Bone status assessment in preterm and term infants by dual-energy X-ray absorptiometry

We assessed the bone status of preterm and term infants by measuring their bone mineral density (BMD) by dual-energy X-ray absorptiometry (DXA). Thirty neonates weighing 699–3590 g were selected as subjects. Infants with multiple anomalies or severe chronic lung disease were excluded. Using the corrected term age (35–48 weeks), we measured their lumbar spinal BMD (L1–L4) by DXA. Alkaline phosphatase (ALP) and skeletal alkaline phosphatase (B-ALP) were measured at the same time. In addition, we compared the BMD values with growth parameters and chemical markers. The term BMD correlated significantly with the birth weight (r = .90), height (r = .85), and gestational age (r = .76). The birth weight correlated more closely with the BMD than with the weight at the time of BMD measurement. The B-ALP level showed an inverse correlation with BMD (r = −0.41). The preterm infants apparently acquired lower BMDs during intrauterine life. The inverse correlation of B-ALP with BMD may be found only in the neonatal period. The BMD measured by DXA and the B-ALP level are very useful parameters for assessing bone status in infants, including extremely low birth weight infants. Received: Aug. 21, 1997 / Accepted: Nov. 6, 1997     

Association of upper arm circumference at muscle flexion with lumbar spine bone mineral density

We investigated the association of upper arm circumference at muscle flexion with lumbar spine (L2–L4) bone mineral density (BMD) in 252 postmenopausal Japanese women (mean age, 62.0 ± 7.6 years; range, 43–78 years) with right-side dominance. Age, age at menopause, years since menopause (YSM), weight, and height were recorded. Dominant upper arm circumference (cm) was measured at muscle flexion. Lumbar spine BMD was measured by dual-energy X-ray absorptiometry (DXA). Correlations between BMD and variables were determined using Pearson's correlation coefficient. Significant predictors of the lumbar spine BMD were determined using stepwise multiple regression analysis. Upper arm circumference, weight, and height were positively correlated with BMD (r = 0.397, 0.343, and 0.323, respectively), whereas YSM and age were inversely correlated with BMD (r = −0.415 and −0.392, respectively). On stepwise multiple regression analysis, YSM, upper arm circumference, and weight were significant predictors of BMD (R ² = 0.322, P < 0.0001). Predicted value of the lumbar spine BMD was calculated by the following formula: Predicted BMD = 0.249 − 0.0078 (YSM) + 0.016 (upper arm circumference) + 0.0046 (weight). Dominant upper arm circumference at muscle flexion in combination with YSM and weight is a useful predictor of lumbar spine BMD. Received: July 21, 1998 / Accepted: April 1, 1999     

PIXImus Bone Densitometer and Associated Technical Measurement Issues of Skeletal Growth in the Young Rat

The PIXImus dual-energy X-ray absorptiometer (DXA) is designed to measure body composition, bone mineral content (BMC), area (BA), and density (BMD) in mice and rats. The aims of this study were to longitudinally measure BMC, BA, and BMD in growing rats and to identify potential technical problems associated with the PIXImus. Total femur and lumbar DXA measurements, body weight, and length of initially 3-week-old rats (n = 10) were taken at weeks 5, 9, and 14. BMC and BMD of femoral metaphyseal and diaphyseal regions rich in trabecular and cortical bone, respectively, were obtained. Results showed significant increases in body weight, total femur BMC and BMD, lumbar area, length, BMC, and BMD at each time point. There was a significant positive correlation between body weight and total femur BMD (r = 0.97, P < 0.001) as well as lumbar BMD (r = 0.99, P < 0.001). BMD values for the femoral metaphyseal region and the lumbar spine were also positively correlated (r = 0.96, P < 0.01). Several technical issues (e.g., positioning of animals), difficulties (e.g., in analysis of images), and limitations (e.g., inability to detect underdeveloped calcified bone in growing animals and bone edge detection) of the software pertinent to the PIXImus were evident. In conclusion, despite limitations in the software, the PIXImus is a valuable tool for studying skeletal development of growing rats.     

Geographic Differences in Bone Mineral Density of Mexican Women

The aim of this study was to generate standard curves for normal spinal and femoral neck bone mineral density (BMD) in Mexican women using dual-energy X-ray absorptiometry (DXA), to analyze geographic differences and to compare these with “Hispanic” reference data to determine its applicability. This was a cross-sectional study of 4460 urban, clinically normal, Mexican women, aged 20–90 years, from 10 different cities in Mexico (5 in the north, 4 in the center and 1 in the southeast) with densitometry centers. Women with suspected medical conditions or who had used drugs affecting bone metabolism, were excluded. Lumbar spine BMD was significantly higher (1.089 ± 0.18 g/cm²) in women from the northern part of Mexico, with intermediate values in the center (1.065 ± 0.17 g/cm²) and lower values (1.013 ± 0.19 g/cm²) in the southeast (p<0.0001). Similarly, femoral neck BMD was significantly higher in women from the north (0.895 ± 0.14 g/cm²), intermediate in the center (0.864 ± 0.14 g/cm²) and lower (0.844 ± 0.14 g/cm²) in the southeast part of Mexico (p<0.0001). Northern Mexican women tend to be taller and heavier than women from the center and, even more, than those from the southeast of Mexico (p<0.0001). However, these differences in BMD remained significant after adjustment for weight (p<0.0001). A significant loss (p<0.0001) in BMD was observed from 40 to 69 years of age at the lumbar spine and up to the eighth decade at the femoral neck. Higher and lower lumbar spine values, as compared with the “Hispanic” population, were observed in Mexican mestizo women from the northern and southeastern regions, respectively. In conclusion, there are geographic differences in weight and height of Mexican women, and in BMD despite adjustment for weight. Received: 1 September 1999 / Accepted: 20 October 1999     

Bone Mineral Density and Lifetime Physical Activity in South African Women

We investigated the relation between lifetime physical activity and bone mineral density (BMD) in South African women using data collected in a case-control study of breast cancer in relation to BMD. Subjects (n = 144) were of black African or mixed ancestral origin, and <60 years of age (mean age 42.6 ± 8.9 years). Cases had newly diagnosed breast cancer (n = 62) and controls were referred for conditions unrelated to BMD or breast cancer (n = 82). Physical activity data consisting of household, occupational and leisure-time activity, and activity for transport, were collected via questionnaire at 4 life stages (epochs), viz. 14–21, 22–34, 35–50, and 50+ years of age. Total energy (MET hrs) and peak strain scores were calculated. Lumbar spine and total proximal femur BMD were measured using dual-energy x-ray absorptiometry. BMD measures were similar between groups, therefore data were combined. BMD measures were unrelated to total lifetime physical activity. However, the major determinants of total proximal femur BMD included age, transport activity including walking and bicycling between the ages of 14 and 21 years, and current weight (adjusted r² = 0.33, P < 0.0001). The major determinants of lumbar spine BMD included age, household energy expenditure between the ages of 14 and 21 years, and current weight (adjusted r² = 0.23, P < 0.0001). Total peak bone strain score for activities between 14–21 years of age was also significantly correlated with lumbar spine BMD (r = 0.18, P < 0.05). Intraclass correlation coefficients to assess tracking of activity through epochs 1, 2, and 3 were high for total energy expenditure (0.96; 95%CI: 0.94–0.97), household (0.98; 95%CI: 0.97–0.99) and occupational activity (0.78; 95%CI: 0.71–0.84) and activity for transport (0.92; 95%CI: 0.89–0.94). These data suggest that walking or activities resulting in impact loading at a young age are associated with higher BMD in later years. In addition, our findings suggest tracking of physical activity over time.     

The relationship between spinal and appendicular bone mass modified by physical, historical, and lifestyle factors

Spinal, radial, and calcaneal bone mineral density (BMD) measured by dual-energy X-ray absorptiometry (DXA) and calcaneal bone mass measured by quantitative ultrasound densitometry (QUS) were compared in 83 healthy Japanese female volunteers. A significant and strong correlation was found within the same methods (r = 0.619 for lumbar spine and radius by DXA, r = 0.760 for lumbar spine and calcaneus by DXA, and r = 0.644 for calcaneus and radius by DXA), and within the same site (r = 0.758 for calcaneus by DXA and QUS). A lesser correlation was found when both the method and site were different (r = 0.521 for radius by DXA and calcaneus by QUS, and r = 0.583 for lumbar spine by DXA and calcaneus by QUS). Relations of spinal and appendicular bone mass were examined together with physical, historical, and lifestyle factors. Multiple correlation coefficients between bone mass at the lumbar spine and appendicular bone were 0.754 to 0.782, and all these increased after modification by physical, historical, and lifestyle factors in whichever appendicular bone. In the correlation between lumbar spine and radial BMD, past weight-bearing activity, age at menarche, family history of fractures, and body weight were chosen. Menstrual status, body weight, past weight-bearing activity, and present arm-using activity were chosen to determine the correlation between lumbar spine BMD and calcaneal bone mass by QUS. These results suggest that the incorporation of those factors improved the correlation between lumbar spine BMD and appendicular bone mass, especially in cases of lumbar spine BMD versus radial BMD or calcaneal bone mass by QUS. Received: Aug. 7, 1999 / Accepted: Oct. 29, 1999     

Vitamin D and bone mineral density

Bone mineral density (BMD) at the lumbar spine and the neck of femur and serum concentrations of 25-hydroxyvitamin D (25OHD), intact parathyroid hormone (PTH), alkaline phosphatase, calcium, albumin, creatinine and phosphate were measured in a group of 166 postmenopausal women (30–79 years) attending a bone clinic for bone density measurements. Four subjects with suspected primary hyperparathyroidism were excluded from analysis. BMD at the lumbar spine was correlated with body mass index (BMI) (r=0.278,p=0.0003), age (r=−0.194,p=0.0134) and serum 25OHD (r=0.188,p=0.0167). BMD at the neck of femur correlated with BMI (r=0.391,p<0.0001), age (r=−0.356,p<0.0001), PTH (r=−0.156,p=0.047) and serum 25OHD (r=0.231,p=0.0031). Stepwise multiple regression analysis showed that age, BMI and serum 25OHD contributed to the variation in BMD at lumbar spine. At the neck of femur, PTH was an additional contributor. We conclude that serum 25OHD makes a contribution to BMD a lumbar spine and neck of femur.     

Continuous Loss of Bone During Chronic Immobilization: A Monozygotic Twin Study

Acute immobilization is associated with rapid loss of bone. Prevailing opinion, based on population cross-sectional data, assumes that bone mass stabilizes thereafter. In order to address whole-body and regional skeletal mass in long-term immobilization, monozygotic twins were studied, one of each twin pair having chronic spinal cord injury (SCI) of a duration ranging from 3 to 26 years. The research design consisted of the co-twin control method using 8 pairs of identical male twins (mean ± SD age, 40 ± 10 years; range 25–58 years), one of each set with SCI. The twins were compared by paired t-tests for total and regional bone mineral content (BMC) and bone mineral density (BMD) measured by dual-energy X-ray absorptiometry. Linear regression analyses were performed to determine the associations of age or duration of injury with the differences between twin pairs for total and regional skeletal bone values. In the SCI twins, total-body BMC was significantly reduced (22%± 9%, p<0.001), with the predominant sites of reduction for BMC and BMD being the legs (42%± 14% 35%± 10%, p<0.0001), and pelvis (50%± 10% and 29%± 9%, p<0.0001). Duration of SCI, not age, was found to be linearly related to the degree of leg bone loss in SCI twins (BMC: r ²= 0.60, p<0.05; BMD: r ²= 0.70, p<0.01). Our findings suggest that pelvic and leg bone mass continues to decline throughout the chronic phase of immobilization in the individual with SCI, and this bone loss appears to be independent of age. Received: 28 September 1998 / Accepted: 28 December 1998     

Bone Mineral Density During Reduction, Maintenance and Regain of Body Weight in Premenopausal, Obese Women

Weight loss may lead to bone loss but little is known about changes in bone mass during regain of reduced weight. We studied changes in bone mineral density (BMD) and bone mineral content (BMC) during voluntary weight reduction and partial regain. The study consisted of three phases: a 3 month weight reduction with very-low-energy diet (VLED), a 9 month randomized, controlled walking intervention period with two training groups (target energy expenditure 4.2 or 8.4 MJ/week) and a 24-month follow-up. The participants were premenopausal women with a mean body mass index of 34.0 (SD 3.6) kg/m². Seventy-four of 85 subjects completed the whole study. Total body, lumbar spine, proximal femur and dominant radius BMD and BMC were measured with dual-energy X-ray absorptiometry (DXA). The mean weight loss during VLED was 13.2 (3.4) kg, accompanied by unchanged total body BMC and decreased lumbar, trochanteric and radial BMD (p<0.05). During months 3–36, an average of 62% of the weight loss was regained, total body BMC decreased and trochanteric BMD increased (p<0.05). At the end of the study, total body BMC and lumbar and femoral neck BMD were lower than initially (p<0.05). Weight change throughout the study correlated significantly with the change in radial (r= 0.54), total body (r= 0.39) and trochanteric (r= 0.37) BMD. Exercise-group assignment had no effect on BMD at weight-bearing sites. In conclusion, the observed changes in BMD and BMC during weight reduction and its partial regain were clinically small and partly reversible. More studies are needed to clarify whether the observed weight changes in BMD and BMC are real or are artifacts arising from assumptions, inaccuracies and technical limitations of DXA. Received: 20 April 2000 / Accepted: 20 September 2000     

Birth Weight as a Predictor of Adult Bone Mass in Postmenopausal Women: The Rancho Bernardo Study

Understanding the determinants of adult bone mass may help to identify women for prevention of osteoporosis. We postulated that birth weight would predict low adult bone mass in old age. Subjects were 305 postmenopausal Caucasian women (mean age 70 years). Bone mineral content (BMC) and bone mineral density (BMD) were measured at the wrist, forearm, hip and lumbar spine. Birth weight was assessed by self-report. Birth weight was positively correlated with BMC at the forearm (r= 0.15), hip (r= 0.12) and lumbar spine (r= 0.18), and the age-adjusted mean BMC increased significantly from the lowest to the highest birth weight tertile. Adjusting for adult weight diminished this association at the forearm and hip, but not at the spine. Adjustment for multiple other covariates, including height, did not materially change these associations. Adult weight and height were significantly correlated with birth weight (r= 0.19 and r= 0.24, respectively). Birth weight was not independently correlated with BMD. Birth weight was thus positively correlated with adult weight and BMC 70 years later. These findings suggest that low birth weight may be a marker for future low bone mass and that different mechanisms exist for establishing the adult bone envelope (estimated by BMC) versus its density (estimated by BMD). Received: 18 August 1999 / Accepted: 21 January 2000     

Risk factors for low bone mineral density and the 6-year rate of bone loss among premenopausal and perimenopausal women

Risk factors that are associated with lower bone mineral density (BMD) may not necessarily be associated with increased bone loss among premenopausal and perimenopausal women. We determined risk factors for lower premenopausal and perimenopausal BMD while simultaneously determining risk factors for increased 6-year rate of bone loss among women aged 24–50 years within a population-based prospective cohort study. BMD of the lumbar spine and femoral neck, reported as t scores, were measured five times within the 6-year study among 614 women who were between the ages of 24 and 44 in 1992/1993. Rates of bone loss were calculated from the repeated BMD measurements. Risk factors for lower BMD over time at the lumbar spine included history of any fracture (P=0.005). The major risk factor for lower BMD over time at the femoral neck was family history of osteoporosis (P<0.002). The major protective factor for greater BMD over time at both skeletal sites was additional body weight (P<0.0001). Other protective factors for greater BMD over time at the femoral neck were modest alcohol consumption (P=0.0002) and high-school sports participation (P=0.002). Risk factors for greater bone loss at either skeletal site included postmenopausal status (P<0.0001 at the lumbar spine; P=0.01 at the femoral neck), and the reporting of a reproductive cancer (P<0.0001 at the lumbar spine; P=0.0008 at the femoral neck). Body weight was protective against bone loss at both skeletal sites (P<0.0001). Baseline age, calcium intake, smoking, and current physical activity were not associated with BMD or bone loss. The understanding of the relative importance of risk factors for both low BMD and bone loss may assist in the identification of women at greater risk for subsequent low postmenopausal BMD.     

A study of bone mineral density and physical growth in very low birth-weight infants after their discharge from hospital

The lumbar spinal bone mineral density (BMD) of very low birth-weight (VLBW) infants was determined by dual-energy X-ray absorptiometry, and its relationship with physical growth was analyzed. The influence of birth-related factors on changes in BMD after discharge from the hospital were also investigated. The BMD increased rapidly until the age of 2 years, in association with improvements in nutritional status and the increase in physical growth after discharge. The Z score, which indicates the degree of attainment of the age-specific standard BMD, was determined to be almost 90% at the age of around 2 years and older. Significant increases in the BMD continued to be noted after the age of 2 years, along with increases in body weight and body height. At the age-adjusted value at less than 1 year, however, the Z score tended to be low when the birth weight (<1000 g) and birth height (<36 cm) were low (P < 0.02, respectively), suggesting that the birth weight and birth height influence the BMD at this age. These results indicate that the condition at birth and nutritional management during hospitalization affect the BMD soon after discharge, but that the nutritional condition after discharge becomes a more important factor at the age of 2 years and older. Received: August 1, 2001 / Accepted: October 26, 2001     

Relative contribution of lean and fat mass component to bone mineral density in males

 We investigated the relative contribution of lean body mass (LBM) and body fat mass to bone mineral density (BMD) in 93 healthy Japanese male volunteers (mean age, 33.1 ± 6.9 years; range, 18–54 years). Age, height (Ht), weight (Wt), and body mass index (BMI, Wt/Ht²) were recorded. Body fat mass, percentage of body fat, body fat mass/Ht², LBM, LBM/Wt, LBM/Ht², and lumbar spine (L2–L4) and total body BMD (TBBMD) were measured by dual-energy X-ray absorptiometry. On the Pearson correlation test, LBM was positively correlated with L2–L4 BMD. LBM, LBM/Wt, and LBM/Ht² were positively correlated with TBBMD. However, body fat mass and body fat mass/Ht² were not correlated with lumbar spine and total body BMD. On the partial correlation test, LBM was still correlated with lumbar spine (r = 0.307, P < 0.05) and total body BMD (r = 0.545, P < 0.0001), irrespective of age and height, whereas body fat mass was not correlated with BMD of these sites (r = −0.069 and −0.169, respectively). We concluded that, in males, LBM is one of the significant determinants of BMD whereas body fat mass is a negligible BMD determinant. Received: February 15, 2002 / Accepted: July 5, 2002 Offprint requests to: T. Douchi     

Higher Osteocalcin Levels and Cross-Links Excretion in Young Men Born with Low Birth Weight

As the result of accelerated growth, the final height of infants born with low birth weight (LBW) is near to the normal. Limited data are available about the bone density and bone turnover just after completion of skeletal development. We have investigated the bone turnover and bone density in 49 apparently healthy young LBW men (age 19–21 years; 21 born small for gestational age (SGA) and 28 appropriate for gestational age (AGA)) and in 16 age-matched controls. Bone mineral density of lumbar spine, femoral neck, and radius midshaft, the markers of calcium homeostasis, biochemical parameters of bone turnover as serum osteocalcin (OC), and urinary pyridinoline (PYD) and deoxypyridinoline (DPD) levels were measured. Bone mineral densities of LBW subjects were not altered. Serum calcium (SGA: 2.44 ± 0.15; AGA:2.41 ± 0.17, control: 2.25 ± 0.09 mmol/liter, P < 0.05), OC (SGA:23.4 ± 9.9; AGA:20.8 ± 7.6; control:13.3 ± 4.6 ng/ml, P < 0.01), total alkaline phosphatase (AP) (SGA:201 ± 61; AGA:193 ± 81, control:117 ± 34 IU/liter, P < 0.01), and urinary DPD/creat (ln.values: SGA:3.10 ± 0.48; AGA:3.17 ± 0.46; control:2.58 ± 0.57 nmol/mmol, P < 0.05) were higher, whereas fractional excretion of calcium (SGA:0.94 ± 0.470; AGA:1.03 ± 0.51, control:1.31 ± 0.75%, P < 0.05) was lower in both SGA and AGA groups. PTH and 25OHD were not different. Significant correlation was obtained between seCa, OC, AP, DPD and birth weight of the subjects, but feCa correlated inversely to the birth weight. It was concluded that the bone turnover of LBW men is accelerated, but well balanced in young adulthood. Further investigation is needed to describe the possible link between accelerated bone turnover and hormonal homeostasis of LBW subjects. Received: 30 November 1999 / Accepted: 9 September 2000 / Online publication: 22 December 2000     

Independent effect of endogenous dehydroepiandrosterone-sulphate levels and birth weight on bone turnover parameters in young adults

Data indicate that bone turnover is higher in young adults born with a low birth weight (LBW). Moreover, several data support the presence of altered adrenal hormone production in this population. The aim of our study was to investigate whether there is any connection between altered bone homeostasis and adrenal hormone levels. Bone mineral density (BMD), serum osteocalcin (OC), and urinary deoxypyridinoline (DPD) excretion were related to dehydroepiandrosterone-sulphate (DHEAS), cortisol, estradiol, testosterone, and sex-hormone binding globulin (SHBG) levels in 47 healthy young women (of those, 33 were LBW) and 65 healthy young men (of those, 49 were LBW). The age of the subjects was 19–21 years. BMD values were normal and did not correlate with any of the factors investigated. Cortisol did not have any independent effect on bone turnover parameters in either men or women. In women, birth weight, DHEAS levels, and free estradiol index were responsible for almost 50% (corrected r² = 0.45) of serum OC variability. Independent positive associations were observed between DHEAS and OC, and between DHEAS and DPD excretion. In men, birth weight and DHEAS levels together were responsible for more than one-third (corrected r² = 0.36) of the variability of serum OC. In contrast with women, DHEAS and OC were inversely correlated in men. Our results suggest that bone turnover depends on the subjects' birth weight. Moreover, DHEAS is also an independent determinant. The effect of DHEAS on bone turnover is different in women and men. DHEAS increases bone turnover in fertile women, while it decreases this in men.     

Evaluation of bone mineral loss in patients with chronic traumatic spinal cord injury in Iran

Abstract

Objectives

We described the associations between demographic and injury-related factors on bone mineral density (BMD) of the spine and the hip among adult patients with chronic spinal cord injury (SCI).

Design

BMD in spinal and femoral bone sites were assessed. Multivariate analysis was performed to evaluate the relationship between anthropometric and injury-related factors with BMD. Serum level and amount of dietary intake of calcium, phosphor, and 25-hydroxy vitamin D were measured.

Setting

A referral tertiary rehabilitation center in Iran.

Participants

Patients with SCI who had no previous history of endocrine disorders and were not on specific medications entered the investigation. Those with non-traumatic SCI, pregnant, or with substance dependency were excluded as well.

Interventions

No interventions were applied.

Main study outcome measures

Dual X-ray absorptiometry was performed to estimate BMD. Body mass index was positively associated with higher femoral (P < 0.01, r = 0.56) and hip (P < 0.0001, r = 0.82) BMD only in female participants. The high prevalence of vitamin D deficiency (60%) was noticeable.

Results

Older male patients revealed lower BMD only in spinal vertebrae (P < 0.02, r = ?0.21). A significant higher BMD loss in lumbar vertebras in male patients with complete spinal cord lesion (P < 0.009) was detected. Spinal reduction of BMD was more severe when the level of injury was above T6 (P < 0.02).

Conclusion

Along with the clarification of age, gender, post injury duration, and the other factors' effect on the BMD in the SCI patients, here we have also shown the noticeable prevalence of the 25-hydoxy vitamin D deficiency in these patients which needs attention.     

The influence of serum ghrelin,IGF axis and testosterone on bone mineral density in boys at different stages of sexual maturity

The aim of our study was to examine the relationship between bone mineral density (BMD) and serum ghrelin, insulin-like growth factor-1 (IGF-1), IGF-binding protein 3 (IGFBP-3), and testosterone levels in boys at different stages of puberty. The study included 60 healthy nonobese Estonian schoolboys at the age of 10–18 years. Subjects were divided in three groups (20 boys in each) based on the results of self-assessment using illustrated questionnaire of pubertal stage (G1, I; G2–G3, II; G3–G4, III). Morning fasting blood samples were collected for analysis of ghrelin, testosterone, IGF-1, and IGFBP-3. Total body BMD, lumbar BMD, lumbar apparent volumetric BMD (BMAD), and bone mineral content (BMC) were measured by DXA. Serum testosterone concentration was the most important biochemical predictor of BMD in the total group, explaining 48.8% of variability in total body BMD, 51.4% in lumbar BMD, and 36.8% in lumbar BMAD. Body mass and height were both related to BMD and BMC throughout puberty. The serum IGF-1/IGFBP-3 ratio was correlated with serum testosterone (r = 0.69) and ghrelin (r = −0.58) levels, but also with total BMD (r = 0.39), lumbar BMD (r = 0.42; P < 0.001 in all cases), BMAD (r = 0.29; P < 0.01), and total BMC (r = 0.48; P < 0.001). We conclude that serum testosterone concentration and serum IGF-1/IGFBP-3 molar ratio are the major determinants of bone mineral density in boys at different pubertal stages. Serum ghrelin concentration did not appear to have a direct independent effect on BMD. If present, the association may be mediated through sex hormones and the GH-IGF-I axis.     

Relation between fibroblast growth factor-23, body weight and bone mineral density in elderly men

Summary  We evaluated the relation between serum FGF23 and bone mineral density (BMD) in a community-based cohort of elderly men. There was a weak correlation between FGF23 and BMD, which was primarily dependent on body weight. Introduction  FGF23 is a hormonal factor produced in bone and regulates serum levels of phosphate (Pi) and vitamin D. FGF23 over-expression is associated with skeletal abnormalities, including rickets/osteomalacia. The relation between FGF23 and Bone Mineral Density (BMD) in the community remains unexplored. Methods  We employed a large, population-based cohort of 3014 Swedish men aged 69–80 years, without known renal disease. BMD was measured with dual X-ray absorptiometry (DXA) in the hip and lumbar spine. Serum intact FGF23 was analyzed with a two-site monoclonal ELISA. Results  There was a weak but significant correlation between FGF23 and BMD in femoral neck (r = 0.04, p < 0.05), femoral trochanter (r = 0.05, p = 0.004), total hip (r = 0.06, p = 0.0015) and lumbar spine (r = 0.07, p = 0.0004). The correlations remained significant when adjusting for biochemical covariates (Pi, calcium, PTH, 25(OH)D and renal function). However, the association became insignificant in all regions when adjusting for established confounding variables including age, height, weight and smoking. Further analysis confirmed a significant correlation between FGF23 and body weight (r = 0.13, p < 0.0001). Conclusions  The weak correlation between FGF23 and BMD in elderly male subjects is mainly due to an association between FGF23 and body weight. Therefore, FGF23 may not play a significant role in the hormonal regulation of BMD. Richard Marsell and Majd A. I. Mirza contributed equally to this work. Funding source: this study was supported by the Swedish Research Council, the Novo Nordisk Foundation, the Swedish Kidney Foundation and the Swedish Society of Medicine.     

Heritability of Spinal Trabecular Volumetric Bone Mineral Density Measured by QCT in the Diabetes Heart Study

The heritability of trabecular volumetric bone mineral density (BMD) determined by quantitative computed tomography (QCT) has not yet been reported. The purpose of this study was to investigate the heritability of BMD as determined by QCT and DXA in 124 women and 120 men (age 39–83 years, BMI 17–75, 84% type 2 diabetics) from 101 families (232 sibling pairs) in the Diabetes Heart Study. Volumetric BMD had a heritability (h²) estimate of 0.73 (SE = 0.15, P < 0.0001) at the lumbar spine and 0.71 (SE = 0.15, P < 0.0001) at the thoracic spine. Areal BMD heritability estimates were 0.56 for PA spine, 0.43 for total hip, 0.43 for femoral neck, 0.45 for distal radius, 0.42 for mid-radius, and 0.52 for whole body (all P < 0.01). After accounting for familial correlation using generalized estimating equations, volumetric BMD was inversely associated with age (r = –0.52, P < 0.0001) and duration of diabetes (r = –0.24, P < 0.01) and positively associated with body weight (r = 0.25, P < 0.01). In multivariate analysis, adjustment for age, sex, and race lowered the h² estimates for volumetric BMD at the lumbar (h² = 0.41, P < 0.01) and thoracic (h² = 0.48, P < 0.001) spine, increased the h² estimate for areal BMD at the mid radius (h² = 0.58, P < 0.0001), and had little effect on the h² estimate for areal BMD at other sites (h² = 0.41–0.55, all P < 0.01). Additional adjustment for BMI, duration of diabetes, and physical activity had little effect on the h² estimates for volumetric BMD or areal BMD except at the hip where they were lowered (h² = 0.31–0.33, all P < 0.05). These data suggest that, like areal BMD, volumetric BMD is highly heritable and may be used in designing linkage studies to locate genes governing bone metabolism.     

Variations in Bone Density among Persons of African Heritage

The epidemiology of bone loss in populations of African heritage is still poorly known. We compared a convenience sample of 47 African-American (AA) residents of Rochester, Minnesota (32 women, 15 men) and 66 recent immigrants from Somalia (all women) with 684 white subjects (349 women, 335 men) previously recruited from an age-stratified random sample of community residents. Areal bone mineral density (BMD, g/cm²) and volumetric bone mineral apparent density (BMAD, g/cm³) were determined for lumbar spine and proximal femur using the Hologic QDR 2000 for white subjects and the QDR 4500 for the others; the instruments were cross-calibrated from data on 20 volunteers. Lumbar spine BMD was 18% higher in AA (p<0.001) and 4% lower in Somali (p= 0.147) than white women. Femoral neck BMD was 27% higher in AA women but also 11% greater in Somali women (both p<0.001) compared with whites. Lumbar spine BMD was 6% higher (p= 0.132) and femoral neck BMD 21% higher (p<0.001) in AA than white men. No Somali men were studied. After correcting for bone size differences, both lumbar spine (p<0.01) and femoral neck BMAD (p<0.001) were greater for Somali than white women, but the difference between Somali and AA women persisted. Lumbar spine and femoral neck BMAD values also remained significantly greater for AA women (both p<0.001) and men (p<0.05; p<0.001) compared with whites. Weight was associated with BMAD at both skeletal sites in all groups, but adjustment for differences in weight did not reduce the discrepancy in BMAD values between Somali and AA women or between the latter group and whites. This heterogeneity among different ethnic groups of African heritage may provide an opportunity for research to better explain race-specific differences in bone metabolism. Received: 4 September 2001 / Accepted: 11 January 2002