A controlled trial of the effect of calcium supplementation on bone density in postmenopausal women.

Background. The effectiveness of calcium in retarding bone loss in older postmenopausal women is unclear. Earlier work suggested that the women who were most likely to benefit from calcium supplementation were those with low calcium intakes. Methods. We undertook a double-blind, placebo-controlled, randomized trial to determine the effect of calcium on bone loss from the spine, femoral neck, and radius in 301 healthy postmenopausal women, half of whom had a calcium intake lower than 400 mg per day and half an intake of 400 to 650 mg per day. The women received placebo or either calcium carbonate or calcium citrate malate (500 mg of calcium per day) for two years. Results. In women who had undergone menopause five or fewer years earlier, bone loss from the spine was rapid and was not affected by supplementation with calcium. Among the women who had been postmenopausal for six years or more and who were given placebo, bone loss was less rapid in the group with the higher dietary calcium intake. In those with the lower calcium intake, calcium citrate malate prevented bone loss during the two years of the study; its effect was significantly different from that of placebo (P less than 0.05) at the femoral neck (mean change in bone density [+/- SE], 0.87 +/- 1.01 percent vs. -2.11 +/- 0.93 percent), radius (1.05 +/- 0.75 percent vs. -2.33 +/- 0.72 percent), and spine (-0.38 +/- 0.82 percent vs. -2.85 +/- 0.77 percent). Calcium carbonate maintained bone density at the femoral neck (mean change in bone density, 0.08 +/- 0.98 percent) and radius (0.24 +/- 0.70 percent) but not the spine (-2.54 +/- 0.85 percent). Among the women who had been postmenopausal for six years or more and who had the higher calcium intake, those in all three treatment groups maintained bone density at the hip and radius and lost bone from the spine. Conclusions. Healthy older postmenopausal women with a daily calcium intake of less than 400 mg can significantly reduce bone loss by increasing their calcium intake to 800 mg per day. At the dose we tested, supplementation with calcium citrate malate was more effective than supplementation with calcium carbonate.

[The measurement of radial bone mineral content in children].

The bone mineral contents of radius of 255 boys and 243 girls (7 to 16 year old of the Han nationality, living in Chengdu) were measured with Bone Mineral Analyzer (Type:SPA-I). The standard values of g/cm was made. There was a positive correlation between the value in boys or girls and chronological age, height or weight. The coefficients were respectively 0.83, 0.77, 0.64 in boys and 0.82, 0.82, 0.82 in girls (P less than 0.005). At the age of 13 (in boys or in girls) the value of the g/cm was the highest.

Dietary calcium, sex hormones, and bone mineral density in men.

OBJECTIVE: To evaluate the factors that determine bone mineral density at axial and appendicular sites in normal men. DESIGN: Measurement of bone mineral density of the radius by single photon absorptiometry and of the lumbar spine and hip by dual photon absorptiometry to assess their relation with various determinants of bone mineral density. Dietary calcium was assessed from a questionnaire validated against a four day dietary record. SETTING: Local community, Sydney, Australia. PATIENTS: 48 Men (aged 21-79, median 44) recruited from the local community including 35 male cotwins of twin pairs of differing sex recruited from the Australian National Health and Medical Research Council twin registry for epidemiological studies on determinants of bone mineral density. MAIN OUTCOME MEASURES: Bone mineral density of the axial and appendicular skeleton and its relation to age, anthropometric features, dietary calcium intake, and serum sex hormone concentrations. RESULTS: Dietary calcium intake (g/day) was a significant predictor of bone mineral density of axial bones, explaining 24% and 42% of the variance at the lumbar spine and femoral neck respectively. This effect was independent of weight. In contrast with the axial skeleton, bone mineral density at each forearm site was predicted by weight and an index of free testosterone but not by dietary calcium intake. CONCLUSIONS: Dietary calcium intake has a role in the determination or maintenance, or both, of the axial but not the appendicular skeleton in adult men.

Calcium supplementation and bone loss in middle-aged women.

This 4-y study investigated the effects of a calcium carbonate supplement on bone loss in 169 women aged 35-65 y, randomly assigned to placebo and treatment (1500 mg Ca/d) groups in a double-blind design. Bone mineral content (BMC) and width (W) were measured bilaterally on the radius, ulna, and humerus. BMC and BMC/W loss rates were consistently lower in treatment than in control subjects. Loss was significantly reduced in the left and right humerus and the right radius. In premenopausal subjects, only left humerus BMC loss was significantly reduced by Ca supplementation. In postmenopausal treatment subjects, BMC and BMC/W bone loss was reduced in all 12 (bilateral radius, ulna, and humerus) of the bone variables measured, 5 at p less than 0.01 and 2 at p less than 0.05. Ca supplementation counteracted a large portion of the additional bone loss attributable to menopause in this population.

Colles' fracture and bone density of the ultradistal radius.

To determine whether Colles' fracture, generally considered a manifestation of postmenopausal osteoporosis, is associated with a decrease in bone density at the site of fracture, we measured bone mineral density of the ultradistal radius (UDR-BMD) by single-photon absorptiometry with computer-assisted image processing. In 119 normal women (ages 22-92 years), UDR-BMD decreased by 17% between ages 30 and 75 years. From UDR-BMD measurements in these normal women and in 40 women (ages 53-80 years) with Colles' fracture alone, a population-based analysis was made to estimate fracture risk at different values of UDR-BMD. Colles' fracture was uncommon at UDR-BMD greater than 0.40 g/cm2 (the "fracture threshold"). As bone density decreased below this level, fractures became more frequent (a "gradient of risk").

The effects of muscle-building exercise on bone mineral density of the radius, spine, and hip in young men.

We previously demonstrated that muscle-building exercise is associated with increases in serum Gla-protein, serum 1,25(OH)2D, and urinary cyclic AMP. These studies were interpreted to mean that this form of exercise increases bone formation and modifies the vitamin D-endocrine system to provide more calcium for bone. The present investigation was carried out in normal young adult white men to determine the effects of exercise on bone mineral density at weight-bearing and nonweight-bearing sites. Twelve men who had regularly engaged in muscle-building exercises (use of weights, exercise machines, or both) for at least 1 year and 50 age-matched controls (aged 19-40 years) were studied. The body weights of the two groups were not different from each other (78 +/- 2 vs. 74 +/- 1 kg, NS). Bone mineral density (BMD) of the lumbar spine, trochanter, and femoral neck was measured by dual-photon absorptiometry, and BMD of the midradius was measured by single photon absorptiometry. It was found that muscle-building exercise was associated with increased BMD at the lumbar spine (1.35 +/- 0.03 vs. 1.22 +/- 0.02 g/cm2, P less than 0.01), trochanter (0.99 +/- 0.04 vs. 0.86 +/- 0.02 g/cm2, P less than 0.01), and femoral neck (1.18 +/- 0.03 vs. 1.02 +/- 0.02 g/cm2, P less than 0.001) but not at the midradius (0.77 +/- 0.02 vs. 0.77 +/- 0.01 g/cm2, NS). These studies provide additional evidence that muscle-building exercise is associated with increases in BMD at weight-bearing sites but not at nonweight-bearing sites.

A comparison of single and multi-site BMC measurements for assessment of spine fracture probability.

In a prospective study of 699 women, 39 new spine fracture cases were observed during a mean follow-up of 3.6 yr. Spine fracture incidence was compared to initial bone mineral content (BMC) of the calcaneus, distal radius, proximal radius, and the lumbar spine. BMC at all four sites was significantly related to spine fracture incidence. Women at -1 s.d. for calcaneal BMC had a sevenfold greater probability of spine fracture than women at +1 s.d.; women at -2 s.d. had a 50-fold greater probability than women at +2 s.d., even after adjustment for the effects of age. Combinations of BMC at two sites further strengthened the relationship to spine fracture; the best two-site combination is calcaneus and distal radius BMC. Thus women can be categorized and stratified according to future fracture risk, and the selection of postmenopausal women for preventive treatments can be guided by measurements of BMC.

Bone mineralisation in preterm infants measured by dual energy radiographic densitometry.

Dual energy radiographic densitometry was used to follow postnatal changes in the bone mineral content of the radii of 15 infants of less than 30 weeks' gestation. The system permitted bone mineral content to be measured with minimal disturbance to the infants in their incubators. Mean bone mineral content at birth was 2.4 mg/mm shaft length, decreasing to 1.9 mg/mm at 6 weeks of age, before starting to rise. Mineralisation was poor compared with that of a fetus at an equivalent postconceptual age. Mean intakes of calcium and phosphate were considerably less than the intrauterine accumulation of these minerals and it is postulated that this was the main cause of the poor mineralisation. Radiographic densitometry is both accurate and precise and has advantages over photon absorptiometry in that it can be used to measure bone mineral in infants who are not only preterm, but also ill enough to require intensive care.

Radial bone mineral content in healthy Mexican women.

Fifty healthy Mexican women from 21 to 70 years of age volunteered to undergo radial bone densitometry. The bone density in ten women per decade was assessed at two sites in the radius of the nondominant forearm; one site was the distal radius at 5 mm of separation from the ulna and the other at one-third of the distal radius. Calcium, inorganic phosphates and alkaline phosphatase were measured in serum samples and the calcium/creatinine ratio in fasting urine samples. Bone density at the distal radius was 360.6 +/- 36.2 mg/cm2, 369.8 +/- 47.9 mg/cm2 and 364.7 +/- 53.7 mg/cm2 in the 21-50 age group. There was no significant difference between these groups; the pooled value of all these samples was 365 +/- 46 mg/cm2. There was significant difference in the 51-60 age group, 290 +/- 48. mg/cm2 (p less than 0.01) and in the 61-70 age group. 277.9 +/- 49.9 mg/cm2 (p less than 0.01). Bone density at the one-third distal radius in the 21-20 age group was 696.3 +/- 60.9 mg/cm2; 31-40, 683.6 +/- 68.4 mg/cm2 and 41-50, 697.9 +/- 53.9 mg/cm2. There was no significant difference among these group; the pool of all these samples showed 692.6 +/- 59.6 mg/cm2. In the 51-60 age group it was 628.0 +/- 63.3 mg/cm2, a non significant difference. On the other hand, the density in the 61-70 group was 573.7 +/- 83.5 mg/cm2, significant (p less than 0.01) when compared to the 21-50 age group.(ABSTRACT TRUNCATED AT 250 WORDS)

Lifetime calcium intake and physical activity habits: independent and combined effects on the radial bone of healthy premenopausal Caucasian women.

Lifetime calcium intake and lifetime physical activity (PA) habits of 181 healthy premenopausal Caucasian women (aged 20-50) were studied. Nondominant arm was measured by single-photon absorptiometry at the distal (Dis) or 5-mm site and the midshaft (Mid) or two-thirds site of the radius. Values of bone mineral content (BMC), bone width (BW), and bone mineral density (BMD) were obtained. An intermediate or high lifetime Ca (greater than 500 mg/d) was significantly associated with a greater DisBMC (p = 0.0031), DisBMD (p = 0.0031), MidBMC (p = 0.0015), and MidBMD (p = 0.0015) when adjusted for PA. Similarly, with Ca adjusted for, a high lifetime PA (greater than or equal to 45 min of moderate to strenuous activity four times a week) was significantly associated with greater DisBMC (p = 0.0032), DisBMD (p = 0.0022), MidBMC (p = 0.0012), MidBW (p = 0.0173), and MidBMD (p = 0.0546). These findings suggest important roles for both adequate Ca intake and PA habits in enhancing peak adult skeletal mass and a trade-off between these two variables, when each was intermediate or higher.

Lower vertebral bone density in male long distance runners.

Bone density in 13 male long distance runners (28.7 +/- 1.2 yr, 67.6 +/- 2.0 kg) and 11 male nonrunners (26.8 +/- 1.3 yr, 71.0 +/- 2.2 kg) was compared. Bone was measured at the lumbar spine and mid-tibia using dual photon absorptiometry and at the mid-radius using single photon absorptiometry. Runners (mean weekly training 92.2 +/- 6.3 km) had significantly lower (P less than 0.05) vertebral bone mineral density (1.12 +/- 0.03 g.cm-2) than nonrunners (1.24 +/- 0.04 g.cm-2). Tibial and radial bone mineral density did not differ between the groups. Daily calcium intake for runners (1,373 +/- 486 mg) and nonrunners (1,267 +/- 236 mg) exceeded the RDA. The results of this study suggest that long distance running may lead to decreased vertebral bone mineral density. The hormonal changes that occur with endurance training may contribute to this decrease.

The effects of altered strain environments on bone tissue kinetics.

This study defines the alteration in bone tissue kinetics responsible for the "adaptive remodeling" response to altered strain environments. Adult beagle dogs were separated into three experimental groups: ulnar osteotomy, ulnar osteotomy with fracture fixation plate spanning the gap and sham surgery. Four sets of double fluorochrome labels were administered. Prior to sacrifice at 1, 3, and 6 months, strains were measured through rosette strain gages on the cranial and caudal surfaces of the intact radius. Histomorphometric analysis indicated that the increased bone mass in response to elevated strain results from increased activation frequency of modeling with more sites undergoing formation processes than resorption processes on periosteal and endocortical surfaces. Increased remodeling activation did not lead to increased bone mass. There was no evidence that elevated strain changes the individual vigor of osteoclasts or osteoblasts, or that the sigma period was altered by elevated strain.

[A clinical study evaluating bone mineral mass in the radius during skeletal growth--single photon absorptiometry].

Using 125-I single photon absorptiometry, bone mineral measurements were performed on 206 healthy Japanese children (2 to 19 years of age). Bone mineral content (BMC), bone width (BW) and BMC/BW values were determined for the radius at distal 1/6 site (metaphysis) and distal 1/3 site (diaphysis). BMC/BW values at both sites correlated well with body height and weight. Bone mass in the diaphysis (distal 1/3 site) increased linearly during the 2-19 years of skeletal growth, but bone mass in the metaphysis (1/6 site) increased steeply during the pubertal period. In children receiving glucocorticoid therapy, bone mass was reduced in proportion to the duration of drug administration. In children under anticonvulsant therapy, the yearly increase in bone mass was significantly low especially in those patients with poor physical activity levels. Bone mineral decrease in the radius occurred in the children with hypopituitalism, hypothyroidism (cretinism), hyperthyroidism and Turner's syndrome.

Correlation of bone mineralization in the radius and humerus of well premature neonates over the first 4 months of life.

To determine how well mineralization correlates in the radius and humerus of neonates, we have measured with photon absorptiometry the bone mineral content (BMC) and bone width (BW) in the humerus and radius of well premature neonates and in the radius alone of well term neonates at birth, 8 and 16 weeks of age. These data allow (1) the correlation of bone mineralization in the humerus and radius at birth and over the first 4 months of life and (2) the correlation between bone mineralization in the radius or humerus at birth and that measured at 8 and 16 weeks in the same bone site. The BMC of the radius was significantly (P less than 0.02) correlated with the BMC of the humerus at birth, 8 and 16 weeks, but the BW of the radius was significantly correlated with the BW of the humerus only at 16 weeks. On the other hand, the BMC of the radius at birth in both term and premature neonates failed to correlate significantly (P = ns) with the BMC of the radius at 8 or 16 weeks. In the humerus, the BMC at birth was significantly (P less than 0.001) correlated with that measured at 8 but not at 16 weeks. These data indicate that the humerus and radius increase in mineral content at a similar rate over the first 4 months of life but that one cannot accurately predict from the BMC at birth what the bone mineral content will be at 8 and 16 weeks of age.

Bone mineral content of the forearm in healthy Dutch women.

Single energy photon absorptiometry is a reliable technique for assessing the bone mineral content (BMC) of cortical bone in the forearm. It can also be used for BMC measurement in the ultradistal part of the forearm, where there is a considerable proportion of trabecular bone. The results of a BMC survey at both sites in healthy Dutch women, aged 26-75 yr, are reported, and the differences and changes with age are discussed. The technique offers possibilities for a rational screening programme in post-menopausal women, because of its high precision, low radiation dose, speed and low cost. The validity of the ultradistal measurement for the detection of abnormally fast bone mineral loss from trabecular bone in the individual patient has yet to be proven.

Sequential bone mineral content in small preterm infants with and without fractures and rickets.

Seventy-four infants with birth weights 1009 +/- 28 grams and gestational age 28.6 +/- 0.3 weeks (M +/- SEM) were studied prospectively to test the hypotheses that bone mineral content (BMC) measured by photon absorptiometry, would be: (1) lower in very low birth weight (VLBW) infants with radiographic evidence of fractures and/or rickets (F/R), and (2) will continue to be lower over the first year when compared to VLBW infants without F/R. BMC and bone width (BW) of the distal one-third of left radius and ulna were measured at 5 weeks (n = 8), 14 weeks (n = 61), 26 weeks (n = 58), 40 weeks (n = 59), and 1 year (n = 52). Standardized radiographs of both forearms, and weight, length, and head circumference were also determined at each study age. Investigators and technicians involved in the photon absorptiometry measurements were unaware of the radiographic findings and vice versa. Twenty-three of 74 infants were found to have F/R. BMC of studied infants remained markedly below our previously determined range of "intrauterine bone mineralization," even at 26 weeks after birth. There was no significant difference in BMC or BW between infants with and without F/R, either at the time of confirmation of F/R or during early follow-up; however, BMC was lower at greater than or equal to 6 months and BW was lower at greater than or equal to 9 months in infants with F/R. We suggest that the extremely low BMC measurements in early infancy predispose all VLBW infants to fractures and rickets.

Measurement of spinal or peripheral bone mass to estimate early postmenopausal bone loss?

This report presents data from 153 healthy, early postmenopausal women who were randomly allocated to two years of treatment with estrogen or placebo. Bone mineral content in the forearms was measured by single-photon absorptiometry, and bone mineral density of the lumbar spine and total-body bone mineral by dual-photon absorptiometry, before and after one and two years of treatment. At the end of the two years, there were highly significant differences of 6 to 7 percent between the estrogen and the placebo groups at all sites measured. The range of the changes of the spine measurement was twice that of the forearm and total-body measurements. It is concluded that measurement of the forearm by single-photon absorptiometry is superior to measurement of the spine by dual-photon absorptiometry both in clinical studies and in the individual patient for detecting estrogen-dependent bone loss and its treatment by estrogen replacement.