The pathogenesis of renal osteodystrophy: role of vitamin D, aluminium, parathyroid hormone, calcium and phosphorus

Biochemical data and bone histology from 44 haemodialysis patients was compared using an histologic technique capable of evaluating separately the individual components of osteodystrophy. Hyperparathyroid bone disease was diagnosed by an elevated osteoclast count, and in advanced disease there was also fibrosis and woven bone. Osteomalacia, defined as an impairment in the rate of bone mineralisation, was present in two distinct forms: osteomalacia type I, characterised by wide osteoid seams, and osteomalacia type II, characterised by extensive thin, inactive osteoid. The histologic diagnoses were hyperparathyroid bone disease (15), osteomalacia type I (3), osteomalacia type II (6), hyperparathyroid bone disease and osteomalacia type I (12), hyperparathyroid bone disease and osteomalacia type II (6), normal (2). Aluminium was evident histochemically in 17 biopsies. Vitamin D metabolite levels were low in most patients and did not correlate with any biochemical or histological parameter. Parathyroid hormone levels were highly correlated with histological features of hyperparathyroid bone disease, and also correlated with plasma calcium, suggesting a degree of autonomy of parathyroid hormone secretion. Urea and creatinine were higher in the hyperparathyroid bone disease than the osteomalacia groups suggesting that poor dialysis contributes to the former. Statistical analysis showed that osteomalacia type I was associated with relatively low plasma calcium and phosphorus levels; osteomalacia type II was associated with increased bone aluminium and with the uraemic process itself, as reflected in the plasma creatinine level. This study shows relationships between renal osteodystrophy and plasma calcium and phosphorus levels, but no relationship with vitamin D metabolites. Aluminium appears to impair mineralisation even at relatively low levels of accumulation. However there are other unidentified factors associated with the uraemic process, contributing to all three components of renal osteodystrophy.

Serum 1,25-dihydroxyvitamin D concentrations in premature infants: preliminary results

Serum 1,25(OH)2D concentrations were measured in serial serum samples from 19 premature infants of 29.6 +/- 1.3 weeks gestation and 1,129 +/- 159 g birthweight. 1,25(OH)2D was always normal or elevated and mean concentrations increased with age (adult, 55.2 +/- 13; infants, 1-2 weeks, 81.5 +/- 37.7 pg/mg; 3 weeks, 65 +/- 21; 6 weeks, 90.0 +/- 17.3; 9 weeks, 99.0 +/- 25.1; 12 weeks, 103.3 +/- 26.6 pg/ml). No correlation was seen with 25-OHD. Infants given 800 IU D2 supplements had lower 1,25(OH)2D levels than infants given 400 IU D2. Breast fed infants had initially higher 1,25(OH)2D levels; however, this was not sustained. These preliminary data suggest that premature infants regulate 1,25(OH)2D production similar to more mature infants and children. Whether the premature infant has a normal gastrointestinal and/or bone responsiveness to 1,25(OH)2D and whether these elevated 1,25(OH)2D concentrations are "adequately elevated" requires further study.

[Interrelation of the epiphysis and parathyroid glands]

Synergism between parathyroidin and epithalamin (an extract from the cattle epiphyses) with relation to phosphorus metabolism was revealed in experiments on guinea-pigs. Both drugs possessed a hypophosphatemic effect. The influence of epithalamin on calcium metabolism was mediated by changes in parathyroid function. An elevation of the parathyroid hormone in the blood was noted after the administration of epithalamin.

Effect of dietary phosphorus levels on porcine renal 25-hydroxyvitamin D-1 alpha- and 24R-hydroxylase activities and plasma 1,25-dihydroxyvitamin D3 concentration

Results of studies on the effect of dietary P deprivation on pig renal 1 alpha- and 24-hydroxylase activities and on concentrations of plasma alkaline phosphatase, Ca, P and vitamin D metabolites are presented. Renal 1 alpha-hydroxylase activity was increased six- to eightfold and plasma 1,25-dihydroxyvitamin D3 concentration increased two- to threefold in pigs fed a low P diet (.085% P) compared with pigs fed a control diet (.6% P). In contrast, renal 24-hydroxylase activity and plasma 25-hydroxyvitamin D concentration did not differ between diet groups. Plasma alkaline phosphatase activity was two to four times higher in pigs fed the low P diet compared with pigs fed the control diet. The rate of gain by pigs fed the low P diet was less than pigs fed the control diet. The low P diet was associated with a prolonged elevation of renal 1 alpha-hydroxylase activity in spite of the presence of a pronounced hypercalcemia.

Plasma calcium, phosphorus, 25-dihydroxyvitamin D3, and 1-25-dihydroxyvitamin D3 of hens with fatty liver syndrome

Plasma was obtained from normal laying hens, 30 weeks of age, and from laying hens, 60 weeks of age, with fatty liver syndrome (FLS). The 60-week-old hens were divided into two groups based on whether they were laying or nonlaying. Plasma phosphorus and calcium was significantly higher for hens with FLS. The younger hens had significantly lower 25-dihydroxyvitamin D3 (25-OH-D3) plasma levels than the older hens. The older hens that were laying had significantly lower 25-OH-D3 plasma levels than the nonlaying hens. Old nonlaying hens with FLS had lower 1, 25-OH-D3 than young hens or old laying hens with FLS; however, the levels were not different for the two groups of laying hens.

25-Hydroxyvitamin D levels during breast-feeding with or without maternal or infantile supplementation of vitamin D

Serum 25-hydroxyvitamin D (25-OHD), calcium, phosphorus, magnesium, and alkaline phosphatase levels of breast-fed infants and their mothers were studied by following 100 healthy term mother-infant pairs with different supplementation protocols of vitamin D. A pilot study in winter revealed that six of eight breast-fed infants without vitamin D supplementation had serum 25-OHD levels below the risk limit for rickets (5 ng/ml) at the age of 8 weeks. In the main study in winter groups, it was found that the 25-OHD levels were low (5.6 +/- 3.7 ng/ml) at the age of 8 weeks in the unsupplemented breast-fed infants, whose mothers were given vitamin D supplementation of 1,000 IU/day during lactation (group I), compared with the levels of those infants receiving either 400 (18.0 +/- 8.4 ng/ml, group II) or 1,000 IU (22.8 +/- 11.2 ng/ml, group III) vitamin D (group I vs. group II or III, p less than 0.001; group II vs. group III, NS). In group I 10 of 18 infants had serum 25-OHD levels less than 5 ng/ml compared with none of the infants in groups II and III. Yet the infants with 25-OHD levels less than 5 ng/ml showed no signs of clinical or biochemical rickets at the age of 8 or 20 weeks. In summer at delivery the maternal 25-OHD levels were good, but decreased thereafter. Also in summer groups, the infantile 25-OHD concentrations decreased; however, because the levels at delivery were high, they stayed in the normal range.(ABSTRACT TRUNCATED AT 250 WORDS)

Bone and parathyroid inhibitory effects of S-2(3-aminopropylamino)ethylphosphorothioic acid. Studies in experimental animals and cultured bone cells

S-2-(3-aminopropylamino)ethylphosphorothioic acid (WR 2721) is a radio- and chemoprotective agent which produces hypocalcemia in humans. Intravenous injection of 30 mg/kg WR 2721 in rats and 15 mg/kg in dogs lowers serum calcium by 19 and 25%, respectively. Hypocalcemia in dogs is associated with a fall in serum immunoreactive parathyroid hormone (PTH), which suggests that the mechanism of its hypocalcemic effect is acute hypoparathyroidism. Despite this effect on PTH, in eight chronically parathyroidectomized rats on a low phosphate diet, WR 2721 reduced serum calcium from 9.4 +/- 0.6 to 7.7 +/- 0.5 mg/dl (P less than 0.01) at 3 h. Furthermore, in dogs rendered hypercalcemic by continuous infusion of PTH, WR 2721 reduced serum calcium from 11.0 +/- 0.5 to 10.6 +/- 0.5 mg/dl (P less than 0.01). To determine whether WR 2721 causes hypocalcemia by enhancing the exit of calcium from the circulation or inhibiting its entry, the drug was infused 3 h after administration of 45Ca to rats. WR 2721 did not significantly increase the rate of disappearance of 45Ca from the circulation even though serum calcium fell by 19%. However, serum 45Ca specific activity was higher at 1.5 h (P less than 0.01) and 3 h (P less than 0.05) in rats given WR 2721 than in rats given vehicle alone, which suggests that WR 2721 blocks the entry of nonradioactive calcium into the circulation, presumably from bone. In incubations with fetal rat long bone labeled in utero with 45Ca, 10(-3) M WR 2721 inhibited PTH-stimulated, but not base-line release of 45Ca. Bone resorption by primary culture of chick osteoclasts was inhibited by WR 2721 at concentrations as low as 10(-4) M in the absence of hormonal stimulation. These studies suggest that WR 2721 lowers serum calcium predominantly by blocking calcium release from bone. This acute hypocalcemic effect is at least in part independent of its effect on the parathyroid glands, and is most likely a direct effect of the agent on bone resorption.

Relationships between radiological and biochemical evidence of rickets in Asian schoolchildren

One hundred Asian schoolchildren provided evidence of the relationships between radiological and biochemical evidence of rickets in a vitamin D-deficient population. In a retrospective study of the X-rays of 56 children the variables serum alkaline phosphatase, inorganic phosphorus and age provided a discriminant function which correctly classified 10 of 11 children with radiological evidence of rickets and 44 of 45 children with negative or marginally abnormal X-rays. When the discriminant function was applied to a prospective study of 44 children, three children with radiological evidence of rickets were correctly classified together with 38 of the remaining 41 children with negative or marginally abnormal X-rays. Serum alkaline phosphatase was the most important variable in the discriminant analysis, followed by serum inorganic phosphorus and age. Low levels of serum 25-hydroxy vitamin D (25-OHD) are of little value in predicting the severity of radiological evidence of rachitic bone disease in a vitamin D-deficient population.

Long-term treatment of postmenopausal osteoporosis with active vitamin D3, 1-alpha-hydroxycholecalciferol (1 alpha-OHD3) and 1, 24 Dihydroxycholecalciferol (1, 24(OH)2D3)

The effects of active vitamin D3 analogues on radial mineral content (RMC) in postmenopausal osteoporosis were examined. Seventy eight subjects with postmenopausal osteoporosis were divided into 5 groups; Group 1 (n = 23) as the control group and Group 2 (n = 27), Group 3 (n = 8), Group 4 (n = 9) and Group 5 (n = 11) which were given 1 microgram of 1, 24(R) (OH)2D3 per day, 1 microgram of 1, 24(S)(OH)2D3 per day, 0.5 and 1 microgram of 1 alpha-OHD3 per day for 6 to 24 months, respectively. After 3-months administration of these drugs, RMC values were significantly increased in Groups 2 (102.8 +/- 1.8%), 4 (103.9 +/- 3.3%) and 5 (114.2 +/- 3.6%), when compared with the controls (97.9 +/- 2.4%). RMC in Group 3 (97.9 +/- 2.4%) was not significantly different from the control value. The administration of 1 alpha-OHD3 caused in increase in RMC in a dose-related manner. A rapid decrease in RMC was observed after withdrawal of the treatment in Groups 2, 4, and 5. A subsequent increase in RMC was observed after re-administration of 1 alpha-OHD3 and 1, 24(R)(OH)2D3. Serum Ca levels were increased in the group treated with 1, 24(R)(OH)2D3 and were decreased after the discontinuation of 1 alpha-OHD3 administration. Serum A1-P activity was decreased by treatment with 1 alpha-OHD3 (1 microgram per day) and a subsequent increase was observed in both groups treated with 1, 24(R)(OH)2D3 and 1 alpha-OHD3. Serum PTH levels were decreased by the administration of 1, 24(R)(OH)2D3 and 1 alpha-OHD3. In the group treated with 1 microgram of 1 alpha-OHD3 per day, hypercalcemia (2 out of 11 cases and these patients took calcium tablets) and an increase in BUN (1 out of 2 hypercalcemic patients) were observed.(ABSTRACT TRUNCATED AT 250 WORDS)

Hyperparathyroidism

A review of hyperparathyroidism and current controversies in diagnosis and management is presented. Accurate diagnosis by the endocrinologist and an experienced surgeon remain the standards for good surgical results. Hyperparathyroidism is a heterogeneous disease, and therapy must be individualized to each patient. Conservative surgical removal of parathyroid tissue is preferred in most patients.

Spurious hyperphosphatemia due to hyperlipidemia

A patient had hyperlipidemia associated with apparent hyperphosphatemia. Further tests on his serum and on the lipemic sera from 15 additional patients revealed a method-dependent overestimation of inorganic phosphorus values. The degree of overestimation was found to correlate positively with the serum triglyceride concentration. Unexplained elevation of the serum phosphorus level should alert the physician to the possibility of spurious hyperphosphatemia due to hyperlipidemia.

Continuous ambulatory and continuous cycling peritoneal dialysis in children. A report of the Southwest Pediatric Nephrology Study Group

Continuous ambulatory peritoneal dialysis (CAPD) and continuous cycling peritoneal dialysis (CCPD) have become acceptable methods of treatment for children with endstage renal disease (ESRD). In this study we have compared the effectiveness of these two modalities of prolonged dwell peritoneal dialysis in 82 children treated at home with CAPD and/or CCPD for a mean of 10.2 months. Forty variables were evaluated during 92 patient periods (63 CAPD, 29 CCPD). There was no difference between the two groups with regard to sex, race, original disease, duration of dialysis, or volume of dialysis fluid. The only difference in biochemical profiles between the two groups was a higher serum creatinine in CCPD patients due in part to this group's greater age. The rate of peritonitis was not different (CAPD 1/4.6, CCPD 1/5.2 months), but the number of patient periods devoid of peritonitis was greater in the CCPD group (14/29 vs. 17/63, P = 0.04). Growth velocity index (GVI) and standard deviation scores (SD scores) were used to evaluate growth in the total group and subsets according to age. Overall GVI was 88% of expected and did not differ between PD groups (CAPD 88% vs. CCPD 89%). There were no significant changes in SD scores for growth during the course of prolonged dwell peritoneal dialysis indicating that the children did not experience further deterioration in growth. Children less than 4 years of age also did not have significant changes in SD scores. We conclude that CAPD and CCPD provide acceptable and comparable modes of dialytic therapy for children with ESRD.

Vitamin D metabolism and osteomalacia in cystic fibrosis

A 25-yr-old black man with cystic fibrosis and cirrhosis developed symptoms of osteomalacia and hypocalcemia, hypophosphatemia, secondary hyperparathyroidism, and low circulating 25-hydroxyvitamin D (25-OHD). Serum 1,25-dihydroxyvitamin D (1,25-[OH]2D) was within the normal range. Iliac crest bone biopsy confirmed the diagnosis of osteomalacia. Oral administration of 50,000 IU of vitamin D2 failed to relieve symptoms or raise serum 25-OHD levels to normal. Intramuscular vitamin D2, 10,000 IU every 8-12 week, improved symptoms, raised serum 25-OHD to normal, and increased circulating 1,25-[OH]2D to values five times normal. Over the next 10 mo circulating 1,25-[OH]2D remained elevated despite normalization of serum calcium, phosphorus, and parathyroid hormone. Repeat bone biopsy 1 yr after parenteral vitamin D showed healing of the osteomalacia. Malabsorption of vitamin D appears secondary to profound steatorrhea due to pancreatic insufficiency and secondary biliary cirrhosis. Although extensive hepatocellular disease was present, hepatic conversion of vitamin D to 25-OHD was intact. Both high and low circulating 1,25-[OH]2D levels during active osteomalacia have been reported; initially, the level was in the normal range and higher values in this patient occurred with repletion of 25-OHD substrate. This study shows that symptomatic osteomalacia may be a major manifestation of cystic fibrosis in those patients surviving into adulthood. Measurements of serum 25-OHD in cystic fibrosis patients may identify those who should receive supplemental vitamin D.

[Vitamin A status of patients with chronic renal failure in relation to renal osteodystrophy]

In patients with chronic renal insufficiency and dialysis patients as well as in normal persons determinations of vitamin A in the serum and in the bone were performed and related to the parameters of the bone metabolism and to the histomorphometric investigation of the bone. The vitamin A serum levels were significantly increased in the two groups of patients, however, did not show any differences between the patients with an osteoidosis or the combination of osteoidosis and fibroosteoclasia. There were no correlations to calcium, phosphorus, PTH and to the alkaline phosphatase as well as to the individual histomorphometric data. The vitamin A content of the bone was low and did not show any differences to the normal persons. On the other hand, there were significant relations between the parathormone and the parameters of the regeneration and the absorption of the bones. An additional influence of vitamin A on the bone disturbance, eventually by the activation of the osteoclasts cannot be excluded.

Primary hyperparathyroidism in pregnancy

The history of a pregnant woman with primary hyperparathyroidism is presented. The patient underwent successful operation during the second trimester and the subsequent pregnancy and delivery were completely normal. Previously, 72 women with an established diagnosis of hyperparathyroidism in pregnancy are reported in the English literature. Twenty-three women underwent operation during pregnancy and 18 normal children were born. Fifty women with a total of 79 pregnancies during a hyperparathyroid state bore 35 normal children while 40 births had different kinds of complications. It is thus clearly documented that the risk of severe fetal complications is much higher if the hyperparathyroidism is left untreated than if the mother undergoes operation during the pregnancy. Therefore when the diagnosis is established the mother should undergo operation, if possible during the second trimester, which minimizes the complication rate significantly in both mother and child. Correction of the hypercalcemic state enables the development of adequate parathyroid gland function in the baby.

Effects of three diets on dogs with induced chronic renal failure

Healthy mixed-bred dogs of both sexes had renal mass surgically reduced and were allowed 2 to 3 months for hypertrophy of the remnant kidney. They were then allotted into 3 groups with equal renal function and were fed 1 of 3 diets that differed in composition. Group 1 dogs (n = 6) were fed moist food that contained 50% protein, 2.34% Ca, and 1.64% P with a P-binding agent (basic aluminum carbonate gel) added. Group 2 dogs (n = 6) were fed a dry diet that contained 24.5% protein, 1.26% Ca, 1.21% P, and the same P-binding agent as used for group 1. Group 3 dogs (n = 7) were fed a moist diet that contained 16.1% protein, 0.38% Ca, and 0.3% P without a P-binding agent. Each group was fed its diet for 92 days and monitored for responses. Mortality associated with uremia occurred in 2 of 6 group 1 dogs, 0 of 6 group 2 dogs, and in 2 of 7 group 3 dogs. Among survivors, clinical signs were seen in the more azotemic dogs of group 1, but not in dogs of groups 2 and 3. The blood urea nitrogen, plasma P concentrations, and PCV values were most favorable in group 3 and least favorable in group 1. Marked differences between groups were not seen in plasma concentrations of protein, albumin, or Ca or in plasma alkaline phosphatase activity. Values for glomerular filtration rate did not change in any group during the experiment.(ABSTRACT TRUNCATED AT 250 WORDS)