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The influence of pretreatment bone turnover on alendronate efficacy is not known. In the FIT, we examined the effect of pretreatment bone turnover on the antifracture efficacy of daily alendronate given to postmenopausal women. The nonspine fracture efficacy of alendronate was significantly greater among both osteoporotic and nonosteoporotic women with higher baseline levels of the bone formation marker PINP.

A 3‐year, randomized, double‐blind, placebo‐controlled trial evaluated the effect of oral alendronate on the BMD of 64 adult patients with osteogenesis imperfecta. The mean increases in the lumbar spine BMD were 10.1 ± 9.8% (p< 0.001) and 0.7 ± 5.7% in the alendronate and placebo groups, respectively. Oral alendronate increases BMD in adult patients with osteogenesis imperfecta.

About one‐half of women with incident fractures have BMD above the WHO diagnostic threshold of osteoporosis. In the OFELY study, low BMD, increased markers of bone turnover, and prior fracture could be used to identify, within osteopenic women, those at high risk of fracture.Introduction: Recent data suggest that about one‐half of women with incident fractures have BMD above the World Health Organization (WHO) diagnostic threshold of osteoporosis (T score ≤ −2.5). We aimed to identify, within osteopenic women, those at high risk of fracture.Materials and Methods: In the 671 postmenopausal women (mean age: 62 years) belonging to the Os des Femmes de Lyon (OFELY) population‐based prospective cohort, we measured at baseline BMD by DXA at the spine and total hip, bone turnover markers (BTM) and clinical risk factors for osteoporosis. All fragility vertebral or nonvertebral fractures, confirmed by radiographs, were assessed during a median follow‐up of 9.1 years (IQ: 2.3).Results: 158 incident fractures were recorded in 116 women: 8% in normal, 48% in osteopenic, and 44% in osteoporotic women. Among osteopenic women, low BMD (−2.5 < T score ≤ −2.0) was associated with an increased fracture risk with an age‐adjusted hazard ratio (HR) of 2.5 (1.3‐4.6). In addition, age, prior fracture, and high BTM—but not other risk factors—were independently associated with an increased fracture risk with an age‐adjusted HR of 2.2 (1.2‐4.3) for prior fractures and 2.2 (1.4‐3.8) for bone alkaline phosphatase (BALP) in the highest quartile. In the whole group of osteopenic women, a large majority of incident fractures occurred in those with a low BMD, prior fractures, or BALP in the highest quartile, with an age‐adjusted HR of 5.3 (2.3‐11.8). The 10‐year probability of fracture in osteopenic women was 26% if at least one predictor was present, contrasting with 6% in those without any of the three risk factors.Conclusions: In postmenopausal women with osteopenia, low BMD, increased BTM, and prior fracture are associated with an increased risk of fracture in the subsequent 10 years. Their assessment may play an important role in identifying women at high risk of fracture who could not be adequately detected by BMD measurement alone and who may benefit from a therapeutic intervention.

We used data from the Fracture Intervention Trial to assess the relationship change in bone turnover after 1 year of alendronate or placebo treatment and subsequent hip, non‐spine, and spine fracture risk among 6186 postmenopausal women. In the alendronate group (n= 3105), greater reductions in one or more biochemical marker were associated with a lower risk of fracture.

Bone marker variability has raised concern for its use in individual patients. Serum osteocalcin (formation) and CTX (resorption) were measured every year for 4 years in 268 postmenopausal women. Seventy percent to 80% of women classified as having high bone turnover at baseline were similarly classified by the same methods 4 years later.

The Asp1211residue of the1209AHDGGR1214sequence of the C‐terminal cross‐linking telopeptide of type I collagen (CTX) can undergo spontaneous post‐translational modifications, namely, racemization and isomerization, which result in the formation of four isomers: the native form (α‐L) and three age‐related forms, that is, an isomerized form (β‐L), a racemized form (α‐D), and an isomerized/racemized (β‐D) form. Previous studies have suggested that changes in the pattern of type I collagen racemization/isomerization, which can be assessed in vivo by measuring the degradation products of the CTX isoforms, may be associated with alterations of bone structure. The aim of this study was to examine prospectively the value of the different urinary CTX isoforms and their related ratio in the prediction of osteoporotic fractures in 408 healthy untreated postmenopausal women aged 50‐89 years (mean, 64 years) who were part of the OFELY cohort. During a median 6.8 years follow‐up, 16 incident vertebral fractures and 55 peripheral fractures were recorded in 65 women. The baseline levels of the four CTX isoforms in women who subsequently had a fracture were compared with those of the 343 women who did not fracture. At baseline, women with fractures had increased levels of ratios of native α‐L‐CTX to age‐related isoforms (β‐L, α‐D, and β‐D) compared with controls (p< 0.01). In logistic regression analysis after adjustment for age, prevalent fractures, and physical activity, women with levels of α‐L/β‐L, α‐L/α‐D, and α‐L/β‐D‐CTX ratios in the highest quartile had a 1.5‐ to 2‐fold increased risk of fractures compared with women with levels in the three lowest quartiles with relative risk (RR) and 95% CI of 2.0 (1.2‐3.5), 1.8 (1.02‐2.7), and 1.5 (0.9‐2.7), respectively. Adjustment of α‐L/β‐Land α‐L/α‐D‐CTX ratios by the level of bone turnover assessed by serum bone alkaline phosphatase (ALP)‐ or femoral neck bone mineral density (BMD) decreased slightly the RR, which remained significant for the α‐L/β‐L‐CTX ratio (RR [95%] CI, 1.8 [1.1‐3.2] after adjustment for bone ALP, 1.8 [1.03‐3.1] after adjustment for BMD, and 1.7 [0.95‐2.9] after adjustment for both bone ALP and BMD). Women with both high α‐L/β‐L‐CTX ratio and high bone ALP had a 50% higher risk of fracture than women with either one of these two risk factors. Similarly, women with both increased CTX ratio and low femoral neck BMD (T score < −2.5) had a higher risk of fracture with an RR (95% CI) of 4.5 (2.0‐10.1). In conclusion, increased urinary ratio between native and age‐related forms of CTX, reflecting decreased degree of type I collagen racemization/isomerization, is associated with increased fracture risk independently of BMD and partly of bone turnover rate. This suggests that alterations of type I collagen isomerization/racemization that can be detected by changes in urinary CTX ratios may be associated with increased skeletal fragility.

The aims of this study performed in ewes were: (1) to confirm in this animal model the effects on bone of ovariectomy (OVX) alone or associated with Lentaron (L), a potent peripheral aromatase inhibitor, used to amplify the effects of OVX and (2) to evaluate the effects of a new selective estrogen receptor modulator (SERM; MDL 103,323) on bone remodeling. Thirty‐nine old ewes were divided into five groups: sham (n= 7); OVX (n= 8); OVX + L (n= 8); OVX + L + MDL; 0.1 mg/kg per day (n= 8); and OVX + L + MDL 1 mg/kg per day (n= 8). The animals were treated for 6 months. Biochemical markers of bone turnover (urinary excretion of type 1 collagen C‐telopeptide [CTX], serum osteocalcin [OC], and bone alkaline phosphatase [BAP]) were measured each month. Bone biopsy specimens were taken at the beginning and after death at the end of the experiment. Bone mineral density (BMD) was measured by dual‐energy X‐ray absorptiometry (DXA) on the lumbar spine and femur. OVX induced a significant increase in biochemical markers. This effect was the highest after 3 months for CTX (+156% vs. sham) and after 4 months for OC and BAP (+74% and +53% vs. sham, respectively). L tended to amplify the effect of OVX on OC and BAP. OVX induced significant increases in the porosity, eroded, and osteoid surfaces in cortical bone but no effect was observed in cancellous bone. MDL treatment reduced the bone turnover as assessed by bone markers, which returned to sham levels as well as histomorphometry both in cortical and in cancellous bone. Cancellous osteoid thickness decreased by 27% (p< 0.05), mineralizing perimeter by 81% (p< 0.05), and activation frequency by 84% (p< 0.02) versus OVX + L. Femoral and spinal BMD were increased by MDL and tended to return to the sham values. The effects of OVX on bone turnover were different on cortical and cancellous bone. These effects on cortical bone were reflected by changes in biochemical markers. MDL markedly reduces bone turnover and increases BMD suggesting that this new agent may prevent postmenopausal bone loss.

It has been suggested that low serum 17β‐estradiol (E2) and sex hormone‐binding globulin (SHBG) may predict hip fracture in postmenopausal women. We have investigated the predictive value of serum E2 and SHBG concentrations and urinary deoxypyridinoline (D‐Pyr) and type I collagen breakdown products (CTX) in a large prospective cohort of 7598 healthy elderly ambulatory women (EPIDOS study), aged 75 years or more. We performed a nested case control study, by matching 212 patients with incident hip fracture with 636 controls. Mean follow‐up was 3.3 years (maximum, 4.9 years). Women having serum E2 below the limit of detection (3 pg/ml), that is, 2% of the population, were not at higher risk, with a relative hazard (RH) of 1.59 (95% CI = 0.45‐5.55). Women having serum E2 below 5, 6, 7, or 8 pg/ml, in the lowest quartile, or below the median had no increased risk of hip fracture. In contrast, women having serum E2 in the highest quartile (i.e., ≥10 pg/ml) were protected, with an RH of 0.66 (0.44‐0.98) that did not remain significant after adjustment for weight (RH = 0.71 [0.47‐1.06]). High serum SHBG values with different cut‐offs tended to be associated with an increased risk of hip fracture. Women in the highest quartile had an RH of 2.5 (1.37‐4.61), compared with those in the lowest quartile, that decreased markedly after adjustment for body weight (1.61 [0.99‐2.62]). The highest quartile of the ratio E2/SHBG, which is an index of free E2, was associated with a lower hip fracture risk (RH = 0.6 [0.4‐0.91]) that was no longer significant after adjustment for weight. In contrast, urinary D‐Pyr and CTX, when elevated above the upper limit of premenopausal values, were predictive of hip fracture, with an RH of 2.07 (1.49‐2.9) and 1.67 (1.19‐2.32), respectively, even after adjustment for body weight, serum E2, and SHBG. We conclude that in healthy elderly French women over 75 years of age, serum E2 and E2/SHBG in the highest quartile are associated with a lower risk of hip fracture and that this association is explained by a higher body weight. In addition, serum levels of E2 and SHBG do not account for the increased risk of hip fracture associated with high levels of bone resorption markers.

The mechanisms leading to increased bone loss and skeletal fragility in women with postmenopausal osteoporosis are still poorly understood. Increased bone resorption, low serum estradiol and high serum sex‐hormone‐binding globulin (SHBG) recently have been reported as predictors of vertebral and hip fractures in elderly women. In a cohort of healthy untreated younger postmenopausal women aged 50–89 years (mean, 64 years), we compared baseline levels of bone markers and endogenous hormones in 55 women who subsequently had a fracture (20 vertebral and 35 peripheral fractures) with levels in the 380 women who did not fracture during a mean 5 years of follow‐up. Women with levels in the highest quartile of four bone resorption markers including urinary‐free deoxypyridinoline (D‐Pyr), urinary type I collagen N‐telopeptides (NTX), and urinary and serum type I collagen C‐telopeptides (CTX) had about a 2‐fold increased risk of fractures compared with women with levels in the three lowest quartiles with relative risk (RR) and 95% CI of 1.8 (1.0‐3.4) for free D‐Pyr, 1.7 (0.9‐3.2) for urinary NTX, 2.3 (1.3‐4.1) for urinary CTX, and 2.1 (1.2‐3.8) for serum CTX. Serum levels of bone alkaline phosphatase (BAP) in the highest quartile were associated with an RR of fracture of 2.4 (1.3‐4.2). Women with serum levels of estradiol and dehydroepiandrosterone (DHEA) sulfate in the lowest quartile had an RR of fracture of 2.2 (1.2‐4.0) and 2.1 (1.2‐3.8), respectively. Increased levels of SHBG and intact parathyroid hormone (PTH) were moderately associated with an increased risk of fracture. Similar results were obtained when the analysis was restricted to symptomatic vertebral and nonvertebral fractures. Adjustment of biochemical markers by hormone levels did not significantly alter the results. Women with both high bone resorption markers and low estradiol (or low DHEA sulfate) had a higher risk of fracture with RRs of 3.0‐3.3 (p< 0.001). After adjustment for bone mineral density (BMD) of the hip, spine, radius, or total body, bone markers and hormones were still predictive of fracture risk with similar RRs. We conclude that high levels of some biochemical markers of bone turnover, low serum estradiol, low DHEA sulfate, high SHBG, and high PTH are associated with increased risk of osteoporotic fracture in postmenopausal women, independently of each other and of BMD. The mechanism by which some postmenopausal women have an increased rate of bone turnover leading to an increased risk of fracture remains to be elucidated.

The ability of biochemical markers to predict the rate of postmenopausal bone loss is still controversial. To investigate this issue further, baseline levels of a panel of specific and sensitive biochemical bone markers were correlated to the rate of change of forearm bone mineral density (BMD) assessed by four measurements over a 4‐year period using dual‐energy X‐ray absorptiometry in a large population‐based prospective cohort of 305 women aged 50–88 years (mean 64 years), 1–38 years postmenopausal. In the whole population, higher baseline levels of bone formation (serum osteocalcin and serum type I collagen N‐terminal propeptide) and bone resorption markers (urinary N‐telopeptides; urinary and serum C‐telopeptides) were significantly associated with faster BMD loss (r= −0.19 to −0.30, p< 0.001), independently of age. In women within 5 years of menopause that have the highest rate of bone loss, the predictive value of bone markers was increased with correlation coefficients reaching 0.53. Women with an abnormally high bone turnover, i.e., with levels of bone markers at baseline 2 SD above the mean of premenopausal women, had a rate of bone loss that was 2‐ to 6‐fold higher than women with a low turnover (p= 0.01–0.0001) according to the marker. When the population was categorized according to quartiles of bone markers at baseline, a similar relationship between increased levels of bone markers and faster rate of bone loss was found (p= 0.008–0.0001). In the logistic regression model, the odds‐ratio of fast bone loss, defined as the rate of bone loss in the upper tertile of the population, was increased by 1.8‐ to 3.2‐fold for levels of biochemical markers in the high turnover group compared with levels within the premenopausal range, with, however, a limited value for identifying individual fast bone losers. We conclude that increased levels of some of the new biochemical markers of bone turnover are associated with greater radial bone loss. Because increased bone loss is associated with an increased risk of fracture, bone turnover markers may be useful to improve the prediction of the risk of osteoporosis in postmenopausal women.

To examine the ability of commercially available biochemical markers of bone formation and resorption to predict hip bone loss, we prospectively obtained serum and timed 2‐h urine specimens from 295 women age 67 years or older who were not receiving estrogen replacement therapy. Serum was assayed for two markers of bone formation: osteocalcin (OC) and bone‐specific alkaline phosphatase (BALP). Urine specimens were assayed for four markers of bone resorption: N‐telopeptides (NTX), free pyridinolines (Pyr), free deoxypyridinoline (Dpyr), and C‐telopeptides (CTX). Measurements of hip bone mineral density were made at the time the samples were collected and then repeated an average of 3.8 years later. Higher levels of all four resorption markers were, on average, significantly associated with faster rates of bone loss at the total hip, but not at the femoral neck. Women with OC levels above the median had a significantly faster rate of bone loss than women with levels below the median, but there was no significant association between levels of BALP and hip bone loss. The sensitivity and specificity of higher marker levels for predicting rapid hip bone loss was limited, and there was considerable overlap in bone loss rates between women with high and low marker levels. We conclude that higher levels of urine NTX, CTX, Pyr, Dpyr, and serum OC are associated with faster bone loss at the hip in this population of elderly women not receiving estrogen replacement therapy, but these biochemical markers have limited value for predicting rapid hip bone loss in individuals.

A new immunoassay (ELISA) based on an antiserum that preferentially recognizes the free form of the pyridinoline (Pyr) crosslink was used to assess the urinary excretion of Pyr in a large normal sample of the population comprising 236 men and 193 women 30–90 years of age. Urinary Pyr increased significantly with age in both sexes. In women Pyr was higher than in men (57 ± 21 versus 46 ± 17 nmol/mmol creatinine, p< 0.001), and the menopause was reflected by a mean 37% increase, from an average 43 to 59 nmol/mm creatinine (p< 0.001). In 52 patients with active Paget's disease of bone, Pyr excretion was markedly increased (206 ± 160 nmol/mmol creatinine, p< 0.001 versus controls) and decreased by 71% after 3 days of IV treatment with the bisphosphonate pamidronate. Free Pyr measured by the ELISA and the total urinary excretion measured by HPLC were highly correlated both in normals (n= 74, r= 0.83, p< 0.001) and in Pagetic patients (n= 20, r= 0.93, p< 0.001). The mean intra‐ and interassay coefficients of variation of the ELISA were below 9 and 15%, respectively. It is concluded that this new convenient immunoassay of Pyr should be valuable for the clinical investigation of patients with osteoporosis and other metabolic bone diseases.

We developed a sensitive and specific two‐site radioimmunoassay (IRMA) for human osteocalcin using human osteocalcin as a standard and two monoclonal antibodies raised against human osteocalcin purified from human cortical bone, a solid‐phase anti‐25–37 region and a tracer anti‐5–13 sequence of the molecule. A wide range of osteocalcin levels (up to 300 ng/ml) can be measured with a sensitivity of 0.4 ng/ml. The intra‐ and interassay coefficients of variation are less than 4 and 6%, respectively. The recovery of human osteocalcin from serum samples ranges from 96 to 103%. IRMA was linear for serial sample dilutions in a wide range of serum osteocalcin levels, even in patients with chronic renal failure on hemodialysis. Depletion of serum in intact osteocalcin demonstrated that IRMA detects, in addition to the intact peptide, a large N‐terminal midregion fragment that represents about 50% of total osteocalcin levels in normals and patients with Paget's disease and up to 75% in patients with chronic renal failure. This large fragment, previously unrecognized because it cannot be distinguished from intact osteocalcin with gel filtration chromatography, is not generated in vitro by incubation of the serum up to 26 h. We measured osteocalcin in the serum of 309 healthy adults (180 men and 129 women, age range 20–95 years), 36 patients with Paget's disease, 12 patients with primary hyperparathyroidism, 70 patients with chronic renal failure on hemodialysis, and 10 patients on corticosteroid therapy, simultaneously with human IRMA and with a conventional radioimmunoassay (RIA) based on bovine reagents. A tight correlation (r= 0.889) was observed between the two assays in the normal population, but the values obtained with IRMA were about threefold higher (mean 23.3 ± 10.5 versus 7.5 ± 3.4 ng/ml) than those obtained with RIA. Reported as Zscores, that is, number of standard deviations from the predicted normal mean adjusted for sex and age, these two assays (IRMA and RIA) gave concordant results in patients with Paget's disease (4.05 ± 6.21 versus 2.41 ± 2.53), primary hyperparathyroidism (4.14 ± 7.17 versus 2.13 ± 2.28), chronic renal failure (25.32 ± 24.49 versus 6.93 ± 5.48), and glucocorticoid treatment (‐1.48 ± 0.78 versus −1.11 ± 0.57). However, IRMA was more discriminant from controls for all these metabolic bone diseases because the absolute values of mean Zscores with IRMA were significantly higher than those obtained with the RIA (p< 0.05–0.0001). We conclude that this new human‐specific IRMA of osteocalcin may be more sensitive than bovine RIA for the clinical investigation of metabolic bone diseases.

An enzyme‐linked immunosorbent assay for measuring type I collagen degradation products in serum (S‐ELISA) was developed. The assay uses a high affinity polyclonal antibody which reacts with an isomerized form of an 8 amino acid sequence of the C‐telopeptides of type I collagen (EKAHD‐β‐GGR). Cross‐reactivity to a nonisomerized synthetic peptide form of the 8 amino acid sequence is less than 0.2%. Values obtained in a group of premenopausal women (age, 33.3 ± 3.11 years) were 69 ± 24 ng/ml (n= 22). In a group of early postmenopausal women (age, 51.8 ± 1.88 years) values obtained were 125 ± 43 ng/ml (n= 46), which represents an increase of 81% (p< 0.001). Values found in untreated patients with Paget's disease were 234 ± 95 ng/ml (n= 15), and for primary hyperparathyroidism we found 335 ± 82 ng/ml (n= 10). Interveneous administration of a bisphosphonate (Pamidronate) to Paget's disease patients for 3 days was reflected in the S‐ELISA by a decrease in the values of 55% when compared with values before treatment (n= 15). Following treatment with another bisphosphonate (Alendronate) for 6 months, values were decreased to 48 ± 19 ng/ml (n= 12), which corresponds to a 62% decrease. Clinical results presented in this context support that the assay is a sensitive and specific index of bone resorption. It may, therefore, prove useful in the follow up of treatment of patients with metabolic bone diseases and in the clinical investigation of osteoporosis.

In Paget's disease of bone, the normal lamellar bone is replaced by a woven structure with an irregular arrangement of collagen fibers. In this study, we investigated whether the degree of β‐isomerization within C‐telopeptide of α1 chain of type I collagen was altered in Paget's disease compared with other bone diseases with no alteration of bone structure. In Paget's disease (n= 26), but not in patients with primary hyperparathyroidism (n= 6) or hyperthyroidism (n= 17), the urinary excretion of nonisomerized (α) fragments derived from degradation of type I collagen C‐telopeptide (CTX) was markedly increased compared with β‐isomerized CTX (+ 13‐fold vs. + 3.5‐fold over controls) resulting in an urinary α CTX/β CTX ratio 3‐fold higher than in controls (2.6 ± 1.0 vs. 0.8 ± 0.3, p< 0.001). In five pagetic patients in complete remission, as demonstrated by normal total alkaline phosphatase activity, the α CTX/β CTX ratio was normal. The immunohistochemistry of normal and pagetic human bone sections showed a preferential distribution of α CTX within woven structure, while lamellar bone was intensely stained with an anti–β CTX antibody, suggesting a lower degree of β‐isomerization of type I collagen in the woven pagetic bone. In collagenase digest of human bone specimens, we found a lower proportion of β‐isomerized type I collagen molecules in pagetic bone (40% of β CTX) than in normal bone taken from trabecular (68%) and cortical compartments (71%). In conclusion, we found that in Paget's disease the α CTX/β CTX ratio in bone and in urine is markedly increased. This altered β isomerization can be accurately detected in vivo by measuring urinary degradation products arising from bone resorption.

We measured the bone mineral density (BMD) at various skeletal sites (total body, hip, anteroposterior [AP] and lateral [lat] spine, and forearm) in a large population‐based cohort of women aged 31–89 years (the OFELY cohort), and results were analyzed according to age and postmenopausal years. A significant apparent bone loss was found before the menopause in cancellous bone, i.e., at the lat spine and Ward's triangle (−10%; p< 0.05–0.001). Cross‐sectional analysis indicated that, after the menopause, apparent bone loss was accelerated within the 10 years following menopause, continued thereafter at all sites except the AP spine, and was again accelerated in elderly menopausal for more than 25 years. Between 30 and 80 years, BMD decreased by 15 to 44% (Tscore −1.6 to −3.4) according to the site. The amount of apparent bone loss was highest at the Ward's triangle when expressed in percentage (44%) and at the mid‐ and distal radius when expressed in number of standard deviations from the peak bone mass (−3.4). As a result, the percentage of women classified as osteoporotic according to the World Heath Organization, i.e., with a T score ≤−2.5, varied substantially from site to site and was highest at the radius (37% and 46%) and lateral spine (25–31%), intermediate at the Ward's triangle, AP spine, and whole body BMD, and lowest at the whole body bone mineral content, femoral neck, and trochanter (10–12%). In conclusion, this cross‐sectional but large study suggests that there is a moderate apparent premenopausal bone loss that occurs only at cancellous bone sites and that apparent bone loss is accelerated at most skeletal sites after the age of 75 years. Because of the highly variable coefficient of variation of the peak bone mass at various skeletal sites, the percentage of postmenopausal women identified as being osteoporotic varies widely according to the site of measurement.

Previous studies have demonstrated an association between bone mineral density (BMD) and a start codon polymorphism (SCP) of the vitamin D receptor (VDR) gene in pre‐ and postmenopausal Caucasian and Japanese women. The SCP can be determined by a restriction fragment length polymorphism defined by the FokI restriction endonuclease. VDR alleles containing the FokI site are denoted by f and alleles lacking the site by F. In this study, the association between BMD and the SCP was examined in a group of 174 premenopausal French women who previously had been studied for a relationship between BMD and the VDR BsmI polymorphism. The SCP genotypes of the French women were FF 40%, Ff 44%, and ff 16% and they were independent of the BsmI genotype. BMD was measured by dual‐energy X‐ray absorptiometry at the lumbar spine, proximal femur, forearm, and total body. In contrast to previous reports, there was no association of BMD with SCP genotype in this group of Caucasian women at any site. We also measured several biochemical indices of calcium homeostasis and bone turnover. We found no statistically significant associations between SCP genotype and calcium, parathyroid hormone, or vitamin D levels. There was a 33.5% higher level of the skeletal resorption marker N‐telopeptides of type I collagen in the women with the ff genotype when compared with women with the FF genotype (p= 0.004). Other bone turnover markers failed to show an association with SCP genotype. In summary, the SCP genotype may not be associated with reduced BMD in all geographical or ethnic populations.

Changes of bone turnover with aging are responsible for bone loss and play a major role in osteoporosis. Although an increase of bone turnover has been documented at the time of menopause, the subsequent abnormalities of bone resorption and formation and their potential role in determining bone mass in the elderly have not been investigated. To address this issue, we have measured a battery of new sensitive and specific markers of bone turnover in a population‐based study of 653 healthy women analyzed cross‐sectionally, including 432 women postmenopausal from 1 to 40 years, and the data were correlated with bone mineral density (BMD) measured by dual‐energy X‐ray absorptiometry (DXA) at different skeletal sites. Bone formation was assessed by serum osteocalcin (OC), serum bone‐specific alkaline phosphatase (B‐ALP), serum C‐propeptide of type I collagen (PICP), and bone resorption by the urinary excretion of two pyridinoline cross‐linked peptides (NTX and CTX). Bone turnover increased in perimenopausal women with both irregular menses and elevated serum follicle stimulating hormone (FSH). Menopause induced a 37–52% and 79–97% increase in the bone formation and bone resorption marker levels, respectively (p< 0.0001 except for PICP). In postmenopausal women, bone formation markers did not decrease with age. When resorption markers were corrected by whole body bone mineral content (BMC), the fraction of bone resorbed per day was not correlated with age in postmenopausal women and remained elevated for up to 40 years after menopause. In premenopausal women, the bone turnover rate accounted for only 0–10% of the variation in whole body BMC, total hip, distal radius, and lumbar spine BMD. With increasing time after menopause, the importance of the bone turnover rate as a determinant of bone mass increased at all sites and accounted for up to 52% of the BMD variance in elderly women. Thus, in women 20 years or more postmenopause, bone turnover was higher in those in the lowest quartile than in those in the highest quartile of BMD. In elderly women, 20 years since menopause and over, but not in younger ones, serum PTH was negatively correlated with serum 25‐hydroxyvitamin D (r= −0.22,p< 0.05) and explained only 5–8% of the bone turnover variance (p< 0.01‐0.001). These data indicate that the overall rates of both bone formation and bone resorption remain high in elderly women. The rate of bone turnover appears to play an increasing role as a determinant of bone mass with increasing time since menopause with a high bone turnover rate being associated with a low bone mass. Thus assessing bone marker levels may be useful in the evaluation of osteoporosis risk. In elderly women, secondary hyperparathyroidism caused in part by reduced serum 25‐hydroxyvitamin D appears to be a marginal determinant of an increased bone turnover rate.

We have measured the free and peptide‐bound type I collagen cross‐link excretions in normal women and in patients with metabolic bone disease using the HPLC technique and immunoassays recognizing specifically the free or peptide‐bound forms of pyridinoline (Pyr). After menopause, free deoxypyridinoline (free D‐Pyr) excretion measured by HPLC without urine hydrolysis and expressed as a fraction of the total excretion was lower than in premenopausal women (45 ± 15% vs. 59 ± 12%, p> 0.005), whereas the fraction of free Pyr was not changed. In normal pre‐ and postmenopausal women (n= 43), the fraction of free D‐Pyr was negatively correlated with bone turnover rate as assessed by the total urinary excretion of Pyr (r= –0.64, p> 0.001). In patients with a variety of metabolic bone diseases characterized by increased bone turnover (osteoporosis, Paget's disease, and hyperthyroidism), the fractions of free Pyr and free D‐Pyr were significantly lower than in premenopausal controls (p> 0.001 for all diseases). After 3 days of intravenous (iv) treatment with the bisphosphonate pamidronate in patients with Paget's disease and osteoporosis, the urinary excretion of cross‐linked peptides measured by high performance liquid chromatography (HPLC) or enzyme‐linked immunoassay (ELISA) (NTX and CrossLaps) was markedly decreased (–52% and –85% for NTX, –71% and –93% for CrossLaps™ in Paget's disease and osteoporosis, respectively). The excretion of total cross‐links was decreased to a lesser extent after treatment (–25% and –25% for total Pyr, –37% and –45% for total D‐Pyr) and, surprisingly, free cross‐links measured either by HPLC without urine hydrolysis or with an ELISA specific for free D‐Pyr were unchanged after treatment. In contrast to bisphosphonate therapy, estrogen treatment of postmenopausal women decreased not only total and cross‐linked peptides but also the free cross‐link excretion that was reduced by about 30–40%. The different effects of bisphosphonate and estrogen therapy on the excretion of peptide‐bound and free cross‐link excretion were confirmed by gel filtration of the urine on Sephadex G 25 before and after treatment. In conclusion, we have shown that increased bone turnover in patients with metabolic bone disease could result in a larger increase of the urinary excretion of cross‐linked peptides over the increase of free cross‐links. Bisphosphonate therapy decreased markedly cross‐linked peptides without significant change in free cross‐link excretion contrasting with a decrease of both free and peptide‐bound cross‐links after estrogen therapy. These data suggest that these two antiresorptive therapies may affect differently the pattern of bone collagen degradation, an intriguing possibility that should be further investigated in vitro.

Three monoclonal antibodies recognizing the 5–13, 25–37, and 43–49 sequence of the human osteocalcin were used in competitive and two‐site radioimmunoassays (RIA) to characterize specifically various immunoreactive forms of circulating human osteocalcin. The intact molecule accounts for 36% of total in normals (2.6 nM), 46% in patients with osteoporosis (3.1 nM), and 26% in chronic renal failure (6.9 nM). Four fragment were detected in addition to the intact molecule in the serum of healthy adults and patients with metabolic bone disease. N‐terminal, mid, and mid C‐terminal fragments were present in minute amounts (each accounting for 5–14% of the total circulating osteocalcin immnoreactivity). In contrast, the N‐terminal mid‐fragment, probably resulting from the cleavage around amino acids 43–44, represents about 30% (2 nM) of the total osteocalcin immunoreactive level in normals and patients with osteoporosis and up to 50% (13 nM) in patients with chronic renal failure. This large N‐terminal midfragment, representing 75–80% of the intact osteocalcin level, is not lower when the plasma assay is performed immediately after sampling (within 20 minutes at 4°C with proteinase inhibitors), indicating that it circulates in vivo. In addition, this fragment was detected in the supernatant of osteoblastic cells, representing about 28% of the intact peptide. Levels of N‐terminal midfragment were not changed after treatment of patients with metabolic bone disease (Paget's disease, reflex sympathetic dystrophy, fibrous dysplasia, and osteoporosis) by bisphosphonate, suggesting that it is not released during bone resorption. The osteocalcin level measured with the two‐site immunoradiometric assay specific for the intact molecule or with a conventional bovine RIA was rapidly decreased after incubation of serum at room temperature (‐20 and −15%, respectively, after 3 h), whereas the total level of intact osteocalcin plus N‐terminal midfragment was not changed. Intact osteocalcin loss can be partially avoided by proteinase inhibitors and by incubating serum at 4°C. In conclusion, we characterized multiple immunoreactive forms of osteocalcin that circulate in addition to the intact molecule, none of them being specifically altered in osteoporosis. The N‐terminal midfragment circulates in a large amount, probably resulting from cleavage of the intact molecule in the circulation and/or at peripheral sites. These fragments can also be generated in vitro by proteolytic degradation of the intact molecule. To obtain reliable intact osteocalcin values but also reliable levels measured with conventional competitive RIA, careful control of the sampling conditions is warranted.

Vitamin D receptor (VDR) gene polymorphisms have been reported to account for most of the well established genetic influence on bone mineral density (BMD). However, discordant studies have been published and it is still not clear whether VDR genotypes influence bone mass accretion and/or postmenopausal bone loss. In this study, we analyzed VDR gene polymorphisms, i.e., that of BsmI, ApaI, and TaqI restriction enzymes in 268 untreated postmenopausal women 1–26 years postmenopausal. There were 37 BBAA homozygote (absence of BsmI and ApaI restriction sites on both alleles), 55 bbaa homozygote (presence of restriction sites on both alleles), and 176 heterozygotes. At baseline, women between the three genotypes did not differ significantly in age, years since menopause, body mass index (BMI), nor dietary calcium intake. We found no relationship between VDR genotypes and bone turnover assessed by three serum markers of bone formation and three urinary bone resorption markers, nor with BMD measured at the spine, hip, forearm, and whole body by dual‐energy X‐ray absorptiometry (DXA). Rates of bone loss assessed by repeated DXA measurements over 2 years were highly significant (p= 0.02–0.0001) at all skeletal sites except for the lumbar spine but did not differ between genotypes at any sites either before or after adjustment for potential confounding factors such as years since menopause, BMI, calcium intake, serum 25 hydroxyvitamin D levels, and baseline BMD. When we restricted the analysis to early postmenopausal women, within 10 years of menopause (n= 128), lumbar spine bone loss became significant, but no significant difference between VDR genotypes in the rate of bone loss measured at any site was found. We conclude that VDR genotypes are not predictive of bone turnover, rate of postmenopausal bone loss, and bone mass in either early or late postmenopausal women. In a subgroup of women with a low calcium intake (below 600 mg/day), we also found no significant differences between genotypes in BMD and the rate of bone loss measured at any site, although the sample size (n= 64) may be too small to detect small differences. In conclusion, these data, along with the absence of relationships between VDR gene polymorphisms and peak bone mass that we recently reported, suggest that the determination of VDR genotypes is probably not a useful clinical test for the risk assessment of osteoporosis.

Bone mineral density (BMD) is under strong genetic control. Polymorphisms at the vitamin D receptor (VDR) gene have been recently suggested to account for up to 75% of this genetic effect. We analyzed these polymorphisms, i.e., that of BsmI, TaqI, and ApaI restriction enzymes by PCR of the DNA in 189 healthy premenopausal women aged 31 to 57 years. For the BsmI polymorphism they were 17% BB homozygotes, 51% Bb heterozygotes, and 32% bb homozygotes, genotype frequencies that are very similar to those previously reported in other Caucasian populations of north European ancestry. Women in the three genotypes for any of the three polymorphisms were matched for age and did not differ in body weight, height, physical activity, nor smoking habits. We found no relationship between the genotype for any of the three polymorphisms nor bone formation and resorption rate assessed by five specific biochemical markers of bone turnover nor with BMD measured at the spine, proximal femur, forearm, and whole body by dual‐energy X‐ray absorptiometry (DXA). We concluded that these polymorphisms are not predictive of bone turnover nor BMD in a sample of healthy premenopausal women drawn from the French population.