 lesions might be explained by differences in aluminum accumulation or PTH levels. The stainable bone surface aluminum level was significantly higher in the patients with osteomalacia compared to that in the group with aplastic bone [61 +/- 5% (+/- SEM) vs. 43 +/- 4%; P less than 0.02]. The rates of bone apposition and bone formation were lower in the group with osteomalacia (P less than 0.01). Plasma amino-terminal PTH was not significantly different in the 2 groups. The increment in plasma aluminum levels after a single infusion of deferoxamine was higher in the osteomalacic group than in the aplastic group, suggesting that the patients with osteomalacia accumulated more total body chelatable aluminum than did those with aplastic bone disease during a comparable length of time on dialysis. We conclude that the excess unmineralized osteoid in aluminum-related osteomalacia results from the high rate of total body aluminum accumulation, which directly causes uncoupling of matrix mineralization and matrix production, independent of PTH levels. Patients with aplastic bone disease who have accumulated lesser amounts of total body aluminum fail to develop excess unmineralized osteoid because production and mineralization of matrix are more closely coupled than in the osteomalacic lesion, despite a decline in osteoblast numbers.

"High-dose" calcitriol for control of renal osteodystrophy in children on CAPD

High doses of calcitriol were used prospectively for 11 to 29 months to raise serum calcium levels in an effort to control renal osteodystrophy in 16 children undergoing CAPD. Serum Ca, P, iPTH and alkaline phosphatase were measured monthly; hand radiographs were obtained every six months, and a semiquantitative score of bone abnormalities was evaluated by two independent observers. During the study, serum Ca increased from 9.9 +/- 0.9 to 11.0 +/- 0.6 mg/dl (P less than 0.001); serum iPTH decreased by 113 +/- 131 microliter Eq/ml (P less than 0.005); serum P was unchanged; and serum alkaline phosphatase fell by 33 +/- 46% (P less than 0.02), 530 +/- 397 to 204 +/- 551 IU/liter. The radiographic score fell from 4.8 +/- 4.6 to 0.9 +/- 1.2 (P less than 0.005). The average and maximal doses of calcitriol were 0.61 +/- 0.37 and 0.95 +/- 0.56 microgram/day or 28 +/- 18 and 46 +/- 28 ng/kg body wt/day, respectively. Transient and asymptomatic hypercalcemia occurred in nine patients and two patients had reversible conjunctivitis in association with the hypercalcemia. Thus, "high dose" calcitriol prevented or controlled progression of hyperparathyroid bone disease in most pediatric CAPD patients. The failure to suppress PTH or reverse secondary hyperparathyroidism until the serum Ca rose to 10.5 to 11.0 mg/dl could reflect an increase in the "set point" for PTH suppression by serum calcium in many uremic children.

Bone histologic response to deferoxamine in aluminum-related bone disease

We have examined the changes in bone histology in 28 uremic patients after long-term treatment with the aluminum chelator, deferoxamine. Marked declines in stainable bone-surface aluminum were associated with increases in bone formation rate and osteoblastic osteoid following deferoxamine. The increased bone formation resulted from increases in bone apposition and length of double-tetracycline labels, the latter being highly correlated with the increase in osteoblastic osteoid (r = 0.85). While bone surface aluminum was highly correlated with bone formation rate (r = .69, p less than .001), bone aluminum content did not correlate with bone formation (r = 0.13) and was often elevated after treatment despite an improvement in bone histology. Patients who had undergone prior parathyroidectomy were less likely to have improved bone histology than those with intact parathyroid glands. We conclude that aluminum chelation therapy with deferoxamine is effective in ameliorating the bone histology of patients with chronic renal failure and bone aluminum accumulation, and that the change in stainable bone-surface aluminum is a more sensitive indicator than the change in bone aluminum content in assessing adequacy of chelation therapy. Patients who need deferoxamine treatment but have undergone a prior parathyroidectomy will probably require a more intensive treatment schedule than those who have intact parathyroid glands.

Plasma aluminum levels in pediatric dialysis patients: comparison of hemodialysis and continuous ambulatory peritoneal dialysis

Accumulation of aluminum occurs in children with renal failure and can cause anemia, disabling osteodystrophy, and encephalopathy. Effects on bone mineralization are of particular concern in pediatric patients with growth potential. We measured plasma aluminum levels in 36 patients on continuous ambulatory peritoneal dialysis (CAPD) and 22 on hemodialysis under surveillance at a single pediatric center. The levels were above normal in 35 and 21 patients, respectively, and the values correlated with the oral dose of aluminum-containing phosphate-binding medications (r = 0.57; P less than 0.001). Younger and smaller children had higher plasma aluminum levels and also received larger doses of oral aluminum-containing compounds. Mean plasma aluminum levels (57.2 +/- 52.8 and 48.7 +/- 32.1 micrograms/liter, respectively) and the daily oral doses of elemental aluminum (47.3 +/- 37.6 and 39.2 +/- 26.7 mg/kg, respectively) were not statistically different in patients on CAPD and those on hemodialysis. Plasma aluminum levels did not correlate with estimated cumulative oral intake of aluminum, total duration of dialysis, serum calcium and phosphorus concentrations, N-terminal parathyroid hormone levels, or transfusion requirements. Retention of aluminum is common in children undergoing dialysis, correlates with the amount of aluminum administered orally, and results in similar elevations of plasma aluminum with CAPD and hemodialysis. Younger and smaller children are at increased risk for accumulation of aluminum. Alternative methods for control of serum phosphorus are needed in children with end-stage renal disease.

Early deposition of aluminum in bone in diabetic patients on hemodialysis

Aluminum-associated bone disease is a special problem in uremic patients on hemodialysis. We have observed this disorder in uremic patients with insulin-dependent diabetes soon after the start of dialysis treatments. We therefore studied bone biopsy specimens from 18 diabetic patients on hemodialysis to determine whether aluminum accumulates on bone surfaces at an accelerated rate in diabetes. We also measured the rates of bone formation, because lower rates may enhance the accumulation of aluminum on bone surfaces. As compared with 18 nondiabetic controls with uremia who were matched for age and duration of dialysis, the patients with diabetes had a higher rate of aluminum accumulation on bone surfaces (2.1 +/- 0.7 vs. 0.4 +/- 0.2 percent per month, P less than 0.01) and a lower rate of bone formation (117 +/- 50 vs. 396 +/- 81 microns 2 per square millimeter per day, P less than 0.01). Also, the patients with diabetes whose cumulative aluminum intake exceeded 0.5 kg had higher serum aluminum levels after an infusion of deferoxamine, as compared with controls matched for aluminum intake (P less than 0.01). These measurements reflected a higher aluminum content in the whole body in patients with diabetes. We suggest that the enhanced rate of aluminum accumulation on bone surfaces in uremic patients with diabetes occurs as a result of a low rate of bone formation and an increased accumulation of aluminum in the whole body.

Iliac crest bone biopsy for diagnosis of aluminum toxicity and a guide to the use of deferoxamine

Diagnosis of aluminum-related bone disease in patients with renal failure often requires a bone biopsy. Percutaneous biopsy of the iliac crest has been safely carried out as an outpatient procedure in over 300 patients. No instances of significant bleeding or infection have occurred. The procedure was well accepted in 85% to 90% of patients recently surveyed. Before biopsy, each patient received two short courses of oral tetracycline, separated by a ten- to 14-day interval. Double tetracycline labeling permits the evaluation of dynamic characteristics of bone for the diagnosis of aplastic disease due to aluminum toxicity. When a diagnosis of aluminum toxicity is established, treatment with the chelating agent deferoxamine (DFO) administered during dialysis is effective for aluminum removal. Initially, a standardized infusion of DFO, 40 mg/kg, is administered over two hours immediately following dialysis treatment. The increase in plasma aluminum 24 to 48 hours following such an infusion provides an index of tissue aluminum stores and provides a guide to the appropriate therapeutic dose of DFO. DFO (2 to 4 g) is administered once weekly during the last two hours of dialysis; in rare cases higher dosages have been used. Reported side effects of DFO therapy include hypotension, hypoferremia, and allergic reactions; other investigators have reported ocular abnormalities and unusual infections. Patients are reevaluated after 6 to 12 months of therapy with a DFO infusion test and/or bone biopsy. However, the duration of therapy needed for the successful treatment of aluminum-related bone disease is uncertain.

Aluminum removal by peritoneal dialysis: intravenous vs. intraperitoneal deferoxamine

Aluminum removal via peritoneal dialysis was evaluated after the administration of deferoxamine in patients treated with CAPD and CCPD. The intravenous administration of deferoxamine, 40 mg/kg, led to a 730 +/- 139% increase in aluminum removal, compared to an increase of 641 +/- 178% after the drug was administered intraperitoneally. The mean dialysate: plasma concentration ratio for aluminum rose from 0.17 +/- 0.03 to 0.32 +/- 0.03 with intravenous deferoxamine administration, and from 0.19 +/- 0.05 to 0.38 +/- 0.07 with the intraperitoneal instillation of deferoxamine. In the seven patients with paired studies using both modalities of administration, there were no significant differences in the increments in plasma aluminum or in aluminum removal over a 24-hour period. In patients from whom effluent dialysate was collected for several days after the administration of deferoxamine, daily aluminum losses increased from 218 +/- 76 micrograms/24 hours before the administration of desferrioxamine to 1521 +/- 339, 1120 +/- 232, and 948 +/- 328 micrograms/24 hours over three successive days after deferoxamine. These data indicate that aluminum is effectively removed after the administration of either intravenous or intraperitoneal deferoxamine. The enhanced rate of removal of aluminum by peritoneal dialysis persists for several days after a single dose of deferoxamine. The efficacy and safety of long-term treatment with intraperitoneal deferoxamine requires further study.

Diagnosis of aluminum-related bone disease and treatment of aluminum toxicity with deferoxamine

Bone disease related to aluminum toxicity (aluminum-related bone disease) presents with variable clinical and biochemical findings in patients with renal failure. Bone pain and muscle weakness are common, although afflicted patients can be asymptomatic. Bone pain can be generalized or localized to the hips, back, feet, or ankles; proximal muscle weakness is common. Most cases in the United States arise from the ingestion of aluminum-containing gels by patients on long-term dialysis treatment. Patients at increased risk for developing aluminum-related bone disease include those with earlier parathyroidectomy, failed renal transplant, previous bilateral nephrectomy, and diabetes mellitus. Biochemical features that are common with aluminum-related bone disease include plasma aluminum levels greater than 100 to 150 micrograms/L, serum parathyroid hormone (PTH) levels equal to or lower than those in dialysis patients without bone disease, and normal or slightly elevated serum calcium levels. Plasma alkaline phosphatase levels are often elevated. In our experience, microcytic anemia has been uncommon. An increase in plasma aluminum levels greater than 200 micrograms/L 24 to 48 hours after the infusion of the chelating agent deferoxamine (DFO) correlates with an increased bone aluminum content, and an increment greater than 400 micrograms/L suggests marked aluminum accumulation. Radiographs are usually nonspecific. When results from indirect diagnostic procedures are equivocal, a bone biopsy is necessary. After a diagnosis of aluminum-related bone disease is established, therapy with DFO may be useful. DFO increases both the total plasma aluminum level and its ultrafilterable fraction. After an infusion of DFO, the removal of aluminum increases from 50 to 300 micrograms to 4 to 8 mg per dialysis session. Aluminum removal is similar during continuous ambulatory peritoneal dialysis after either intravenous (IV) or intraperitoneal (IP) administration of DFO. Usually, 2 to 4 g of DFO is administered once weekly, but the optimal dose and duration of therapy have not been determined. Symptoms usually improve after 4 to 12 weeks, and bone biopsies show improvement after treatment for 6 to 12 months. Further experience with DFO is needed, both to identify the optimal dosage and to clarify the risks of long-term therapy in patients with renal failure.

The effects of aluminum loading on the renal response to parathyroid hormone in the vitamin D-replete rat

Aluminum (Al) may cause vitamin D-resistant osteomalacia and depress the serum levels of immunoreactive parathyroid hormone (iPTH) in patients treated with maintenance dialysis and those on total parental nutrition (TPN). Both conditions have been associated with low serum levels of 1,25(OH)2-vitamin D (1,25(OH)2D). Al may inhibit PTH secretion in vitro; however, induction of hypocalcemia can enhance endogenous PTH secretion in Al-loaded dogs and TPN patients. Despite hypocalcemia and/or increased endogenous iPTH levels, Al-loaded TPN patients fail to show the expected rise in serum 1,25(OH)2D levels. Such observations suggest that Al may impair the renal response to PTH. We studied vitamin D-replete rats given Al or saline vehicle IP for 5 days. Al and control rats then received a saline infusion with an IV bolus of PTH 1-34. Urinary cyclic AMP and P excretion rose in Al and control rats by 1 hr post-PTH, without differences between the groups. Serum P and ionized Ca levels were not different between Al and control rats. In other Al and control rats, serum 1,25(OH)2D levels were measured after saline without PTH. Serum 1,25(OH)2D levels were higher in controls given PTH than in those without, but 1,25(OH)2D levels were not different between Al rats given PTH and those with none. Thus, aluminum does not affect cyclic AMP or P excretion but may impair 25(OH)D-1 alpha-hydroxylase activity in response to PTH.

Comparison of parathyroid hormone assays with bone histomorphometry in renal osteodystrophy

Bone biopsies were studied in 67 dialysis patients to determine if a PTH RIA specific for intact plasma PTH is a better predictor of osteitis fibrosa than a RIA that measures inactive carboxy-terminal/midregion plasma PTH fragments. An amino-terminal-specific antiserum that cross-reacts with intact PTH, but not midregion or carboxy-terminal fragments, and an antiserum that cross-reacts with the 44-68 region of the PTH molecule and measures both intact and midregion/carboxy-terminal PTH fragments were used in the comparisons. Plasma PTH concentrations measured by both assays correlated positively with bone formation rate, bone apposition rate, osteoblastic osteoid, osteoclast number, and marrow fibrosis. The optimum predictive value of the amino-terminal PTH assay for osteitis fibrosa was 88%, compared to 74% for the midregion PTH assay. This difference in predictive value could be attributed to the highly significant correlation of marrow fibrosis with plasma amino-terminal PTH. In conclusion, these data suggest that a PTH RIA that uses an amino-terminal-specific antiserum may be a better predictor of osteitis fibrosa in patients undergoing maintenance hemodialysis.