The duration of exercise as a regulator of bone turnover

The relationship between duration of exercise and serum remodeling markers of bone turnover was evaluated by osteocalcin (OC), carboxy-terminal propeptide of type I collagen (PICP), total and bone-specific alkaline phosphatase (ALP) and carboxyterminal cross-linked telopeptide of type I collagen (ICTP) in 24 male premier league soccer players exercising 12 hours/week (range 8–18), 19 third league players exercising 8 hours/week (range 3–18) and 20 sixth league players exercising 6 hours/week (range 2–10). Twenty-seven volunteers served as controls. Forty-six former male soccer players (mean age 38 years, range 19–47), mean 15 years older than the current players, were compared with 41 matched controls. Data is presented as mean ± SEM. Active male players had 18 ± 4% higher OC, 37 ± 9% higher bone ALP and 36 ± 7% higher ICTP than controls (all P < 0.01). There were no differences in remodeling markers within the three groups of active players but each group had higher OC and ICTP than controls (both P < 0.05). Former players had no difference in bone remodeling markers compared to matched controls, but 39 ± 4% lower OC and 69 ± 8% lower ICTP than active players (both P < 0.001). Duration of activity was correlated with bone ALP and ICTP (both r = 0.3, P < 0.05) in individuals exercising 6 hours/week or less. No correlation was found in those exercising above this level. It seems as if the bone turnover, evaluated by serum bone remodeling markers, adapts to the current activity needed to maintain bone strength, and a duration of exercise above that level seems to confer no additional benefits.     

Relationships Between Bone Mass Measurements and Lifetime Physical Activity in a Swedish Population

Lifetime occupational and leisure time activities were assessed by a questionnaire in order to evaluate their relationship to bone mass measurements and biochemical markers of bone metabolism in a population of 61 women and 61 men, randomly selected from a Swedish population register, to represent ages between 22 and 85 years. We also considered possible confounders by using questions about smoking habits, milk consumption, hormone replacement therapy (HRT), and menopausal age. Bone mineral density (BMD) and bone mineral content (bone mass, BMC) of the total body, lumbar spine, and proximal femur (neck, trochanter, Ward's triangle) were measured by dual energy X-ray absorptiometry (DXA), and BMD of the forearm with single energy X-ray absorptiometry (SXA). In addition, both DXA and SXA provided information on bone area. Quantitative ultrasound measurements (QUS) at the heel were performed to assess the speed of sound (SOS) and broadband ultrasound attenuation (BUA). Fasting blood samples were analyzed for biochemical markers of bone metabolism as well as parathyroid hormone (PTH) and total serum calcium. After adjustment for confounding factors, neither BMD nor QUS measurements were consistently related to lifetime leisure time or occupational activities; nor were there any consistent patterns relating biochemical markers of bone metabolism to bone mass measurements. However, physical activity seemed to influence bone mass, area, and width more than density. In men, high levels of leisure time activity were associated with raised values for lumbar spine area (6.2%) and width (3.3%) as well as for femoral neck area (5.5%) compared with their low activity counterpart. Men exposed to high levels of occupational activity demonstrated lower lumbar spine BMD (10.9%) and area (5.3%) than men with low activity levels. Within an unselected Swedish population, estimation of lifetime occupational and sport activities as well as bedrest, using a questionnaire, demonstrated no major effects on bone density. However, the association between high levels of lifetime activity and raised values for bone mass, area, and width indicate that geometrical changes in bone may provide better estimations of mechanically induced bone strength than bone density, at least in men. Received: 20 May 1997 / Accepted: 15 October 1997     

Molecularly Defined Lactose Malabsorption,Peak Bone Mass and Bone Turnover Rate in Young Finnish Men

Lactose malabsorption (LM; adult-type hypolactasia), an autosomal recessive condition, results from the down-regulation of the activity of lactase enzyme in the intestinal wall. In previous studies the effect of LM on bone mass, bone turnover rate, development of osteoporosis and osteoporotic fractures has remained controversial. We have recently identified a single nucleotide polymorphism (SNP), a C to T change residing 13910 base pairs upstream of the lactase (LCT) gene at chromosome 2q21-22, which shows complete association with lactase persistence, with the C/C_–13910 genotype defining LM and the genotypes C/T_–13910 and T/T_–13910 lactase persistence. The present study was undertaken to examine the relationship of the C/T_–13910 polymorphism to peak bone mass, bone turnover rate, and stress fractures among young Finnish men. The study population comprised 234 young men, aged 18.3 to 20.6 years, 184 men were recruits of the Finnish Army, and 50 were men of similar age who had postponed their military service for reasons not related to health. Bone mineral content (BMC), density (BMD), and scan area were measured in the lumbar spine and upper femur by dual-energy X-ray absorptiometry (DXA). Blood was sampled for genotyping of the C/T_–13910 polymorphism and determination of serum 25-hydroxyvitamin D (25OHD), intact parathyroid hormone (iPTH), type I procollagen aminoterminal propeptide (PINP), and tartrate-resistant acid phosphatase 5b (TRACP5b). Second-void urine samples were collected for the determination of type I collagen aminoterminal telopeptide (NTX). The prevalence of the C/C_–13910-genotype of these young adults did not differ significantly from the corresponding population prevalence of C/C_–13910 (17.1% vs 18.1%) among Finnish blood donors. Fifteen recruits of the army experienced a stress fracture; 3 of them (20%) had the C/C_–13910-genotype. Calcium intake was similar for the three genotypes as were the unadjusted BMCs, scan areas, and BMDs at different measurement sites. The adjustments for age, height, weight, smoking, alcohol consumption, and physical exercise in the multiple regression analysis did not reveal any significant relationships between the lactase genotypes and BMDs at lumbar (P = 0.16), femoral neck (P = 0.99) or total hip (P = 0.96) sites. Serum 25OHD, iPTH, and bone marker levels were similar for the C/C_–13910 C/T_–13910 and T/T_–13910 genotypes. In summary, in young Finnish men, molecularly defined lactose malabsorption does not alter bone turnover rate and impair the acquisition of peak bone mass. Moreover, the C/C_–13910 genotype does not seem to be a risk factor for stress fractures in army recruits.N. Enattah and V.-V. Välimäki equally contributed to the study.     

Calcaneal Ultrasound but Not Bone Turnover Predicts Fractures in Vitamin D Deficient Frail Elderly at High Risk of Falls

Background Biochemical markers of bone turnover have been reported to predict fracture risk independent of bone mass in postmenopausal women. We investigated their use in predicting fractures in the frail elderly. Methods Cases were 151 low trauma fractures. For each case, a control was selected marched for sex, age, institution type and follow-up period. We measured two bone resorption markers (serum ICTP and serum CTX-I) and two bone formation markers (serum PINP and serum BAP). Quantitative Ultrasound (QUS) was measured in the calcaneus. Fractures were ascertained by x-ray reports. Results The mean age of subjects was 86.8 years (± 5.8 SD) and 86% were female. 76% had hypovitaminosis D (a serum 25 hydroxy vitamin D (25OHD) level < 39 nmol/L) and 81% had BUA < 67.4 dB/MHz (corresponding to a BMD T-score < −2.5). No significant differences in bone turnover markers were detected between fracture cases and their matched controls. In contrast, there was a significant difference between cases and controls for both broadband ultrasound attenuation (BUA) and velocity of sound (VOS) (both P < 0.05). These results remained the same after adjusting for weight, lower leg length and walking aids as well as the higher falls incidence in cases than controls (average 2.7 vs 0.9 falls respectively; P < 0.001) during the follow-up period. Conclusion In the frail elderly with vitamin D deficiency and high falls risk, calcaneal ultrasound but not markers of bone turnover were associated with fractures.     

Bone Turnover Markers and PTH Levels in Surgical Versus Natural Menopause

In order to assess similarities and differences in women that suffer surgical versus natural menopause, a series of bone, clinical, and biochemical parameters was assayed in a clinical sample of 35 women with surgical menopause and 112 women with natural menopause. Biochemical parameters included hormones [parathyroid hormone (PTH) and the sex steroids estradiol and testosterone] and several markers of bone turnover measured in urine (N-telopeptide and calcium/creatinine ratio) or serum (osteocalcin, total alkaline phosphatase, total and ionic calcium, phosphate, and magnesium). In addition to type of menopause, women were divided by years since menopause (ysm 2 or >2). To detect differences and relationships between variables, ANOVA, ANCOVA, and linear regression analyses were used. Only N-telopeptide, one resorption marker, was significantly affected by the variable years since menopause 2 or >2 (P <0.01), but not by type of menopause. The age-corrected level of PTH was significantly decreased in the surgical menopause group (P < 0.05). In conclusion, type of menopause did not impose significant differences in bone turnover markers. PTH, one powerful resorption hormone, was diminished in surgical menopause.     

Geographic Differences in Bone Turnover: Data from a Multinational Study in Healthy Postmenopausal Women

Biochemical markers of bone metabolism (bone markers) are used increasingly to monitor response to therapy and may be predictors of bone loss and fractures. The relationship between fracture rates, which differ between countries, and the rate of bone turnover has not been examined. Therefore, we explored the geographic variability of bone turnover in a selected, healthy study population of 619 postmenopausal women, ages 40–61, participating in a clinical trial of raloxifene hydrochloride for osteoporosis prevention. The subjects were distributed among 38 investigative sites in 10 countries (9–211 subjects/country) on four continents (North America, n = 277, Europe, n = 168, Australia, n = 125, and Africa, n = 49). Specimens for serum osteocalcin (OC), bone-specific alkaline phosphatase (BSAP), and urine type I collagen fragment/urinary creatinine ratio (CTX) were handled in a uniform fashion and assayed in a central laboratory. Mean levels of OC (P < 0.001), BSAP (P= 0.006), and CTX (P < 0.001) varied significantly by country (ANOVA), with the lowest values typically in German and Spanish subjects and the highest in American and Canadian subjects. The consistent pattern and wide ranges of mean bone marker values (OC 1.6-fold, BSAP 1.7-fold, CTX 3.1-fold) between countries suggest clinically significant differences in bone turnover. Geographic differences in bone markers were not explained by the determined potential confounders of age, years posthysterectomy, total serum cholesterol, and serum follicle stimulating hormone (FSH). We conclude that bone marker values vary substantially by country in this selected study population, suggesting systematic geographic differences in bone metabolism that potentially relate to osteoporotic fracture rates. Received: 28 November 1997 / Accepted: 23 March 1998     

The Role of Cytokines in the Changes in Bone Turnover Following Bone Marrow Transplantation

Osteoporosis is a common disease among patients undergoing transplantation and a loss of bone mass is usually detected after bone marrow transplantation (BMT), particularly during the immediate post-BMT period. Post-BMT bone loss is primarily related to gonadal dysfunction and immunosuppression. Cytokines, especially interleukin 6, play an important role in the pathogenesis of postmenopausal osteoporosis. However, the pathogenetic role of cytokines in post-BMT bone loss is unknown and data on the changes of cytokines in accordance with bone turnover markers are scarce. The aim of this study was to assess the relationship between bone turnover markers and cytokines, which are regularly sampled at peripheral blood and bone marrow before and after allogeneic BMT. This prospective study included two analyses. The first was a study of 46 BMT recipients (M/F 28/18), examining the relationship between bone turnover markers and serum cytokines that were measured before and at 1 week, 2 weeks, 3 weeks, 4 weeks and 3 months after BMT. Serum intact parathyroid hormone was measured before BMT and at 3 weeks after BMT and its relation to other cytokines and bone turnover markers was evaluated. The second analysis was a study of 14 (M/F 9/5) of 46 patients in whom bone marrow plasma cytokines [interleukin 6 (IL-6) and tumor necrosis factor alpha (TNF-α)] were measured at 3 weeks after BMT. The relationship between bone marrow plasma cytokines and bone turnover markers was studied because bone marrow is the microenvironment where the real changes in bone turnover occur. Serum type I collagen carboxyterminal telopeptide (ICTP), a bone resorption marker, increased progressively until 4 weeks (peak) after BMT and then decreased thereafter. Serum osteocalcin, a bone formation marker, decreased progressively until 3 weeks after BMT and then increased thereafter. Serum IL-6 increased until 2 weeks after BMT and declined thereafter. Serum TNF-a increased until 3 weeks after BMT and declined thereafter. There was a significant positive correlation between serum ICTP and bone marrow IL-6 levels at 3 weeks after BMT, when a marked change in bone metabolism occurs following BMT. However, a correlation between bone turnover markers and bone marrow TNF-aor peripheral blood cytokines was not found. At 3 months after BMT, there was a significant negative correlation between the mean daily steroid dose and the serum osteocalcin level (r=−0.43, p<0.05). The correlation between the mean daily steroid dose and serum ICTP was also significant (r= 0.41, p<0.05). Our data suggest that the progressive increase in bone resorption during the immediate post-BMT period is related to both steroid dose and the increase in bone marrow IL-6, which is a potent stimulator of bone resorption in vivo. Received: 29 November 2000 / Accepted: 1 August 2001     

A 3-Year Physical Activity Intervention Program Increases the Gain in Bone Mineral and Bone Width in Prepubertal Girls but not Boys: The Prospective Copenhagen School Child Interventions Study (CoSCIS)

The aim of this study was to evaluate the effect of increasing the amount of time spent in physical education classes on bone mineral accrual and gain in bone size in prepubertal Danish children. A total of 135 boys and 108 girls, aged 6–8 years, were included in a school-based curriculum intervention program where the usual time spent in physical education classes was doubled to four classes (180 min) per week. The control group comprised age-matched children (62 boys and 76 girls) recruited from a separate community who completed the usual Danish school curriculum of physical activity (90 min/week). Dual-energy X-ray absorptiometry was used to evaluate bone mineral content (BMC; g), bone mineral density (g/cm²), and bone width at the calcaneus and distal forearm before and after 3 years of intervention. Anthropometrics and Tanner stages were evaluated on the same occasions. General physical activity was measured with an accelerometer worn for 4 days. In girls, the intervention group had a 12.5% increase (P = 0.04) in distal forearm BMC and a 13.2% increase (P = 0.005) in distal forearm scanned area compared with girls in the control group. No differences were found between the intervention and control groups in boys. Increasing the frequency of physical education classes for prepubertal children is associated with a higher accrual of bone mineral and higher gain in bone size after 3 years in girls but not in boys.     

Low Bone Density with Normal Bone Turnover in Ovariectomized and Streptozotocin-Induced Diabetic Rats

Diabetes and estrogen deficit are known causes of osteopenia, diabetes being associated with a low bone turnover and estrogen deficit with a high bone turnover. In the present work, we studied the effect of combined ovariectomy and diabetes on bone mineral content (BMC) and bone mineral density (BMD) and several bone markers in the rat. Four groups of rats were studied: control (C), ovariectomized (O), diabetic (D), and ovariectomized and diabetic (DO). Twelve weeks after starting the experiments, BMC and BMD of the first six lumbar vertebrae were measured; a bone formation marker (BGP) and a bone resorption marker (free collagen cross-links, PYD) were also analyzed. Diabetic rats showed diminished gain in bone mass, BMC (D: 0.417 ± 0.028 g, DO: 0.422 ± 0.020 g) and BMDs (D: 0.171 ± 0.006 g/cm², DO: 0.174 ± 0.006 g/cm²) both being significantly (P < 0.001) lower than those of control (C: BMC 0.727 ± 0.024 g and BMD 0.258 ± 0.004 g/cm²) and ovariectomized (O: BMC 0.640 ± 0.044 g and BMD 0.240 ± 0.009 g/cm²) groups. Moreover, the BMC and BMD of the C group were significantly (P < 0.05) higher than that of the O group. BGP and PYD levels were significantly (P < 0.01) higher in the O group (BGP: 138.2 ± 16.8 ng/ml, PYD: 270.2 ± 17.8 nM/mM) than those found in the control rats (BGP: 44.7 ± 4.8 ng/ml, PYD: 165.6 ± 12.5 nM/mM); the D group showed significantly (P < 0.01) lower values (BGP: 27.4 ± 14.6 ng/ml, PYD: 55.0 ± 7.4 nM/mM) than those of the control group. The DO group showed similar levels (BGP: 43.4 ± 5.1 ng/ml, PYD: 146.7 ± 14.6 nM/mM) to those found in the C group. Although bone marker levels in the O and D groups were in accordance with those expected in these situations, in the DO group the corresponding levels are apparently ``normal.' Also, the decrease of gain in bone mass observed after combining estrogen deficit and diabetes (DO group) did not seem to be more marked than that caused by diabetes alone. Received: 7 January 1997 / Accepted: 7 August 1997     

Evaluation of Ability of Biochemical Markers of Bone Turnover to Predict a Response to Increased Doses of HRT

Antiresorptive therapy is usually given in a fixed dose, and we hypothesized that some patients receiving standard doses of hormone replacement therapy (HRT) might benefit from a higher dose, particularly if their bone turnover decreases after increasing the dose of HRT. Eighty-eight women who had been receiving standard-dose (0.625 mg/day) conjugated equine estrogens (CEE) for at least one year were randomized to take either standard-dose (0.625 mg/day, n = 36) or high-dose (1.25 mg/day, n = 52) therapy. Subjects with a uterus were allowed to take either 10 mg of medroxyprogesterone cyclically or 5 mg daily, according to personal preference. Bone Mineral Density (BMD) and biochemical markers of bone turnover were followed for 2 years. Mean bone turnover decreased significantly (–4.1% to –19.1%) after 6 months of high-dose CEE. Decreases in serum BSAP (bone-specific alkaline phosphatase) and serum or urine NTX (N-terminal telopeptide crosslink of type I collagen) on high-dose therapy were not predictive of an improvement in BMD, but a decrease in serum CrossLaps did predict an improvement in BMD. Mean change in BMD in subjects with a significant decrease in serum CrossLaps at the anteroposterior spine was 3.1% ± 3.9% versus 1.2% ± 2.9% for subjects with no significant change in CrossLaps, P < 0.02. There was, however, a wide range of changes in BMD in patients with or without a significant change in CTX on high-dose HRT, making it impossible to predict an improvement in BMD based on an individuals changes in turnover. Measuring of bone density and bone turnover with better precision might be more successful in guiding individual dosing of antiresorptive therapy.This work is supported by a grant from the National Institutes of Health, grant #5 K08 AG000680-04; and from the William H. Milton Fund, Harvard Medical School, Boston, MA; and from Eli Lilly and Company, Indianapolis, IN; and from Mission Pharmacal, San Antonio, TX; and from the Upjohn Company, Kalamazoo, MI; and by NCRR grant RR 01032 supporting the General Clinical Research Center of Beth Israel Deaconess Medical Center.     

Acute Effects of Calcitonin Nasal Spray on Serum C-telopeptide of Type 1 Collagen (CTx) Levels in Elderly Osteopenic Women with Increased Bone Turnover

Salmon calcitonin is a potent inhibitor of osteoclastic activity. The effect of calcitonin in elderly women with high bone turnover at higher risk of developing osteoporosis has not been studied. To investigate acute effects of calcitonin treatment on bone resorption markers in elderly women, we conducted a randomized trial in women >65 years of age with high bone turnover assessed as urinary N-telopeptide of type-I collagen (NTx) levels 1 SD higher than mean premenopausal levels, which was irrespective of bone density. A total of 98 elderly women were randomly assigned to receive either 200 IU calcitonin nasal spray (n = 75) with calcium (500 mg) and vitamin D (200 IU) or calcium and vitamin D (n = 23) alone for 6 months. Blood and urine samples were collected at 0, 2, 4, and 6 months and analyzed for urinary NTx and serum C-telopeptide of type-1 collagen (CTx). At baseline, mean age was 72.1 ± 4.7 (mean ± SD) in the calcitonin group and 72.2 ± 6 years in the control group. The spine and total hip BMD, serum PTH levels and urinary calcium/creatinine ratios were similar in both groups. Mean BMD was in the osteopenic range in both groups. Calcitonin treatment resulted in significant decreases in serum CTx levels, 2, 4 and 6 months after treatment as compared to baseline, and after 4 and 6 months as compared to controls. A maximum decrease from baseline of 33% was seen at 6 months. The urinary resorption marker, urine NTx, showed a significant decrease in the calcitonin group when compared to baseline only at the 6-month time point. Analysis of least significance change (LSC) showed that 70% of calcitonin patients were categorized as responders using serum CTx after 6 months of treatment. We conclude that 200 IU calcitonin effectively decreases bone resorption within 60 days of therapy, thus preventing further bone loss in elderly women who are at a high risk of developing osteoporosis.     

Biochemical Measurements of Bone Turnover in Children and Adolescents

Biochemical measurements of bone turnover are helpful in the study of the pathophysiology of skeletal metabolism and growth. However, interpretation of their results is difficult because they depend on age, pubertal stage, growth velocity, mineral accrual, hormonal regulation, nutritional status, circadian variation, day-to-day variation, method of expression of results of urinary markers, specificity for bone tissue, sensitivity and specificity of assays. Three markers of bone formation have been described including their bone specificity and age-related changes: osteocalcin, alkaline phosphatase and its skeletal isoenzyme, procollagen I extension peptides. Bone resorption markers (hydroxyproline; deoxypyridinoline; pyridinoline; peptides containing these crosslinks such as N-telopeptide to helix in urine (NTX), C-telopeptide-1 to helix in serum (ICTP) and C-telopeptide-2 in urine and serum (CTX); tartrate-resistant acid phosphatase; hydroxylysine and its glycosides) are described with special attention to methodologic issues, mainly ways of expression of their results. Changes of bone turnover during growth are described during four periods: infancy, prepubertal period, puberty and the postpubertal period. Pubertal changes of bone markers are described with special attention to gender differences and hormonal mechanisms of the growth spurt which determine differences related to the pubertal stage. Disturbances of bone turnover in four conditions are described to illustrate the impact of such diseases on growth and formation of peak bone mass: prematurity, malnutrition, growth hormone deficiency and corticosteroid-treated bronchial asthma. Available data suggest biochemical markers of bone remodeling may be useful in the clinical investigation of bone turnover in children in health and disease. However, their use in everyday clinical practice is not advised at present.     

Physical Activity and Bone Turnover Markers: A Cross-Sectional and a Longitudinal Study

Strenuous physical activity in young individuals has an important effect on both bone mass and bone turnover but the effect of moderate physical activity in adults remains uncertain. In a large cohort (N = 530) of healthy premenopausal women, bone formation markers (osteocalcin and N-terminal propeptide of type 1 procollagen [P1NP]), but not serum C-telopeptide of type 1 collagen (sCTX), were found to be significantly associated with the level of physical activity, and this association remained significant after adjusting the data (ANCOVA) by age and body mass index. Mean spine and hip bone mineral density (BMD) values were positively associated with physical activity but this was statistically significant (P = 0.050) only for adjusted values of spine BMD. Twenty-four healthy sedentary premenopausal women, subscribing to participate in a community exercise program lasting a month, and 18 age-matched controls were included in the longitudinal study. Serum osteocalcin and P1NP, but not sCTX, rose significantly, by ca. 25%, only in the active group after a month of exercise. The changes in the two bone formation markers remained statistically significant for values adjusted for body weight, which fell significantly in the exercise group. In conclusion, both the cross-sectional and the longitudinal parts of our study demonstrate that even minor changes in physical activity are associated with a clear effect on bone formation markers.     

Marathon running accompanied by transient decreases in urinary calcium and serum osteocalcin levels

Summary We evaluated the effects of marathon running on bone metabolism in 23 noncompetitive athletes (15 women, 8 men, age range 23–55 years). The volunteers were studied 10 days before, immediately after, and 1, 3, and 5 days after the run. Serum osteocalcin levels were decreased on average by 20% (from 4.9 to 3.9 g/liter, P=0.005) in men and by 10% (from 4.9 to 4.4 g/liter, P<0.05) in women at the end of the marathon, with lowest osteocalcin levels (67–55% of the prerun levels) encountered 1 day after the marathon. The activity of bone alkaline phosphatase was decreased in women (from 66.3 to 62.3 U/liter, P<0.05) after the run, and this drop was detectable at each checkup after the run. Urinary excretion of calcium was lowered on average by 82% in men (from 2.8 to 0.5 mol/minute, P<0.05) and by 76% in women (from 2.5 to 0.6 mol/minute, P<0.005) after the run, but had already returned to prerun levels 1 day after the marathon. Urinary excretion of hydroxyproline tended to rise in both men and women, but the change did not reach statistical significance in either sex. These changes suggest a transient suppression in osteoblast function during the marathon.Children's Hospital     

Biochemical Markers of Bone Turnover Reflect Femoral Bone Loss in Elderly Women

Although over 90% of hip fractures occur in patients over age 70, few data are available on femoral bone loss in this age group. To examine the relationship between biochemical markers of bone turnover and femoral bone loss in the elderly, 36 female and 17 male, healthy, community-dwelling elderly over age 65 (mean ± SD age: women 71 ± 4 years, men 75 ± 5 years) were followed for 3 years. Annual bone mineral density measurements of the hip and lumbar spine by dual-energy x-ray absorptiometry (DXA) were obtained and biochemical markers of bone resorption (urinary N-telopeptide crosslinks, free pyridinoline, total pyridinoline, total deoxypyridinoline, and hydroxyproline) and bone formation (serum osteocalcin, bone-specific alkaline phosphatase) were obtained at the end of year 3. In elderly women, longitudinal bone loss at the total hip was negatively correlated with markers of bone resorption (r =−0.39 to −0.52, P < 0.05), bone formation (r =−0.38, P < 0.05), and age (r =−0.39, P < 0.05). Markers of bone resorption were correlated with markers of bone formation (r = 0.63 to 0.74, P < 0.01). In multiple regression analysis, urinary N-telopeptide crosslinks (marker of resorption), serum osteocalcin (marker of formation), and serum parathyroid hormone explained 43% of the variability of bone loss at the total hip in women. These parameters were not related to bone loss in men. We conclude that femoral bone loss increases with age in women over 65. Measurements of specific biochemical markers of bone turnover are correlated with longitudinal bone loss in elderly women. These markers may help identify women at greatest risk for bone loss who would benefit most from therapeutic interventions. Received: 28 January 1996 / Accepted: 3 May 1996     

A 12-Month Prospective Study of the Relationship Between Stress Fractures and Bone Turnover in Athletes

Bone remodeling may be involved in the pathogenesis of stress fractures in athletes. We conducted a 12-month prospective study to evaluate bone turnover in 46 female and 49 male track and field athletes aged 17–26 years (mean age 20.3; SD 2.0) 20 of whom developed a stress fracture. Baseline levels of bone turnover were evaluated in all athletes and monthly bone turnover levels were evaluated in a subset consisting of the 20 athletes who sustained a stress fracture and a matched comparison group who did not sustain a stress fracture. Bone formation was assessed using serum osteocalcin (OC) measured by human immunoradiometric assay and bone resorption by urinary excretion of pyridinium cross-links (Pyr and D-Pyr); high performance liquid chromatography and N-telopeptides of type 1 collagen (NTx) using ELISA assay. Athletes who developed stress fractures had similar baseline levels of bone turnover compared with their nonstress fracture counterparts (P > 0.10). Results of serial measurements showed no differences in average levels of Pyr, D-Pyr, or OC in those who developed stress fractures (P= 0.10) compared with the control group. In the athletes with stress fractures, there was also no difference in bone turnover levels prior to or following the onset of bony pain. Our results show that single and multiple measurements of bone turnover are not clinically useful in predicting the likelihood of stress fractures in athletes. Furthermore, there were no consistent temporal changes in bone turnover associated with stress fracture development. However, our results do not negate the possible pathogenetic role of local changes in bone remodeling at stress fracture sites, given the high biological variability of bone turnover markers and the fact that levels of bone turnover reflect the integration of all bone remodeling throughout the skeleton. Received: 12 August 1997 / Accepted: 8 January 1998     

Genetic and Constitutional Influences on Bone Turnover Markers: A Study of Male Twin Pairs

Biochemical markers of bone turnover originating from type I procollagen synthesis or type I collagen breakdown were examined in men using a classic twin study design based on monozygotic (MZ) and dizygotic (DZ) twins. The aim was to estimate the influence of heredity (genes and shared family childhood elements) and constitutional factors in determining procollagen type I amino-terminal propeptide (PINP), type I collagen carboxy-terminal telopeptide (ICTP), and urinary amino-terminal type I collagen telopeptide (NTx) marker levels in a sample of in 98 MZ and 108 DZ male twin pairs. We are not aware of any prior studies conducted in men that address the influence of genetic factors on bone turnover marker variability. The findings support a dominant role for heredity in the variation of bone resorption marker levels in men, with additive genetic effects explaining two-thirds of the variance in the bone resorption markers NTx and ICTP. Genetic factors may contribute less for PINP, a marker of bone formation. The genetic loci influencing PINP or NTx and body weight/disc axial area, although related in part, appeared to be largely independent, indicating that genetic effects on bone turnover are unlikely to be to a large degree a result of genetic regulation of individual body weight.     

骨重建中的骨代谢指标

骨重建是破骨细胞和成骨细胞共同完成的旧骨退化,等量新骨取代的骨组织更新过程,在骨重建过程中,许多激素和细胞、体液因子以及细胞代谢产物影响骨的重建.目前国内外通过生物化学检测技术获得的骨代谢指标分为骨代谢调节激素、细胞与体液因子、骨吸收、骨形成标志物.笔者将影响骨重建生物化学指标的生理作用、临床意义进行综述.骨代谢指标虽不能作为骨质疏松诊断的金标准,但已广泛应用于临床,评价骨代谢状态、骨质疏松诊断分型、预测骨折风险、观察药物治疗的疗效,以及代谢性骨病的鉴别诊断.并且在抗骨质疏松药物的研究及流行病学研究方面具有重要应用价值.