Bone Mineral Parameters Research Articles

Bone mineral density and mandibular bone quality in patients receiving dental implants: reply to Dr. Taguchi

Dear Editor, I would like to thank Professor Akira Taguchi for his comments. In response to his questions about my research “Comparative study of axial and femoral bone mineral density and parameters of mandibular bone quality in patients receiving dental implant” [1]. I would like to reply as follows: In this study three researchers determined the cortical shape according to Klemetti’s classification. The investigators are clinicians, one of whom has a great deal of experience with this classification working in multicentric research with great number of samples, and the other two specialized in radiology and were oriented for this rating; Klemetti’s classification is not often used and is not well known in Latin America. The mandible trabecular classification was made based on the images from the panoramic radiograph, and the analyzed region was the site where the dental implant was placed. It is not likely that the implant site would be affected by the infection, as the etiological factor was removed longer than 9 years previously, as shown in Table 1 of our original article (dental loss period). This is more than enough time to eliminate any infection. The dental implants were placed according to the protocol established by Branemark [2], which states that an implant must not be placed in patients with any kind of oral infection. In our work, which assessed the mandible cortical through Klemetti’s classification, there was a relation with bone mineral density (BMD) but with no statistical significance due to the small sample size.

Comparative study of axial and femoral bone mineral density and parameters of mandibular bone quality in patients receiving dental implants

In view of the increase in the life expectancy of humans and in edentulism of the population above 50 years of age, in which the prevalence of osteoporosis is also higher, it is fundamental to better understand the effects of systemic bone mass loss on the healing process of dental implants and to determine the quality of the bone that surrounds them. The objective of the present study was to compare systemic osteoporosis (axial and femoral) and parameters of mandibular bone quality, and to evaluate osseointegration in postmenopausal women receiving dental implants. The sample consisted of 39 women aged 48-70 years, 19 with a densitometric diagnosis of osteoporosis in the lumbar spine and femoral neck and 20 controls with a normal densitometric diagnosis. Bone mineral density was measured in the patients and controls by dual-energy X-ray absorptiometry. Eighty-two osseointegrated dental implants were placed in the mandible, 39 of them in the osteoporosis group and 43 in the control group. Mandibular bone quality was evaluated by classifying mandibular inferior cortical and trabecular bone on panoramic radiographs and by histomorphometric analysis of a mandibular bone biopsy. Osseointegration was analyzed after 9 months. No significant difference was observed between patients with osteoporosis and controls when comparing individuals with a normal cortex and those with a severely or moderately eroded cortex determined on panoramic radiographs, although patients with MEC/SEC had lower femoral neck BMD than those with NC (0.688 +/- 0.17 vs. 0.814+/- 0.144 g/cm2, P<0.012). Histomorphometric analysis also revealed no difference in the parameters of bone formation or resorption between the two groups. Implant failure was observed in only one case. We conclude that there is an association between low femoral neck BMD and poor mandibular bone quality as assessed by panoramic radiography. The loss of one implant (1.2%) is compatible with the literature and cannot be attributed to systemic osteoporosis.

Plasma adiponectin concentration in healthy pre- and postmenopausal women: relationship with body composition, bone mineral, and metabolic variables

The aim of the current investigation was to determine the possible relationships of fasting adiponectin level with body composition, bone mineral, insulin sensitivity, leptin, and cardiorespiratory fitness parameters in 153 women. Subjects were classified as premenopausal (n = 42; 40.8 +/- 5.7 yr) if they had regular menstrual periods, early postmenopausal (n = 49; 56.7 +/- 3.6 yr) if they had been postmenopausal for more than >1 yr but <7 yr (5.5 +/- 1.3 yr), and postmenopausal (n = 62; 72.2 +/- 4.5 yr) if they had been postmenopausal for >7 yr. All women studied had a body mass index (BMI) <30 kg/m(2). Adiponectin values were higher (P < 0.05) in middle-aged (12.0 +/- 5.1 microg/ml) and older (15.3 +/- 7.3 microg/ml) postmenopausal women compared with middle-aged premenopausal women (8.4 +/- 3.2 microg/ml). Mean plasma adiponectin concentration in the total group of women (n = 153) was 12.2 +/- 6.3 microg/ml and was positively related (P < 0.05) to age, indexes of overall obesity (BMI, body fat mass), and cardiorespiratory fitness (PWC) values. In addition, a negative association (P < 0.05) between adiponectin with central obesity (waist-to-hip and waist-to-thigh ratio), fat-free mass, bone mineral (bone mineral content, total and lumbar spine bone mineral density), and leptin and insulin resistance (insulin, fasting insulin resistance index) values was observed. However, multivariate regression analysis revealed that only age, fasting insulin resistance index, and leptin were independent predictors of adiponectin concentration. In conclusion, circulating adiponectin concentrations increase with age in normal-weight middle-aged and older women. It appears that adiponectin is independently related to age, leptin, and insulin resistance values in women across the age span and menstrual status.

Calcium supply, bone mineral density and genetically defined lactose maldigestion in a cohort of elderly men

To examine a relationship of molecularly defined lactose malabsorption (LM; by LCT-polymorphism) to calcium supply, bone mineral density (BMD) and parameters of bone metabolism in an elderly male cohort. Furthermore, to reveal gender differences in BMD, calcium consumption rates and parameters of bone metabolism according to LCT polymorphism in an existing female cohort. A total of 239 men, aged 61+/-9 yr, were available from a former population based study cohort. All men were of Caucasian origin and came from the same region. Blood was sampled for genotyping of the LCT polymorphism and determination of markers of bone metabolism. All participants underwent physical examination, measurement of bone density and completed a standardized calcium questionnaire. Identical procedures had been carried out in a female cohort before (no. 350). Distribution of the LCT genotype in the study cohort was 27% CC (associated with LM; adult-type hypolactasia), 55% TC and 18% TT (lactase persistence). Amounts of total ingested calcium were similar among the three genotype groups. Amounts of consumed milk were generally low in men, LCT polymorphism did not influence rates of milk consumption for men preferred other sources of calcium. BMD, markers of bone metabolism and fracture rates did not differ. General anthropometric characteristics did not differ between the LCT groups either. Under conditions of low milk intake LCT polymorphism does not alter bone density, markers of bone metabolism and fractures in this cohort of elderly Caucasian men.

Changes in serum calcium, phosphate, and PTH and the risk of death in incident dialysis patients: A longitudinal study

Elevated bone mineral parameters have been associated with mortality in dialysis patients. There are conflicting data about calcium, parathyroid hormone (PTH), and mortality and few data about changes in bone mineral parameters over time. We conducted a prospective cohort study of 1007 incident hemodialysis and peritoneal dialysis patients. We examined longitudinal changes in bone mineral parameters and whether their associations with mortality were independent of time on dialysis, inflammation, and comorbidity. Serum calcium, phosphate, and calcium-phosphate product (CaP) increased in these patients between baseline and 6 months (P<0.001) and then remained stable. Serum PTH decreased over the first year (P<0.001). In Cox proportional hazards models adjusting for inflammation, comorbidity, and other confounders, the highest quartile of phosphate was associated with a hazard ratio (HR) of 1.57 (1.07-2.30) using both baseline and time-dependent values. The highest quartiles of calcium, CaP, and PTH were associated with mortality in time-dependent models but not in those using baseline values. The lowest quartile of PTH was associated with an HR of 0.65 (0.44-0.98) in the time-dependent model with 6-month lag analysis. We conclude that high levels of phosphate both at baseline and over follow-up are associated with mortality in incident dialysis patients. High levels of calcium, CaP, and PTH are associated with mortality immediately preceding an event. Promising new interventions need to be rigorously tested in clinical trials for their ability to achieve normalization of bone mineral parameters and reduce deaths of dialysis patients.

Comparative study of axial and femoral bone mineral density and parameters of mandibular bone quality in patients receiving dental implants

In view of the increase in the life expectancy of humans and in edentulism of the population above 50 years of age, in which the prevalence of osteoporosis is also higher, it is fundamental to better understand the effects of systemic bone mass loss on the healing process of dental implants and to determine the quality of the bone that surrounds them. The objective of the present study was to compare systemic osteoporosis (axial and femoral) and parameters of mandibular bone quality, and to evaluate osseointegration in postmenopausal women receiving dental implants. The sample consisted of 39 women aged 48-70 years, 19 with a densitometric diagnosis of osteoporosis in the lumbar spine and femoral neck and 20 controls with a normal densitometric diagnosis. Bone mineral density was measured in the patients and controls by dual-energy X-ray absorptiometry. Eighty-two osseointegrated dental implants were placed in the mandible, 39 of them in the osteoporosis group and 43 in the control group. Mandibular bone quality was evaluated by classifying mandibular inferior cortical and trabecular bone on panoramic radiographs and by histomorphometric analysis of a mandibular bone biopsy. Osseointegration was analyzed after 9 months. No significant difference was observed between patients with osteoporosis and controls when comparing individuals with a normal cortex and those with a severely or moderately eroded cortex determined on panoramic radiographs. Histomorphometric analysis also revealed no difference in the parameters of bone formation or resorption between the two groups. Implant failure was observed in only one case. We conclude that there is no association between systemic osteoporosis (axial and femur) and parameters of poor mandibular bone quality. The loss of one implant (1.2%) is compatible with the literature and cannot be attributed to systemic osteoporosis.

Estimated Risk Score for Spine Fracture in the Specific Bending Activity of Normal Taiwanese Men and Women

To investigate the effects of biologic age, as well as chronologic age, on the vertebral ultimate load (strength) and risk score of vertebral fracture (Phi) between the genders. Previous studies have shown a good correlation between the biomechanical strength of vertebral bodies and measured bone mineral parameters, whereas other factors also contribute to the bone strength and risk of fractures. Combining multiple factors into a single assessment may provide more comprehensive and individualized estimations of the fracture risk. In this study, we applied the measured bone mineral content (BMC) and bone projection area of the second through the fourth lumbar vertebrae (L2-L4) to assess the biomechanical strength of lumbar vertebrae. In addition, we used the body segment model to estimate the load of the L3 vertebral body during a bending-forward activity, to then estimate the risk score (Phi) of vertebral compression fracture in healthy Chinese volunteers in Taiwan, and to analyze the effects of gender and age on the risk score (Phi). A total of 611 females and 235 males aged 22-80 years were included in this study. The anteroposterior BMC and projection area of lumbar spine were measured by a Norland XR-26 dual energy radiograph absorptiometer (Norland Corp., Ft. Atkinson, WI). The estimated ultimate strength (L) of lumbar spine was calculated from the regression equation using anteroposterior lumbar BMC and bone area according to Bassman et al (Paper presented at: 39th Annual Meeting of Orthopedic Research Society; February 1993; San Francisco, CA). The estimated spinal load (F) for a person bending over with back horizontal, either with hand free (F0), lifting a 20 kg weight (F20), or a 30 kg weight (F30), was calculated from a force diagram according to William and Lissner. Risk score (Phi) was defined as the quotient of F/L. The results showed an age-related decrease of bone mineral density (P < 0.001) in both genders corrected for weight and height. Using the multiple linear regression analysis and analysis of covariance, Phi for F0, F20, and F30 increased significantly, with increasing age only in females (P < 0.0001), especially after menopause, but not in males. The Phi of postmenopausal females was significantly larger than those of younger females (i.e., F0 (Phi) 0.533 +/- 0.075 vs. 0.458 +/- 0.064, P < 0.001; F20 (Phi) 0.903 +/- 0.101 vs. 0.789 +/- 0.080, P < 0.001; and F30 (Phi) 1.087 +/- 0.117 vs. 0.954 +/- 0.090, respectively, P < 0.001). In females, the ultimate load of the spine and Phi began to decrease to a significant level since the fifth decade, whereas in the males, the similar trends occurred since the sixth decade. Comparing both genders, the F0 (Phi) was slightly yet significantly larger in the young males (< 50 years) than the premenopausal females with similar ages (P < 0.001), but older females had higher F0 (Phi) values than males older than 60 years. Moreover, the Phi increased more prominently in the postmenopausal females with the weight lifted. As a result, both F20 (Phi) and F30 (Phi) were significantly larger in females older than 50 years as compared to males with the similar ages (P < 0.001). Our findings emphasize the importance of Phi, which considers BMC, bone size, body weight, body height, and weight lifted, for evaluating a more individualized risk of spine fracture in elderly men and postmenopausal women. The Phi increased more prominently with lifting weight and increased with aging only in the early postmenopausal females. The study showed that a combination of bone mass and anthropometric parameters provides a more individualized assessment of fracture risk than bone mineral density alone.

Vitamin D Receptor Fok1 Polymorphisms Affect Calcium Absorption, Kinetics, and Bone Mineralization Rates During Puberty

Few studies of the VDR polymorphisms have looked at calcium metabolism or long-term effects. We measured bone mineralization and calcium metabolic parameters longitudinally in a group of 99 adolescents. We found a significant relationship between calcium absorption and skeletal calcium accretion and the Fok1, but not other VDR or related, genetic polymorphisms. It seems that the Fok1 polymorphism directly affects bone mineralization during pubertal growth through an effect on calcium absorption. There are few data regarding the relationship between genetic markers for low bone mass and changes in calcium metabolism in childhood or adolescence. We sought to identify the effects of polymorphisms of the vitamin D receptor (VDR) on calcium and bone mineral metabolism in a longitudinal study of pubertal adolescents. Adolescents (n = 99) received comprehensive stable isotope studies of calcium absorption, bone calcium kinetics, and bone mineralization. Studies were repeated 12 months later. Polymorphisms of putative genetic markers were determined and related to bone mineralization and calcium metabolic finding. Results were analyzed by ANOVA in which changes over time were determined using the initial value as a covariate. Polymorphisms of the Fok1 gene of the VDR were significantly related to calcium absorption (p = 0.008) and whole body BMC (p = 0.03) and BMD (p = 0.006). The Fok1 effect on whole body BMD was significant for those with Ca intake >800 mg/day (p < 0.001), whereas for those with Ca intake < or = 800 mg/day, the Fok1 genotype did not have a significant effect on whole body BMD (p = 0.40). The Fok1 genotype was significantly related to the changes during the year in whole body calcium accretion, with the ff genotype having a 63 +/- 20 mg/day deficit compared with the FF genotype (p = 0.008). The Fok1 polymorphism of the VDR receptor seems to directly affect bone mineral accretion during pubertal growth through an effect on calcium absorption. The relationship between different genetic polymorphisms and bone mineral metabolism may vary by life stage as well as diet.

Intermittent ibandronate preserves bone quality and bone strength in the lumbar spine after 16 months of treatment in the ovariectomized cynomolgus monkey.

The dose-dependent effect of ibandronate treatment on bone mass and architecture was assessed in a large animal study of OVX monkeys using microCT for quantitative bone morphometry and biomechanical testing for measures of bone strength. The study showed that intermittent ibandronate preserved lumbar spine bone quality and strength in these animals after 16 months of treatment. Ibandronate is a bisphosphonate, which is a class of compounds that, in pharmacologically active doses, not only suppresses bone resorption and turnover but also prevents loss of bone mass and strength in the ovariectomized (OVX) rat. We evaluated the effects of ibandronate on bone mass and architecture in the OVX cynomolgus macaque. Sixty-one adult female macaques were divided into five groups (N = 11-15): sham control, OVX control, and OVX low- (10 microg/kg), medium- (30 microg/kg), and high- (150 microg/kg) dose ibandronate. Treatment was administered by intravenous bolus injection every 30 days for 16 months starting at ovariectomy. This dosing schedule is equivalent to a 3-monthly dosing regimen in human subjects over 4 years. Animals were killed at the conclusion of the study, and excised bone specimens of the first lumbar vertebra (L1) were evaluated for quantitative bone densitometry, morphometry, and mechanical properties. Architectural parameters were assessed by microCT including direct 3D bone morphometry. A measure of specimen strength was obtained using destructive compression testing. A significant loss of bone mass and related changes in bone architecture after ovariectomy resulted in a reduction of whole bone strength as expressed by high correlations between architectural and mechanical properties. In this analysis, BMC was the best single predictor of whole bone strength (r2 = 67%). Nevertheless, including architectural indices in a multiple linear regression analysis increased that prediction to 88%. With respect to the treatment, the medium- and high-dose groups were not significantly different from the sham group for all bone mineral and structural parameters. Additionally, significant differences were seen for all measured parameters between the high-dose group and the OVX group, and for some parameters, between the medium-dose group and the OVX group. Intermittent ibandronate treatment effectively and dose-dependently prevented bone loss, architectural deterioration, and strength reduction in the lumbar spine of OVX monkeys.

Prevalence of vitamin D insufficiency in postmenopausal south Indian women

To evaluate the dietary calcium and vitamin D status in south Indian postmenopausal women. Postmenopausal women (n = 164) were evaluated for their daily dietary calcium intake, phytate to calcium ratio, and bone mineral parameters. Their serum leutinizing hormone (LH), follicle-stimulating hormone (FSH), 25-hydroxyvitamin D (25[OH]D), and parathyroid hormone levels (PTH) were measured. Their age and BMI were 59.5 +/- 8 years and 27 +/- 5 kg/m2, respectively. Their daily dietary intake of calcium was 323 +/- 66 mg/day; phytate to calcium ratio, 0.56+/-0.1; LH, 26 +/- 13.5 microIU/l; and FSH, 62.6 +/- 30 microIU/l. Their dietary intake of calcium was low compared with the recommended daily/dietary allowance (RDA) of the Indian Council of Medical Research (ICMR) for the Indian population. Of the 164 patients studied, based on population-based reference values, 126 (77%) had normal 25(OH)D levels (9-37.6 ng/ml), and 38 (23%) had 25(OH)D deficiency. Using functional health-based reference values, 30 (18%) patients had normal 25(OH)D levels (> 20 ng/ml), 85 (52%) had 25(OH)D insufficiency (10-20 ng/ml), and 49(30%) had 25(OH)D deficiency (< 10 ng/ml). PTH and serum alkaline phosphatase (SAP) was significantly high in patients with 25(OH)D deficiency (p < 0.05) compared with those with normal 25(OH)D levels. There was a negative correlation between 25(OH)D and PTH (r = -0.2; p < 0.007) and SAP (r = -0.2; p < 0.001). Dietary calcium correlated positively with dietary phosphates (r = 0.8; p < 0.001) and phytate to calcium ratio (r = 0.75; p < 0.001). Population-based reference values underdiagnosed vitamin D insufficiency and overdiagnosed normal vitamin D status. The diet was insufficient in calcium and high in phytate. About 82% of the study group had varying degrees of low 25-hydroxyvitamin D levels. The quality of diet has to be improved with enrichment/supplementation of calcium and vitamin D to suppress secondary hyperparathyroidism-induced bone loss and risk of fractures.

Effects of Rice Bran Inclusion on Performance and Bone Mineralization in Broiler Chicks

Rice bran, a by-product of the rice industry, is available for animal feeds. However, it has not been a common part of poultry rations in Argentina. Hydrolytic and oxidative rancidity development, phytate content, enzyme inhibitor, and high fiber content are the most important antinutritive factors cited as limiting factors for its use. An experiment utilizing 1-d-old male broiler chicks was conducted to determine the responses of zootechnical and bone mineralization parameters to diets with different concentrations of rice bran. The feed conversion and tibia ash were more sensitive than weight gain to detect antinutritive factors in rice bran. High concentrations of rice bran (in excess of 20%) produced a significant reduction in body weight. Furthermore, feed conversion and bone mineralization variables were impaired by feeding 10% rice bran diets. The adverse effects of rice bran on weight gain, feed conversion, and mineralization in the current studies suggest that rice bran should be included in broiler diets at a level between 10 and 20% if strategies are not used to decrease the antinutritive activity.

Slight decrease in bone mineralization in cow milk-sensitive children.

Patients with cow milk allergy (CMA) are potentially at risk for osteopenia because their milk-free diet usually contains a low calcium content. In our study, different parameters of bone mineralization in children with CMA were investigated. Twenty-seven CMA patients (mean age, 4.3 years; range, 3-8 years) were enrolled in the study. During a mean milk-free diet period of 11.8 months, children were fed extensively hydrolyzed or soy-based formulas. After a milk challenge test, 7 patients showed allergic symptoms, and the other 20 children had transient CMA. From the sera of all patients, the levels of sodium, potassium, chloride, calcium, phosphate, and magnesium ions, as well as alkaline phosphatase (AP), parathyroid hormone (PTH), osteocalcin, and beta-crosslaps, were determined. These values were compared with those of 20 healthy age-matched controls. Bone mineral density was measured as well. The AP and PTH concentrations were higher in CMA patients than in the control group (AP: 610.2 U/L vs. 499.7 U/L, P < 0.01; PTH: 1.56 pmol/L vs. 0.83 pmol/L, P< 0.03), but all values were in the normal range. The osteocalcin concentration was similar in both groups, and the beta-crosslaps concentration was lower in CMA patients than in controls (0.92 vs. 1.47 ng/mL, P< 0.001). The mean Z score of bone mineral density in patients with CMA was -0.6. In 10 cases, the Z score was less than the -1 SD value. On the basis of the Z score, CMA patients were divided into two groups. The PTH concentration was significantly elevated in the group with lower Z score (2.24 pmol/L vs. 1.16 pmol/L; P< 0.03). The results suggest that, in children with CMA who are on a cow milk-free diet, slight disturbances of bone mineralization can be observed by osteodensitometry.

Slight Decrease in Bone Mineralization in Cow Milk–Sensitive Children

ABSTRACTBackgroundPatients with cow milk allergy (CMA) are potentially at risk for osteopenia because their milk‐free diet usually contains a low calcium content. In our study, different parameters of bone mineralization in children with CMA were investigated.Patients and MethodsTwenty‐seven CMA patients (mean age, 4.3 years; range, 3–8 years) were enrolled in the study. During a mean milk‐free diet period of 11.8 months, children were fed extensively hydrolyzed or soy‐based formulas. After a milk challenge test, 7 patients showed allergic symptoms, and the other 20 children had transient CMA. From the sera of all patients, the levels of sodium, potassium, chloride, calcium, phosphate, and magnesium ions, as well as alkaline phosphatase (AP), parathyroid hormone (PTH), osteocalcin, and beta‐crosslaps, were determined. These values were compared with those of 20 healthy age‐matched controls. Bone mineral density was measured as well.ResultsThe AP and PTH concentrations were higher in CMA patients than in the control group (AP: 610.2 U/L vs. 499.7 U/L, P &lt; 0.01; PTH: 1.56 pmol/L vs. 0.83 pmol/L, P &lt; 0.03), but all values were in the normal range. The osteocalcin concentration was similar in both groups, and the beta‐crosslaps concentration was lower in CMA patients than in controls (0.92 vs. 1.47 ng/mL, P &lt; 0.001). The mean Z score of bone mineral density in patients with CMA was −0.6. In 10 cases, the Z score was less than the −1 SD value. On the basis of the Z score, CMA patients were divided into two groups. The PTH concentration was significantly elevated in the group with lower Z score (2.24 pmol/L vs. 1.16 pmol/L;P &lt; 0.03).ConclusionThe results suggest that, in children with CMA who are on a cow milk–free diet, slight disturbances of bone mineralization can be observed by osteodensitometry.

Bone mineral density and body composition in underweight and normal elderly subjects.

The importance of malnutrition as a risk factor in osteoporosis is emphasized by the evidence that patients with fractures of the proximal femur are often undernourished. In this study, nutritional status, bone mineral mass and its association with body composition were investigated in underweight and normal weight elderly subjects. Moreover the hypothesis that malnutrition in elderly is associated with a higher risk of osteoporosis was tested. The participants were 111 elderly subjects divided into two groups according to body mass index (BMI): 51 patients were underweight (BMI < 22 kg/m2) while in 60 subjects BMI ranged from 22 to 30 kg/m2. In all patients anthropometric parameters and blood indices of malnutrition and of bone turnover were measured. Fat-free soft mass (FFSM), fat mass (FM), bone mineral content (BMC) and bone mineral density (BMD) 'total body' and at the hip were obtained by dual-energy X-ray densitometry. Dietary intake was evaluated with the diet history method, while resting energy expenditure (REE) was measured by indirect calorimetry. Underweight subjects had other signs of malnutrition, such as low visceral proteins, sarcopenia, and an inadequate energy intake. Moreover they showed a significant reduction of BMC and BMD compared with normal subjects. In men with BMI <22 kg/m2, T-score was below -2.5 (-3 at femoral neck and -2.7 at total hip) while men in the control group had normal bone mineral parameters. T-score at different sites was lower in underweight women than in underweight men, always showing values under -3.5, with clear osteoporosis and a high fracture risk. In healthy women the T-score values indicated the presence of mild osteoporosis. In underweight subjects, low levels of albumin (< 35 g/l) were associated with higher femoral bone loss. Using a partial correlation model, BMC, adjusted for age, bone area, knee height and albumin showed a significant association with FM in women (r = 0.48; p < 0.01) and with FFSM in men (r = 0.48; p < 0.05). Albumin, when adjusted for other variables, was significantly correlated (r = 0.52; p < 0.05) with femoral neck BMC only in women. In conclusion, the underweight state in the elderly is associated with malnutrition and osteoporosis; other factors occurring in malnutrition, besides body composition changes, such as protein deficiency, could be involved in the association between underweight and osteoporosis. Moreover bone mineral status seems to be related to fat-free soft mass tissue in men while in women it is much more closely associated with total body fat.

Effects of delaying puberty on bone mineralization in female rats.

The effect of delaying puberty on bone mineralization was studied using female rats as a model. Repeated injections of gonadotrophin-releasing hormone antagonist (GnRHa) were used to suppress the onset of puberty from the age of 6-10 weeks. A group of control female rats was given aqueous solution injections at the same age and for the same duration. The effect of delaying puberty on bone mineralization was examined using dual energy X-ray absorptiometry (DXA) and peripheral quantitative computerized tomography (QCT), both methods being adapted for small animals. Bone mineral parameters were measured at baseline and at the ages of 10, 17 and 24 weeks in total body, femur and spine. Compared to controls, bone mineral content (BMC) and bone mineral density (BMD), as measured by DXA, were significantly decreased in GnRHa-treated rats in total body and femur at 10 and 24 weeks of age (P < 0.05). The results were even more significant after adjusting for weight. After this adjustment, spine BMC and BMD at 10, 17 and 24 weeks were significantly lower in the treatment group (P < 0.05). Trabecular BMD at the distal femur in the GnRHa treated group as measured by peripheral QCT was significantly lower (P < 0.05). However, cortical bone in the mid-femur had higher BMD, concurrent with lower cortical thickness in the treatment group. In conclusion, a delay in the onset of sexual maturation may cause prolonged, possibly irreversible defect in bone mineralization.

BONE MINERAL DENSITY IN MEN TREATED WITH SYNTHETIC GONADOTROPIN-RELEASING HORMONE AGONISTS FOR PROSTATIC CARCINOMA

Purpose We evaluate the relationship between the use of synthetic gonadotropin-releasing hormone (Gn-RH) agonists and bone loss in men. Materials and Methods Bone mineral density and parameters of mineral metabolism were evaluated in 12 patients with stage C prostatic carcinoma before and after 6, 12 and 18 months of treatment with 3.75 mg. triptorelin intramuscularly every 4 weeks. Results Of the 12 patients 9 were evaluated after 6, 7 after 12 and 6 after 18 months of therapy. In comparison with month 0, the lumbar and femoral neck bone mineral density tended to decrease at month 6 (-3 and -2.7%, p = 0.31 and 0.17, respectively), at month 12 (-4.6 and -3.9%, p = 0.13 and 0.13) and at month 18 (-7.1 and -6.6%, p = 0.12 and 0.027). A second analysis revealed that the lumbar and femoral neck bone mineral density was significantly decreased on the last evaluation compared to month 0 (p = 0.05 and 0.028, respectively). The serum osteocalcin was increased during treatment, suggesting an accelerated bone turnover in men treated with Gn-RH agonists. Conclusions The use of Gn-RH agonists in men may induce an accelerated bone loss. Further studies are needed to confirm these results and to evaluate the incidence of osteoporotic fractures in men treated with Gn-RH agonists.

Does the vitamin D receptor genotype predict bone mineral loss in haemodialysed patients?

It has been suggested that the vitamin D receptor (VDR) gene BsmI-polymorphism is a genetic determinant of bone metabolism. To test this hypothesis, the relationship between VDR genotypes, bone mineral density (baseline and after 18 months) and parameters of calcium metabolism and bone turnover were investigated prospectively in 88 haemodialysed patients not receiving active vitamin D metabolites. Whole body, lumbar spine and femoral neck bone mineral density (BMD) were assessed by dual energy X-ray absorptiometry (DEXA). In addition calcium, phosphorus, 25(OH)D3, 1,25(OH)2D3, osteocalcin serum concentrations, alkaline phosphatase activity and intact 1,84 PTH levels were measured. VDR genotype BB, Bb and bb were found in 27, 49 and 24% of patients. Initial BMD (g/cm2) of whole body, lumbar spine and femoral neck did not differ between genotypes (whole body: BB 1.055 +/- 0.120, Bb 1.082 +/- 0.102, bb 1.128 +/- 0.120; lumbar spine: BB 1.075 +/- 0.199, Bb 1.079 +/- 0.185, bb 1.099 +/- 0.170; femoral neck: BB 0.808 +/- 0.160, Bb 0.862 +/- 0.127, bb 0.842 +/- 0.125; mean +/- SD), but the decrease of whole body and femoral neck BMD during 18 months was significantly (P < 0.02) different between the genotype groups (whole body: BB -0.048 +/- 0.028, Bb -0.031 +/- 0.029, bb -0.024 +/- 0.023; femoral neck BB -0.044 +/- 0.069, Bb -0.032 +/- 0.081, bb -0.012 +/- 0.029 g/cm2). This preliminary study suggests faster mineral loss in BB genotype of VDR in haemodialysed patients.

Differential effects of bone mineral content and bone area on vertebral strength in a swine model.

Since the biomechanical competence of a vertebral body may be closely related to the content and distribution of the bone mineral, we have evaluated the effects of projected vertebral bone area (BA) and bone mineral parameters [bone mineral content (BMC) or bone mineral density (BMD)] on their biomechanical competence. We used dual-energy X-ray absorptiometry (DXA) to assess the bone mineral parameters of 36 swine thoracic vertebrae (T1-T12) and 15 lumbar vertebrae (L1-L5) after removal of the posterior elements. The failure load, compressive stress, and the stored strain energy of these vertebral bodies were assessed by a uniaxial compressive test using an MTS 810 testing system. Multiple regression analysis showed a significantly negative effect of BA and significantly positive effect of BMC on the biomechanical competence (compressive stress, r2 = 0.67, P < 0.0001; failure load, r2 = 0.75, P < 0.0001). However, the stored strain energy was only related to the BMC (r2 = 0.35, P < 0.0001). The contributory effects of BMC and BA on the biomechanical competence were not equal. The effects of BMC was larger than BA in determining the failure load and stored strain energy, whereas the reverse was found for the compressive stress. Using the log-transformed parameters as the regressors resulted in similar results. These results suggested the differential effects of BA and BMC in determining the biomechanical competence of vertebral bodies. We recommend the use of both parameters instead of BMD alone for evaluation of the vertebral biomechanical competence.

Effect of estrogen deficiency on cancellous and cortical bone structure and strength of the femoral neck in rats.

Eighty mature Sprague-Dawley rats were weight matched before ovariectomy (Ovx) or Sham surgery (Sham). Sham rats had free access to food and water throughout the experiment, whereas Ovx rats were kept on the pair-fed diet. Rats were euthanized at 4, 8, and 12 weeks after surgery, and had received fluorochrome bone markers at 9 and 2 days prior to euthanasia. In addition 10 rats were euthanized at the time of surgery serving as baseline controls. All rats were also scanned for body composition and bone mineral parameters by DEXA before surgery and euthanasia. Left proximal femurs (femoral necks) were used for bone histomorphometry, whereas right femurs were used for in vitro DEXA measurements and mechanical testing. Despite pair-feeding, ovariectomized rats had increased body weights and fat body mass, whereas the percent lean body mass steadily declined throughout the experiment. Mineral density of the whole femur and femoral neck was significantly higher in the Sham rats relative to Ovx animals. Ovariectomy reduced trabecular number and thickness, and increased trabecular separation and bone marrow space at the femoral midneck location. The structure of the remaining trabeculae was dramatically changed toward simpler struts as revealed by nodal analyses. Cortical thickness in Ovx rats was reduced because of the high endocortical resorption, which, in addition to cancellous bone resorption, resulted in fewer endocortico-trabecular connections. Femoral necks obtained from ovariectomized rats had reduced strength and were less stiff relative to controls. Because of the enormous clinical significance of the proximal femur for osteoporosis in humans, and the opportunity for studying bone BMD, mass, structure, and strength at the same skeletal location, the femoral neck appears superior to other skeletal sites routinely used for bone histomorphometry or mechanical testing in the Ovx rat model.

Bone mineralization and bone mineral metabolism in children with juvenile rheumatoid arthritis.

To identify mechanisms of the osteopenia associated with juvenile rheumatoid arthritis (JRA) by determining parameters of bone mineralization, and bone mineral content and density (BMC and BMD), in children with JRA. BMC and BMD were measured by dual x-ray absorptiometry in 41 children with JRA and 62 healthy children. Serum samples were analyzed for concentrations of minerals, vitamin D, parathyroid hormone, osteocalcin, bone-specific alkaline phosphatase (BAP), procollagen I carboxy-terminal propeptide, and tartrate-resistant acid phosphatase (TRAP), and urinary excretion of deoxypyridinoline crosslinks and calcium. BMD was decreased in all sites in JRA patients. BMD, corrected for age, height, weight, and bone area, was decreased at cortical bone sites (1/3 radius, upper and lower extremities, and whole body). Low concentrations of osteocalcin and BAP suggested reduced bone formation, and low TRAP levels suggested decreased resorption. Clinical scales of disease severity were negatively correlated with measures of bone mass. Laboratory markers of disease severity were highly correlated with decreases in markers of bone formation, but not with those of resorption. Although laboratory findings were similar for children with oligoarticular and polyarticular disease, differences in bone mass were greater in children with polyarticular disease. These data suggest an association between decreased bone mineralization in JRA and low bone formation that is related to disease severity. Efforts to stimulate bone formation, therefore, need to be considered clinically in prepubertal children with active JRA.