Is it time to consider population screening for fracture risk in postmenopausal women? A position paper from the International Osteoporosis Foundation Epidemiology/Quality of Life Working Group.

The IOF Epidemiology and Quality of Life Working Group has reviewed the potential role of population screening for high hip fracture risk against well-established criteria. The report concludes that such an approach should strongly be considered in many health care systems to reduce the burden of hip fractures. INTRODUCTION: The burden of long-term osteoporosis management falls on primary care in most healthcare systems. However, a wide and stable treatment gap exists in many such settings; most of which appears to be secondary to a lack of awareness of fracture risk. Screening is a public health measure for the purpose of identifying individuals who are likely to benefit from further investigations and/or treatment to reduce the risk of a disease or its complications. The purpose of this report was to review the evidence for a potential screening programme to identify postmenopausal women at increased risk of hip fracture. METHODS: The approach took well-established criteria for the development of a screening program, adapted by the UK National Screening Committee, and sought the opinion of 20 members of the International Osteoporosis Foundation's Working Group on Epidemiology and Quality of Life as to whether each criterion was met (yes, partial or no). For each criterion, the evidence base was then reviewed and summarized. RESULTS AND CONCLUSION: The report concludes that evidence supports the proposal that screening for high fracture risk in primary care should strongly be considered for incorporation into many health care systems to reduce the burden of fractures, particularly hip fractures. The key remaining hurdles to overcome are engagement with primary care healthcare professionals, and the implementation of systems that facilitate and maintain the screening program.

Biochemical bone turnover markers in hormonal disorders in adults: a narrative review.

BACKGROUND: Hormonal disorders are often associated with abnormal levels of bone turnover markers (BTMs). N-terminal propeptide of type I procollagen (PINP) and serum C-terminal cross-linking telopeptide of type I collagen (CTX-I) are the reference markers of bone formation and bone resorption, respectively. METHODS: A comprehensive literature search within the MEDLINE and Web of Science databases was performed. RESULTS: Acromegaly is associated with higher BTM levels, which decrease during the remission after treatment. Adult-onset growth hormone deficiency is often associated with decreased BTM levels. Growth hormone replacement therapy stimulates bone turnover and increases BTM levels. Hypothyroidism is characterized by general slowing of bone metabolism which is reflected by lower BTM levels. The replacement thyroid hormone therapy increases the bone turnover rate and BTM levels increase. Patients with thyroid cancer receive a suppressive dose of thyroid hormones and may have slightly elevated BTM levels. Patients with overt hyperthyroidism had higher BTM levels and anti-thyroid therapy induces a rapid decrease in the BTM levels. Patients with overt primary hyperparathyroidism have higher BTM levels, whereas those with asymptomatic and normocalcemic hyperparathyroidism usually have normal BTM levels. Hypoparathyroidism is characterized by slightly decreased BTM levels. Cushing's syndrome is characterized consistently by markedly decreased osteocalcin concentration, whereas data on other BTMs are discordant. CONCLUSIONS: BTMs help us to better understand mechanisms of the impact of hormonal disorders and their treatment on bone metabolism. However, it is unknown whether BTMs may be used to monitor the effect of their treatments on bone in the clinical practice.

Use of CTX-I and PINP as bone turnover markers: National Bone Health Alliance recommendations to standardize sample handling and patient preparation to reduce pre-analytical variability.

The National Bone Health Alliance (NBHA) recommends standardized sample handling and patient preparation for C-terminal telopeptide of type I collagen (CTX-I) and N-terminal propeptide of type I procollagen (PINP) measurements to reduce pre-analytical variability. Controllable and uncontrollable patient-related factors are reviewed to facilitate interpretation and minimize pre-analytical variability. INTRODUCTION: The IOF and the International Federation of Clinical Chemistry (IFCC) Bone Marker Standards Working Group have identified PINP and CTX-I in blood to be the reference markers of bone turnover for the fracture risk prediction and monitoring of osteoporosis treatment. Although used in clinical research for many years, bone turnover markers (BTM) have not been widely adopted in clinical practice primarily due to their poor within-subject and between-lab reproducibility. The NBHA Bone Turnover Marker Project team aim to reduce pre-analytical variability of CTX-I and PINP measurements through standardized sample handling and patient preparation. METHODS: Recommendations for sample handling and patient preparations were made based on review of available publications and pragmatic considerations to reduce pre-analytical variability. Controllable and un-controllable patient-related factors were reviewed to facilitate interpretation and sample collection. RESULTS: Samples for CTX-I must be collected consistently in the morning hours in the fasted state. EDTA plasma is preferred for CTX-I for its greater sample stability. Sample collection conditions for PINP are less critical as PINP has minimal circadian variability and is not affected by food intake. Sample stability limits should be observed. The uncontrollable aspects (age, sex, pregnancy, immobility, recent fracture, co-morbidities, anti-osteoporotic drugs, other medications) should be considered in BTM interpretation. CONCLUSION: Adopting standardized sample handling and patient preparation procedures will significantly reduce controllable pre-analytical variability. The successful adoption of such recommendations necessitates the close collaboration of various stakeholders at the global stage, including the laboratories, the medical community, the reagent manufacturers and the regulatory agencies.

Family resemblance of bone turnover rate in mothers and daughters--the MODAM study.

UNLABELLED: We studied bone turnover markers (BTM) and bone microarchitecture (using high-resolution peripheral quantitative computed tomography (HR-pQCT)) in 171 postmenopausal women and their 210 premenopausal daughters. BTM levels correlated positively between mothers and daughters. The mother-daughter pairs with high BTM levels had lower cortical density than those with low BTM levels. INTRODUCTION: We assessed the correlation of serum bone turnover markers (BTM) between postmenopausal mothers and their premenopausal daughters as well as possible determinants of this association and its impact on resemblance of bone microarchitecture between mothers and their daughters. METHODS: Cross-sectional analysis was performed in 171 untreated postmenopausal mothers (54 sustained fragility fractures) and their 210 premenopausal daughters. Intact N-terminal propeptide of type I collagen (PINP) and ß-isomerized C-terminal crosslinking telopeptide of type I collagen (CTX-I) were measured in the fasting status. Bone microarchitecture was assessed using HR-pQCT. RESULTS: After adjustment for age, weight, lifestyle factors, hormones, and mother's fracture status, BTM levels correlated positively between mothers and daughters (Intraclass Correlation Coefficient = 0.22-0.27, p <0.005). Average BTM levels were ∼ 0.6 SD higher among daughters of mothers in the highest BTM quartile vs. the ones in the lowest BTM quartile. The variability of BTM levels explained ≤ 10 and ≤ 14% of variability of bone microarchitecture in the daughters and mothers, respectively. Cortical density was lower by 2.3-2.9% (0.6 SD, p <0.05 to <0.005) in the daughters from the mother-daughter pairs with high BTM levels (defined by generation-specific quartiles) than in the daughters from the pairs with low BTM levels. Corresponding differences for the mothers were 4.5-4.8% (0.5 SD, p <0.05 to <0.01). CONCLUSION: BTM levels correlated between postmenopausal mothers and their premenopausal daughters after adjustment for age, weight, mother's fracture status, lifestyle, and hormonal factors. Family resemblance of BTM levels may contribute to family resemblance of some bone microarchitectural parameters, especially of cortical density.

Severe abdominal aortic calcification in older men is negatively associated with DKK1 serum levels: the STRAMBO study.

CONTEXT: Experimental data show that dickkopf-1 (DKK1) may be involved in the regulation of arterial calcification. However, clinical data on the association between serum DKK1 levels and severity of abdominal aortic calcification (AAC) are scarce. OBJECTIVE: Our aim was to determine the association between serum DKK1 concentration and AAC severity in men. DESIGN: This is a cross-sectional analysis in the STRAMBO cohort. SETTING: The cohort was recruited from the general population. PARTICIPANTS: We examined 1139 male volunteers aged 20 to 87 years. No specific exclusion criteria were used. INTERVENTIONS: We collected blood samples and assessed AAC severity on the lateral spine scans obtained by a Discovery A Hologic device using the semiquantitative Kauppila score. MAIN OUTCOME MEASURES: We tested the hypothesis that low DKK1 levels are associated with AAC severity in men. RESULTS: In men aged 20 to 60 years, serum DKK1 levels were not associated with other variables. In men aged 60 years and older, lower DKK1 levels were associated with higher odds of severe AAC (AAC score >5). After adjustment for confounders, odds of severe AAC increased with decreasing DKK1 levels (odds ratio = 1.42, 95% confidence interval = 1.13-1.79, P < .005) and was higher below vs above the median DKK1 level (odds ratio = 2.19, 95% confidence interval = 1.37-3.49, P < .005). Heavy smoking, hypertension, ischemic heart disease, and elevated levels of fibroblast growth factor 23 were associated with severe AAC significantly, independently of DKK1 and additively with low DKK1 levels. CONCLUSION: In older men, lower serum DKK1 levels are associated with severe AAC regardless of age and other potential confounders.

Severity of aortic calcification is positively associated with vertebral fracture in older men--a densitometry study in the STRAMBO cohort.

UNLABELLED: In older men, severe abdominal aortic calcification and vertebral fracture (both assessed using dual-energy X-ray absorptiometry) were positively associated after adjustment for confounders including bone mineral density. INTRODUCTION: Abdominal aortic calcification (AAC) is associated with higher fracture risk, independently of low bone mineral density (BMD). Dual-energy X-ray absorptiometry (DXA) can be used to assess both vertebral fracture and AAC and requires less time, cost, and radiation exposure. METHODS: We conducted a cross-sectional study of the association between AAC and prevalent vertebral fractures in 901 men≥50 years old. We used DXA (vertebral fracture assessment) to evaluate BMD, vertebral fracture, and AAC. RESULTS: Prevalence of vertebral fracture was 11%. Median AAC score was 1 and 12% of men had AAC score>6. After adjustment for age, weight, femoral neck BMD, smoking, ischemic heart disease, diabetes, and hypertension, AAC score>6 (vs ≤6) was associated with 2.5 (95% CI, 1.4-4.5) higher odds of vertebral fracture. Odds of vertebral fracture for AAC score>6 increased with vertebral fracture severity (grade 1, OR=1.8; grade 2, OR=2.4; grade 3, OR=4.4; trend p<0.01) and with the number of vertebral fractures (1 fracture, OR=2.0, >1 fracture, OR=3.5). Prevalence of vertebral fracture was twice as high in men having both a T-score<-2.0 and an AAC score>6 compared with men having only one of these characteristics. CONCLUSIONS: Men with greater severity AAC had greater severity and greater number of vertebral fractures, independently of BMD and co-morbidities. DXA can be used to assess vertebral fracture and AAC. It can provide a rapid, safe, and less expensive alternative to radiography. DXA may be an important clinical tool to identify men at high risk of adverse outcomes from osteoporosis and cardiovascular disease.

Poor trabecular microarchitecture in male current smokers: the cross-sectional STRAMBO study.

Current smoking (but not past smoking) is associated with higher risk of fracture independent of areal bone mineral density (aBMD); however, the pathophysiologic mechanism underlying this association is not clear. In 810 men aged 60-87, aBMD was measured by dual-energy X-ray absorptiometry. Bone microarchitecture at the distal radius and distal tibia was assessed by high-resolution peripheral quantitative computed tomography using the Xtreme CT Scanco device. Current smokers (n = 47) had lower trabecular volumetric density (Dtrab), lower trabecular number (TbN), more heterogenous trabecular network (higher trabecular spacing standard deviation [TbSpSD]), as well as higher urinary deoxypyridinoline and higher C-reactive protein levels in comparison with 261 men who never smoked (adjusted for age, weight, height, time spent outdoors, physical activity, and intake of alcohol, caffeine, and calcium). Abnormal values (lower Dtrab and TbN, higher TbSpSD, deoxypyridinoline, and C-reactive protein) were found mainly in 21 current smokers who smoked eight or more cigarettes per day. Cortical parameters and aBMD did not differ from the never-smokers. In 502 former smokers, aBMD and all bone microarchitectural parameters did not differ from the never-smokers. At the tibia (not radius), Dtrab decreased, whereas TbSpSD slightly increased across quartiles of smoking intensity (number of pack-years). In conclusion, older men who are moderate current smokers have poor trabecular (but not cortical) microarchitecture, which is not reflected by a decrease in aBMD.

Cortical bone status is associated with serum osteoprotegerin concentration in men: the STRAMBO study.

CONTEXT: Osteoprotegerin (OPG) is an inhibitor of bone resorption, but its relationship to bone microarchitecture remains unclear. OBJECTIVE: Our objective was to study the relationship between OPG concentration and bone microarchitecture in men. DESIGN, SETTING, AND PARTICIPANTS: We conducted a cross-sectional study of a population-based cohort of 1149 men aged 20-87 yr. INTERVENTIONS: We assessed bone microarchitecture at the distal radius and tibia by high-resolution peripheral quantitative computed tomography (XtremeCT Scanco) and measured serum OPG concentration and bone turnover markers: osteocalcin, bone-specific alkaline phosphatase, N-terminal extension type I collagen propeptide, C-terminal type 1 collagen telopeptide, and urinary deoxypyridinoline. MAIN OUTCOME MEASURES: Differences were assessed in bone microarchitectural parameters across the OPG quartiles in the models adjusted for age, weight, height, physical activity, ischemic heart disease, diabetes mellitus, calcium intake, serum levels of free testosterone, bioavailable 17ß-estradiol, PTH, 25-hydroxycholecalciferol, and creatinine. RESULTS: After adjustment for the confounders, men in the highest (fourth) quartile of OPG levels (>4.55 pmol/liter) had higher total cross-sectional area and trabecular area at the distal radius and distal tibia (3.3-6.0%, P < 0.05). At both skeletal sites, the highest OPG quartile was associated with lower cortical thickness (8.2%, P < 0.001, and 3.7%, P < 0.05) and volumetric bone mineral density (vBMD, 2.7%, P < 0.001, and 1.6%, P < 0.005) compared with the three lower quartiles combined. Associations of OPG level with trabecular vBMD, number, thickness, and distribution were not significant. Men in the fourth OPG quartile had higher levels of bone resorption markers (11.8-13.1%, P < 0.01-0.001). CONCLUSIONS: Men with higher serum OPG concentration had lower cortical thickness and vBMD, probably due to accelerated endo- and intracortical bone turnover, but higher cross-sectional area possibly due to periosteal apposition.

Role of sex steroids in the regulation of bone morphology in men. The MINOS study.

In ageing men, skeletal fragility is associated with reduced cortical thickness and decreased bone density. To better understand the role of testosterone and 17beta-estradiol regarding these characteristics of skeletal fragility, we correlated their circulating levels with the estimates of mechanical bone properties derived from areal bone mineral density (aBMD) measured by DXA. External diameter and BMD were used to estimate cortical thickness, cross-sectional area (CSA), section modulus, buckling ratio and strength index of the femoral neck and distal radius on 760 men aged 40-85 years. The 17beta-estradiol level was an independent positive determinant of CSA, aBMD and estimated cortical thickness of both bones. In multivariate models adjusted for age, body weight, height, lean body mass and testosterone concentration, men in the lowest quartile of 17beta-estradiol had lower CSA at the femoral neck (4.8%, P<0.001) and distal radius (3.6%, P<0.01) compared with men in the highest quartile. They had also thinner cortical bone at the femoral neck and distal radius (4.8%, P<0.001 and 4.6%, P<0.001, respectively). Furthermore 17beta-estradiol had a negative association with indices of cortical instability (buckling ratio) and a positive association with bending strength (section modulus, strength index) both at femoral neck and radius. Men in the lowest quartile of 17beta-estradiol had higher buckling ratios (femoral neck 4.8%, P<0.002; radius 5.1%, P<0.005), lower strength index (femoral neck 8.5%, P<0.001, radius 6.1%, P<0.01) and greater section modulus at the femoral neck. However, there were no between-quartile differences in external diameter in any bone sites. Similar, even though somewhat smaller, between-quartile differences were found for bioavailable 17beta-estradiol. Neither total testosterone nor apparent free testosterone concentration was associated with any bone variables after adjusting for age, body weight, body height, and lean body mass and 17beta-estradiol level. In conclusion, in elderly men, low concentration of 17beta-estradiol (total and bioavailable) was associated with a decreased cortical thickness and with a deterioration of biomechanical parameters of long bones (lower section modulus and strength index, higher buckling ratio).

Insulin-like growth factor I is a determinant of hip bone mineral density in men less than 60 years of age: MINOS study.

Several studies show that in elderly men bone mineral density (BMD) is not correlated with the insulin-like growth factor (IGF-I) level, but data are scanty in young men. Results of studies correlating insulin-like growth factor binding protein 3 (IGFBP-3) and BMD in men are discordant. As different hypotheses can explain the discordant results, we evaluated the correlation of BMD with serum IGF-I, IGFBP-3, and IGF-I/IGFBP-3 index in a large cohort of 721 men aged 19-85 years taking into account age, body weight, 17beta-estradiol, free testosterone, and parathyroid hormone. Serum IGF-I and IGFBP-3 decreased with age (r = -0.44 and r = -0.36, P = 0.0001). After adjustment for confounding variables, IGF-I correlated weakly positively with BMD and with bone mineral apparent density (BMAD) of hip as well as with cortical thickness of femoral neck, both of which are determined mainly by bone resorption, but not with bone size determined by periosteal apposition. IGF-I correlated weakly positively with BMD at the whole body and at the third lumbar vertebra IGFBP-3 and IGF-I/IGFBP-3 index did not correlate with densitometric parameters. In men aged 19-60 years, IGF-I correlated with BMD and BMAD of total hip and with cortical thickness of femoral neck positively and more strongly than in the entire cohort but not with the size of proximal femur. BMD of total hip was 6% higher in men in the highest quartile of IGF-I than in men in the lowest quartile. IGF-I, IGFBP-3, and IGF-I/IGFBP-3 index did not correlate with densitometric parameters of other sites. In the men aged more than 60 years, neither IGF-I nor IGFBP-3 nor IGF-I/IGFBP-3 index correlated with BMD, BMAD, or bone size. In men aged 19-60 years, the most significant hormonal determinants of BMD and BMAD of the hip and of the cortical thickness of femoral neck were 17beta-estradiol and IGF-I (P < 0.05-0.0001). In men aged more than 60 years, the most significant determinants of hip BMD were 17beta-estradiol and PTH. In conclusion, IGF-I seems to contribute to the inhibition of bone resorption and to maintaining bone mass of the proximal femur during the phase of slow bone loss in men aged less than 60 years. IGFBP-3 and IGF-I/IGFBP-3 index were not correlated with BMD or bone size.

Increased bone resorption in moderate smokers with low body weight: the Minos study.

Tobacco was found to be a risk factor for osteoporosis, mainly in postmenopausal women. We studied the effect of smoking on bone mineral density (BMD) and bone turnover in a cohort of 719 men, aged 51-85 yr, composed of 83 current smokers, 405 former smokers, and 231 men who never smoked. Most current and former smokers were moderate smokers (median, 10 cigarettes/d). Current smokers were younger, thinner, and drank more coffee and more alcoholic beverages. After adjustment for age, body weight, alcohol intake, and caffeine intake, current and former smokers had similar BMD, except at the forearm. Former smokers had lower BMD compared with never-smokers at most skeletal sites. Men who had smoked more than 7120 packs (third quartile) had lower BMD of total hip (P < 0.01) and distal forearm (P = 0.03) compared with men in the 2 lower tertiles. In the 3 groups, levels of bone formation markers did not differ. After adjustment for confounding variables, levels of urinary markers of bone resorption (beta-isomerized C-terminal telopeptide, free and total deoxypyridinoline) were higher in the current smokers than in former smokers and never-smokers. Concentrations of T, total 17beta-E2, and androstenedione were higher, whereas that of 25-hydroxyvitamin D was lower, in current smokers. When men were divided according to tertiles of body weight, increased bone resorption, decreased BMD and biochemical indexes of secondary hyperparathyroidism were observed in current smokers in the lowest tertile of body weight (<75 kg) compared with the never-smokers, but not in men in the two highest tertiles of body weight. Current smokers had a higher prevalence of vertebral deformities after adjustment for age and body weight (13% vs. 5%; P < 0.005). In summary, in moderate smokers with low body weight (<75 kg), increased bone resorption, not matched by increased bone formation, results in decreased BMD and an increased prevalence of vertebral deformities. In this group, low serum 25-hydroxyvitamin D and secondary hyperparathyroidism may explain, at least partly, the effect of tobacco on bone turnover. In former smokers, bone resorption is not increased, but BMD remains lower compared with that in never-smokers.

Cross-sectional evaluation of bone metabolism in men.

There are relatively few data concerning age-related changes of bone turnover in men. The aim of the study was to evaluate age-related changes of the levels of serum and urinary biochemical markers of bone metabolism in a large cohort of 934 men aged 19-85 years and to investigate their association with bone mineral density (BMD). Bone formation was evaluated using serum levels of osteocalcin (OC), bone alkaline phosphatase (BAP), and N-terminal extension propeptide of type I collagen (PINP). Bone resorption was evaluated by measurement of urinary excretion of beta-isomerized C-terminal telopeptide of collagen type I beta-CTX) of free deoxypyridinoline (fDpyr) and total Dpyr (tDPyr) and of the serum level of beta-CTX. Levels of biochemical bone markers were very high in young men and decreased rapidly until the age of 40 years and then more slowly until 60 years of age. After the age of 60 years, markers of bone formation remained stable while resorption markers showed a moderate and variable increase with aging. Serum and urinary beta-CTX levels were elevated only in about 5% of elderly men. The age-related increase of urinary excretion of tDpyr and of its free and peptide-bound fractions was related to the presence of elevated levels in a subgroup of about 15% of elderly men. Before 60 years of age, levels of biochemical bone markers were not correlated with BMD, whereas after 60 years of age, they were correlated negatively with BMD. After adjustment for age and body weight, BMD in men with the highest levels of biochemical bone markers (i.e., in the upper quartile) was 1.8-12.5% (i.e., 0.25-0.89 SD) lower than in men with levels of biochemical bone markers in the lowest quartile. In conclusion, bone turnover in men is high in young adults and decreases to reach a nadir at 55-60 years of age. After the age of 60 years, bone resorption markers--but not bone formation markers--increase in some men and are associated with lower BMD, suggesting that this imbalance is responsible for increasing bone loss in elderly men.

Osteoprotegerin serum levels in men: correlation with age, estrogen, and testosterone status.

Previous studies have suggested an important role for androgens and estrogens in bone metabolism in men. However, their local mode of action has not been clearly established. Osteoprotegerin (OPG) is a secreted decoy receptor that inhibits osteoclast formation and activity by neutralizing its cognate ligand. To assess the role of OPG on bone metabolism in men, we conducted a study aimed at evaluating OPG serum levels and their correlation with age, bone mineral density, biochemical markers of bone turnover, and testosterone and estradiol levels in 252 men, aged 19-85 yr. Serum concentrations of OPG increased significantly with age (r = 0.41; P = 0.0001), and were positively correlated with free testosterone index and free estradiol index (r = 0.20; P < 0.002 and r = 0.15; P < 0.03, respectively) after adjustment for age and body weight. Beyond the age of 40 yr, OPG serum concentrations were negatively correlated with urinary excretion of total deoxypyridinoline (r = -0.20; P < 0.01) and PTH serum levels (r = -0.23; P < 0.01). In contrast, there was no correlation with biochemical markers of bone formation, 25-hydroxyvitamin D(3) levels, or bone mineral density at any site. Our data reveal that age as well as androgen and estrogen status are significant positive determinants, whereas PTH is a negative determinant, of OPG serum levels in men. These data suggest that OPG may be an important paracrine mediator of bone metabolism in elderly men and highlight the role of estrogens in the homeostasis of the male skeleton.

Bioavailable estradiol may be an important determinant of osteoporosis in men: the MINOS study.

During recent years, experimental data, case reports, and epidemiological studies have suggested an important role for estradiol in bone metabolism in men. In a cohort of 596 men, aged 51-85 yr, we measured bone mineral density (BMD) of the lumbar spine, hip, total body, and forearm; serum levels of sex steroid hormones [total and free testosterone, total estradiol (17betaE(2)), bioavailable estradiol (bio-17betaE(2)), androstenedione, and sex hormone-binding globulin]; and markers of bone turnover [serum osteocalcin, bone alkaline phosphatase, N-terminal extension propeptide of type I collagen, and beta-isomerized C-terminal telopeptide of collagen type I (betaCTX)], as well as urinary excretion of betaCTX and deoxypyridinoline (DPyr). An age-related decrease was found for bio-17betaE(2) (r = -0.16; P < 0.001), free testosterone (r = -0.25; P < 0.001), free testosterone index (r = -0.32; P < 0.001), and androstenedione (r = -0.22; P < 0.001), but not for total 17betaE(2) or total testosterone. 17betaE(2) and bio-17betaE(2), but not other hormones, were correlated with BMD after adjustment for age and body weight. In men with a bio-17betaE(2) level in the lowest quartile, the average BMD was lower than in men having a bio-17betaE(2) level in the highest quartile by 6.6-8.7% according to the site of measurement, which corresponded to 0.45-0.65 SD. In age- and body weight-adjusted models, bio-17betaE(2), but not other hormones, was negatively correlated with bone markers (e.g., osteocalcin: r = -0.14; P < 0.001; urinary betaCTX: r = -0.20; P = 0.0001; DPyr: r = -0.14; P < 0.001). In men with the lowest concentration of bio-17betaE(2) (first quartile), the concentrations of markers of bone turnover were higher by 11-35% (or 0.4-0.7 SD) than in men having the highest bio-17betaE(2) level (upper quartile). In men in the lowest quartile for bio-17betaE(2) and in the highest quartile for urinary DPyr or betaCTX, the BMD of total hip and that of distal forearm were 8% and 10% lower than in men in the highest quartile for bio-17betaE(2) and in the lowest quartile for DPyr or ssCTX. In the age- and body weight-adjusted multiple regression models, bio-17betaE(2) contributed significantly to the explanation for the variability in all markers. In summary, we found in a cross-sectional analysis of a cohort of men that low levels of bio-17betaE(2) are associated with high bone turnover and low BMD. These data suggest that the age-related decrease in bio-17betaE(2) contributes to bone loss in elderly men by increasing bone turnover. Low 17betaE(2) levels may be an important risk factor for osteoporosis in men.

Influence of vitamin D and retinoids on the gammacarboxylation of osteocalcin in human osteosarcoma MG63 cells.

Osteocalcin (OC) is a bone matrix protein, synthesized by osteoblasts, which contains three residues of gammacarboxyglutamic acid (GLA). A fraction of circulating OC, which is not fully carboxylated and does not bind to hydroxyapatite, is called undercarboxylated OC (ucOC). In elderly institutionalized women, we have shown an increase of circulating ucOC level which may result not only from vitamin K deficiency but also from vitamin D deficiency (Szulc et al., J Clin Invest 91:1769; 1993). This intriguing finding prompted us to study the effect of vitamin D on the secretion of ucOC by osteoblastic cells in vitro in the presence of warfarin, an inhibitor of gammacarboxylation of GLA-containing proteins. The potential influence of retinoic acid (RA) was also studied, because its mechanism of action involves pathways that are similar to vitamin D. In the presence of warfarin (0.05 microg/mL), 1alpha,25(OH)2D (10(-8)-10(-6) mol/L) decreased dose dependently ucOC secretion by human osteosarcoma MG63 cells (from 3.87 +/- 0.96 to 2.12 +/- 0.13 ng/10(6) cells). When expressed as a fraction of total OC, secretion ucOC decreased from 47.4 +/- 1.4% to 24.8 +/- 3.2% in the MG63 cells. The secretion of total OC was stimulated by RA and by Ro 13-7410, which is a specific ligand of retinoic acid receptor (RAR), but not by 9-cis retinoic acid (9-cisRA), which is a physiologic ligand of retinoid X receptor (RXR). RA and Ro 13-7410 decreased ucOC secretion and ucOC% in warfarin-treated MG63 cells (RA: from 50.4 +/- 13.3% to 13.5 +/- 2.8%; Ro 13-7410: from 28.4 +/- 8.2% to 11.3 +/- 8.4%). 9-cisRA had no effect on OC gammacarboxylation. These results show that vitamin D, RA, and Ro 13-7410, but not 9-cisRA, may modify the gammacarboxylation of OC in human MG63 cells.