Bone mineral mass consolidation in young British adults

Medial supracondylar stress fracture in an adolescent pitcher/

We report the occurrence of a medial supracondylar stress fracture in an adolescent pitcher. To our knowledge, this fracture has not been described in the literature, and awareness of this entity allows initiation of therapy and precludes further unnecessary work-up. The radiographic, computed tomography, and magnetic resonance imaging appearances are reviewed and the mechanism of injury is discussed.

Calcium economy in human pregnancy and lactation

Pregnancy and lactation are times of additional demand for Ca. Ca is transferred across the placenta for fetal skeletal mineralisation, and supplied to the mammary gland for secretion into breast milk. In theory, these additional maternal requirements could be met through mobilisation of Ca from the skeleton, increased intestinal Ca absorption efficiency, enhanced renal Ca retention or greater dietary Ca intake. The extent to which any or all of these apply, the underpinning biological mechanisms and the possible consequences for maternal and infant bone health in the short and long term are the focus of the present review. The complexities in the methodological aspects of interpreting the literature in this area are highlighted and the inter-individual variation in the response to pregnancy and lactation is reviewed. In summary, human pregnancy and lactation are associated with changes in Ca and bone metabolism that support the transfer of Ca between mother and child. The changes generally appear to be independent of maternal Ca supply in populations where Ca intakes are close to current recommendations. Evidence suggests that the processes are physiological in humans and that they provide sufficient Ca for fetal growth and breast-milk production, without relying on an increase in dietary Ca intake or compromising long-term maternal bone health. Further research is needed to determine the limitations of the maternal response to the Ca demands of pregnancy and lactation, especially among mothers with marginal and low dietary Ca intake, and to define vitamin D adequacy for reproductive women.

The effect of gonadotrophin-releasing hormone agonist treatment over 3 years on bone mineral density and body composition in girls with central precocious puberty

OBJECTIVE

Puberty is a period characterized by growth spurt and rapid change in body composition. The effect of GnRH agonist therapy for central precocious puberty on bone mineral density is unclear. We demonstrated changes in bone mineral density in subjects with central precocious puberty, who were treated with GnRH agonist for more than 3 years.

DESIGN

The changes in bone mineral density and body compositions were tested with analysis of variance with repeated measures to identify statistical significance over the treatment period.

PATIENTS

One hundred ninety-five Korean girls with central precocious puberty were treated with GnRH agonist, and among these subjects, 39 patients were treated for more than 3 years.

MEASUREMENTS

Dual-energy X-ray absorptiometry was performed on the subjects at the initial evaluation and once yearly thereafter while on the treatment.

RESULTS

The bone mineral density parameters for chronological age tended to decrease near the mean for the treatment period; however, they increased significantly for bone age excluding bone mineral apparent density. An increment of the BMI was not significant for the chronological age.

CONCLUSIONS

Three-year treatment with GnRH agonist in central precocious puberty patients did not impair bone maturation. GnRH agonist could be effectively commenced in girls with precocious puberty from an early age.

Osteoporosis: social and economic impact

The epidemiology of osteoporosis is reviewed, with a discussion of secular changes in incidence, geographical variation, and economic costs. The morbidity and mortality associated with hip, vertebral, and forearm fractures are outlined. The main pathogenetic factors contributing to age-related bone loss and osteoporosis are reviewed. Finally, there is a discussion of the recent advances in fracture risk prediction and the use of independent clinical risk factors to improve bone mineral density-based prediction.

Oral contraceptive use and bone density in adolescent and young adult women

BACKGROUND

Most of the millions of oral contraceptive (OC) users are under 30 years of age and in the critical period for bone mass accrual.

STUDY DESIGN

This cross-sectional study of 606 women aged 14-30 years examined both OC duration and estrogen dose and their association with bone mineral density (BMD) at the hip, spine, and whole body (dual-energy X-ray absorptiometry).

RESULTS

Of 389 OC users and 217 nonusers enrolled, 50% were adolescents (14-18 years). Of OC users, 38% used "low-dose" OCs [<30 mcg ethinyl estradiol (EE)]. In adolescents, mean BMD differed by neither OC duration nor EE dose. However, 19- to 30-year-old women's mean BMD was lower with longer OC use for spine and whole body (p=.004 and p=.02, respectively) and lowest for >12 months of low-dose OCs for the hip, spine and whole body (p=.02, .003 and .002, respectively).

CONCLUSIONS

Prolonged use of today's OCs, particularly <30 mcg EE, may adversely impact young adult women's bone density while using these agents.

Lumbar spine peak bone mass and bone turnover in men and women: a longitudinal study

Peak bone mass is an important determinant of bone mass in later life, but the age of peak bone mass is still unclear. We found that bone size and density increase and bone turnover decreases until age 25. It may be possible to influence bone accrual into the third decade.

INTRODUCTION

Peak bone mass is a major determinant of bone mass in later life. Bone growth and maturation is site-specific, and the age of peak bone mass is still unclear. It is important to know the age to which bone accrual continues so strategies to maximise bone mass can be targeted appropriately. This study aims to ascertain the age of lumbar spine peak bone mass.

METHODS

We measured lumbar spine BMC, estimated volume and BMAD by DXA and biochemical markers of bone turnover in 116 healthy males and females ages 11 to 40, followed up at an interval of five to nine years.

RESULTS

The majority of peak bone mass was attained by the mid-twenties. Increases in BMC in adolescents and young adults were mostly due to increases in bone size. Bone turnover markers decreased through adolescence and the third decade and the decreasing rate of change in bone turnover corresponded with the decreasing rate of change in lumbar spine measurements.

CONCLUSIONS

Skeletal maturation and bone mineral accrual at the lumbar spine continues into the third decade.

Management of Renal Osteodystrophy: THe Heart and Bone of Pediatric Dialysis

Control of mineral homeostasis is a particularly challenging task in children and adolescents on dialysis. Treatment efforts must not only ensure patient survival and the absence of debilitating complications of bone disease, but in view of a potentially long lifespan, must also consider how to best promote long-term cardiovascular health and successful psychosocial transition into adult life. In that context, avoidance of cardiovascular calcifications and accomplishment of adequate statural growth and a normal final height are major objectives of uremic bone disease management in children. Unfortunately, current pediatric management guidelines operate on a small evidence base, and major controversy surrounds key issues such as optimal target ranges for serum parathyroid hormone, calcium, and phosphorus in the individual childhood phases, and individual risk–benefit ratios for the use of phosphate binders, vitamin D analogs, and calcimimetics in children. The present review summarizes the current state of knowledge and outlines future research requirements in bone disease associated with pediatric end-stage renal disease.

Comparisons of body size, composition, and whole body bone mass between North American and South African children

We compared whole body BMC of 811 black, white, and mixed ancestral origin children from Detroit, MI; Johannesburg, South Africa; and Cape Town, South Africa. Our findings support the role of genetic and environmental influences in the determination of bone mass in prepubertal children.

INTRODUCTION

Higher bone mass and lower fracture rates have been shown in black compared with white children and adults in North America.

MATERIALS AND METHODS

We compared whole body BMC (WBBMC), whole body fat mass (WBFM), and whole body fat free soft tissue (WBFFST) data between three ethnic groups of children from Detroit, MI (n = 181 white, USW; n = 230 black, USB), Johannesburg, South Africa (n = 73 white, SAW; n = 263 black, SAB), and Cape Town, South Africa (n = 64 mixed ancestral origin, SAM).

RESULTS

SAB and SAW groups were slightly older than USW and USB groups (9.5 +/- 0.3 versus 9.3 +/- 0.1 yr); however, USB and USW boys were significantly taller, were heavier, and had a higher BMI than SAM and SAB boys. USB girls were significantly taller than SAB girls and heavier than SAB and SAM girls. In South Africa and the United States, black children had a significantly higher WBBMC than white children, after adjusting for selected best predictors. After adjusting for age, weight, and height, WBBMC was significantly higher in the SAB and SAW boys than in USW and USB and in the SAM group compared with the USW and USB groups. WBFFST and WBFM made significant contributions to a best linear model for log(WBBMC), together with age, height, and ethnicity. The best model accounted for 79% of the WBBMC variance. When included separately in the model, the model containing WBFFST accounted for 76%, and the model containing WBFM accounted for 70%, of the variance in WBBMC.

CONCLUSIONS

WBBMC is lower in children of European ancestry compared with African ancestry, irrespective of geographical location; however, South African children have significantly higher WBBMC compared with USB and USW groups, thereby acknowledging the possible contribution of environmental factors. Reasons for the significantly higher WBBMC in the children of mixed ancestral origin compared with the other groups need to be studied further.

Bone mass in Chinese premenarcheal girls: the roles of body composition, calcium intake and physical activity

The association of growth and anthropometric characteristics and lifestyle factors with bone mass and second metacarpal radiogrammetry parameters was evaluated in 373 healthy Chinese premenarcheal girls aged 9–11 years. Bone mineral content (BMC) and density (BMD) and bone area (BA) of distal forearm, proximal forearm and total body, bone mineral-free lean (BMFL) mass and fat mass were measured by dual-energy X-ray absorptiometry. Metacarpal bone periosteal and medullary diameters were measured. Dietary intakes were assessed by 7d food record and physical activity (PA) by questionnaire. BMFL and fat mass together explained 6·3 and 51·6% of the variation in total body BMC and BMD, respectively. BMFL mass contributed to a substantial proportion of the variation in forearm BMC and BMD and periosteal diameter (10·4–41·0%). The corresponding BA explained 14·8–80·4% of the variation in BMC. Other minor but significant predictors of total body bone mass were Ca intake, height, age and PA score (BMD only), and of forearm bone mass were PA score, bone age, height and fat mass. Nevertheless, after adjusting for bone and body size and for age or bone age, subjects with Ca intake above the median (417mg/d) had 1·8% greater total body BMC (P<0·001), and subjects with PA scores above the median had 2·4–2·5% greater distal and proximal forearm BMC (P<0·05) than those below. Vitamin D intake negatively associated with medullary diameter (partialR21·7%). The results indicate that premenarcheal girls should be encouraged to optimise nutrition and Ca intake and exercise regularly to achieve maximum peak bone mass.

Vitamin D status and its relationship with parathyroid hormone and bone mineral status in older adolescents

Osteoporosis is an important contributor to the global burden of disease, and in the UK alone results in one in three women and one in twelve men aged >50 years experiencing a fragility fracture. Optimising peak bone mass in early adulthood is thought to reduce osteoporosis risk by offsetting bone losses in later life. Ensuring sufficient vitamin D status (measured as 25-hydroxyvitamin D (25OHD) in plasma), among other factors, is believed to facilitate the achievement of optimum peak bone mass. Lower 25OHD is associated with a higher plasma concentration of parathyroid hormone (PTH). As PTH is associated with increased bone turnover and bone loss, maintenance of sufficient 25OHD is thought to have a protective effect on bone health. However, there is a lack of consensus internationally on what constitutes an optimum 25OHD concentration, and values between 30 and 80 nmol/l have been suggested. These values have been based on findings from various studies in adults in which PTH has been observed to plateau at a 25OHD concentration of >30 nmol/l; however, not all studies have found such a plateau. Although studies in younger adolescents (14–16 years) have shown an inverse relationship between PTH and 25OHD, the concentration of 25OHD required for achievement of optimum peak bone mass is unknown. The present review examines the evidence defining vitamin D insufficiency thresholds, and the relevance of such thresholds to adolescent bone health.

Diet, nutrition and the prevention of osteoporosis

Objective:

To review the evidence on diet and nutrition relating to osteoporosis and provide recommendations for preventing osteoporosis, in particular, osteopototic fracture.

Approach:

Firstly, to review the definition, diagnosis and epidemiology of osteoporosis, to discuss the difficulties in using bone mineral density to define osteoporosis risk in a world-wide context and to propose that fragility fracture should be considered as the disease endpoint. Secondly, to provide an overview of the scientific data, the strengths and weaknesses of the evidence and the conceptual difficulties in interpreting studies linking diet, nutrition and osteoporosis. The following were considered: calcium, vitamin D, phosphorus, magnesium, protein and fluorine. Other potential dietary influences on bone health were also discussed, including vitamins, trace elements, electrolytes, acid–base balance, phyto-oestrogens, vegetarianism and lactose intolerance.

Conclusions:

There is insufficient knowledge linking bone mineral status, growth rates or bone turnover in children and adolescents to long-term benefits in old age for these indices to be used as markers of osteoporotic disease risk. For adults, the evidence of a link between intakes of any dietary component and fracture risk is not sufficiently secure to make firm recommendations, with the exception of calcium and vitamin D. For other aspects of the diet, accumulating evidence suggests that current healthy-eating advice to decrease sodium intake, to increase potassium intake, and to consume more fresh fruits and vegetables is unlikely to be detrimental to bone health and may be beneficial.

Osteoporosis in the aging male: treatment options

In elderly women, loss in bone mass and micro-architectural changes are generally attributed to the onset of menopause. Men do not experience menopause, they do, however, experience age-related acceleration in bone loss and micro-architecture deterioration. The incidence of osteoporotic fractures in elderly men, just as in aged women, increases exponen-tially with age; the rise in men, however, is some 5-10 years later than in women. Up to 50% of male osteoporotics have no identifiable etiology; however elderly males have much higher likelihood of having an identifiable secondary cause than younger men. Therefore, clinical and laboratory evaluation of aged male osteoporotics must be thorough and should be aimed at identifying lifestyle or conditions contributing to bone loss and fragility. It is essential to identify and treat secondary causes and ensure adequate vitamin D and calcium intake before embarking upon treatment with pharmacological agents. The evidence from a limited number of trials suggests that bisphosphonates, especially alendronate and risedronate, are effective in improving BMD, and seem to be the treatments of choice in aged men with osteoporosis. In cases where bisphosphonates are contra-indicated or ineffective, teriparatide or alternatives such as strontium should be considered.

Establishment of peak bone mineral density in Southern Chinese males and its comparisons with other males from different regions of China

Peak bone mineral density (PBMD) is an important determinant of osteoporotic fracture and a precondition for correct diagnosis of osteoporosis. The objective of this study was to establish the reference data of PBMD at the lumber spine and hip in Southern Chinese males. Bone mineral density (BMD) was measured at the lumbar spine and hip (femoral neck, trochanter, intertrochanter, and total) in 1155 Chinese men aged 15-39 years, using dual-energy X-ray absorptiometry (DXA). We utilized a fit curve method to determine the best age range over which to calculate PBMD. Our results indicated that the PBMD was observed at the age range of 18-25 years at the various sites. The mean value and standard deviation of PBMD was 0.753 +/- 0.117, 1.156 +/- 0.148, 0.896 +/- 0.120, 0.989 +/- 0.122, and 0.980 +/- 0.116 g/cm2 at the trochanter, intertrochanter, femoral neck, total hip, and spine, respectively. When the present PBMD reference was compared with the documented PBMD reference of males from other regions of China, we found great difference in standardized PBMD between Changsha males and those from other regions of China. The PBMD for Chinese males in Changsha at the various sites were 3.19%-11.33% lower than that for American Caucasian males. In conclusion, the PBMD at the spine and hip may be used as normal reference data for Southern Chinese males in Changsha instead of documented PBMD from other regions of China and the manufacturer's reference data.

Lifestyle questionnaire to evaluate risk for reduced bone mineral density in women

OBJECTIVE

To determine the contribution of various risk factors to quantitative ultrasound parameters in a sample of women, and to develop a tool to assess osteopenia risk, with a view to targeted early intervention.

DESIGN

Questionnaire study.

SETTING

A local center comprising a fitness center, conference center, and administrative offices for various businesses and sports.

PATIENTS OR PARTICIPANTS

A convenience sample of 187 Caucasian women who volunteered as part of a free public health screening initiative.

MAIN OUTCOME MEASUREMENTS

A questionnaire was designed to collect data on history of osteoporosis, current physical activity, calcium, alcohol and caffeine intakes, smoking, and various reproductive measures. Historical physical activity data were also collected, and lifetime energy expenditure and impact scores were calculated. Quantitative ultrasound was performed on the left calcaneus. Odds ratios (ORs) were calculated to determine the odds of being osteopenic (T-score < or =-1 SD) against not being osteopenic (T-score >-1SD), due to exposure to the aforementioned risk factors.

RESULTS

: Significant ORs were obtained for age (OR: 1.042; 95% CI: 1.016-1.068), current physical activity (> or =3 times/wk; OR: 0.320; 95% CI: 0.140-0.732), and lifetime energy expenditure score (OR: 0.957; 95% CI: 0.926-0.989). A regression model based on age and current physical activity correctly identified 57% of women with or without osteopenia.

CONCLUSIONS

Although the model we developed was not sensitive or specific enough to assess osteopenic risk accurately, the results show that frequency of physical activity, independent of age, is an important lifestyle factor to consider when quantifying osteopenic risk.

Age of attainment of peak bone mass is site specific in Swedish men--The GOOD study

Results from this study suggest that PBM has been attained in the spine and femoral neck, but not in the radius or tibia, in 18- to 20-year-old men, in which an endosteal contraction and increase in cortical volumetric BMD is observed.

INTRODUCTION

Peak bone mass (PBM) is an important determinant for the risk of osteoporosis. In men, the age of attainment of PBM has been under some controversy. The objective of this study was to determine if peak bone mass had been attained, and whether it is site specific, in 18- to 20-year-old Swedish men.

MATERIALS AND METHODS

The Gothenburg Osteoporosis and Obesity Determinants (GOOD) Study consists of 1068 men, 18.9 +/- 0.6 years of age. BMD was measured using both DXA and pQCT. Environmental factors, such as dietary intake and physical activity, were assessed through questionnaires. The independent predictors of BMD were assessed through multiple linear regression, including age, height, weight, calcium intake, smoking, and physical activity.

RESULTS AND CONCLUSIONS

We show, in a large well-characterized cohort, that age was not an independent predictor of BMD of the lumbar spine, femoral neck, or total body, indicating that peak BMD has been achieved in these skeletal sites, whereas it was an independent predictor of BMD of the radius, suggesting that peak BMD has not yet been attained in the long bones. pQCT analyses of the radius and the tibia revealed that age was associated with cortical volumetric BMD and endosteal contraction of the radius and tibia. These results show that the age of attainment of PBM is site specific.

Effects of school milk intervention on cortical bone accretion and indicators relevant to bone metabolism in Chinese girls aged 10-12 y in Beijing

BACKGROUND

We previously reported that increased milk consumption enhances growth and bone mineral accretion in Chinese girls aged 10-12 y.

OBJECTIVE

Our objective was to evaluate the effects of milk supplementation on cortical bone accretion and to study the physiologic mechanisms underlying the observed changes in bone.

DESIGN

Chinese girls aged 10 y were randomly assigned into calcium-fortified milk (Ca milk), calcium and vitamin D-fortified milk (CaD milk), and control groups according to their schools in a 24-mo school milk intervention trial. Periosteal and medullary diameters of metacarpal bone were measured at baseline and 24 mo in the Ca milk (n = 177), CaD milk (n = 210), and control (n = 219) groups. Insulin-like growth factor I (IGF-I), parathyroid hormone (PTH), bone alkaline phosphatase (BAP), osteocalcin, and deoxypyridinoline concentrations were measured at baseline and at 12 and 24 mo in the Ca milk (n = 43), CaD milk (n = 44), and control (n = 41) groups.

RESULTS

After adjustment for pubertal status and clustering by school, 24-mo supplementation led to greater increases in periosteal diameter (1.2%) and cortical thickness (5.7%) and to smaller gains in medullary diameter (6.7%) than did the control (P < 0.05). The CaD milk group had lower serum BAP at 12 mo (19.9%) and lower serum PTH at 12 (46.2%) and 24 (16.4%) mo than did the control group (P < 0.05). The effect of milk supplementation on increasing IGF-I concentrations at 24 mo (16.7-23.3%) was significant in individual analyses but not after adjustment for clustering by school.

CONCLUSIONS

Milk supplementation showed positive effects on periosteal and endosteal apposition of cortical bone.

Effect of habitual dietary calcium intake on calcium supplementation in 12-14-y-old girls

BACKGROUND

There is no agreement on how much calcium young girls need for optimal bone mineralization.

OBJECTIVE

We evaluated whether the effect of calcium supplementation on whole-body bone mineral accretion depends on habitual calcium intake.

DESIGN

This was a randomized, double-blind, placebo-controlled, 1-y calcium intervention study of girls aged 12-14 y selected from a larger group according to habitual calcium intake: subgroup A (n = 60) habitually consumed 1000-1307 mg/d (40th-60th percentile), and subgroup B (n = 53) habitually consumed <713 mg/d (<20th percentile). The girls from each subgroup were randomly assigned to receive either 500 mg Ca/d or placebo. Whole-body bone mineral content (BMC), bone area (BA), bone mineral density (BMD), and BMC adjusted for BA, height, and weight (size-adjusted BMC) were measured at baseline and after 1 y.

RESULTS

There was no significant effect modification of baseline habitual calcium intake on the relation between calcium supplementation and height, weight, BMC, size-adjusted BMC, BA, BMD, or alkaline phosphatase. Calcium supplementation had an effect on BMD (0.8%; P = 0.049) and tended to show signs of an effect on size-adjusted BMC (0.5%; P = 0.08).

CONCLUSION

A modest effect of calcium supplementation on BMD was shown. However, the effect was independent of habitual calcium intake.

Lifestyle influences on 9-year changes in BMD in young women

The effects of dietary calcium intake and physical activity on longitudinal changes in BMD over a mean of 9.4 years were examined in 62 healthy young women. Proximal femur BMD declined, lumbar spine BMD increased, and physical activity was associated with BMD change at intertrochanter and total hip sites.

INTRODUCTION

Maximizing premenopausal BMD is an important strategy for the prevention of osteoporosis and resultant fractures later in life.

MATERIALS AND METHODS

Young women who previously participated in a placebo-controlled 2-year calcium intervention study at a mean age of 18.5 +/- 0.3 years were remeasured at 27.8 +/- 1.0 years of age. DXA (Hologic QDR 1000W) was used to measure changes in BMD, and lifestyle factors were ascertained by questionnaire.

RESULTS AND CONCLUSIONS

Early decline in BMD at the neck of femur (-3.3%/decade) and the converse gain in BMD at the lumbar spine (+4.3%/decade) and intertrochanter (+1.9%/decade) suggest site-specific changes in BMD in young premenopausal women. No effect of previous calcium supplementation was seen on current BMD or changes in BMD (p > 0.10). Lifestyle predictors of change in BMD were determined using hierarchical regression analysis after forced correction for the covariates baseline BMD and previous calcium supplementation. Physical activity was positively associated with change in BMD at total hip and intertrochanter sites (beta-coefficients, beta = 0.26 and 0.26 respectively; p < 0.05). Calcium intake was negatively associated with change in BMD at the lumbar spine (beta = -0.27, p < 0.05). Parity was negatively associated with change in BMD at all sites (beta = -0.40 to -0.26, p < 0.05). These data show that BMD is already declining at the proximal femur in these healthy young women. Physical activity assists in maintenance of BMD at some sites and thus may contribute to lifelong fracture prevention. There was no positive association between calcium intake and change in BMD.

Bone mineral density and total body bone mineral content in 18- to 22-year-old women

One hundred sixty-four (164) healthy, young Caucasian women enrolled as midshipmen at the United States Naval Academy with no known disease or bone injury were followed for 3.6 years. Change in bone mineral density (BMD) of the hip, lumbar spine and distal tibia, and total body bone mineral content (TBMC) was measured by dual energy X-ray absorptiometry (DXA). Bone mineral density and TBMC of these women were measured within 2 months (60 +/- 4 days) of entering the Academy and annually. Over the study period, hip BMD increased 2.26% (P < 0.001), lumbar spine BMD increased 3.27% (P < 0.001) and distal tibia BMD increased 5.2% (P < 0.001). Total body bone mineral content showed a 5.25% (P < 0.001) increase during the study period. In this group of young women, gain in BMD and TBMC continued until age 22. These results suggest that bone mass may accrue in certain groups of women beyond age 22. The significance of this increase in bone mass during early adulthood on risk for osteoporotic fractures in later life and its impact on exercise-related bone injuries are unknown and warrant further examination.

Attainment of peak bone mass at the lumbar spine, femoral neck and radius in men and women: relative contributions of bone size and volumetric bone mineral density

The age at which peak bone mineral content (peak BMC) is reached remains controversial and the mechanism underlying bone mass "consolidation" is still undefined. The aims of this study were to investigate; (1) the timing of peak BMC by studying bone size and volumetric BMD (vBMD) as separate entities and (2) to determine the relative contributions of bone size and vBMD to bone mass "consolidation". A total of 132 healthy Caucasian children (63 boys and 69 girls, ages 11-19 years) and 134 healthy Caucasian adults (66 men and 68 women, ages 20-50 years) were studied. BMC was measured by DXA at the AP and lateral lumbar spine (LS) femoral neck (FN) and ultradistal radius (UDR). vBMD and bone volume (size) were estimated. Bone mass "consolidation" was examined between age 16 years to the age peak bone values were attained. During growth, BMC and bone size increased steeply with age and approximately 80-90% of peak values were achieved by late adolescence. vBMD at the spine and UDR (in women) increased gradually, but vBMD at the FN and UDR in men remained almost constant. During "consolidation", bone size continued to increase with little change in vBMD. Peak vBMD at the lumbar spine was reached at 22 and 29 years in men and women, respectively, but earlier at the FN at 12 years. At the UDR peak vBMD was achieved at age 19 years in women, with little change in men. In conclusion, peak vBMD and bone size are almost fully attained during late adolescence. Although speculative, the lack of change in vBMD during consolidation implies that the continued increase in bone mass may primarily be due to increases in bone size rather than increases in either trabecular volume, cortical thickness or the degree of mineralisation of existing bone matrix (vBMD). Skeletal growth and maturation is heterogeneous, but crucial in understanding how the origins of osteoporosis may begin during childhood and young adulthood.

Effect of a calcium and exercise intervention on the bone mineral status of 16-18-y-old adolescent girls

BACKGROUND

Osteoporosis may be prevented or delayed by maximizing peak bone mass through diet modification and physical activity during adolescence.

OBJECTIVE

We studied whether increases in calcium intake and physical activity effectively increase the bone mineral status of adolescent girls aged 16-18 y.

DESIGN

We conducted a 15.5-mo study of calcium supplementation (1000 mg Ca/d as carbonate) in 144 adolescent girls aged 17.3 +/- 0.3 y ( +/- SD). The subjects were randomly allocated to an exercise (three 45-min exercise-to-music classes/wk during term time) or nonexercise group. Dual-energy X-ray absorptiometry of the whole body, spine, forearm, and hip was performed before and after intervention.

RESULTS

The mean (+/- SD) percentage of subjects compliant with supplement taking was 70 +/- 27% and with exercise class attendance was 36 +/- 25%. Baseline calcium intake was 938 +/- 411 mg/d. Calcium supplementation significantly increased size-adjusted bone mineral content. The effect was stronger in subjects with good compliance (percentage difference +/- SE): whole body, 0.8 +/- 0.3% (P < or = 0.01); lumbar spine, 1.9 +/- 0.5% (P < or = 0.001); ultradistal radius, 1.3 +/- 0.6% (P < or = 0.05); total hip, 2.7 +/- 0.6% (P < or = 0.001); femoral neck, 2.2 +/- 0.7% (P < or = 0.001); trochanter, 4.8 +/- 0.9% (P < or = 0.001). Attendance at > 50% of the exercise sessions was significant at the total hip (1.4 +/- 0.7%; P < or = 0.05) and trochanter (2.6 +/- 1.2%; P < or = 0.05).

CONCLUSIONS

Calcium supplementation and exercise enhanced bone mineral status in adolescent girls. Whether this is a lasting benefit, leading to the optimization of peak bone mass and a reduction in fracture risk, needs to be determined.

Bone mineral contents and plasma osteocalcin concentrations of Gambian children 12 and 24 mo after the withdrawal of a calcium supplement

BACKGROUND

Our randomized, placebo-controlled supplementation study of 160 rural Gambian children aged 8.3-11.9 y showed that an increase in calcium intake of 714 mg/d for 12 mo resulted in a 5% increase in forearm bone mineral acquisition and a 22% decrease in plasma osteocalcin concentration, a bone formation marker, but had no effect on height or bone dimensions.

OBJECTIVE

We investigated whether these results were sustained after supplement withdrawal.

DESIGN

All participants were followed up 12 (FU1) and 24 (FU2) mo after supplementation ended. Bone mineral content (BMC), bone mineral density (BMD), and BMC adjusted for bone width, body weight, and height (size-adjusted BMC) were measured at the midshaft and distal radius. Plasma osteocalcin concentration was measured at FU1.

RESULTS

At follow-up, the calcium group had greater bone mineral status than did the placebo group at the midshaft radius (mean difference +/- SE), FU1: BMC (4.7 +/- 1.6%; P = 0.004), BMD (5.1 +/- 1.1%; P </= 0.0001), size-adjusted BMC (5.0 +/- 1.1%; P </= 0.0001); FU2: BMC (3.8 +/- 1.6%; P = 0.02), BMD (2.7 +/- 1.3%; P = 0.04), size-adjusted BMC (2.5 +/- 1.3%; P = 0.06). Similar differentials were observed at the distal radius but were not significant. No significant differences in plasma osteocalcin concentrations (FU1: -0.5 +/- 6.5%; P = 0.9) were observed between groups.

CONCLUSION

Although some of the effects of calcium supplementation were still evident at follow-up, further studies are required to determine whether short-term increases in calcium intake have lasting benefits for Gambian children.

Familial resemblance of bone mineral density between females 18 years and older and their mothers

Potential determinants of bone mass were investigated in a group of 70 young females (mean age 26.6 years), daughters of women studied in premenopause. Nutritional data, leisure physical activity level, lifestyle habits as well as familial similarities were assessed. The daughters' bone mineral density (BMD), measured by dual-energy absorptiometry, was significantly correlated with their body mass index (BMI) (r = 0.22), dietary vitamin D intake (r = 0.19) and their mothers' BMD (r = 0.44). Multiple regression analysis indicated that only the mothers' BMD remained an independent predictor of bone mass. Mother-daughter correlations were also observed for body weight (r = 0.24), height (r = 0.39), BMI (r = 0.29), dietary calcium intake (r = 0.20), and calcium (r = 0.20) or vitamin D (r = 0.25) intakes from dairy products. Hence, these observations support the evidence that mothers' BMD is the strongest predictor of bone mass of young women in their third decade.

The relative contribution of diet and genotype to bone development

The present review addresses the relative contribution of diet and genotype to variability in human bone growth and mineralisation in the context of the aetiology of osteoporosis. Heritability studies indicate that 60-70 % of the variability in bone mineral mass or bone mineral density (BMD) can be accounted for by genetic variation. Cross-trait analyses suggest that a proportion of this variation reflects genetic influences on bone and body size, such as height and lean body mass. Candidate-gene studies have demonstrated associations between several genetic polymorphisms and bone mineral mass but, as yet, genotype determinations have proved unhelpful in identifying individuals at increased risk of osteoporosis. Variations in diet and other environmental factors contribute 30-40 % to total phenotypic variance in bone mineral mass or BMD. Correlations between intakes of individual nutrients and BMD have been reported, but these relationships are subject to confounding due to size. However, no specific dietary factor has been identified from prospective and twin studies as making a significant contribution to environmental variability in BMD or bone loss. This finding may reflect the difficulties in quantifying environmental exposures. both current and over a lifetime. In addition, the influence of diet on bone health may depend on the genotype of the individual. Optimisation of nutrition and lifestyle remains an attractive strategy for the reduction of fracture risk, but more research is required to fully define optimal dietary requirements.

Sex steroids and bone

Sex steroids are essential for skeletal development and the maintenance of bone health throughout adult life, and estrogen deficiency at menopause is a major pathogenetic factor in the development of osteoporosis in postmenopausal women. The mechanisms by which the skeletal effects of sex steroids are mediated remain incompletely understood, but in recent years there have been considerable advances in our knowledge of how estrogens and, to a lesser extent androgens, influence bone modeling and remodeling in health and disease. New insights into estrogen receptor structure and function, recent discoveries about the development and activity of osteoclasts, and lessons learned from human and animal genetic mutations have all contributed to increased understanding of the skeletal effects of estrogen, both in males and females. Studies of untreated and treated osteoporosis in postmenopausal women have also contributed to this knowledge and have provided unequivocal evidence for the potential of high-dose estrogen therapy to have anabolic skeletal effects. The development of selective estrogen receptor modulators has provided a new approach to the prevention of osteoporosis and other major diseases of menopause and has implications for the therapeutic use of other steroid hormones, including androgens. Further elucidation of the mechanisms by which sex steroids affect bone thus has the potential to improve the clinical management not only of osteoporosis, both in men and women, but also of a number of other diseases related to sex hormone status.

Dual X-ray absorptiometry total body bone mineral content and bone mineral density in 18- to 22-year-old caucasian men

Eighty-six healthy, young Caucasian 18-year-old men with no known disease or bone injury were recruited to this study at the United States Naval Academy. Change in bone mineral density (BMD) of the hip, lumbar spine, and distal tibia, and total body bone mineral content (TBMC) was measured by dual-energy X-ray absorptiometry (DXA). BMD and TBMC of these men were measured within 2 months (67 +/- 3 days) of entering the Academy, and, at the end of their first, second, and fourth years. Hip BMD was unchanged during the study period (p > 0.05). Lumbar spine BMD increased 3% (p < 0.001) and distal tibia BMD increased 5% (p < 0.001). TBMC showed a 7.5% increase over the study period. In this group of young men, gain in BMD and TBMC is greatest to age 21 years, with minimal further increase after age 21. The significance of this rise in bone mass during early adulthood on risk for osteoporotic fractures in later life or its impact on exercise-related bone injuries is unknown and warrants further examination.

Percent body fat and bone mass in healthy Canadian females 10 to 19 years of age

The primary aim of the investigation was to assess the relationship between whole-body fat expressed as a percentage of body weight with whole-body bone mineral content relative to age and anthropometry. Sixty females between 10 and 19 years of age were recruited to this cross-sectional study, which included measurements of weight and height and whole-body fat and bone mineral content using dual-energy X-ray absorptiometry. To assess bone mineral content, data were expressed as a weight or standard deviation scores using age and bone area. Relationships between outcome variables were determined using multiple correlation analysis followed by multiple linear regression with age, weight, height, and fat as predictor variables for outcomes of bone mineral content and density. Correlation analysis indicated that whole-body fat expressed as a percent was significantly related to weight (p < 0.01), but was not related to age or bone mineral content or density unless bone mineral content was corrected to age or bone area using standard deviation scores. In addition, body fat was associated with bone area for age and height (p < 0.01). However, multiple linear regression yielded opposite results. When included in regression, body fat had a negative impact on bone mineral content (p = 0.003), mineral content corrected to bone area (p = 0.02), and bone density (p = 0.003), while age, weight, and height had positive impacts on these outcome measurements. The data suggest that for younger children, the relative influence of percent body fat will be greater and could be linked with suboptimal attainment of peak bone mass. The females in this study appeared to be within reference limits for percent body fat. However, greater amounts of body fat relative to weight could be a marker for lifestyles that do not support attainment of optimal peak bone mass.

Effect of calcium supplementation on bone mineral accretion in gambian children accustomed to a low-calcium diet

BACKGROUND

Rural Gambian children have poor growth, delayed puberty, a low bone mineral content, and a low calcium intake.

OBJECTIVE

We investigated the effect of a calcium supplement on bone mineral accretion in rural Gambian children.

DESIGN

A randomized, double-blind, placebo-controlled study was conducted in 160 children (80 boys, 80 girls) aged 8.3-11.9 y. Bone mineral content (BMC), bone mineral density (BMD), and BMC adjusted for bone width, body weight, and height (size-adjusted BMC) were measured at the midshaft and distal radius. Each child received either 1000 mg Ca/d (as calcium carbonate) or a placebo 5 d/wk for 12 mo. Supplementation increased calcium intake from 342 to 1056 mg/d (8.6 to 26.4 mmol/d).

RESULTS

Calcium supplementation resulted in a higher BMC, BMD, and size-adjusted BMC (&xmacr; difference +/- SE): midshaft radius-BMC (3.0 +/- 1.4%; P = 0.034), BMD (4.5 +/- 0.9%; P </= 0.0001), and size-adjusted BMC (4.6 +/- 0.9%; P </= 0.0001); distal radius-BMC (8. 4 +/- 3.2%; P = 0.009), BMD (7.0 +/- 2.7%; P = 0.011), and size-adjusted BMC (5.5 +/- 2.7%; P = 0.042). Supplementation had no significant effect on height, weight, or bone width at the midshaft radius or distal radius. At the end of the study, the calcium group had a significantly lower mean plasma osteocalcin concentration than the placebo group after adjustment for baseline concentration, sex, and pubertal status (-21.9 +/- 6.5%; P = 0.001).

CONCLUSIONS

Increased calcium intake resulted in increased bone mineral status, possibly in association with a decreased bone remodeling space. Further studies are needed to determine whether an increased calcium intake has long-term benefits in Gambian children.

Cross-sectional assessment of age-related bone loss in men: the MINOS study

There are few data on osteoporosis in men, but cross-sectional studies have shown that age-related bone loss in men is of lower magnitude than in women. To elucidate some controversies related partially to methodological aspects, we measured bone mineral density (BMD) by dual-energy X-ray absorptiometry (DEXA) at various skeletal sites (spine, hip, and whole body using a Hologic QDR-1500 device; forearm using an Osteometer DTX 100 device) in a large cohort of 1040 men, aged 19-85 years. The final investigation was performed on 934 men, aged 19-85 years, after exclusion of 106 men with disease or treatment known to affect bone metabolism. Peak BMD was achieved at 25 and 29 years at the lumbar spine and hip, respectively, but only at 40 and 37 years at the distal forearm and whole body, respectively. The magnitude of bone loss between peak bone mass and 80 years of age was linear at most sites and averaged 13%-18%; that is, SD of 1.1-1.8 from peak BMD, except for Ward's triangle, which showed a marked bone loss of 43% (i.e., 2.5 SD), and for the lumbar spine. In the entire cohort, increase of the average lumbar spine BMD after the age of 55 years was related to the development of osteoarthritis, because, in men without severe arthritis, lumbar spine BMD continued to decrease. Height-adjusted partial correlations indicate that both the mineral content and the area of long bones of the limbs increased with age up to 50 years, followed by a significant decrease of BMD without change of bone surface. SD of mean BMD increased significantly with age at most skeletal sites. In summary, age-related change of BMD varied according to skeletal site in men with peak bone mass achieved earlier at sites rich in trabecular bone than at those rich in cortical bone. Bone loss varied according to skeletal site from 14% to 43%. The variability of BMD increased with age, which may reflect interindividual variability of age-related bone loss.

Bone mass after allogeneic BMT for childhood leukaemia or lymphoma

The bone mass was measured by dual energy X-ray absorptiometry in 25 survivors of childhood leukaemia or lymphoma (21 with ALL) who had received TBI and allogeneic BMT a median of 8 years ago (range 4-13). Results were compared with local data on 463 healthy controls and 95 survivors of childhood ALL treated without BMT. Adjusted for sex and age, the mean whole-body bone mineral content (BMC) and bone mineral areal density were significantly less than in healthy controls (0.8 and 0.5 s.d. less than predicted). The reduced BMC was caused by a significantly reduced height for age, whereas bone area for height and BMC for bone area were similar to controls. Less bone mass tended to be related to additional cranial irradiation and age above 20 years at follow-up. Controlled for this, the whole-body bone mass seemed to be unrelated to previous chemotherapy and endocrine status at follow-up and tended to be only marginally less in BMT patients than in ALL survivors treated without BMT. In conclusion, 8 years after allogeneic BMT for childhood leukaemia or lymphoma, the whole-body bone mass was only slightly reduced and the size-adjusted bone mass (BMC for bone area) was normal. Bone Marrow Transplantation (2000) 25, 191-196.

An investigation of ethnic differences in bone mineral, hip axis length, calcium metabolism and bone turnover between West African and Caucasian adults living in the United Kingdom

The aim of the study was to investigate factors relating to calcium and bone metabolism which might explain the low incidence of osteoporotic fracture among Africans. Adult bone mineral status, hip axis length and biochemical indices were investigated in 20 Caucasians (10 male, 10 female) and 19 Gambians (12 male, 7 female) living in the UK. Bone mineral content (BMC), bone mineral density (BMD) and BMC adjusted for bone area, body weight and height (size-adjusted BMC) were measured for the whole-body, lumbar spine, femoral neck, trochanter, radius shaft and radius wrist using dual-energy X-ray absorptiometry. There were no significant differences in whole body or regional BMC; values tended to be lower in the Gambians. Gambian men had higher size-adjusted BMC at the femoral neck (Gambian-British = 21%, 95% CI = 6 to 36%, p < 0.01), associated with a smaller bone area (Gambian-British = -11%, 95% CI = -20 to -2%, p = 0.02). BMD was affected similarly. No other significant differences in BMD or size-adjusted BMC were observed. Gambians had shorter hip axis length (Gambian British, after accounting for sex, = -5%, 95% CI = -9 to -1%, p = 0.02). There were no significant differences in bone turnover (osteocalcin, bone isoenzyme of alkaline phosphatase, urinary deoxypyridinoline) or calciotropic hormone levels (parathyroid hormone, 1,25-dihydroxyvitamin D, calcitonin). Gambian men had lower 25-hydroxyvitamin D concentrations (Gambian = 26.3 SD 12.0 nmol/L, British = 55.5 SD 13.9 nmol/L, p < 0.0001), a difference not seen among the women. Gambian men and women excreted significantly less phosphate and potassium than British subjects by 30-60%; urinary calcium and sodium excretion were similar in the two groups. This study revealed few ethnic differences that could account for the disparity in osteoporotic fracture rates between Africans and Caucasians, with the possible exception of anatomical differences in the hip.

Lean mass and physical activity as predictors of bone mineral density in 16-20-year old women

OBJECTIVE

The aim of the study was to quantify the inter-relationship between bone mineral density and physical activity, muscle strength, and body mass composition in a group of healthy 16-20-year-old women.

DESIGN

A cross-sectional study.

SETTING

Reykjavik area.

SUBJECTS

Two-hundred and fifty-four Icelandic Caucasian women aged 16, 18 and 20 years, randomly selected from the registry of Reykjavik.

MAIN OUTCOME MEASURES

Bone mineral content (BMC) and density (BMD) in lumbar spine, hip, distal forearm and total skeleton and lean mass and fat mass were measured with dual energy X-ray absorptiometry (DEXA) and compared with grip strength measured with a dynamometer and physical activity as assessed by a questionnaire.

RESULTS

The lean mass had the strongest correlation with BMC and BMD, stronger than weight, height and fat mass, both in univariate analysis (r = 0.41-0.77; P<0.001) and in linear regression analysis. The total skeletal BMD was logarithmically higher by hours of exercise per week (P<0.001)). About 30% of variability in total skeletal BMD in this age group can be predicted by lean mass and physical exercise.

CONCLUSIONS

Modifiable factors, such as exercise and adequate muscle seem to be significant predictors of the attainment of peak bone mass in women.

Appendicular bone mass in children with a high prevalence of low dietary calcium intakes

We have previously documented evidence of dietary calcium deficiency in black children living in a rural community in the eastern part of South Africa. The present study determined the bone mass of the distal one-third of the radius in a random sample of children living in the same community and compared their bone mass measurements with those of black children living in a similar rural community but without evidence of dietary calcium deficiency. Further, factors (weight, height, serum corrected total calcium, phosphorus, and alkaline phosphatase [ALP]) that might influence appendicular bone mass were assessed and correlated with the bone mass measurements. A random sample of 306 boys and 345 girls between the ages of 1 and 20 years were included in the study. Hypocalcemia was found in 6.5% of the boys and 5% of the girls, while elevated ALP values were recorded in 20 and 26% of the boys and girls, respectively. After adjusting for differences in age, weight, and height, bone mineral density (BMD) and bone mineral apparent density (BMAD) were significantly lower and bone width (BW) greater in study than control children. In a stepwise regression analysis, weight and/or height accounted for the majority of the observed variance in BMC, BW, and BMD; however, a significant effect of serum calcium (positively) and ALP (negatively) on BMC and BMD was also found. In boys, but not girls, serum ALP also had a positive effect on BW.BMAD was negatively correlated to ALP and positively correlated to serum calcium in both boys and girls. Those children with hypocalcemia or elevated ALP levels had significantly lower BMC, BMD, and BMAD and a trend toward greater BW than children with normal biochemistry. The findings suggest that low dietary calcium intake may have a detrimental effect on appendicular bone density in rural black children. Whether or not these effects are disadvantageous in the long-term is not known.