SEARCH · PubMed Health
Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
X-ray dual photon absorptiometry has replaced isotopic mono and dual photon absorptiometry in the assessment of metabolic bone diseases. This method is a valuable tool for epidemiologic studies. Individual examinations give poor in vivo accuracy and precision. Further technical improvements are needed to give bone densitometry a predictive value for osteoporotic risk.
The suggestion that norethisterone acetate (NETA) stimulates bone formation prompted us to investigate calcium and bone metabolism in post-menopausal women treated with a continuous combination of oestrogen and NETA. The study included 49 healthy post-menopausal women. After an initial examination the women were randomly allocated to 2 yr of treatment with either hormones or placebo; 43 women completed the study. Within the first year of treatment the hormone group showed a slight, but significant, increase in bone mineral content in the forearms (single photon absorptiometry) and in the total skeleton (dual photon absorptiometry). After this initial increase the bone mass remained constant throughout the trial. Bone mineral density of the spine (dual photon absorptiometry) showed a significant increase of more than 5% in the hormone group. There were significant decreases of 4-7% in bone mass in the placebo group over 2 yr. Biochemical estimates of bone turnover (plasma bone Gla protein, serum alkaline phosphatase, fasting urinary calcium and fasting urinary hydroxyproline) fell significantly in the hormone group, but remained unchanged in the placebo group. We conclude that continuous administration of NETA in combination with oestrogen provides effective prophylaxis against post-menopausal bone loss, although it does not produce a persistent positive calcium balance in early post-menopausal women.
Serum concentrations of parathyroid hormone are frequently increased in elderly subjects. How much this increase may contribute to the development of osteoporosis in such subjects is unknown. Long-standing hypoparathyroidism has been reported to be accompanied by an increase in skeletal density. In seven consecutive women, aged 40 to 83 years, with hypoparathyroidism of at least 18 years duration, the mineral density in the lumbar vertebrae was measured by quantitative computed tomography (QCT) and dual photon absorptiometry (DPA). In these subjects, the bone mineral density by dual photon absorptiometry was 1.4 to 6.2 standard deviations above mean values for age-matched normal women. However, the mineral density of vertebral trabecular bone as determined by quantitative computed tomography was only slightly increased above values reported for normal women. The differences between the values determined by dual photon absorptiometry and quantitative computed tomography indicate that most of the increase in mineral density was a reflection of increased cortical bone. Roentgenograms of the metacarpals did not reveal consistent differences between normals and the hypoparathyroid subjects. These findings suggest the possibility that control of parathyroid function might be of value in treating osteoporotic patients.
With the use of photon absorptiometry, bone mineralization was measured at birth and 8 and 16 weeks after delivery in 12 very-low-birth-weight premature (mean +/- SD gestational age, 31 +/- 1.5 weeks) infants who required minimal medical support. Simultaneously, 19 healthy term infants were studied. Throughout the study, each neonate received modified 84-kJ/30 mL formula containing no added calciferol. The recommended daily allowance (400 IU) of calciferol was given to each infant as an oral supplement. Serum 25-hydroxyvitamin D, calcium, phosphorus, and parathyroid hormone concentrations were monitored biweekly and were normal. Bone mineral content and bone width significantly differed at birth between the term and premature infants. However, by 16 weeks after delivery, the premature infants had exceeded the bone mineral status of the term infants at birth, and their bone mineral content was not significantly lower than that of the term infants. These data indicate improved bone mineralization as compared with previously reported data from very-low-birth-weight neonates.
OBJECTIVE: To determine the effect of the timing of initiation and the duration of postmenopausal estrogen therapy on bone mineral density (BMD). DESIGN: Cross-sectional study. SETTING: White, middle-class to upper middle-class community-dwelling women. PARTICIPANTS: A total of 740 women aged 60 to 98 years who participated in a study of osteoporosis. MEASUREMENTS: Questionnaire, validated medication use, and height and weight. Bone mineral density at the ultradistal radius and midshaft radius using single-photon absorptiometry (SPA) and at the hip and lumbar spine using dual-energy x-ray absorptiometry (DEXA). RESULTS: Of the 740 women, 69% had used oral estrogen after menopause and 30% were current users. Five groups of estrogen use were identified: never users, past users who started at menopause, past users who started after age 60 years, current users who started after age 60 years, and current users who started at menopause. At all 4 bone sites, current users who started at menopause had the highest BMD levels, which were significantly higher than never users or past users who started at menopause (with 10 years' duration of use). These differences persisted after controlling for all major risk factors for osteoporosis. Among current users, there was no significant difference in BMD levels at any site between those who started estrogen at menopause (with 20 years of use) and those who started after age 60 years (with 9 years of use). CONCLUSIONS: Estrogen initiated in the menopausal period and continued into late life is associated with the highest bone density. Nevertheless, estrogen begun after age 60 years and continued appears to offer nearly equal bone-conserving benefit.
BACKGROUND: Substantial changes in mineral and skeletal metabolism occur during pregnancy and lactation. The purpose of this study was to compare three contrasting osteopenic states in the rat: (1) physiological (lactation), (2) endocrine-deficiency (ovariectomy), and (3) lack of mechanical usage (immobilization). METHODS: One group of female rats went through a pregnancy and 21 days of lactation (LAC). Another group was ovariectomized (OVX) for 6 weeks, and another group had one hind limb immobilized (IMM) for 6 weeks. Bone mineral density was determined by photon absorptiometry, and changes in cancellous and cortical bone were determined by backscattered electron imaging (BSE), scanning electron microscopy (SEM), structural morphometry, and fluorochrome-based histomorphometry. RESULTS: The LAC group gained the most weight but had the least bone mineral density and metaphyseal bone mass. The OVX and IMM groups also had less bone mass than controls (CONT). Changes in cancellous bone structure occurred in all groups, but the IMM group had a more uniform distribution of metaphyseal bone loss. Longitudinal bone growth was greater in the IMM and OVX groups but less in the LAC group. Cancellous bone formation rates were greater in the OVX and LAC group. Cortical bone width was less in the LAC, IMM, and OVX groups. Periosteal bone formation was greater in the OVX group but less in the LAC group. CONCLUSIONS: Considerable osteopenic changes occur in cancellous and cortical bone during the first reproductive cycle in the rat. The osteopenia of lactation is somewhat similar to that observed after ovariectomy, likely because both are hypoestrogenic conditions. Because this bone loss occurs during a normal physiological event, these data suggest that before the first reproductive cycle, the female rat has a skeletal mass in excess of that needed for normal mechanical usage.
Black and white women in the United States differ with respect to bone mass and the risk of developing osteoporosis. It has been suggested that greater body size among U.S. blacks may contribute to greater bone density in this group. It is not known whether the fat or lean component contributes more to this relationship. Bone density was measured at seven sites in 161 normal black and white women using single and dual photon absorptiometry. The first principal component accounted for 73% of the variance in the sample and constitutes an index of skeletal mass. The second principal component added another 10% and contrasts the axial and appendicular sites. Both the regional bone densities and the first principal component showed significantly greater bone densities for blacks; adjustment for body size reduced bone mass differences by approximately 50%. Body composition analysis done on a subset of these women indicated that the fat component of body mass may be the more important factor in its effect on bone mass.
Nine-month-old female rats were subjected to right hindlimb immobilization or served as controls for 0, 2, 10, 18, and 26 weeks. They were double-labeled with bone markers prior to sacrifice. Experimental unloading was produced by immobilizing the right limb against the abdomen with an elastic bandage. Single-photon absorptiometry was performed on the intact femurs; static and dynamic histomorphometry were performed on 20-micron thick toluidine blue-stained, undecalcified cross sections of the tibial shafts. Changes in the continuously immobilized tibiae were compared to those in both tibiae of age-matched controls. Unloading shut off nearly all periosteal bone formation and accelerates bone marrow expansion over that which occurs in age-related controls. The effect of unloading appeared to be mediated by recruiting fewer osteoblasts which showed inhibited activity. Furthermore, unloading increased endocortical percentage eroded surface. These histological changes lowered cortical bone mass by inhibiting diaphyseal cross sectional expansion and enlarging the bone marrow cavity. The results support Frost's suggestion that decrease mechanical usage depresses bone modeling-dependent bone gain by decreasing activation of modeling in the formation mode. It also stimulates bone remodeling-dependent bone loss by increasing activation of remodeling in the resorption mode.
We present a rapid technique for determining cancellous bone mineral changes in small experimental animals. We used the distal centimeter of the right femur from ovariectomized (OX) (N = 30) and shamovariectomized (ShOX) (N = 28) rats, aged 90 days at surgery and killed at times from 125-540 days postsurgery. We used dual photon absorptiometry to scan the segment three times: intact, after parasagittal splitting, and after removing all cancellous bone. We equated the difference between the second and third scans to cancellous bone mineral content (Cn.BMC). To validate this, we compared it with histomorphometrically determined bone volume (BV/TV) of the proximal tibial metaphysis of the same rat. Parasagittally splitting the segment removed no detectable mineral. OX rats had 40% less Cn.BMC than ShOX rats. However, OX rats had 80% lower BV/TV than ShOX rats. The subtraction technique not only makes a rapid, reasonable assessment of cancellous bone loss in OX rats but permits a smaller sample size than histomorphometry. The histomorphometric technique finds a greater difference between OX and ShOX rats because it examines a region where cancellous bone loss is more marked than does the scanning technique. The current technique measures bone of not only the central secondary spongiosa but also the juxtacortical region and the primary spongiosa, where OX-related differences are less prominent. The principles of this subtraction technique proved workable. However, for the future, we recommend a two-scan technique using a dual energy X-ray scanner. It is likely to take only 20-30 min per specimen to assess cancellous bone mineral.
For approximately 2 years, bone loss was measured in women with early stages of rheumatoid arthritis (RA) and in control subjects, using serial computed tomography and dual photon absorptiometry. Rapid trabecular bone loss from the distal radius was observed in the RA patients but not the controls. The bone loss correlated with initial plasma levels of parathyroid hormone and 1,25-dihydroxyvitamin D3 (calcitriol) concentrations. It has been suggested that these humoral factors may interact with cytokines or other mediators produced in the adjacent wrist joint. Losses of the cortical bone of the radial midshaft and the lumbar spine were modest and were comparable in the 2 groups. Indices relating to both bone formation and bone resorption predicted bone loss at these 2 sites, but changes in the parathyroid hormone and calcitriol concentrations did not.
Measurements by scanning electron microscopy (SEM) of femoral hemisections confirmed and amplified results by single-photon absorptiometry that had shown a marked increase in lactation osteopenia in rats fed a low-calcium diet (LCD, 0.04% Ca) as compared with a medium-(adequate) calcium diet (ACD, 0.4% Ca). SEM of bones from rats at the end of lactation on either diet showed a large loss of trabecular bone, increased porosity of endosteal surfaces, and cortical thinning. These changes were much more striking in LCD rats than in ACD rats. Backscattered electron imaging of cross sections of the femora revealed marked cortical thinning at midshaft after lactation, especially in rats on the LCD; this method also showed a marked increase in newly formed, less dense diaphyseal bone on the endosteal surface when dietary calcium had been made available to the LCD rats after lactation ceased. Unlike the rats fed the ACD after lactation, the rats continued on the LCD for the first 3 weeks postlactation failed to recover bone mineral, even though there was a marked decrease in resorbing surfaces of the femora as revealed by morphologic examination. When the diet was changed from the LCD to the ACD for the second 3 weeks postlactation (week 4-6), the bone mineral increased substantially. Overall, these results demonstrate the marked loss of bone during lactation, especially severe in rats fed a low-calcium diet, and the rapid postlactational recovery of bone when adequate dietary calcium was made available, even if the recovery had been delayed for the first 3 weeks by feeding a diet very low in calcium.
This study reports a method to describe and analyze the structure of the trabecular pattern seen on radiographs of the distal radius. The structure is measured and related to the bone mineral density (BMD) of the lumbar spine measured by dual-photon absorptiometry. Radiographs of hand and wrist combined with additional information of the bone mineral density of the vertebrae serve as testing material. With a computer-aided imaging system, a part of the depicted radius is scanned. The image is filtered and segmented into a bilevel picture consisting of a light network with dark meshes. Seven features of the bilevel picture are measured and analyzed. It is shown that six features correlate significantly with the bone mineral density measured at the lumbar spine, although the correlations between the trabecular pattern and the BMD are too weak to allow precise predictions of BMD values for individuals. Nevertheless, the correlations confirm the existence of a relationship between the radiographic trabecular pattern and the bone mineral density of the lumbar spine. The method is worth being further developed for use on individual patients. It provides a noninvasive tool to make an objective and quantitative assessment of the trabecular pattern.
The load-carrying capacity of cortical bone is closely related to its geometry and to its fundamental material properties, including mineral content (BMC). Together these determine the bending stiffness EI, where I is the cross-sectional moment of inertia and E is Young's modulus of elasticity. To assess the relationship of BMC and bone width (BW) to EI in healthy women, we used mechanical response tissue analysis (MRTA), a noninvasive method that involves analysis of tissue responses to ulnar vibration. A total of 48 healthy women were enrolled into an older (64 +/- 1y, n = 25) and a younger (25 +/- 0.6y, n = 23) group. BMC and BW of the dominant ulna were measured by single-photon absorptiometry (SPA). EI was determined by MRTA. BMC (0.75 +/- 0.02 versus 0.63 +/- 0.02 g/cm), BMC/BW (0.75 +/- 0.02 versus 0.63 +/- 0.02 g/cm2), and EI (27.7 +/- 1.3 versus 21.3 +/- 1.1 N.m2) were significantly greater (p less than 0.005) in the young subjects. BW did not change with age (1.00 +/- 0.01 versus 1.01 +/- 0.01 cm). In young women, simple correlations of BMC and BW with EI were both significant. By multiple regression analysis only BW independently predicted EI (EI = -0.35 + 39.1 x BMC, R2 = 0.52). In older women BMC and BW correlated with EI, but in multiple regression only BMC was significant (EI = -34.5 + 62.1 x BW; R2 = 0.45). When this analysis of older women included only those whose BMC values were within 2 SD of the young mean, BMC remained the only significant predictor of EI.(ABSTRACT TRUNCATED AT 250 WORDS)
An automated image comparison procedure was developed to optimize the precision of bone mineral density measurements by dual-photon absorptiometry. Changed acquisition conditions cause differences between two images to be compared. Alignment of one image with respect to the other is performed by a transformation that involves a rotation, a horizontal or vertical shift, and a correction for the soft tissue level. The best possible transformation is found in a stepwise search, guided by initial estimations of its parameters. After optimum transformation of one image, the region of interest of the other image is applied to both of them. Duplicate measurements of 9 patients and 15 normal subjects were performed; automated analysis yielded improved precision with respect to manual analysis. The coefficient of variation (CV) was also computed. The CV for automated analysis was 2.00% for patients and 1.04% for normal subjects compared to 3.55 and 1.93%, respectively, for manual analysis. For phantoms, the precision was 2.67% for manual analysis and 0.49% for automated analysis.
This study was undertaken to examine the effect of estrogen replacement therapy alone and estrogen replacement therapy plus variable-resistance weight training on the bone mineral content of surgically menopausal women. A total of 20 surgically menopausal women were randomized and treated with either 0.625 mg conjugated estrogen daily or the same dose of estrogen plus a closely monitored exercise program involving the use of Nautilus muscle strengthening/endurance equipment. After 1 year's observation, the bone mineral density (BMD) of the spine determined by dual-photon absorptiometry increased in the exercising subjects by 8.3 +/- 5.3% (p = 0.004), 95% confidence limits (CL) 3.9-12.8%; the group with estrogen replacement therapy alone maintained their BMD: 1.5 +/- 12.4% (p = 0.36; 95% CL = -6.9-9.8%). The total body BMD of the exercising group increased by 2.1 +/- 1.5% (p = 0.003; 95% CL = 0.8-3.3%); the nonexercising women had a nonsignificant 0.6 +/- 2.9% change (p = 0.30; 95% CL = -1.4-2.5%). A significant increase of 4.1 +/- 4.3% (p = 0.01; 95% CL = 0.8-7.4%) in the radial midshaft BMD of the exercising group was found; the estrogen alone group recorded a nonsignificant change of -0.3 +/- 3.1% (p = 0.33; 95% CL = -1.7-2.4%). The results of this study suggest that variable-resistance training in estrogen-replete women adds bone to both the axial and appendicular skeleton.
Bone disease is one of the most important clinical manifestations of primary hyperparathyroidism. Recent studies have shown that the loss of bone in "modern" hyperparathyroidism is not homogeneous throughout the skeleton. Whereas measurements of the spine and the trabecular portion of iliac crest are normal or even slightly increased, the wrist and the cortical bone of the iliac crest are significantly lower than expected. Thus, knowledge of the percentage of trabecular bone at each measurement site is important. These include distal radius, 80%; midradius, 5%; vertebrae, 19-25%; vertebral body, 33-42%; and femoral neck, 43%. Knowledge of the precision and its relationship to ranges and rates of change of bone mass are essential. For an individual, the bone mass should change by 2.8 times the precision before one can determine with 90% confidence that the change was real, not due to measurement error. Noninvasive methods of measuring bone mass that are commercially available include single- and dual-photon absorptiometry, quantitative computed tomography, and dual-energy x-ray absorptiometry. The precision of these techniques varies, with the best values reported using dual-energy x-ray absorptiometry. Research should be done to describe more completely the patterns of bone loss in this disease, including longitudinal studies on rates of loss at different skeletal sites. Studies that relate the bone mass at a particular site to fractures must be done in populations with hyperparathyroidism to see if the risk of fracture is similar to the risk in normal or osteoporotic individuals.
Bone densitometry using dual-photon absorptiometry (DPA) or dual-energy x-ray absorptiometry (DXA) has become a standard method for assessing bone mineral content in the spine and other skeletal regions. A projected areal density, referred to as bone mineral density (BMD,g/cm2), is normally calculated to assess regional bone density and strength. We demonstrate that this measure can be misleading when used to compare bones of different sizes due to inherent biases caused by bone thickness differences. For example, assuming that volumetric bone density remains constant and bony linear dimensions are proportional to height, a 20% increase in height would result in a 20% increase in both the thickness and the BMD of any bone. We describe new analysis methods to reduce the confounding effect of bone size, and we introduce a parameter, bone mineral apparent density (BMAD, g/cm3), that better reflects bone apparent density. Using this parameter, we calculate a quantity that serves as an index of bone strength (IBS, g2/cm4) for whole vertebral bodies. These analyses were applied to lumbar spine (L2-4) DXA measurements in a population of women 17-40 years old and appear to offer advantages to conventional techniques.
Age-related changes in bone density contribute to the risk of fractures. To describe the relationship between age and bone mass in elderly women, we studied a large cohort of women over age 65 years who were recruited from population-based lists in four cities in the United States. Bone density in g/cm2 was measured by single-photon absorptiometry (SPA) and dual x-ray absorptiometry (DXA) at the distal and proximal radius, the calcaneus, the lumbar spine, and the proximal femur. Centralized data collection was used to control data quality and consistency. We found a strong inverse relationship between bone density and age for most sites. Decrements in bone density between women aged 65-69 years and women 85 years and older exceeded 16% in all regions except the spine, where the difference between the two age groups was 6%. Ward's triangle and the calcaneus exhibited the largest decrements, with 26 and 21%, respectively. The estimates of annual changes in bone mineral density by linear regression at sites other than the spine ranged from -0.82% at the femoral neck and trochanter to -1.30% at Ward's triangle. Correlations between the different regions ranged from r = 0.51 between the proximal radius and Ward's triangle to r = 0.66 between the distal radius and calcaneus. We conclude that the inverse relationship between age and bone mass measured by absorptiometry techniques in white women continues into the ninth decade of life. The relationship is strongest for bone density of Ward's triangle and the calcaneus and weakest for the spine.