Sex hormone status may modulate rate of expansion of proximal femur diameter in older women alongside other skeletal regulators

CONTEXT

Little is known of associations between hip geometry and skeletal regulators. This is important because geometry is a determinant of both hip function and resistance to fracture.

OBJECTIVE

We aimed to determine the effects of sex hormone status and other candidate regulators on hip geometry and strength.

SUBJECTS AND METHODS

A random sample of 351 women aged 67-79 had two to four hip dual-energy x-ray absorptiometry scans performed over 8 yr of follow-up. Hip structural analysis software was used to measure subperiosteal diameter (PD) and the distance from the center of mass to the lateral cortical margin (d-lat) on three 5-mm-thick cross-sectional regions: narrow neck, intertrochanter, and shaft. Section modulus (Z), bone mineral density (grams per centimeter squared), and an index of bone mineral content (cross-sectional area) were calculated as estimators of bone strength. Serum analytes measured at baseline included SHBG, estradiol, PTH, creatinine, albumin, vitamin D metabolites, and glutamate- and gamma-carboxyglutamate-osteocalcin (OC). A linear mixed model was used to model associations with predictor variables, including testing whether the predictors significantly modified the effect of aging.

RESULTS

Aging was associated with increasing PD and d-lat, and higher baseline SHBG significantly modified this effect, in the case of PD, increasing the rates of change at the narrow neck region by 19% for SHBG level 2 sd higher than population mean (P = 0.026). Higher baseline creatinine was independently associated with faster increases in PD and d-lat with aging (P < 0.041). Z declined faster with aging if baseline PTH was higher, and higher albumin had a contrary effect. Z was positively associated with free estradiol and inversely associated with SHBG and glutamate-OC.

CONCLUSION

These results show large effects of SHBG on the regulation of proximal femur expansion and bending resistance, probably acting as a surrogate for low bioavailable estrogen. Potentially important effects for fracture resistance in old age were also revealed for PTH, markers related to renal function and the nutritional markers albumin and undercarboxylated OC.

A prospective study of change in bone mineral density over one year in adults with cystic fibrosis

BACKGROUND

Low bone mineral density (BMD) is prevalent in adults with cystic fibrosis. To identify appropriate therapeutic strategies and the optimal time for intervention, it is necessary to document the natural history of cystic fibrosis related low BMD.

METHODS

114 adults with cystic fibrosis underwent bone densitometry a median (25-75% interquartile range) of 12 (12-13) months after initial assessment of bone density. BMD was measured in the lumbar spine, femoral neck, total hip, and distal forearm on recruitment to the trial and at follow up.

RESULTS

In patients <or=24 years of age (n=55, mean (SD) age 19.5 (2.6) years) in whom an annual increase in BMD would normally be expected, BMD increased by a mean (95% CI) 2.9% (1.6 to 4.2) per year in the distal forearm (p<0.001), but decreased by 2.5% (95% CI -3.8 to -1.2) per year in the femoral neck (p<0.001) and by 2.2% (95% CI -3.3 to -1.0) per year in the total hip (p<0.001). In patients >or=25 years of age (n=59, mean (SD) age 30.3 (5.4) years) in whom no annual change in BMD would normally be expected, BMD decreased by 1.9% (95% CI -2.9 to -0.8) per year in the femoral neck (p<0.001), by 1.5% (95% CI -2.4 to -0.6) per year in the total hip (p=0.001), and by 0.8% (95% CI -1.5 to -0.1) per year in the distal forearm (p=0.026). There was no significant annual change in lumbar spine BMD in either patient cohort.

CONCLUSIONS

Reduced rates of bone accretion and accelerated rates of bone loss explain the high prevalence of low BMD in adults with cystic fibrosis.

The impact of atmospheric pollution on vitamin D status of infants and toddlers in Delhi, India

AIMS

To compare the vitamin D status of 34 children, 9-24 months old, living in an area of Delhi renowned for high levels of atmospheric pollution (Mori Gate), with a comparable age matched group of children from a less polluted (Gurgaon) area of the city.

METHODS

Serum concentrations of calcium, alkaline phosphatase (ALP), parathyroid hormone (PTH), 25-hydroxyvitamin D (25(OH)D), and 1,25-dihydroxyvitamin D (1,25(OH)2D) were measured. Haze scores, regarded as a surrogate marker of solar UVB radiation reaching ground level, were measured in both areas.

RESULTS

Mean 25(OH)D of children in the Mori Gate area was 12.4 (7) ng/ml, compared with 27.1 (7) ng/ml in children living in the Gurgaon area (p < 0.001). The median ALP (p < 0.05) and mean PTH (p < 0.001) concentrations were higher in children living in the Mori Gate area than in the Gurgaon area. The mean haze score in the Mori Gate area (2.1 (0.5)) was significantly lower (p < 0.05) than in the Gurgaon area (2.7 (0.4)), indicating less solar UVB reaching the ground in Mori Gate.

CONCLUSION

We suggest that children living in areas of high atmospheric pollution are at risk of developing vitamin D deficiency rickets and should be offered vitamin D supplements.

Bisphosphonates in the treatment of Charcot neuroarthropathy: a double-blind randomised controlled trial

AIMS/HYPOTHESIS

The management of charcot neuroarthropathy, a severe disabling condition in diabetic patients with peripheral neuropathy, is currently inadequate with no specific pharmacological treatment available. We undertook a double-blind randomised controlled trial to study the effect of pamidronate, a bisphosphonate, in the management of acute diabetic Charcot neuroarthropathy.

METHODS

Altogether 39 diabetic patients with active Charcot neuroarthropathy from four centres in England were randomised in a double-blind placebo-controlled trial. Patients received a single infusion of 90 mg of pamidronate or placebo (saline). Foot temperatures, symptoms and markers of bone turnover (bone specific alkaline phosphatase and deoxypyridinoline crosslinks) were measured over the 12 months, in 10 visits. All patients also had standard treatment of the Charcot foot.

RESULTS

Mean age of the study group (59 % Type II (non-insulin-dependent) diabetes mellitus) was 56.3 +/- 10.2 years. The mean temperature difference between active and control groups was 3.6 +/- 1.7 degrees C and 3.3 +/- 1.4 degrees C, respectively. There was a fall in temperature of the affected foot in both groups after 2 weeks with a further reduction in temperature in the active group at 4 weeks (active and placebo vs baseline; p = 0.001; p = 0.01, respectively), but no difference was seen between groups. An improvement in symptoms was seen in the active group compared with the placebo group (p < 0.001). Reduction in bone turnover (means +/- SEM) was greater in the active than in the control group. Urinary deoxypyridinoline in the pamidronate treated group fell to 4.4 +/- 0.4 nmol/mmol creatinine at 4 weeks compared with 7.1 +/- 1.0 in the placebo group (p = 0.01) and bone-specific alkaline phosphatase fell to 14.1 +/- 1.2 u/l compared with 18.6 +/- 1.6 u/l after 4 weeks, respectively (p = 0.03).

CONCLUSION/INTERPRETATION

The bisphosphonate, pamidronate, given as a single dose leads to a reduction in bone turnover, symptoms and disease activity in diabetic patients with active Charcot neuroarthropathy.

Effect of intravenous pamidronate on bone mineral density in adults with cystic fibrosis

BACKGROUND

Low bone mineral density (BMD) is prevalent in adults with cystic fibrosis. The aim of this study was to assess the effect of intravenous pamidronate on BMD in these subjects.

METHODS

Patients were invited to participate if they had a BMD Z score of -2 or less in the lumbar spine, proximal femur, or distal forearm. Patients were randomised to receive either 30 mg intravenous pamidronate every 3 months + 1 g calcium daily (pamidronate group) or 1 g calcium daily (control group). All pancreatic insufficient patients were prescribed oral vitamin D supplements.

RESULTS

After 6 months of treatment the pamidronate group (n=13) showed a significant increase in absolute BMD compared with the control group (n=15) in the lumbar spine (mean difference 5.8% (CI 2.7% to 8.9%)) and total hip (mean difference 3.0% (CI 0.3% to 5.6%)). However, the pamidronate group showed a reduction in BMD compared with the control group in the distal forearm (mean difference -1.7% (CI -3.7% to 0.3%)). The use of pamidronate was associated with a high incidence of bone pain in non-corticosteroid treated individuals.

CONCLUSION

Intravenous pamidronate increases axial BMD in adults with cystic fibrosis, but the high incidence of bone pain associated with this treatment might limit its use.

Vitamin D nutrition and bone disease in adults

The consequences of vitamin D deficiency upon the skeleton are well known and management in the absence of renal failure is relatively straightforward. Vitamin D, either by mouth or parenterally will correct the deficiency and heal the osteomalacia. The mechanisms underlying the causation of vitamin D deficiency are now better understood and indicate the importance of underlying calcium malabsorption and secondary hyperparathyroidism leading to 1,25(OH)2D-induced catabolism of 25(OH)D and possibly also of vitamin D itself. In such situations, e.g., gastrointestinal and pancreaticobiliary disease, calcium supplementation in addition to vitamin D is indicated. The reasons behind nutritional vitamin D deficiency and the possible role of meat in protecting from osteomalacia await further elucidation, but from epidemiological studies, calcium deficiency, per se, is not implicated in the etiopathogenesis. The concept of vitamin D insufficiency is poorly understood, and difficult to define since a single value or close range of serum 25(OH)D values is unlikely to predict the needs of all subjects. Oral calcium intake and renal function are also likely to be relevant to the level of 25(OH)D which is found to be sufficient or insufficient for any given individual to maintain a normal serum calcium level without secondary hyperparathyroidism. There is increasing evidence that vitamin D insufficiency, by leading to sustained hyperparathyroidism, is prejudicial to the skeleton, particularly cortical bone. Since it is without symptoms until fractures occur, it should be actively sought in those clinical situations now recognized as contributing to risk. It can only be identified by the periodic measurement of serum 25(OH)D and the calcitropic hormones PTH and 1,25(OH)2D. In addition, BMD should be measured in a predominantly cortical site such as the proximal forearm, as well as the more conventional sites of spine and hip. The implications of these recommendations are an increase in the use of assays for PTH and vitamin D metabolites in the groups of subjects discussed in this review. Patients with chronic malabsorption states might reasonably be expected to have measurements performed twice-yearly. When vitamin D insufficiency is found, treatment with either vitamin D, calcium or both will be necessary, depending on the etiology of the insufficiency state in the inividual. In some malabsorptive states, calcium malabsorption is the cause of hyperparathyroidism and oral calcium alone can be used to reverse excess PTH activity in those with an adequate state of vitamin D nutrition. However, even in those vitamin D replete individuals, vitamin D catabolism will be enhanced and a small additional oral dose of vitamin D can do no harm. Regular monitoring of PTH and vitamin D metabolites will remain a necessity to ensure continued efficacy of treatment. Current recommendations for dietary supplements of vitamin D are clearly inadequate [61]. There is compelling evidence for supplements of 800 IU per day in the elderly and other high risk populations. Such a dose is safe and without side effects. The available evidence suggests that this should be combined with calcium supplements of 1200 mg/day [19] and that the current UK recommendations for a daily calcium intake of 700 mg contrast with those from the USA at 1,200 mg for people over 50 years old. Physicians need to be aware of both the small but important problem of vitamin D depletion and osteomalacia with its sometimes ambiguous presentation, and the more common but covert vitamin D (and calcium) insufficiency with its widespread and varied clinical associations.

The role of insulin-like growth factor I in age-related changes in calcium homeostasis in men

The aim of this study was to evaluate hormonal influences on age-related changes in calcium homeostasis in men. We recruited 178 healthy men, ages 20-79 (about 30 per decade). We measured serum calcium, phosphate, urinary calcium, and creatinine clearance. Dietary calcium intake and use of fish oils were determined by questionnaire. Fractional calcium absorption was estimated using the stable strontium technique in a subgroup of 60 men. PTH, 1, 25-dihydroxyvitamin D [1,25(OH)(2)D], 25-hydroxyvitamin D (25OHD), serum insulin-like growth factor I (IGF-I), and testosterone were measured in all men. There was no change in serum calcium with age. There were decreases in serum phosphate, urinary calcium, and creatinine clearance with age (P: < 0.02). Dietary calcium was unchanged. Strontium absorption decreased (P: < 0.01), and PTH increased (P: < 0.001) with age. The data for 1,25OH(2)D were biphasic, reaching a peak at age 55 yr (P: = 0.003). There was a linear increase in 25OHD with age (P: = 0.009) that persisted after correcting for seasonal variation and was positively associated with fish oil use, therefore, the age-related changes in 25OHD were masked by self medication. There were log-linear decreases in IGF-I and testosterone with age (P: < 0.0001). Strontium absorption was not related to 25OHD or 1,25(OH)(2)D, but was positively correlated with IGF-I. 1,25(OH)(2)D correlated negatively with serum phosphate and calcium, but not PTH or creatinine clearance. IGF-I was positively associated with creatinine clearance, serum calcium, and phosphate and negatively associated with PTH (P: < 0.001). In this cross-sectional study of otherwise healthy, normally aging men, age-related decreases in IGF-I seem to have a greater impact on mineral absorption than does vitamin D status.

Down-regulation of human osteoblast PTH/PTHrP receptor mRNA in end-stage renal failure

BACKGROUND

Resistance to the action of parathyroid hormone (PTH) has been demonstrated in end-stage renal failure and is considered to be important in the pathogenesis of secondary hyperparathyroidism. The mechanism of resistance is unknown. However, altered regulation of cellular PTH/PTH-related protein (PTH/PTHrP) receptor (PTH1R) has been assumed to be important.

METHODS

We have used in situ hybridization to examine PTH1R mRNA expression by osteoblasts in human bone and have compared the expression in high- and low-turnover renal bone disease, high-turnover nonrenal bone disease (healing fracture callus and Pagetic bone), and normal bone. Bone biopsies were formalin fixed, ethylenediaminetetraacetic acid decalcified, and paraffin wax embedded. A 1.8 kb PTH1R cDNA probe, labeled with 35S, was used, and the hybridization signal was revealed by autoradiography. The density of signal over osteoblasts was quantitated using a semiautomated Leica image analysis software package.

RESULTS

The mean density of PTH1R mRNA signal over osteoblasts in renal high-turnover bone was only 36% of that found in nonrenal high-turnover bone (P < 0.05) and 51% of that found in normal bone (P < 0.05). Osteoblast PTH1R mRNA signal in adynamic bone from individuals with diabetes mellitus was 28% of normal bone (P < 0.05) and 54% of that found in renal high-turnover bone (P < 0.05).

CONCLUSIONS

These results demonstrate a down-regulation of osteoblast PTH1R mRNA in end-stage renal failure in comparison to normal and high-turnover bone from otherwise healthy individuals, and provide an insight into the mechanisms of "skeletal resistance" to the actions of PTH.

1 alpha,25-dihydroxyvitamin D(3) inhibits angiogenesis in vitro and in vivo

Modulation of angiogenesis is now a recognized strategy for the prevention and treatment of pathologies categorized by their reliance on a vascular supply. The purpose of this study was to evaluate the effect of 1 alpha,25-dihydroxyvitamin D(3) [1, 25(OH)(2)D(3)], the active metabolite of vitamin D(3), on angiogenesis by using well-characterized in vitro and in vivo model systems. 1,25(OH)(2)D(3) (1 x 10(-9) to 1 x 10(-7) mol/L) significantly inhibited vascular endothelial growth factor (VEGF)-induced endothelial cell sprouting and elongation in vitro in a dose-dependent manner and had a small, but significant, inhibitory effect on VEGF-induced endothelial cell proliferation. 1, 25(OH)(2)D(3) also inhibited the formation of networks of elongated endothelial cells within 3D collagen gels. The addition of 1, 25(OH)(2)D(3) to endothelial cell cultures containing sprouting elongated cells induced the regression of these cells, in the absence of any effect on cells present in the cobblestone monolayer. Analysis of nuclear morphology, DNA integrity, and enzymatic in situ labeling of apoptosis-induced strand breaks demonstrated that this regression was due to the induction of apoptosis specifically within the sprouting cell population. The effect of 1,25(OH)(2)D(3) on angiogenesis in vivo was investigated by using a model in which MCF-7 breast carcinoma cells, which had been induced to overexpress VEGF, were xenografted subcutaneously together with MDA-435S breast carcinoma cells into nude mice. Treatment with 1,25(OH)(2)D(3) (12.5 pmol/d for 8 weeks) produced tumors that were less well vascularized than tumors formed in mice treated with vehicle alone. These results highlight the potential use of 1,25(OH)(2)D(3) in both the prevention and regression of conditions characterized by pathological angiogenesis.

Altered calbindin mRNA expression and calcium regulating hormones in rat diabetic pregnancy

Offspring of rats with diabetes mellitus are at risk of reduced calcium and bone mineral content. Altered expression of the maternal calcium binding proteins, calbindin-D(9K) and calbindin-D(28K), which are involved in renal and placental calcium transport, may underlie these problems.We have investigated the effect of diabetes on circulating concentrations of regulatory hormones with respect to calbindin-D mRNA concentrations. Three rat groups were studied; control (CP), streptozotocin-induced diabetic (DP), and insulin-treated diabetic (DPI) pregnant rats. Calbindin-D(9K) and calbindin-D(28K) mRNA abundance in placenta and maternal kidney were measured at days 7, 15, 18 and 21 of gestation, together with serum or plasma concentrations of 1,25 dihydroxyvitamin D(3) (1, 25(OH)(2)D(3)), parathyroid hormone (PTH), PTH-related protein (PTHrP), calcitonin, oestradiol and IGF-I. An increase in placental calbindin-D(9K) mRNA abundance between days 18 and 21 in CP and DPI rats was severely blunted in the DP rats. In contrast, renal calbindin-D(28K) mRNA abundance was greater at days 7, 15 and 18 in DP compared with CP rats, as was calbindin-D(9K) at day 18. Calcitonin concentrations showed no differences between the groups, and both PTH and IGF-I were reduced over the first half of gestation, unlike the calbindins. In contrast, the concentrations of PTHrP and 1,25(OH)(2)D(3) were reduced at term in the DP group compared with the other two groups. Plasma oestradiol concentrations were lower in DP than in CP rats at days 7, 15 and 18, and most striking was the absence in DP rats of the peak of oestradiol seen at day 18 in CP rats. Despite the similarity between changes in placental calbindin mRNA and 1,25(OH)(2)D(3), previous work has shown placental calbindin-D(9K) regulation to be vitamin-D-independent. These studies produce suggestive evidence, therefore, that PTHrP and oestradiol may be involved in the altered calbindin-D expression by kidney and placenta in rat diabetic pregnancy.

Low bone mineral density in adults with cystic fibrosis

BACKGROUND

Patients with cystic fibrosis have several risk factors for the development of low bone mineral density (BMD). To identify the prevalence and clinical correlates of low BMD in adult patients with cystic fibrosis, densitometry was performed in 151 patients (83 men) aged 15-52 years.

METHODS

BMD was measured in the lumbar spine (L1-4) using dual energy x ray absorptiometry (DXA) and quantitative computed tomography (QCT). It was also measured in the proximal femur (total hip and femoral neck) using DXA, and in the distal and ultra distal forearm using single energy x ray absorptiometry (SXA). Biochemical markers of bone turnover, vitamin D levels, parathyroid hormone levels, and a variety of anthropometric variables were also assessed.

RESULTS

The mean (SD) BMD Z score was -0.73 (0.85) in the distal forearm, -0.31 (0.92) in the ultra distal forearm, -1.21 (1. 18) in the lumbar spine using DXA, -0.56 (1.36) in the lumbar spine using QCT, -1.25 (1.30) in the femoral neck, and -1.01 (1.14) in the total hip. 34% of patients had a BMD Z score of -2 or less at one or more skeletal sites. Body mass index (0.527, p = 0.01), percentage predicted forced expiratory volume in one second (0.388, p = 0.01), and physical activity (0.249, p = 0.05) were positively related to the mean BMD Z score. Levels of C reactive protein (-0.328, p = 0. 01), parathyroid hormone (-0.311, p = 0.01) and biochemical markers of bone turnover (osteocalcin -0.261 and bone specific alkaline phosphatase -0.249, p = 0.05) were negatively related to the mean BMD Z score. Vitamin D insufficiency (25-hydroxyvitamin D <15 ng/ml) was prevalent (53/139 patients, 38%) despite supplementation with 900 IU vitamin D per day.

CONCLUSIONS

Low bone density is prevalent in adult patients with cystic fibrosis. Current levels of vitamin D supplementation appear to be inadequate.

Hip fracture and bone histomorphometry in a young adult with cystic fibrosis

A 25-yr-old male with cystic fibrosis sustained a fragility fracture of the left femoral neck, which required surgical correction. He had several risk factors for the development of low bone density and despite treatment with an oral bisphosphonate, his bone mineral density reduced further. The patient died 2 yrs after sustaining the fracture. Bone specimens obtained at post mortem demonstrated severe cortical and trabecular osteopenia, but the histological features were not typical of osteoporosis or osteomalacia. Osteoporosis is thought to be a common complication of cystic fibrosis. The novel histomorphometric appearances reported here suggest that the bone disease of cystic fibrosis may be more complex and possibly unique. Labelled bone biopsies are required to clarify the bone defect leading to low bone density in cystic fibrosis patients so that appropriate therapeutic strategies can be developed.

Autocrine control of vitamin D metabolism in synovial cells from arthritic patients

OBJECTIVE

This study was designed to investigate whether 1, 25-dihydroxyvitamin D3 (1,25-(OH)2D3), produced by activated synovial fluid macrophages, promotes its own catabolism by upregulating vitamin D-24-hydroxylase (24-OHase) in synovial fibroblasts through a vitamin D receptor (VDR) mediated mechanism.

METHODS

Synovial macrophages and fibroblasts were derived from patients with rheumatoid arthritis. Expression of VDR and 24-OHase mRNAs was determined using in situ hybridisation. Vitamin D hydroxylase activity was determined by incubating cells with [3H]-25-(OH)D3, or [3H]-1,25-(OH)2D3, and metabolite synthesis quantified using high performance liquid chromatography.

RESULTS

1, 25-(OH)2D3 increased expression of mRNA for both VDR and 24-OHase in fibroblasts by approximately threefold over 24 hours. 1,25-(OH)2D3 increased fibroblast 24-OHase activity, yielding 24-hydroxylated, and more polar, metabolites. In co-culture, fibroblasts were able to catabolise macrophage derived 1,25-(OH)2D3.

CONCLUSIONS

1, 25-(OH)2D3 is produced by macrophages in vitro at biologically relevant concentrations and can increase its own catabolism by synovial fibroblasts; this effect is probably mediated via upregulation of both synovial fibroblast VDR and 24-OHase.

Prostaglandin E2 regulates vitamin D receptor expression, vitamin D-24-hydroxylase activity and cell proliferation in an adherent human myeloid leukemia cell line (Ad-HL60)

The effects of prostaglandin E2, forskolin, and phorbol 12-myristate 13-acetate on cell proliferation, cell surface antigen expression, vitamin D-24-hydroxylase activity and vitamin D receptor (VDR) expression have been studied in an adherent variant (Ad-HL60) of the human HL60 promyelomonocytic leukemia cell line. Ad-HL60 cells have a more differentiated phenotype than the nonadherent HL60 cells from which they were derived and, unlike the parent cell line, constitutively express vitamin D-24-hydroxylase activity. Treatment of Ad-HL60 cells with 1 microM PGE2 resulted in a decrease in the rate of cell proliferation (cell numbers were approximately 23% of control values after 72 h treatment), a change in expression of leukocyte surface antigens (decreased CD13 and CD14, increased CD11b and CD49d expression), an increase in the synthesis of 24,25-dihydroxyvitamin D3 from substrate 25-hydroxyvitamin D3 (control 5.76 +/- 0.17, 72 h PGE2-treated cells 12.10 +/- 1.90 pmol/h/10(6) cells), and an increase in receptors for the active metabolite of vitamin D, 1 alpha,25-dihydroxyvitamin D3, from 3910 to 11285 receptors per cell in control and 7-day treated cells, respectively. Prostaglandin E2 may be acting via a mechanism involving cyclic AMP in these cells, as we have also demonstrated that 10 microM forskolin, an adenylate cyclase activator, has similar effects. Phorbol 12-myristate 13-acetate had little effect on any of the parameters measured in this cell line.

Novel mutations in the 1alpha-hydroxylase (P450c1) gene in three families with pseudovitamin D-deficiency rickets resulting in loss of functional enzyme activity in blood-derived macrophages

Pseudovitamin D-defiency rickets (PDDR) is an autosomal recessive disorder characterized by hypocalcemia, rickets (which are resistant to treatment with vitamin D), and low or undetectable serum levels of 1,25-dihydroxyvitamin D (1,25(OH)2D). The symptoms are corrected with 1,25(OH)2D treatment, and the disease is now believed to result from a defect in the cytochrome P450 component (P450c1; CYP27B1) of the renal 25-hydroxyvitamin D-1alpha-hydroxylase (1-OHase). We have studied genomic DNA from three families with PDDR and have identified the same homozygous mutation in the P450c1 gene in two of the index cases, causing a frameshift in exon 8, resulting in a premature stop codon in the heme-binding domain. The two cases in the third kindred were compound heterozygotes with missense mutations in exons 6 and 9. We have also identified a C/T polymorphism in intron 6 of the P450c1 genomic DNA. Interferon gamma-inducible 1-OHase activity in blood-derived macrophages was shown by 1,25(OH)2D synthesis in all control cells tested (37-184 fmol/h/106 cells) and those from the PDDR family parents (34-116 fmol/h/106 cells) but was totally absent from the patients' cells, indicating a defect in their macrophage 1-OHase, similar to the presumed renal defect. The assumption of similarity between the renal and macrophage P450c1 was supported by our ability to clone a 514 bp sequence, including the heme-binding region of the macrophage P450c1 cDNA from controls, which was identical to that published for both the renal and keratinocyte P450c1 cDNAs.

Bone loss in celiac disease is related to secondary hyperparathyroidism

Celiac disease is a major cause of intestinal malabsorption. Previous studies have demonstrated that celiac disease is associated with significant osteoporotic bone loss. These studies have suggested that successful treatment of the malabsorption is associated with amelioration of the bone loss. Such studies have failed to examine bone mass at peripheral skeletal sites which is more likely to be responsive to changes in parathyroid hormone (PTH) in response to calcium malabsorption. We have examined bone density in the lumbar spine, femoral neck, and distal forearm in 35 patients with celiac disease who had been established on gluten-free diet. In addition, the concentrations of PTH and 1,25-dihydroxyvitamin D (1,25(OH)2D) were measured. Bone density was below that expected for the subject's age and gender at all sites. This was most marked in the distal forearm where the bone density was 1.40 SD below expected (p < 0.0001). In the forearm, there was a negative relationship between bone density and PTH concentration (r = -0.49, p = 0.009). In the forearm and lumbar spine, there was a negative relationship between 1,25(OH)2D concentration and bone density. Bone mass was not related to the concentration of 25-hydroxyvitamin D at any of the skeletal sites measured. Bone density is reduced in the peripheral skeleton in celiac disease and this deficit persists despite treatment with apparent normalization at axial skeletal sites. This reduction in bone mass is related to the presence of secondary hyperparathyroidism which should be sought in all patients with treated celiac disease.

Expression of genes involved in calcium absorption in human duodenum

BACKGROUND

The role of vitamin D metabolites in the regulation of expression of genes involved in dietary calcium absorption by the human intestine remains poorly understood despite much work in animals.

MATERIALS AND METHODS

To investigate this, we measured the expression of transcripts for two of these genes, calbindin-D9k and the basolateral membrane calcium pumping ATPase, PMCA1, in duodenal endoscopic biopsies from 40 subjects. Northern blots were hybridized with previously characterized probes, and the signal was quantified by phosphor imaging. These transcript levels were related to circulating vitamin D metabolites and also analysed according to the vitamin D receptor gene TaqI polymorphism determined in DNA from blood.

RESULTS

Plasma 1,25-dihydroxycholecalciferol correlated significantly with calbindin-D9k RNA (r = 0.4, P < 0.02) but not with PMCA1. Plasma 25-OH-cholecalciferol was not correlated with transcripts for either gene and, furthermore, the mean levels of these transcripts did not differ significantly when grouped by vitamin D receptor genotype.

CONCLUSION

In normal humans, 1, 25-dihydroxycholecalciferol has a small but significant relationship to duodenal expression of calbindin-D9k, but not to PMCA1 expression.

Vitamin D receptors in the rheumatoid lesion: expression by chondrocytes, macrophages, and synoviocytes

OBJECTIVES

The active form of vitamin D3, 1 alpha,25 dihydroxyvitamin D3 (1,25D3), through its interaction with vitamin D receptors (VDR), is reported to effect a variety of anabolic and catabolic events, especially in bone and cartilage tissues. As cartilage degradation and tissue remodelling are characteristic features of the rheumatoid lesion, the distribution and expression of VDR at sites of cartilage erosion was examined.

METHODS

Immunolocalisation techniques using a rat monoclonal antibody to VDR and an alkaline phosphatase conjugated avidin/biotin detection system were used to examine VDR in 18 specimens of cartilage-pannus junction, 10 specimens of rheumatoid synovium or cartilage tissue, and four primary cultures of adherent rheumatoid synovial cells (RSC). For comparison, VDR expression was examined in 10 specimens of normal, healthy age matched articular cartilage.

RESULTS

VDR was demonstrated in 15 of 18 cartilage-pannus junctions either at the interface (8 of 18), within the pannus tissue (12 of 18), and by chondrocytes often close to the erosive lesion (10 of 18). All the rheumatoid synovial tissue and 5 of 10 cartilage specimens showed cells with positive staining, but the extent of this was variable. Negligible VDR staining was observed for normal cartilage. Primary cultures of RSC also showed variability in both the numbers and proportions of macrophages or synovial fibroblasts stained for VDR (range 10-50%), this being more common in cultures with a high proportion of macrophages.

CONCLUSIONS

VDR expression has been demonstrated by most specimens of cartilage-pannus junction; was associated with various cell types, including chondrocytes, but not exclusively with CD68+ macrophages. The focal nature of VDR expression within the rheumatoid lesion suggests a contributory role for 1 alpha,25D3 in the pathophysiological processes of rheumatoid arthritis.

Surface-associated protein from Staphylococcus aureus stimulates osteoclastogenesis: possible role in S. aureus-induced bone pathology

OBJECTIVE

Staphylococcus aureus is the cause of bone destruction in osteomyelitis, bacterial arthritis and orthopaedic implant failure. We have previously shown that gentle saline extraction of S. aureus has revealed the presence of an extremely potent stimulator of osteoclast activation in both the murine calvarial bone resorption assay and the isolated chick osteoclast resorption assay. In order to investigate the mechanism of action of this surface-associated material (SAM), we have investigated its capacity to recruit osteoclasts.

METHODS

The murine bone marrow osteoclast recruitment assay was used. The ability of the recruited cells to resorb dentine slices was also investigated. Results. The SAM from S. aureus dose dependently stimulated tartrate-resistant acid phosphatase (TRAP)-positive osteoclast formation and pit formation on dentine slices. Neutralization of the cytokines tumour necrosis factor alpha and interleukin (IL)-6 totally inhibited, but antagonism of IL-1 only partially blocked, the stimulated maturation of osteoclast-like cells.

CONCLUSION

These findings suggest that bone destruction associated with local infection by S. aureus is due to the stimulation of osteoclast formation induced by the action of the easily solubilized SAM, and could explain the large numbers of osteoclasts found in infarcted bone in osteomyelitis.

Detection of canine distemper virus in 100% of Paget's disease samples by in situ-reverse transcriptase-polymerase chain reaction

Previous evidence implicating paramyxoviruses in the aetiopathology of Paget's disease of bone has been controversial. While several groups have demonstrated the presence of paramyxoviruses using electron microscopy, immunohistochemistry, and molecular biological techniques, others have found no evidence of viruses using reverse transcriptase-polymerase chain reaction (RT-PCR). We have previously provided evidence that canine distemper virus (CDV) is present in approximately 65% of samples of pagetic bone, using in situ hybridization and RT-PCR; however, these results have been criticized. To further investigate the possible Role of CDV, we have now developed the technique of in situ-RT-PCR (IS-RT-PCR) to examine for the presence of CDV-nucleocapsid (CDV-N) ribonucleic acid (RNA) in pagetic bone. Control samples consisted of uninvolved sites from patients with the disease, normal bone, and several active remodeling states. IS-RT-PCR was optimized to detect CDV-N using distemper-infected vero cells. The specificity of the technique was confirmed using vero cells infected with CDV, which showed amplified signal following IS-RT-PCR, and cells infected with measles virus (MV), in which no positive signal for CDV was detected by IS-RT-PCR. Following conventional in situ hybridization, CDV-N was detectable in 10 of 15 pagetic bone samples. However, after five, and particularly 10, cycles of IS-RT-PCR, CDV-N was found in all 15 samples. There was no evidence of CDV in four samples from uninvolved sites from pagetic patients, or in any of the other control samples. In this study, using the novel technique of IS-RT-PCR, CDV was found to be present in 100% of pagetic samples examined. There was no evidence of the virus in any of the control samples, including samples of bone from uninvolved sites from patients with Paget's disease. These results provide additional proof that CDV is present within pagetic bone and further support the hypothesis that paramyxoviruses are involved in the etiopathology of Paget's disease.

Ascorbic acid-induced chondrocyte terminal differentiation: the role of the extracellular matrix and 1,25-dihydroxyvitamin D

Chondrocyte terminal differentiation is associated with cellular hypertrophy increased activity of plasma membrane alkaline phosphatase and the synthesis of collagen type X. The hypertrophic phenotype of cultured chondrocytes can be stimulated by ascorbic acid but the underlying mechanisms for this phenotypic change are unclear. As ascorbic acid is central to many hydroxylation reactions, the possibility was examined that its pro-differentiating effects are mediated by its effects on collagen and vitamin D metabolite formation. In vitro studies indicated that ascorbic acid-induced chondrocyte alkaline phosphatase activity was inhibited by the addition of both collagen and proteoglycan synthesis inhibitors. The addition of arginine-glycine-aspartic acid (RGD)-containing peptides also resulted in lower alkaline phosphatase activity. Chicks supplemented with dietary ascorbic acid had higher concentrations of both collagen and proteoglycans within their growth plates but the chondrocyte maturation rate was unaltered. No evidence was obtained to suggest that ascorbic acid-induced collagen production was mediated by lipid peroxidation. In addition, supplementation with dietary ascorbic acid resulted in higher serum 1,25-dihydroxyvitamin D3 concentrations and increased chondrocyte vitamin D receptor number. Ascorbic acid-treated chondrocytes maintained in vitro also had increased vitamin D receptor numbers but chondrocyte receptor affinity for 1,25-dihydroxyvitamin D3 was unaltered. These results indicate that ascorbic acid promotes both chondrocyte matrix production and 1,25-dihydroxyvitamin D3 synthesis, accompanied by upregulation of the vitamin D receptor. Thus, ascorbic acid may be causing amplification of the vitamin D receptor-dependent genomic response to 1,25-dihydroxyvitamin D, resulting in promotion of terminal differentiation. Strong evidence is provided to support the hypothesis that ascorbic acid-induced chondrocyte terminal differentiation is mediated by interactions between integrins and RGD-containing cartilage matrix proteins.

Unique 24-hydroxylated metabolites represent a significant pathway of metabolism of vitamin D2 in humans: 24-hydroxyvitamin D2 and 1,24-dihydroxyvitamin D2 detectable in human serum

We have produced evidence for a new metabolic pathway for vitamin D2 in humans involving the production of 24-hydroxyvitamin D2 (24OHD2) and 1,24-dihydroxyvitamin D2 [1,24-(OH)2D2]. These metabolites were produced after either a single large dose (10(6) IU) of vitamin D2 or repeated daily doses between 10(3) and 5 x 10(4) IU. We developed assay systems for the metabolites in human serum and showed that in some chronically treated patients, the concentration of 1,24-(OH)2D2 equalled that of 1,25-(OH)2D2 at about 100 pmol/L. The metabolites were identified by high performance liquid chromatography with diode array spectrophotometry for 24OHD2 and by high resolution gas chromatography-mass spectrometry for 1,24-(OH)2D2. We show that 1,24-(OH)2D2 synthesis can be stimulated by PTH, indicating a renal origin for this metabolite and postulate that it is formed from 24OHD2, which may be synthesized in liver. We conclude from this study that vitamin D2 gives rise to two biologically active products, 1,24-(OH)2D2 and 1,25-(OH)2D2, and that 1,24-(OH)2D2 could be an attractive naturally occurring analog of 1,25-(OH)2D3 for clinical use.

A novel cyclic adenosine monophosphate analog induces hypercalcemia via production of 1,25-dihydroxyvitamin D in patients with solid tumors

The treatment of cancer patients with conventional chemotherapy is sometimes associated with severe systemic toxicity and only a minimal survival benefit. Because of this, new less toxic and more efficacious treatments have been sought. 8-Chloro-cAMP (8-Cl-cAMP) is one of a new generation of anticancer drugs that act at the level of signal transduction. In preclinical models, 8-Cl-cAMP modulates protein kinase A (PKA) leading to growth inhibition and increased differentiation of cancer cells. 8-Cl-cAMP was given to 16 patients with advanced cancer as an infusion via an indwelling subclavian venous catheter. We showed that 8-Cl-cAMP had a parathyroid hormone-like effect leading to increased synthesis of renal 1,25-dihydroxyvitamin D [up to 14 times the baseline value, median 3.6 times; P = 0.00001 (Student's paired t test)]. This produced the dose-limiting toxicity of reversible hypercalcemia that could not be controlled by the administration of either pamidronate or dexamethasone. The treatment was otherwise well tolerated, and other cAMP-dependent pathways (cortisol and TSH) were not affected, emphasizing the marked differences between organs in their sensitivity to this cAMP analog. Our results have shown that 8-Cl-cAMP is biologically active, and it is feasible that if the hypercalcemia can be controlled, then this drug may have a role as a single agent, or as a short infusion between cycles of chemotherapy.

Measurement of plasma 1,25 dihydroxyvitamin D using a novel immunoextraction technique and immunoassay with iodine labelled vitamin D tracer

We evaluated a novel assay for the measurement of 1,25 dihydroxyvitamin D (1,25 (OH)2D). Immunoextraction of 1,25(OH)2D is performed using a mini column containing a solid-phase monoclonal antibody followed by radioimmunoassay (RIA) using an 125I-labelled 1,25(OH)2D derivative tracer and Sac-cell separation. The mean recovery of 1,25(OH)2D3 was 101%, linearity was excellent, inter- and intra-assay coefficients of variation were 9, 8 and 13% and 11, 10 and 14% at low, medium and high concentrations of 1,25 (OH)2D3, respectively. The cross-reactivity of vitamin D metabolites was < 0.0015% for 25-hydroxyvitamin D3, 24, 25 dihydroxyvitamin D3 and dihydrotachysterol and 0.54% for 1 alpha calcidol. 1,25 dihydroxyvitamin D2 cross-reactivity was 79%. The detection limit of the assay was 5 pmol/L. Comparison with a commercial radio receptor assay (RRA) and an in-house RIA gave regression equations of y = 0.94x + 11.8 (r = 0.98) and y = 0.91x-1.7 (r = 0.95), respectively, with no major discrepancies between the methods in all patient groups studied. Plasma concentrations of 1,25(OH)2D obtained with the assay were as follows: normal, unsupplemented subjects: mean 88, range 48-155 pmol/L, n = 68, patients with chronic renal failure: mean 11, range 3-36 pmol/L, n = 27, primary hyperparathyroidism: mean 198, range 130-299 pmol/L, n = 23, Paget's disease: mean 92, range 42-149 pmol/L, n = 24, osteomalacia: mean 43, range 27-61 pmol/L, n = 9. A minimum sample volume of 300 microL is required, the hands-on time is significantly less than other commercial assays and the measuring procedure is gamma counting rather than scintillation counting. The assay offers several advantages over previous methods and should allow more laboratories to offer measurement of 1,25(OH)2D as part of their repertoire.

Quantification of vitamin D receptor mRNA in tissue sections demonstrates the relative limitations of in situ-reverse transcriptase-polymerase chain reaction

In situ-reverse transcriptase-polymerase chain reaction (IS-RT-PCR) is a recently described technique that is used to localize low levels of mRNA within cells and tissue sections. One of the major criticisms levelled at this technique is that positive results may be meaningless, as amplification is required to demonstrate the transcripts of interest. The use of IS-RT-PCR to demonstrate mRNA for receptors for 1,25-dihydroxyvitamin D3 (VDR) in sections of human kidney and bone has previously been described. To ascertain whether the levels of VDR mRNA detected following IS-RT-PCR were transcriptionally significant, computerized image analysis was used to determine the mean silver grain density in human kidney and bone cells following conventional in situ hybridization and after various cycles of IS-RT-PCR. Only a few cycles of PCR were needed to produce an optimum signal, but amplification of signal following IS-RT-PCR was found to be relatively inefficient. Following the optimum number of cycles of IS-RT-PCR in kidney sections, there was a less than four-fold increase in signal. Similarly, in bone, the optimum signal detected was only approximately five times greater than that found with conventional in situ hybridization. These results clearly demonstrate that the increase in signal following IS-RT-PCR follows a more linear pattern and is relatively inefficient, compared with the usual exponential increase with conventional solution phase RT-PCR.

Demonstration of estrogen receptor mRNA in bone using in situ reverse-transcriptase polymerase chain reaction

Falling estrogen levels affect the female skeleton profoundly. Following menopause, estrogen lack is a major cause of osteoporosis. The site of estrogen action in human bone, however, is unclear, but responsive cells must express the estrogen receptor (ER). One obstacle to localizing these cells is that mRNA for ER is expressed in low copy number. Hence, conventional molecular techniques are either too insensitive to detect receptor transcripts (in situ hybridization) or necessitate amplification of RNA extracted from tissue [Northern analysis and polymerase chain reaction (PCR)], thus failing to identify the specific target cells within the mixed-cell population of bone. In situ PCR (IS-PCR) is a technique that combines the sensitivity of PCR with the localization of conventional in situ hybridization. The technique has previously been used primarily to detect single-copy genes and viral DNA within cells. More recently, incorporation of a reverse-transcriptase reaction (IS-RT-PCR) has allowed the technique to be used to identify rare mRNAs within tissues. We have therefore applied the technique of IS-RT-PCR to localize ER mRNA first in human breast tumors, a known positive tissue, and then in bone. Using conventional riboprobe in situ hybridization, ER transcripts were not detectable in any bone cells within sections taken from normal bone and several actively remodeling bone tissues, namely, Paget's disease, renal hyperparathyroidism, and healing fracture callus. The technique of IS-RT-PCR, however, allowed amplification of transcripts to a detectable level. Following two cycles of amplification, hybridization signal was observed in osteoblasts and to a lower level in osteoclasts and occasional osteocytes. This positive signal was more obvious after five cycles, particularly in osteoclasts and osteocytes. After ten cycles, although signal was increased in osteoclasts and osteocytes, it appeared to be decreased in osteoblasts, suggesting that overamplification leads to loss of target complex from these cells. We conclude that several cell types in human bone express ER mRNA in vivo.

Increased catabolism of 25-hydroxyvitamin D in patients with partial gastrectomy and elevated 1,25-dihydroxyvitamin D levels. Implications for metabolic bone disease

Serum vitamin D metabolites and PTH were measured in seven subjects with a history of previous partial gastrectomy (PGX) and metabolic bone disease. The elimination t1/2 of [3H]25-hydroxyvitamin D3 ([3H]25OHD3) in serum was assessed after an iv pulse dose of 5 microCi [26,27-3H]25OHD3. Median serum 25OHD3 was 37.5 (27.5-101.3) nmol/L, [normal range (NR) 10.8-58.5 nmol/L], mean serum 1,25-dihydroxyvitamin D [1, 25-(OH)2D3] was raised at 175 +/- 72 pmol/L, (NR 48-120 pmol/L) and mean PTH was also high, 67 +/- 27 ng/L, (NR 10-60 ng/L). Serum t1/2 [3H]25OHD3 ranged from 10.9-21.2 days. A strong negative correlation existed between t1/2 [3H]25OHD3 and serum 1,25-(OH)2D3 [Spearman's rank correlation coefficient (r = -0.82, P = 0.002)] and PTH [Spearman's rank correlation coefficient (r = -0.81, P = 0.001)]. Four subjects who had high initial PTH concentrations (60-115 ng/L) and elevated 1,25-(OH)2D levels (162-300 pmol/L) were reassessed after calcium supplementation to suppress secondary hyperparathyroidism (2 degrees HPT). In this subgroup, after-treatment PTH fell from 82 +/- 24 to 52 +/- 24 ng/L (mean +/- SD), not significant; 1,25-(OH)2D fell from 210 +/- 61 to 116 +/- 28 pmol/L, P = 0.015; and t1/2 [3H]25OHD3 increased from 13.2 +/- 1.9 to 18.9 +/- 3.1 days, P = 0.012. Patients with PGX and evidence of 2 degrees HPT with elevated 1,25-(OH)2D have a reduced t1/2 [3H]25OHD3, and this may explain the increased susceptibility of the subjects to osteomalacia. Calcium supplementation suppresses 2 degrees HPT, increases t1/2 [3H]25OHD3 and may protect against PGX osteoporosis and osteomalacia.

Serum 1,25-dihydroxyvitamin D may be related inversely to disease activity in breast cancer patients with bone metastases

1,25-dihydroxyvitamin D (1,25-(OH)2D) stimulates differentiation and controls proliferation in breast cancer cells. The role of endogenous 1,25-(OH)2D and its relation to PTH related protein (PTHrP) during the progression of breast cancer is not known; we therefore investigated these hormones in two studies. In a cross-sectional study of patients with breast cancer at different stages of disease, serum 1,25-(OH)2D levels (mean +/- SE) were highest in early disease (102 +/- 3.7 pmol/L), fell in normocalemic patients with bone metastases (52 +/- 5.3 pmol/L; P < 0.01), and were lowest in hypercalcemic patients (33 +/- 5.6 pmol/L; P < 0.001). PTHrP was detectable in the serum of only one normocalcemic patient with progressive metastases but was present in 11 of the 12 hypercalcemic patients, thus PTHrP did not stimulate 1,25-(OH)2D synthesis. In a 6-month longitudinal study of normocalcemic patients with bone metastases undergoing hormonal therapy, serum 1,25-(OH)2D concentrations fell in patients whose disease progressed (P = 0.0056), but remained constant in those who were stable or responded to treatment. These changes in 1,25-(OH)2D preceded clinical signs of progression and predicted disease response. In the progressive group, five of whom died during the study, 1,25-(OH)2D decreased between the initial and final samples, PTH fell significantly from 24.8 to 13.5 ng/L (P = 0.025), serum calcium rose from 2.27 to 2.39 mmol/L (P = 0.017), and the urinary calcium/creatinine ratio rose from 0.37 to 0.68 (P = 0.046). PTH and 1,25-(OH)2D were significantly correlated in the final samples from this group, Spearman's rank correlation = 0.80, P = 0.022. The results indicate that normocalcemia in these patients is maintained, at the expense of suppressing PTH and 1,25-(OH)2D, in the face of increased calcium released from lytic lesions in bone. Loss of the antiproliferative effects of 1,25-(OH)2D may then permit more rapid secondary growth of the tumor.

Growth plate chondrocyte vitamin D receptor number and affinity are reduced in avian tibial dyschondroplastic lesions

Tibial dyschondroplasia (TD) is a condition of rapidly growing poultry in which a mass of unmineralized cartilage extends distally from the tibiotarsal growth plate, leading to deformity and lameness. The lesion is characterized by the accumulation of prehypertrophic chondrocytes, probably because the maturing chondrocytes are unable to differentiate fully. The condition can be prevented by feeding 1,25-(OH)2D3. We have investigated the possibility that vitamin D receptors (VDR), through which 1,25-(OH)2D3 exerts its differentiating effects on chondrocytes, may be defective in TD birds. Chondrocytes were isolated from the proliferating and hypertrophic zones of normal tibiotarsi and from the proliferating zone and lesion of affected birds and receptors were characterized by Scatchard analysis. Results showed that, while cells from the proliferating zone in TD birds had normal receptors, those from the TD lesion had significantly lower numbers and affinity for 1,25-(OH)2D3 compared to all other zones. Lesion VDR had low affinity; Kd 83.9 +/- 20.6 pM compared to 30.0 +/- 2.8, 37.8 +/- 3.1, and 33.0 +/- 4.0 pM (p < 0.001), and low receptor number per cell, 920 +/- 74, compared to 1329 +/- 151, 1664 +/- 167, and 1360 +/- 104 (p < 0.01) in the normal proliferating, normal hypertrophic, and TD proliferating cells, respectively. These findings were confirmed by immunohistochemical localization of VDR in sections of normal and TD growth plates using monoclonal antibody 9A7 gamma. In normal growth plate, most cells were VDR positive with intense staining in the mature hypertrophic chondrocytes; in TD growth plates, proliferating zone cells stained well but signal was largely absent from chondrocytes in the lesion. Image analysis showed integrated nuclear staining density per cell of 168.2 +/- 36.9 arbitrary units in normal hypertrophic cartilage compared to 98.8 +/- 60.2 units in the top of the lesion and 2.2 +/- 2.0 units in the midlesion. We conclude that both numbers and affinity of VDR are reduced in TD and this may explain the failure of chondrocytes to differentiate to the mature form. The adverse consequences of defective receptors may be partly overcome by treatment with 1,25-(OH)2D3.

Demonstration of vitamin D receptor transcripts in actively resorbing osteoclasts in bone sections

The effects of the active metabolite of vitamin D, 1,25 dihydroxyvitamin D3 (1,25D), are mediated via the vitamin D receptor (VDR). 1,25D is known to have profound effects on bone resorption, but proof that the human osteoclast expresses VDR in vivo is absent. Receptors have been demonstrated in osteoblasts, and it has been generally accepted that the effects of 1,25D on formed osteoclasts are mediated via osteoblasts. Using conventional riboprobe in situ hybridization, VDR transcripts were readily detectable in osteoblasts within sections taken from normal bone and several actively remodelling bone tissues, namely, Paget's disease, renal hyperparathyroidism, and healing fracture callus. However, VDR transcripts also appeared to be present at low levels within osteoclasts from two pagetic samples and two hyperparathyroid samples. To examine this latter finding further, we have used the novel technique of in situ-reverse transcriptase-polymerase chain reaction (IS-RT-PCR) for specific amplification and detection of VDR mRNA within sections taken from the same conditions described above, and also from osteoclastoma samples. As expected, VDR transcripts were amplified and detected in osteoblasts and marrow cells, but were also prominently found in osteoclasts at approximately 50% of the level detected in osteoblasts in normal bone and at 60% in the active bone tissues. This suggests that in addition to effects on osteoclast precursors and those mediated via osteoblasts, 1,25D could exert direct effects on the active bone resorbing cells in vivo.

Novel and sensitive detection systems for the vitamin D receptor--in situ-reverse transcriptase-polymerase chain reaction and immunogold cytochemistry

The receptor for the active metabolite of vitamin D, 1,25(OH)(2)D(3), known as the vitamin D receptor (VDR), belongs to the steroid hormone nuclear receptor superfamily. We have developed novel methods for detection of VDR mRNA and protein within a human promyelomonocytic cell line, HL-60. Using the newly developed technique of in situ-reverse transcriptase-polymerase chain reaction (IS-RT-PCR), low levels of VDR mRNA could be amplified and demonstrated unequivocally within these cells, and also within a human kidney proximal tubule cell line, CL-8. Use of a novel immunogold cytochemical technique has allowed clear and sensitive detection of VDR protein expression within the HL-60 cells. Further development of IS-RT-PCR has allowed us to apply this technique to tissue sections. We have shown clear amplification of VDR transcripts within sections of formalin-fixed paraffin-embedded human kidney and liver. These techniques will be useful to localise specifically the VDR within cell types that contain low levels of mRNA and protein, and will permit further investigation of the role played by 1,25(OH)(2)D(3) in cellular regulatory mechanisms.

Hypercalcaemia, hypermagnesaemia, hyperphosphataemia and hyperaluminaemia in CAPD: improvement in serum biochemistry by reduction in dialysate calcium and magnesium concentrations

Phosphate binders are necessary to control hyperphosphataemia in the majority of dialysis patients. Whilst aluminium salts are efficient phosphate binders, their use is associated with toxic side effects. Calcium salts are a widely used alternative, but hypercalcaemia is a common side effect, limiting their use and raising concern about metastatic calcification. Reduction of the dialysis fluid calcium concentration has been shown to reduce hypercalcaemia in haemodialysis patients, with an associated decrease in serum PTH. We analysed the effect of reduced calcium/magnesium (1.25/0.25 mmol/l), 40 mmol/l lactate, PD fluid (PD4) on 11 CAPD patients with uncontrollable hypercalcaemia (> 2.65 mmol/l) and hyperphosphataemia (> 1.80 mmol/l). Only 1 patient remained hypercalcaemic, while phosphate fell in 6 patients (2.23 +/- 0.16 on no binder, to 1.68 +/- 0.08 mmol/l at 6 months (p < 0.05), but was unchanged in 5 (2.10 +/- 0.15 to 2.48 +/- 0.14 mmol/l [p = NS]). Overall mean calcium x phosphate product changed little. However, in a subgroup it fell significantly (p < 0.05). Geometric mean iPTH rose, but not significantly. The subgroup of patients whose calcium x phosphate product fell, exhibited a much smaller rise in iPTH than the others (57.3-73.2 vs. 52.8-167.1 pg/ml). 1.25-Dihydroxyvitamin D3 was subnormal in all patients. Mean serum magnesium fell from 1.24 +/- 0.06 to 0.89 +/- 0.04 mmol/l (p < 0.001), whilst mean serum bicarbonate rose significantly (25.2 +/- 0.4 to 28.9 +/- 1.2 mmol/l; p < 0.01). Withdrawal of aluminium-containing phosphate binders resulted in mean serum aluminium falling significantly from 31.1 +/- 5.7 at start of PD4 to 15.4 +/- 2.7 mu g/l at 6 months (p < 0.05). In summary, in around 50% of CAPD patients with persistent hypercalcaemia and hyperphosphataemia, reduction in PD fluid calcium can produce significant improvement in phosphate, reduction of calcium x phosphate product, and enable avoidance of aluminium-containing phosphate binders. Patients whose calcium and phosphate control remains poor, still benefit from the reduction, or cessation, of oral aluminium intake.

Vitamin D intoxication causes hypercalcaemia by increased bone resorption which responds to pamidronate

OBJECTIVE

Vitamin D intoxication is a relatively rare but treatable cause of hypercalcaemia. In the past this has been undertaken using corticosteroids. Previous observations have suggested that there is increased bone resorption in hypervitaminosis D. If this were to be the case, specific inhibitors of bone resorption might provide more effective treatment. We have therefore studied the mechanisms of hypercalcaemia and response to therapy in a group of patients with vitamin D intoxication.

DESIGN

Vitamin D metabolites were measured in six patients with vitamin D intoxication; in five of these the components of hypercalcaemia were calculated. These measurements were repeated following treatment with corticosteroids (two patients) or the bisphosphonate, pamidronate (three patients).

RESULTS

In each case the serum 25-hydroxyvitamin D was grossly elevated and there was a more modest elevation in serum 1,25-dihydroxyvitamin D. The components of hypercalcaemia suggest that there was a significant degree of bone resorption in all six patients and that this is the major determinant of hypercalcaemia. Pamidronate treatment resulted in a brisk reduction in plasma calcium concentration. Following corticosteroids the return of calcium to normal was more delayed.

CONCLUSION

The hypercalcaemia of vitamin D intoxication is mediated by increased bone resorption and bisphosphonates have a role in its management.

Regulators of chondrocyte differentiation in tibial dyschondroplasia: an in vivo and in vitro study

Tibial dyschondroplasia (TD) is a disorder of endochondral bone growth and results in the retention of a mass of unmineralized, avascular cartilage extending into the metaphysis. We have studied various parameters of chondrocyte differentiation, both in isolated chick chondrocytes and growth plate sections, in an attempt to determine whether the inhibition in chondrocyte differentiation seen in TD is a consequence of an inherent incapability of chondrocytes to differentiate terminally and mineralize. Results from in vitro experiments indicated that both normal and lesion chondrocytes synthesized a matrix that stained with antibodies to types II and X collagen and displayed foci of mineralization. Alkaline phosphatase activity in lesion chondrocytes was significantly increased in comparison to that in normal hypertrophic chondrocytes. In addition, normal and lesion chondrocytes in culture synthesized transforming growth factor-beta and 24,25(OH)2D3 but not 1,25(OH)2D3. There was no significant difference in the production rate of these growth regulators between normal and lesion chondrocytes. In contrast, in growth plate sections, alkaline phosphatase activity was markedly reduced in the lesion chondrocytes and sites of mineralization were not evident. Type II collagen was located throughout the growth plate and lesion, but type X collagen was not present within the lesion except at sites of vascularization. These results indicate that, in culture, lesion chondrocytes have the ability to differentiate terminally and mineralize, and suggest that the primary abnormality in TD is related to a developmental fault which is only operative in vivo. This may include a defect in cartilage vascularization and/or impairment of chondrocyte differentiation by mechanisms that have not yet been elucidated but may involve the abnormal production of regulatory factors.

Interaction between dietary 1,25-dihydroxycholecalciferol and calcium and effects of management on the occurrence of tibial dyschondroplasia, leg abnormalities and performance in broiler chickens

1. Two experiments were performed to compare the relative effectiveness of feeding 1,25-dihydroxycholecalciferol (1,25-DHCC) in minimising leg abnormalities in broilers with other methods and to investigate interactions between dietary 1,25-DHCC and calcium. 2. Adding 5 micrograms 1,25-DHCC/kg to a diet containing 12 g calcium/kg was more effective than early food restriction or meal feeding in preventing leg abnormalities but was found to cause a growth depression. 3. The second experiment, which had a factorial design, with diets containing 7.5, 10.0 and 12.5 g calcium and 0, 2.0, 3.5 and 5.0 micrograms 1,25-DHCC/kg, showed linear and quadratic interactions between these dietary factors. Diets with higher concentrations of both 1,25-DHCC and calcium resulted in growth depression associated with hypercalcaemia. 4. The incidence of tibial dyschondroplasia (TD) at 3 weeks of age was highest with the basal diet containing 7.5 g calcium/kg and was markedly reduced by addition of 1,25-DHCC and/or calcium. The incidence was very low or non-existent when 1,25-DHCC was fed at 3.5 micrograms/kg or greater. 5. Feeding 5 micrograms/kg 1,25-DHCC had no effect on plasma 1,25-DHCC concentrations, although at the higher dietary calcium contents plasma concentrations of 25-hydroxy- and 24,25-dihydroxy-cholecalciferol were lower in those birds fed 1,25-DHCC. 6. It is concluded that 1,25-DHCC is most effective in preventing TD without accompanying growth depression when it is fed in conjunction with diets containing less than 10 g calcium/kg.

Calbindin-D9K gene expression in rat chorioallantoic placenta is not regulated by 1,25-dihydroxyvitamin D3

The aim of this study was to investigate whether 1,25-dihydroxyvitamin D3 (1,25(OH)2D3), the active metabolite of vitamin D, regulates the expression of rat placental calbindin-D9K mRNA. One group of rats (-D) was fed a vitamin D-deficient diet before and during pregnancy, whereas a second group (+D) was fed a vitamin D-replete diet over the same period. Animals were killed on d 21 of gestation, and plasma concentrations of 1,25(OH)2D3 for +D and -D animals were significantly (p < 0.05) different (260 +/- 78 and 39 +/- 8 pM in maternal plasma and 122 +/- 39 and 42 +/- 10 pM in fetal plasma, respectively; mean +/- SE, n = 4-5). Vitamin D deficiency had no effect on placental weight, fetal weight, fetal ashed weight, fetal calcium accretion, or the maternofetal calcium gradient. Hybridization of RNA from maternal duodena (used as a positive control tissue) and placentas of +D and -D rats with a rat calbindin-D9K cDNA revealed a single 0.6-kb transcript in both tissues. The abundance of this transcript was markedly lower (p = 0.06) in the duodena of -D compared with +D rats (mean change -68 +/- 9%) but there was no difference between the placentas of the two groups (mean change +13 +/- 22%). These changes were significantly (p < 0.05) different between the two tissues and the response of each tissue to vitamin D deficiency was significantly different (p < 0.01). These data indicate that 1,25(OH)2D3 does not regulate the expression of calbindin-D9K mRNA in rat placenta.

Preliminary in situ identification of estrogen target cells in bone

Although estrogens profoundly influence skeletal growth and maturation, their mechanism of action is still unclear. To identify their target cells in bone, estrogen receptors were located by immunofluorescence using the H222 monoclonal antibody in cryosections (both undecalcified and briefly decalcified) of hyperplastic mandibular condyle (persistent asymmetric mandibular growth) from a 14-year-old girl and radius and ulna from an 18-month-old female pig (epiphyseal fusion) and from a 3-month-old guinea pig (epiphyses open). Bone was removed from the animals at the peak of estrus. The most striking feature in all three species was the high proportion (approximately 50%) of receptor positive osteocytes. Although all sections contained active bone-forming surfaces, we were unable to identify clearly osteoblasts or lining cells that were estrogen receptor positive. In pig bone only, distinctive groups of receptor positive chondrocytes, with a pericellular localization of collagen type 1, were detected above the growth plate but below secondary centers of ossification. This observation suggests that osteocytes are major skeletal estrogen target cells and may be involved in coordinating the response of surface bone cells to the hormone, and further that chondrocytes may be involved in estrogen-induced epiphyseal growth plate fusion.

Gastrointestinal calcium absorption and dietary calcium load: relationships with bone remodelling in vertebral osteoporosis

Patients with vertebral osteoporosis have a wide range of bone loss rates, bone remodelling rates and capacities for gastrointestinal (GI) calcium absorption. To test the hypothesis that variations in GI absorptive capacity determine rates of bone loss or remodelling, we have sought relationships between calcium absorption or vitamin D metabolite levels on the one hand and rates of cancellous and cortical bone loss (measured by serial quantitative computed tomography in the radius; n = 25) or indices of bone remodelling in tetracycline-prelabelled transiliac biopsies (n = 41) on the other, in a sequential untreated group. Calcium absorption (net and true) was measured in 18-day balances and by a two-isotope deconvolution method (fractional absorption and maximum absorption rate, MAR). There was no significant seasonal effect on any of these four measures of calcium absorption (variance ratio, F = 0.52-1.61, p > 0.1) or on 1,25-dihydroxyvitamin D levels (F = 0.13, p > 0.1; range 11-69 pg/ml), notwithstanding the expected seasonal effect on 25-hydroxyvitamin D levels (mean 18.7 ng/ml, zenith mid July, semi-amplitude 7.5 ng/ml; F = 6.82, p < 0.01). Neither this metabolite nor 1,25-dihydroxyvitamin D correlated with any index of calcium absorption (p > 0.1). No measure of calcium absorption (or intake) had a significant relationship with radial cortical or cancellous bone loss (p all > 0.1) but cancellous bone loss was associated with the rate of endogenous calcium excretion (r = 0.50, p < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Constitutive synthesis of 1,25-dihydroxyvitamin D3 by a human small cell lung cancer cell line

One of 16 human small cell lung cancer cell lines examined was shown to synthesize a metabolite resembling 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3]. The NCI H82 line converted 25-hydroxyvitamin D3 (25OHD3) into a compound indistinguishable from 1,25-(OH)2D3 in 3 different high performance liquid chromatography systems. Electron impact mass spectra for the trimethylsilylethers of the metabolite and authentic 1,25-(OH)2D3 were indistinguishable. Binding to an anti-1,25-(OH)2D3 antibody was identical for the metabolite and authentic 1,25-(OH)2D3, whereas administration to rats in vivo caused equivalent stimulation of calcium transport measured in vitro in duodenal sacs. Activity of the H82 1 alpha-hydroxylase appears to be substrate dependent and is not stimulated by PTH, suggesting that it is similar to the enzyme expressed by activated macrophages and other cell types at extrarenal sites. Inhibition by ketoconazole indicates that, like the renal and extrarenal enzymes, the H82 enzyme is cytochrome P450 dependent. These data indicate that the H82 small cell lung cancer cell line constitutively expresses 25-hydroxyvitamin D3-1 alpha-hydroxylase and can synthesize 1,25-(OH)2D3.

Improvement in glucose tolerance and beta-cell function in a patient with vitamin D deficiency during treatment with vitamin D

Glucose metabolism was studied in a patient with vitamin D deficiency during its treatment with small doses of vitamin D. A continuous infusion of glucose test was performed to assess glucose tolerance and insulin sensitivity and beta-cell function were derived by mathematical modelling. Fasting glucose was 5.6 mmol/l and achieved glucose after the infusion was 10.4 mmol/l confirming diabetes. The test was repeated 0.5, 1, 3 and 5 months after starting treatment. Serum calcium increased glucose intolerance from 1.76 to 2.0, 2.08, 1.96 and 2.0 mmol/l, respectively; vitamin D reached supraphysiological levels initially and returned to normal levels, and parathyroid hormone levels were normalized. Her weight did not change during treatment. Glucose tolerance improved during treatment and achieved glucose was 9.4, 8.6, 9.2 and 9.0 mmol/l at 0.5, 1, 3 and 5 months, respectively; insulin sensitivity did not change. Beta-cell function improved from 101% at diagnosis to 126%, 147%, 173% and 198% at 0.5, 1, 3 and 5 months, respectively. Improvement in beta-cell function and consequently in glucose tolerance is likely to have been due to correction of hypocalcaemia, vitamin D deficiency and secondary hyperparathyroidism.

Abnormal synthesis of 1,25-dihydroxyvitamin D in patients with malignant lymphoma

High serum concentrations of 1,25-dihydroxyvitamin D [1,25-(OH)2D] can occur with hypercalcemia in malignant lymphoma. We have investigated the potential for abnormal vitamin D metabolism by giving a single oral dose of 25-hydroxyvitamin D (25OHD) in 10 lymphoma patients (8 Hodgkin's and 2 T-cell) and 7 controls. Serum 25OHD increased similarly in both groups (peak concentrations, 114.1 +/- 9.5 vs. 123.9 +/- 9.6 nmol/L). In controls, serum calcium and PTH did not change after treatment [calcium, 2.31 +/- 0.02 and 2.33 +/- 0.02 mmol/L (mean +/- SEM); PTH, 21.6 +/- 4.0 and 25.4 +/- 4.3 ng/L] 1,25-(OH)2D increased within the normal range from [median (range)] 81 (48-125) to 117 (91-156) pmol/L. In lymphoma patients, serum calcium increased from 2.29 +/- 0.04 to 2.40 +/- 0.06 mmol/L (P = 0.03), PTH decreased from 12.9 +/- 2.6 to 8.0 +/- 1.9 ng/L (P = 0.06), and one patient became hypercalcemic (2.92 mmol/L). Serum 1,25-(OH)2D became supranormal in 6 lymphoma patients; the group median rose from 74.5 (46-180) to 151 (120-487) pmol/L; this peak response differed from that in the controls (P = 0.019). Lymph node and spleen cells from a patient with T-cell lymphoma synthesized [3H]1,25-(OH)2D3 from [3H] 25OHD3 in vitro. The data suggest that abnormal production of 1,25-(OH)2D in lymphoma may be more common than previously recognized given an adequate supply of precursor 25OHD and provide further evidence for the extrarenal synthesis of 1,25-(OH)2D in this condition.

Cyclosporin A and vitamin D metabolism: studies in patients with psoriasis and in rats

1. Cyclosporin A, an immunosuppressive drug used to treat psoriasis, stimulates renal synthesis of 1,25-dihydroxyvitamin D in rats. 1,25-Dihydroxyvitamin D can also reduce the activity of psoriasis, and in the present study we have examined the possibility that cyclosporin A mediates some of its actions in psoriasis by renal or extra-renal production of 1,25-dihydroxyvitamin D. 2. Treatment of 12 psoriatic patients with cyclosporin A (5 mg day-1 kg-1) for 3 months significantly improved the psoriasis activity and severity index and reduced glomerular filtration rate, but serum 1,25-dihydroxyvitamin D levels were not changed. However, 1-3 months after stopping cyclosporin A treatment, an increase in the psoriasis activity and severity index score was accompanied by a small, but significant, increase in serum 1,25-dihydroxyvitamin D concentration. Plasma 1,25-dihydroxyvitamin D levels in rats gavaged with cyclosporin A (15 mg day-1 kg-1 for 2 weeks) were significantly increased compared with controls, but a lower dose of cyclosporin A (2.4 mg day-1 kg-1) had no effect. Renal 25-hydroxyvitamin D-24-hydroxylase activity in rat kidney homogenates was not different between control and cyclosporin A-treated rats. Renal 25-hydroxyvitamin D-1 alpha-hydroxylase activity was not detectable in these homogenates. Extra-renal production of 1,25-dihydroxyvitamin D by activated macrophages isolated from the synovial fluid of patients with inflammatory arthritis was reduced after incubation with cyclosporin A (0.1-10 mumol/l) for 30 h or 5 days.(ABSTRACT TRUNCATED AT 250 WORDS)

Histological, radiological, and biochemical features of the adynamic bone lesion in continuous ambulatory peritoneal dialysis patients

Adynamic bone is being found with increasing frequency in dialysis patients. Little is known about its aetiology, and even less about its natural history. We found 10 cases of asymptomatic adynamic bone among a group of 32 continuous ambulatory peritoneal dialysis patients, most of whom had never been exposed to aluminium-containing phosphate binders. Compared to the remaining 22 patients, they had an older mean age (54 +/- 11.4 vs. 42 +/- 11.8 years; p < 0.05), probably a longer pre-dialysis duration of renal failure (10.9 vs. 7.1 years), higher mean ionized calcium (1.30 +/- 0.04 vs. 1.15 +/- 0.02 mmol/l; p < 0.01), and lower mean intact parathyroid hormone (31.5 vs. 200.3 pg/ml; p < 0.001). The bone density was not different between the two groups, but 9 of the 10 adynamic patients had significant vascular calcification seen on plain radiology as compared with only 7 of 20 in the comparison group (p < 0.05). Follow-up of the adynamic patients showed a close association with serum intact parathyroid hormone and ionized calcium levels. With one exception, adynamic bone did not appear to be associated with lower bone density than other types of osteodystrophy, but a longer-term study is required to determine the complete natural history of this lesion.

Impaired glucose tolerance and insulin insensitivity in primary hyperparathyroidism

OBJECTIVE

A high prevalence of diabetes mellitus has been shown in patients with primary hyperparathyroidism (PHPT). However, it is unclear whether this is related to the metabolic abnormalities in PHPT or to the presence of other risk factors for glucose intolerance in these patients. The aim of our study was to determine whether glucose intolerance and insulin insensitivity occur in subjects with PHPT who do not have other risk factors for diabetes mellitus.

DESIGN

Cross-sectional study of glucose metabolism in PHPT patients without other risk factors for diabetes mellitus, compared to age and body mass index (BMI) matched healthy subjects.

SUBJECTS

Nineteen non-obese, non-diabetic, normotensive patients with PHPT and 11 age and BMI matched healthy subjects.

MEASUREMENTS

The continuous infusion of glucose test was used to assess glucose tolerance. Plasma glucose and insulin were measured during a 1-hour continuous infusion of glucose (5 mg/kg ideal body weight/min); insulin sensitivity and beta-cell function were derived from the glucose and insulin data by mathematical modelling. Fasting serum concentrations of parathyroid hormone, ionized calcium and 1,25-dihydroxyvitamin D (1,25(OH)2D) were measured in all subjects.

RESULTS

PHPT patients attained higher plasma glucose levels at the end of the glucose infusion (median 9.0 (interquartile range 8.1-9.8) mmol/l) than did controls (7.9 (7.1-8.9) mmol/l, P < 0.05), and 8 (42%) PHPT patients had impaired glucose tolerance. Insulin sensitivity was lower in PHPT (60.3% (49.8-85.4)) than in controls (113.7% (89.3-149.2), P < 0.001); beta-cell function was not different in PHPT subjects. PHPT subjects with impaired glucose tolerance had reduced beta-cell function compared to PHPT subjects with normal glucose tolerance (89.9% (70.5-106.4) vs 120% (98.8-156.6) respectively, P < 0.05). No significant correlations were found between insulin sensitivity and PTH (rs = -0.21), 1,25(OH)2D (rs = -0.14), ionized calcium (rs = -0.11) and inorganic phosphate (rs = 0.34). Beta-cell function did not correlate with PTH (rs = 0.15), 1,25(OH)2D (rs = 0.04), ionized calcium (rs = 0.23) or inorganic phosphate (rs = -0.35).

CONCLUSION

Insulin insensitivity is present in PHPT even in the absence of hypertension and obesity, and may be the cause of glucose intolerance and diabetes. PHPT subjects with reduced beta-cell function are more likely to develop glucose intolerance.

Correlation of bone histology with parathyroid hormone, vitamin D3, and radiology in end-stage renal disease

We analyzed transiliac bone biopsy specimens from 30 end-stage renal failure patients, taken at the time of admission for CAPD training. Results were compared with values of iPTH, bone alkaline phosphatase, 1,25-dihydroxyvitamin D3, skeletal survey, quantitative computed tomography (QCT) and single photon absorptiometry (SPA) bone density measurements. Osteitis fibrosa was the most common histological diagnosis, present in 15 of the 30 patients (50%), with eight classified as "severe" and seven as "mild." Eight patients (27%) had adynamic bone lesion, four mixed renal osteodystrophy (13%), and two (7%) osteomalacia. The mean age of the adynamic group was higher than the osteitis fibrosa group (41 +/- 12.1 vs. 56 +/- 10.2 years; P < 0.01), and than the mixed group (39 +/- 7.5 vs. 56 +/- 10.2 years; P < 0.02). Levels of iPTH enabled discrimination between groups, but not between individual patients, and values correlated with bone alkaline phosphatase (r = 0.62; P < 0.001). Erosion of the terminal phalanges was seen on the plain X-rays of 7 of 15 patients with mild or severe OF, and in three patients with another diagnosis. The majority of patients (> 90%) had bone density measurements within the normal range. No significant correlation existed between QCT or SPA scores and any of the histomorphometric parameters, or iPTH. We conclude that iPTH is the most helpful non-invasive investigation in this group of patients. Plain X-ray of the hands is the most useful radiological investigation, but single measurements of bone density are not diagnostic.