Familial resemblance and diversity in bone mass and strength in the population are established during the first year of postnatal life

Chronic hypoparathyroidism is associated with increased cortical bone density evaluated using high-resolution peripheral quantitative computed tomography

PURPOSE

This cross-sectional study aimed to assess bone mineral density (BMD), bone microarchitecture and fracture prevalence in women with chronic postsurgical hypoparathyroidism (hypoPT).

METHODS

Twenty-seven women with postsurgical hypoPT and 44 age-matched healthy women were included. Dual-energy X-ray absorptiometry was used to evaluate areal BMD and vertebral fracture assessment. High-resolution peripheral quantitative computed tomography assessed microarchitecture and volumetric BMD at the distal radius and tibia. Biochemical parameters, including fibroblast growth factor 23, C-terminal cross-linking telopeptide of type I collagen (ICTP), and procollagen type I N-terminal propeptide (P1NP), were also measured. Previous low-impact fractures were assessed and the 10-year fracture risk was estimated using the FRAX tool for the Brazilian population.

RESULTS

No participant had prevalent clinical fractures, and both groups showed low risk for major and hip based on FRAX tool, but two hypoPT patients had moderate to severe morphometric vertebral fractures. Women with hypoPT had increased aBMD in the lumbar spine, femoral neck and total hip (p < 0.05) and higher cortical vBMD in the radius (p = 0.020) and tibia (p < 0.001). Trabecular bone was not affected. Both P1NP and ICTP suggested low bone turnover rates, but no significant correlation was observed between bone density or microstructure and any of the biochemical parameters.

CONCLUSIONS

The prevalence of fragility fractures was low in HypoPT women and compatible with low fracture risk estimated by the FRAX tool. Patients had a higher aBMD and cortical vBMD than those of healthy control women, but the association with decreased bone turnover remains unclear.

Bone Mineral Content and Density in Healthy Term Indian Infants at the Age of 1 and 2 Years Assessed by Dual-Energy X-Ray Absorptiometry

There is a paucity of data on the bone mineral status of infants, with no data from India. This study was undertaken to assess the bone mineral content (BMC) of the healthy term Indian infants at 1 and 2 y of age, and the influence of factors such as birth weight, gender, current size, and vitamin D levels on BMC. Anthropometry, serum 25-hydroxyvitamin-D levels, and dual-energy X-ray absorptiometry (DXA) for the lumbar spine and whole-body BMC were performed at the ages of 1 and 2 y.Mean whole-body BMC was 214.1 ± 40.8 g at 1 y (n = 131) and 327.6 ± 87.4 g at 2 y (n = 73); lumbar spine BMC was 6.9 ± 1.8 g at 1 y and 10.2 ± 3.8 g at 2 y. The chief determinants of BMC were the weight and length/height of the infant, with no effect of vitamin D levels. The BMC of Indian infants at 1 y was similar to that reported previously for Caucasian infants.

Cortical bone development, maintenance and porosity: genetic alterations in humans and mice influencing chondrocytes, osteoclasts, osteoblasts and osteocytes

Cortical bone structure is a crucial determinant of bone strength, yet for many years studies of novel genes and cell signalling pathways regulating bone strength have focused on the control of trabecular bone mass. Here we focus on mechanisms responsible for cortical bone development, growth, and degeneration, and describe some recently described genetic-driven modifications in humans and mice that reveal how these processes may be controlled. We start with embryonic osteogenesis of preliminary bone structures preceding the cortex and describe how this structure consolidates then matures to a dense, vascularised cortex containing an increasing proportion of lamellar bone. These processes include modelling-induced, and load-dependent, asymmetric cortical expansion, which enables the cortex's transition from a highly porous woven structure to a consolidated and thickened highly mineralised lamellar bone structure, infiltrated by vascular channels. Sex-specific differences emerge during this process. With aging, the process of consolidation reverses: cortical pores enlarge, leading to greater cortical porosity, trabecularisation and loss of bone strength. Each process requires co-ordination between bone formation, bone mineralisation, vascularisation, and bone resorption, with a need for locational-, spatial- and cell-specific signalling pathways to mediate this co-ordination. We will discuss these processes, and a number of cell-signalling pathways identified in both murine and human genetic studies to regulate cortical bone mass, including signalling through gp130, STAT3, PTHR1, WNT16, NOTCH, NOTUM and sFRP4.

Bone trait ranking in the population is not established during antenatal growth but is robustly established in the first postnatal year

Efforts to understand the pathophysiology of bone fragility must focus on bone traits during growth. We hypothesized that variance in individual trait ranking in the population distribution is established by genetic factors and is reflected in foetal trait ranking in early pregnancy, but intrauterine factors modify trait ranking in late pregnancy, followed by the reinstating of this ranking during the first postnatal year. Thus, relations with paternal factors are present in early pregnancy but are then lost and subsequently reinstated postnatal. We recruited 399 healthy pregnant women aged 20–42 years from The Mercy Hospital for Woman in Melbourne, Australia. Foetal femur length (FL) and knee-heel length (KHL) were measured by ultrasound during gestation, and FL, KHL, body length and weight were measured in neonates, infants, and parents. The z-scores were calculated using Royston models. Pearson correlation was used to assess tracking and linear mixed models to test the associations. Correlations between FL and KHL z-scores of the same trait at 20 and 30 weeks gestation, at birth, and at 12 and 24 months of age (r = 0.1–0.3) and of body length and weight at birth, and 6, 12 and 24 months (r = 0.3–0.5) became more robust after 6–12 months (r = 0.4–0.8). FL and KHL z-scores at 20 weeks gestation accounted for 4–5% of total variance, while FL, KHL, body length and weight z-scores at birth accounted for 13–26% of total variance in the same traits at 24 months. Maternal FL and KHL were associated with foetal FL and KHL at 20 and 30 weeks, but there were no such associations for paternal FL and KHL with foetal traits during gestation. Both maternal and paternal traits were associated with infant traits. Tracking in traits is not established antenatal but is robustly established at 6–12 months of age.

Childhood growth predicts higher bone mass and greater bone area in early old age: findings among a subgroup of women from the Helsinki Birth Cohort Study

We examined the associations between childhood growth and bone properties among women at early old age. Early growth in height predicted greater bone area and higher bone mineral mass. However, information on growth did not improve prediction of bone properties beyond that predicted by body size at early old age.

INTRODUCTION

We examined the associations between body size at birth and childhood growth with bone area, bone mineral content (BMC), and areal bone mineral density (aBMD) in early old age.

METHODS

A subgroup of women (n = 178, mean 60.4 years) from the Helsinki Birth Cohort Study, born 1934-1944, participated in dual-energy X-ray absorptiometry (DXA) measurements of the lumbar spine and hip. Height and weight at 0, 2, 7, and 11 years, obtained from health care records, were reconstructed into conditional variables representing growth velocity independent of earlier growth. Weight was adjusted for corresponding height. Linear regression models were adjusted for multiple confounders.

RESULTS

Birth length and growth in height before 7 years of age were positively associated with femoral neck area (p < 0.05) and growth in height at all age periods studied with spine bone area (p < 0.01). Growth in height before the age of 7 years was associated with BMC in the femoral neck (p < 0.01) and birth length and growth in height before the age of 7 years were associated with BMC in the spine (p < 0.05). After entering adult height into the models, nearly all associations disappeared. Weight gain during childhood was not associated with bone area or BMC, and aBMD was not associated with early growth.

CONCLUSIONS

Optimal growth in height in girls is important for obtaining larger skeleton and consequently higher bone mass. However, when predicting bone mineral mass among elderly women, information on early growth does not improve prediction beyond that predicted by current height and weight.

Gender differences in the heritability of musculoskeletal and body composition parameters in mother-daughter and mother-son pairs

Bone mass and body composition traits are genetically programmed, but the timing and gender and site specificities of their heritability are unclear. Mother-child correlations of bone mineral density (BMD) and bone mineral content, lean mass, and fat mass were studied in 169 premenopausal mothers and their 239 children. Heritability estimates of lean mass, fat mass, BMD, and area were derived for each gender and pubertal stage. There were significant correlations for most densitometry-derived variables at the spine, hip, femoral neck (FN), and total body (r=0.192-0.388) in mother-postmenarcheal daughter pairs, for bone areas at all sites in early puberty (r=0.229-0.508) and for volumetric-derived density at FN and spine (r=0.238-0.368) in mother-son pairs. Fat mass correlations were significant in both genders after puberty (r=0.299-0.324) and lean mass in postmenarcheal girls only (r = 0.299). Heritability estimates varied between 21% and 37% for mother-daughter and 18% and 35% for mother-son pairs for density-derived variables and between 26% and 40% for body composition variables. Maternal inheritance of bone traits is expressed in early-pubertal boys for several skeletal site traits but consistently involves most site traits in girls and boys by late puberty. Body composition inheritance is more variable.

Concerted actions of insulin-like growth factor 1, testosterone, and estradiol on peripubertal bone growth: a 7-year longitudinal study

A better understanding of how bone growth is regulated during peripuberty is important for optimizing the attainment of peak bone mass and for the prevention of osteoporosis in later life. In this report we used hierarchical models to evaluate the associations of insulin-like growth factor 1 (IGF-1), estradiol (E(2) ), and testosterone (T) with peripubertal bone growth in a 7-year longitudinal study. Two-hundred and fifty-eight healthy girls were assessed at baseline (mean age 11.2 years) and at 1, 2, 3.5, and 7 years. Serum concentrations of IGF-1, E(2) , and T were determined. Musculoskeletal properties in the left lower leg were measured using peripheral quantitative computed tomography (pQCT). Serum levels of IGF-1, E(2) , and T increased dramatically before menarche, whereas they decreased, plateaued, or increased at a lower rate, respectively, after menarche. IGF-1 level was positively associated with periosteal circumference (PC) and total bone mineral content (tBMC) throughout peripuberty but not after adjustment for muscle cross-sectional area (mCSA). On the other hand, IGF-1 was associated with tibial length (TL) independently of mCSA before menarche. T was positively associated with TL, PC, tBMC, and cortical volumetric bone mineral density, independent of mCSA, before menarche but not after. E(2) was associated with TL positively before menarche but negatively after menarche. These findings suggest that during puberty, circulating IGF-1 promotes bone periosteal apposition and mass accrual indirectly, probably through stimulating muscle growth, whereas the effects of sex steroids on bone growth differ before and after menarche, presenting a biphasic pattern. Hence the concerted actions of these hormones are essential for optimal bone development in peripuberty.

Trabecular bone of growth plate origin influences both trabecular and cortical morphology in adulthood

Skeletal fragility is common at metaphyseal regions of long bones. The cortices of this region are derived by coalescence of trabeculae around the periphery of the growth plate, not by periosteal apposition, as occurs in the diaphyses. We therefore hypothesized that trabecular bone in childhood predicted both cortical and trabecular morphology in adulthood. To test this hypothesis, we measured distal radial and tibial structure using high-resolution peripheral quantitative computed tomography in 61 daughter-mother pairs, mean age 12.5 years (range 7 to 19 years) and 44.1 years (range 32 to 50 years), respectively. The daughters' trabecular bone volume (BV/TV), thickness, number, and separation predicted the corresponding traits in their mothers. Their trabecular BV/TV also predicted their mothers' cortical thickness (r = 0.32, p = .02). By contrast, the daughters' cortical thickness did not predict their mothers' cortical thickness. The daughters had higher trabecular BV/TV than their mothers (mean ± SD, radius 0.134 ± 0.024 versus 0.124 ± 0.033, p = .03; tibia 0.145 ± 0.021 versus 0.135 ± 0.032, p < .01) owing to greater trabecular number, not thickness, and less trabecular separation. Abnormalities in the development of metaphyseal trabecular bone are likely to influence fragility in both trabecular and cortical bone of this region in adulthood.

The accrual of bone mass during childhood and puberty

PURPOSE OF REVIEW

To assess factors that influence the tempo of bone mass accrual with emphasis on obesity, exercise, and nutritional factors.

RECENT FINDINGS

The prevalence of childhood obesity has increased dramatically throughout the world. Recent studies suggest that adiposity may be detrimental to development of bone strength parameters, and bone mass accrual during growth. Weight-bearing exercise during prepubertal and peripubertal period appears to enhance bone strength parameters. Maternal ultraviolet B radiation exposure and vitamin D status has been shown to have a positive effect on neonatal bone status, which appears to track up to the prepubertal period. Administration of vitamin D with or without calcium, but not calcium alone, during the prepubertal period might be an important 'window' for improving skeletal mineralization.

SUMMARY

Obesity in children appears to be detrimental to development of bone strength parameters and bone mass accrual. Weight-bearing exercise during prepubertal and peripubertal period and vitamin D supplementation during pregnancy, infancy, and peripubertal period might be important for bone mass accrual. However, adequately powered randomized controlled trials with follow-up into adulthood are needed to determine if these interventions improve the tempo of bone mass accrual.