Urinary excretion of type I collagen crosslinked N-telopeptides in healthy Japanese adults: age- and sex-related changes and reference limits

Bone Turnover Markers: Basic Biology to Clinical Applications

Bone turnover markers (BTMs) are used widely, in both research and clinical practice. In the last 20 years, much experience has been gained in measurement and interpretation of these markers, which include commonly used bone formation markers bone alkaline phosphatase, osteocalcin, and procollagen I N-propeptide; and commonly used resorption markers serum C-telopeptides of type I collagen, urinary N-telopeptides of type I collagen and tartrate resistant acid phosphatase type 5b. BTMs are usually measured by enzyme-linked immunosorbent assay or automated immunoassay. Sources contributing to BTM variability include uncontrollable components (e.g., age, gender, ethnicity) and controllable components, particularly relating to collection conditions (e.g., fasting/feeding state, and timing relative to circadian rhythms, menstrual cycling, and exercise). Pregnancy, season, drugs, and recent fracture(s) can also affect BTMs. BTMs correlate with other methods of assessing bone turnover, such as bone biopsies and radiotracer kinetics; and can usefully contribute to diagnosis and management of several diseases such as osteoporosis, osteomalacia, Paget's disease, fibrous dysplasia, hypophosphatasia, primary hyperparathyroidism, and chronic kidney disease-mineral bone disorder.

Asymmetries of the Muscle Mechanical Properties of the Pelvic Floor in Nulliparous and Multiparous Women, and Men: A Cross-Sectional Study

This study aimed to identify if the muscle mechanical properties (MMPs) of both sides of pelvic floor muscles (PFMs) are symmetrical in different populations of both sexes. Between-sides comparisons of MMPs of PFMs, assessed with manual myotonometry, were performed in three groups, with 31 subjects each, composed of healthy nulliparous women (without any type of delivery or pregnancy), multiparous women (with at least two vaginal deliveries), and healthy adult men. Intra-group correlations between MMPs and age, body mass index (BMI), or clinical state of pelvic floor were also obtained. The nulliparous women and the men showed no between-sides differences in any MMP of PFMs. However, the multiparous women showed that the right side displayed less frequency (−0.65 Hz, 95% CI = −1.01, −0.20) and decrement (0.5, 95% CI = 0.11, 0.01), and more relaxation (1.00 ms, 95% CI = 0.47, 1.54) and creep (0.07 De, 95% CI = 0.03, 0.11), than the left side. Further, MMPs were related to age, sex, and BMI, also depending on the population, with the multiparous women being the only group with some between-sides asymmetries, which in this case were positive and of fair intensity for the left side of the PFMs, between BMI, and frequency and stiffness (rho Spearman coefficient: 0.365 and 0.366, respectively). The symmetry of MMPs of the PFMs could depend on the subject’s condition. Multiparous women show a higher tendency to asymmetries than nulliparous women and men, which should be considered in research and clinical settings.

Tissue Fixation System ligament repair cures major pelvic organ prolapse in ageing women with minimal complications - a 10-year Japanese experience in 960 women

INTRODUCTION

Japan's ageing crisis has brought major prolapse and incontinence problems. We hypothesized the problem was collagen leaching out of ligaments which support organs and could be corrected by the TFS (Tissue Fixation System) minisling which uses 7 mm wide tapes to create new collagen for ligament reinforcement.We analysed our 10-year experience (2009-2019) with TFS minisling prolapse repair with regard to one main question: "Is this technology of benefit to the ageing Japanese population?".

MATERIAL AND METHODS

Retrospective analysis from two tertiary referral units; 3100 tapes were implanted (variously) into cardinal, uterosacral, arcus tendineus fascia pelvis (ATFP), perineal body ligaments of 960 Japanese women (mean age 69.6 years), to repair POPQ 3rd or 4th degree prolapse (918/960), 50% under local anesthesia/sedation, remainder general/spinal anesthesia.

RESULTS

Patient discharge within 24 hours indicated minimal intra-operative problems. Prolapse cure at 12 months reached 90%. Complications requiring intervention were infected rectal perforation by tape, 3 delayed ileus complications. Eroded tapes (2.4-3.5%) were trimmed in the clinic. De novo long-term pain and major urine loss were virtually absent.

CONCLUSIONS

The TFS system works by restoring ligament support (pubourethral, ATFP, cardinal, uterosacral, perineal body), differently from mesh sheets which work by blocking organ descent, which can lead to fibrosis of the vagina, and may cause chronic pain and massive incontinence. We had no such problems, because tapes have small volume, are applied transversely, with little vaginal contact. Specific ligament reinforcement with collagenopoietic tapes seems to be an important new direction for aged women with major prolapse, with high cure rate, acceptable complications, low erosions and virtually no long-term pain.

Pelvic-floor function, dysfunction, and treatment

The pelvic floor functions as a holistic entity. The organs, bladder, bowel, smooth and striated muscles, nerves, ligaments and other connective tissues are directed cortically and reflexly from various levels of the nervous system. Such holistic integration is essential for the system's multiple functions, for example, pelvic girdle stability, continence, voiding/defecation, and sexuality. Pelvic floor dysfunction (PFD) is related to a variety of pelvic pain syndromes and organ problems of continence and evacuation. Prior to treatment, it is necessary to understand which part(s) of the system may be causing the dysfunction (s) of Chronic Pelvic Pain Syndrome (CPPS), pelvic girdle pain, sexual problems, Lower Urinary Tract Symptoms (LUTS), dysfunctional voiding, constipation, prolapse and incontinence. The interpretation of pelvic floor biomechanics is complex and involves multiple theories. Non-surgical treatment of PFD requires correct diagnosis and correctly supervised pelvic floor training. The aims of this review are to analyze pelvic function and dysfunction. Because it is a holistic and entirely anatomically based system, we have accorded significant weight to the Integral Theory's explanations of function and dysfunction.

Native tissue repair of cardinal/uterosacral ligaments cures overactive bladder and prolapse, but only in pre-menopausal women

INTRODUCTION

The aim of this article was to study the effect of native tissue cardinal/uterosacral ligament repair on overactive bladder (OAB) and pelvic organ prolapse (POP).

MATERIAL AND METHODS

Inclusion criteria included decrease of urge symptoms following insertion of a gauze tampon in the posterior fornix of vagina ('simulated operation'). Exclusion criteria included SUI, POP grades 3-4. The surgery consisted of plication of cardinal/uterosacral ligaments. Post-operative assessment was performed at3, 6, 12 and 18 months after surgery and included evaluation by stage of prolapse, Urinary Distress Inventory Short Form 6 (UDI-6), Overactive Bladder Questionnaire (OAB-q), Pelvic Floor Impact Questionnaire- Short Form 7 (PFIQ-7), and International Consultation on Incontinence Questionnaire - Urinary Incontinence Short Form (ICIQ-SF) questionnaires and voiding diary.

RESULTS

At 3 months, cure rates for frequency, urgency, nocturia and prolapse were comparable. By the 6-month review, catastrophic failure commenced in the postmenopausal group, parallel for all pa-rameters, starkly contrasting with premenopausal group. At 18 months, % cure rates for pre-menopausal (post-menopausal in brackets) were 79.6 (15.4) for POP, 67.3 (20.5) for urgency, 87.7 (20.5) for nocturia and 59.2 (15.4) for frequency.

CONCLUSIONS

We hypothesize the stepwise parallel recurrence of POP and symptoms in the menopausal group was a consequence of collagen deficiency in the plicated ligaments. Nevertheless, plication of uterosacral-cardinal ligament complex is simple, inexpensive, effective, especially applicable pre-menopausally for POP and as an alternative treatment option in that difficult group of pre-menopausal women who have major OAB/nocturia symptoms but only minimal prolapse.

A low cost artisan tension-free tape technique cures pelvic organ prolapse and stress urinary incontinence - proof of concept

INTRODUCTION

The primary cause of pelvic organ prolapse (POP) is weak cardinal/uterosacral (CL/USL) ligaments and for stress urinary incontinence, weak pubourethral ligaments (PUL).

MATERIAL AND METHODS

A 1 cm wide tape cut from a mesh sheet was applied tension-free to reinforce already plicated CL/USLs for cure of prolapse and directly to PUL for cure of stress urinary incontinence (SUI). 40 tapes were inserted, 10 midurethrally for SUI and 30 for 2nd/3rd degree prolapse: 15 to uterosacral ligaments and 15 to cardinal ligaments.

RESULTS

At 12 months follow-up there was 72% cure for POP, 70% for SUI and improvement in urge/nocturia symptoms in 82% of patients.At 36 months 8/15 patients were evaluated. Anatomic cure for POP III was 2/4, for POP I-II 6/6.

CONCLUSIONS

Though a 'proof of concept' study, our results may be sufficient to provide, in time, an alternative individual pathway for surgeons wishing to provide more certainty to a prolapse repair than 'native tissue' for an individual patient. The method questions whether expensive mesh kits are really necessary: our data though small, actually part of a learning curve, was within 15 percentage points of more sophisticated, more expensive tensioned slings. Intraoperative complications were low with no tape erosions seen at 12 months. Further validation with larger prospective and comparative trials is required.

Understanding the mechanics of closure is key to optimal midurethral sling technique

The animal experiments and prototype midurethral sling operations demonstrated that the sling provided new collagen to reinforce weak pubourethral ligaments (PUL). The now strengthened PULs were able to restore the contractile power of the 3 oppositely-acting directional closure forces. By contraction, these three forces exponentially altered the intraurethral resistance to flow when they closed the urethra to sustain continence. Relaxation of the forward force allowed the two posterior forces to uninhibitedly open the posterior urethral wall just prior to detrusor contraction, to facilitate evacuation of urine. The aim of this work is to examine the mechanics of the component anatomical structures which contribute to these functions, to analyse how subtle details impact on the actual surgical technique of the midurethral sling operations to optimize success, contribute to complications and how to prevent and fix them.

Gender-Affirming Hormone Treatment Decreases Bone Turnover in Transwomen and Older Transmen

Sex steroids play a key role in bone turnover and preserving BMD; hence, gender-affirming hormone treatment (HT) in transgender people affects bone metabolism. Most studies have looked into the effect of HT on changes in BMD; however, they do not provide insights into changes in bone metabolism caused by HT. This study investigated changes in bone turnover markers (BTMs) and sclerostin, as well as their correlations with change in BMD in transwomen and transmen during the first year of HT. Transwomen received estradiol and antiandrogens; transmen received testosterone. Sclerostin; P1NP; alkaline phosphatase (ALP); CTx; and BMD of the total hip, the femoral neck, and the lumbar spine were evaluated at baseline and after 1 year of HT. There were 121 transwomen (median age 30 years, interquartile range [IQR] 24 to 41 years) and 132 transmen (median age 24 years, IQR 21 to 33 years) included in the study. In transwomen, ALP decreased in 19% (95% CI, -21 to-16), CTx in 11% (95% CI, -18 to-4), and sclerostin in 8% (95%CI, -13 to-4) of study participants after 1 year of HT. In contrast, in transmen P1NP, ALP, and sclerostin increased in 33% (95% CI, 24 to 42), 16% (95% CI, 12 to 20), and 15% (95% CI, 10 to 20) of study participants, respectively, after 1 year of HT. No age differences were seen in transwomen, whereas in transmen aged ≥50 years a decrease in all BTMs was found in contrast with the other age groups. These transmen had low estrogen concentration at the start of HT based on their postmenopausal state before the start of HT; their estradiol concentrations increased during testosterone treatment. Changes in BTMs and BMD were weakly correlated (correlation coefficient all <0.30). To conclude, 1 year of HT resulted in decreased bone turnover in transwomen and older transmen, whereas it increased in younger transmen. The decrease in bone resorption in older transmen shows the importance of estrogen as a key regulator of bone turnover. © 2019 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals, Inc.

Relationship Between Urinary Cross-Linked N-Telopeptide of Type-I Collagen and Heel Stiffness Index Measured by Quantitative Ultrasound in Middle-Aged and Elderly Men

The aim of the present study was to investigate the age-related patterns and the relationship between levels of urinary cross-linked N-telopeptide of type-I collagen (NTx) and heel stiffness index measured by quantitative ultrasound (QUS) in men with a special reference to age groups of aged 40 to 59 years and ≥60 years.A total of 379 men participated in this study. Heel stiffness index (bone mass) was measured by QUS. Spot urine samples were collected, and urinary NTx was measured. The values were corrected for creatinine (Cre) concentration.Stiffness index was significantly lower in men aged ≥60 years compared with men aged 40 to 59 years (P < 0.0001). There was no significant difference of Log (NTx/Cre) by 10-year age groups. Multiple regression analysis showed that higher level of urinary NTx/Cre was significantly correlated with lower stiffness index after adjusting for age and body mass index in men aged ≥60 years, but not in men aged 40 to 59 years.Higher rates of bone resorption were associated with lower stiffness index only in elderly men. Our results may indicate a different mechanism of low bone mass among different age groups.

Usefulness of urinary CTX-II and NTX-I in evaluating radiological knee osteoarthritis : the Matsudai knee osteoarthritis survey

BACKGROUND

To assess the usefulness of the urinary crosslinked C-telopeptide of type II collagen (uCTX-II) or crosslinked N-telopeptide of type I collagen (uNTX-I) for evaluating radiological knee osteoarthritis (OA), a cross-sectional study was conducted in the cohorts of the Matsudai knee osteoarthritis survey performed in Niigata, Japan.

METHODS

Urine specimens and standing knee AP X-rays were obtained from 1040 subjects who provided informed consent. The relationship between these markers and gender, age (patients aged 40-59 or 60-79 years), use of bisphosphonates, and OA grades (K-L classification) were analyzed. The diagnostic ability of uCTX-II to detect radiological knee OA was confirmed in the over 60-year-old subjects using a ROC curve.

RESULTS

The over 60-year-old men with OA grade 3,4 group had significantly higher uCTX-II levels than the other OA grade groups. In the over 60-year-old women, the uCTX-II levels significantly increased according to the progression of the knee OA grade. No significant difference was observed between the uNTX-I levels in the different OA grade groups. From the standpoint of biomarkers, the higher quartiles of the uCTX-II and uNTX-I levels gradually included higher numbers of grade ≥2 OA subjects in the over 60 year-old women. The area under the curve (AUC) in ROC analysis of uCTX-II exhibited a significant association with the diagnosis of knee OA in women (AUC 0.63), although the accuracy was evaluated to be low in the single measurement of our health checkup-based analysis.

CONCLUSIONS

This population-based study indicates that the uCTX-II level is strongly correlated with the knee OA grade in women over age 60. A further analysis is needed to clarify its predictive accuracy.

Biochemical markers of bone turnover - uses and limitations

Bone turnover markers of resorption and formation are released during the process of bone remodelling. These markers have been extensively studied in a number of therapeutic trials of osteoporosis during the past decade. This has led to better understanding of their physiology, clinical applications and possible ways to optimize analytical techniques. Bone markers can complement the results of bone mineral density in the management of osteoporosis, but their use in clinical practice is challenged by pre-analytical and analytical variability. This review will discuss different types of bone markers, their limitations, use in different metabolic bone diseases and current recommendations from the International Osteoporosis Foundation and the International Federation of Clinical Chemistry and Laboratory Medicine bone marker standards working group.

Does anastrozole affect bone resorption similarly in early and late postmenopausal women?

The aim of this study was to determine whether the bone-resorption response to anastrozole differed according to initial patient age in postmenopausal women with breast cancer in a cross-sectional study. Second-morning void urines were collected for measurement of urinary cross-linked N-telopeptide of type I collagen (uNTx, corrected for creatinine and log-transformed) from postmenopausal women, 99 with breast cancer on anastrozole (ABC), 88 with newly diagnosed breast cancer (NDBC), and 137 community-dwelling healthy control (HC) women. Bone mineral density (BMD) was also measured at the lumbar spine (LS, L2-L4) and the femoral neck (FN) in the ABC group. uNTx (nanomole bone collagen equivalents/millimole creatinine) levels increased with age in HC subjects. In patients <70 years, anastrozole treatment led to a significant increase in uNTx compared with age-related HC subjects (1.74 vs. 1.55, P < 0.005). Patients >70 years showed no such increase compared to HC (1.72 vs. 1.69, nonsignificant); however, NDBC women >70 years had uNTx levels significantly lower than HC women (1.59 vs. 1.69, P < 0.05). There was no difference in uNTx levels above and below the age of 70 years in NDBC women (1.56 vs. 1.59, nonsignificant). ABC women were more likely to have a positive LS BMD z score than age-matched controls. Anastrozole treatment increases bone turnover more in younger postmenopausal women with breast cancer than in older women compared to healthy controls. Higher LS BMD in ABC patients may help protect against fracture.

The differences of femoral neck geometric parameters: effects of age, gender and race

This study aims at investigating the effects of age, sex, and ethnicity on five femoral neck geometric parameters (FNGPs): femoral neck periosteal diameter, cross-sectional area, cortical thickness, sectional modulus, and buckling ratio and found that the three factors would influence the FNGPs.

INTRODUCTION

Bone geometry is one of the most important predictors of bone strength and osteoporotic fractures. This study aims at investigating the effects of age, sex, and ethnicity on five femoral neck geometric parameters (FNGPs): femoral neck periosteal diameter (W), cross-sectional area (CSA), cortical thickness (CT), sectional modulus (Z), and buckling ratio (BR).

METHODS

In the studied 861 Caucasian subjects and 3,021 Chinese individuals, CSA, CT, and Z displayed trends of decrease with age, but W and BR showed increasing trends with age in both Chinese and Caucasian females and males (p < 0.05). W, CSA, CT, and Z were significantly higher (p <or= 0.001) in Caucasians than in Chinese and higher in males than in females except for BR between Chinese males and Chinese females.

CONCLUSION

In conclusion, the differences of FNGPs according to gender and ethnicity provide important implications in the different prevalence of osteoporotic fracture among different gender and ethnic groups.

Bone resorption in stroke and institutionalized subjects

Stroke increases the risk of hip fracture on the affected side. Although bone is lost by 1 year, rapidity of onset and relationship with immobility are uncertain. Using the bone resorption marker urinary cross-linked N telopeptide of type I collagen (uNTx), we examined bone resorption in the first 4 weeks after stroke, relating uNTx with bone density and mobility in subjects over 60 years. Two separate control groups acted as comparators, healthy (HC) and institutionalized (IC) controls, the latter to control for the effects of institutionalization. uNTx, urinary calcium (both related to creatinine and log-transformed), heel bone mineral density (BMD), Tinetti scores, and Barthel scores for prestroke function were measured. Log uNTx/Cr was lower in males compared with females, but this difference was not evident in stroke or IC subjects. Log uNTx/Cr was inversely related with BMD in females from both control groups and in male stroke subjects. Tinetti scores were divided into tertiles and were lower in stroke than IC subjects (P < 0.01). Log uNTx/Cr was similar in stroke and IC subjects in the lowest Tinetti tertile. Log uNTx/Cr was higher in stroke subjects of both sexes in the lowest tertile compared with the higher two tertiles combined (P < 0.05) and higher in all tertiles compared with HC subjects (P < 0.05). Subjects with a prestroke Barthel index of < or = 17 had higher log uNTx/Cr compared with HCs. Log uCa/Cr was higher only in male stroke patients. Bone resorption in stroke starts early, and measures to reduce this are merited.

Relationship between radiological knee osteoarthritis and biochemical markers of cartilage and bone degradation (urine CTX-II and NTX-I): the Matsudai Knee Osteoarthritis Survey

Biochemical markers of cartilage and bone degradation are becoming increasingly important in the evaluation of knee osteoarthritis (OA). To clarify the correlation between radiological knee OA and urine CTX-II (C-terminal crosslinking telopeptide of collagen type II) or urine NTX-I (N-terminal crosslinking telopeptide of type I collagen), we conducted a cross-sectional study in the cohorts of the epidemiological knee survey at the Matsudai district in Niigata Prefecture, Japan. Urine specimens were collected from 296 subjects, and CTX-II and NTX-I were measured using ELISA. Standing knee AP X-rays were obtained and graded according to the Kellgren-Lawrence classification. The subjects were then divided by gender, age (40- to 59-year-old group and 60- to 79-year-old group), and the X-ray grade (Grade 0, 1, Grade 2, and Grade 3, 4). In non-OA (Grade 0, 1) subjects, the 60- to 79-year-old group had significantly higher CTX-II values than the younger group only in females. The subjects of both genders aged over 60 years of age with OA Grade 3, 4 had significantly higher CTX-II values than the Grade 0, 1 group or the Grade 2 group. For NTX-I, there were no significant differences between each OA grade although the Grade 3, 4 group females from 60 to 79 years of age had higher values than the Grade 2 group. In addition, in the 60- to 79-year-old subjects of both genders, a positive correlation was observed between the urine CTX-II and urine NTX-I. For the subjects ranging from 60 to 79 years of age in both genders, the urine CTX-II values indicate the progression of OA. In addition, the weak but positive correlation between urine CTX-II and urine NTX-I in the subjects ranging from 60 to 79 years of age in both genders suggests that bone resorption and cartilage degradation appear to develop in parallel.

Reference intervals of serum tartrate-resistant acid phosphatase type 5b activity measured with a novel assay in Japanese subjects

Among the isotypes of serum tartrate-resistant acid phosphatase (TRACP), only type 5b (TRACP-5b) is derived from osteoclasts, and it is necessary to develop an assay specific for this TRACP-5b for evaluation of osteoclastic activity. Recently, a novel assay system for TRACP-5b called the fragments absorbed immunocapture enzymatic assay (FAICEA) has been developed. With two unique monoclonal antibodies, one that is highly specific for TRACP-5b and another which absorbs inactive TRACP-5b fragments that interfere with measuring active TRACP-5b, this assay provides correct measurement of TRACP-5b activity in the serum without interference by the inactive fragments of TRACP-5b and other isotypes of TRACP, especially TRACP-5a. To study the reference data of Japanese subjects, we measured TRACP-5b activity in the serum of 320 men (age, 20-82 years) and 466 women [315 premenopausal (age, 18-55 years) and 151 postmenopausal (age, 45-77 years)] with this novel assay. In men, serum TRACP-5b activity did not vary significantly with age. The postmenopausal women had significantly higher serum TRACP-5b activity than the premenopausal women. The reference intervals (logarithmic mean +/-1.96 SD) for men, premenopausal women, and postmenopausal women were 1.7-5.9 U/l, 1.2-4.4 U/l, and 2.5-7.6 U/l, respectively.

Increased cathepsin K and tartrate-resistant acid phosphatase expression in bone of streptozotocin-induced diabetic rats

The effect of insulin-dependent diabetes mellitus (IDDM) on bone metabolism was evaluated using the streptozotocin (STZ)-induced diabetic rat 1 week after the induction of diabetes. The urinary excretion of cross-linked N-telopeptides of type I collagen (NTx) and deoxypyridinoline (Dpd) in diabetic rats increased to 3.6-fold and 1.2-fold the control level, respectively. The amount of hydroxyproline and calcium in the distal femur of diabetic rats significantly decreased to 76% and 90% of the control, respectively. The levels of serum osteocalcin and alkaline phosphatase (ALP) activity in the distal femur of the diabetic rats were significantly reduced to about 40% and 70% of the control levels, respectively. The decrease in the expression osteocalcin was observed in distal femur of the diabetic rats, although the level of ALP mRNA was unchanged. The activity and the mRNA level of tartrate-resistant acid phosphatase (TRAP) increased to 1.5- and 2.3-fold the control level, respectively, in distal femur of the diabetic rats. The activity, protein, and mRNA levels of cathepsin K of diabetic rats also elevated to about 2-, 2.3-, and 2-fold the control levels, respectively. These results suggest that IDDM contributes to bone loss through changes in gene expression of TRAP and cathepsin K in osteoclasts as well as osteocalcin in osteoblasts resulting in increased bone resorptive activity and decreased bone formation.

Age-related changes in bone biochemical markers and their relationship with bone mineral density in normal Chinese women

Measurements of bone biochemical markers are increasingly being used to evaluate the state of bone turnover in the management of bone metabolic diseases, especially osteoporosis. However, changes in the bone turnover rate vary with age. The aim of this study was to establish the laboratory reference range of serum bone-specific alkaline phosphatase (sBAP), serum type I collagen cross-linked C-terminal telopeptide (sCTx), and urine CTx (uCTx), based on values from 665 healthy Chinese women aged 20-80 years. We measured the levels of sBAP, sCTx, serum alkaline phosphatase (sALP), and uCTx and evaluated the age-related changes and their relationship with bone mineral density (BMD) in the anteroposterior (AP) lumbar spine, hip, and left forearm. We found significant correlations between biochemical markers and age, with coefficients of determination (R (2)) of 0.358 for sBAP, 0.126 for sCTx, 0.125 for uCTx, and 0.336 for sALP. The net changes in different biochemical markers were inversely correlated with the rates of BMD loss in the AP lumbar spine. After correction for age, body weight, and height, the levels of the markers had significant negative correlations with the BMD of the AP lumbar spine, femoral neck, and ultradistal forearm. All four biochemical markers had the highest negative correlation with BMD of the AP lumbar spine (partial correlation coefficients of -0.366, -0.296, -0.290, and -0.258 for sBAP, sCTx, uCTx, and sALP, respectively). The mean and SD values of these markers in premenopausal and postmenopausal women with normal BMD values were used as the normal reference ranges. The reference ranges of sBAP, sCTx, and uCTx for pre- vs postmenopausal women were 17.3 +/- 6.23 vs 18.9 +/- 7.52 U/l, 3.18 +/- 1.49 vs 3.23 +/- 1.57 nmol/l, and 15.5 +/- 11.4 vs 16.2 +/- 12.4 nM bone collagen equivalents/mM urinary creatinine, respectively. Levels of the bone formation marker (sBAP) and bone resorption markers (sCTx, uCTx) increased rapidly in women with osteopenia or osteoporosis, indicating that they may be sensitive markers to determine the bone turnover rate in healthy Chinese women.

Reference database of biochemical markers of bone turnover for the Japanese female population. Japanese Population-based Osteoporosis (JPOS) Study

The present study was conducted as a part of the Japanese Population-based Osteoporosis (JPOS) Study to establish reference values on the biochemical markers of bone turnover in the general Japanese female population over an applicable age range. The study recruited 3250 women aged 15-79 years, randomly selected from five municipalities throughout Japan, and obtained measurements of serum osteocalcin (OC) and bone-specific alkaline phosphatase (BAP); free and total forms of immunoreactive deoxypyridinoline, free pyridinolines and type I collagen cross-linked C-terminal telopeptide (CTx) in urine; serum intact parathyroid hormone (PTH) and 1,25 dihydroxy vitamin D (1,25 (OH)2D); and bone density at the spine, hip and distal forearm. After excluding subjects with apparent or suggested abnormalities affecting bone mass, 2535 (78%) subjects were further analyzed. The authors presented 5-year age-specific mean values of the markers and mean marker levels derived from women aged 30-44 years with normal bone density as a healthy young adult reference. Values of the markers decreased with increasing age before the age of 40, increased steeply among subjects in their 50s, and remained elevated in the elderly. Serum calcium, phosphorus, PTH and 1,25 (OH)2D levels were higher in postmenopausal women than in premenopausal women. However, 1,25 (OH)2D was lower among early postmenopausal subjects. The levels of OC, BAP, CTx, PTH and 1,25(OH)2D were significantly greater for women with osteoporosis than for those without. The diagnostic value of the markers was limited as the sensitivity and specificity ranged from 55% to 60%. These findings will aid health professionals in the correct assessment of bone turnover status in Japanese women over a wide range of age.

Estrogen, androgen, and the pathogenesis of bone fragility in women and men

During growth, estrogen deficiency in females may produce increased bone size as a result of removal of inhibition of periosteal apposition, while failed endosteal apposition produces thin cortices and trabeculae in the smaller bone. In males, androgen deficiency produces reduced periosteal and endosteal apposition, reduced bone size, and cortical and trabecular thickness. At completion of longitudinal growth, advancing age is associated with emergence of a negative bone balance in each basic multicellular unit (BMU) because of reduced bone formation. Bone loss occurs, but slowly because the remodeling rate is slow. In midlife, in females, estrogen deficiency increases remodeling rate, increases the volume of bone resorbed, and decreases the volume of bone formed in each of the numerous BMUs remodeling bone on its endosteal (endocortical, trabecular, intracortical) surfaces so bone loss accelerates. In males, remodeling rate remains slow and is driven largely by reduced bone formation in the BMU. Hypogonadism in 20% to 30% of elderly men contributes to bone loss. In both sexes, calcium malabsorption and secondary hyperparathyroidism may partly be sex-hormone dependent and contributes to cortical bone loss. Concurrent periosteal apposition partly offsets endosteal bone loss, but less so in women than in men. More women than men fracture because their smaller skeleton incurs greater architectural damage and adapts less by periosteal apposition. Sex hormone deficiency during growth and aging is pivotal in the pathogenesis of bone fragility.

Invited Review: Pathogenesis of osteoporosis

Patients with fragility fractures may have abnormalities in bone structural and material properties such as larger or smaller bone size, fewer and thinner trabeculae, thinned and porous cortices, and tissue mineral content that is either too high or too low. Bone models and remodels throughout life; however, with advancing age, less bone is replaced than was resorbed within each remodeling site. Estrogen deficiency at menopause increases remodeling intensity: a greater proportion of bone is remodeled on its endosteal (inner) surface, and within each of the many sites even more bone is lost as more bone is resorbed while less is replaced, accelerating architectural decay. In men, there is no midlife increase in remodeling. Bone loss within each remodeling site proceeds by reduced bone formation, producing trabecular and cortical thinning. Hypogonadism in 20-30% of elderly men contributes to bone loss. In both sexes, calcium malabsorption and secondary hyperparathyroidism increase remodeling: more bone is removed from an ever-diminishing bone mass. As bone is removed from the endosteal envelope, concurrent bone formation on the periosteal (outer) bone surface during aging partly offsets bone loss and increases bone's cross-sectional area. Periosteal apposition is less in women than in men; therefore, women have more net bone loss because they gain less on the periosteal surface, not because they resorb more on the endosteal surface. More women than men experience fractures because their smaller skeleton incurs greater architectural damage and adapts less by periosteal apposition.

Bone resorption parameters [carboxy-terminal telopeptide of type-I collagen (ICTP), amino-terminal collagen type-I telopeptide (NTx), and deoxypyridinoline (Dpd)] in MGUS and multiple myeloma

Skeletal morbidity is a major problem in multiple myeloma. Histomorphometric studies have demonstrated that increased bone resorption can be present even in the absence of radiographic abnormalities. To overcome diagnostic problems in estimating the activity of bone resorption, new laboratory parameters that reflect bone metabolism accurately are urgently needed. We analyzed three parameters of osteoclastic bone destruction, i.e. deoxypyridinoline (Dpd) and amino-terminal collagen type-I telopeptide (NTx) in urine and carboxy-terminal telopeptide of type-I collagen (ICTP) in serum, of 75 patients with multiple myeloma (n = 57) or monoclonal gammopathy of undetermined significance (MGUS, n = 18) by ELISA/RIA techniques. Serum ICTP and urinary Dpd levels increased parallel to the stage of the disease and differed significantly (P < 0.001 for ICTP and P = 0.03 for Dpd) between MGUS, myeloma stage I, and myeloma in stages II and III according to Salmon and Durie. ICTP and Dpd were significantly elevated in patients with multiple myeloma in stage I compared to individuals with MGUS, while no significant difference was found for NTx. In this first study comparing the prognostic relevance of ICTP, NTx, and Dpd in multiple myeloma patients, ICTP was found to be a prognostic factor for overall survival in the Kaplan-Meier analysis (log-rank test: P < 0.03). Urinary NTx showed borderline significance (P = 0.05), and Dpd had no prognostic value in the survival analysis. Our data show that serum ICTP and urinary Dpd levels increase in parallel to advanced disease stages, and gives the first report on a significant difference in the bone resorption parameters ICTP and Dpd between individuals with MGUS and patients with myeloma in stage I. Among the bone resorption parameters studied serum ICTP was found to be the best prognostic factor for survival in multiple myeloma.

Screening for osteoporosis in patients with inflammatory bowel disease by using urinary N-telopeptides

BACKGROUND

Patients with inflammatory bowel disease are at increased risk of osteoporosis.

DESIGN AND METHODS

We carried out a prospective study of bone mineral density and biochemical markers of bone metabolism like osteocalcin and urinary N-telopeptides in 72 patients with inflammatory bowel disease and evaluated if one of these markers detects osteoporosis. In addition, bone mineral density and N-telopeptides were analysed retrospectively in a second series of 93 patients with inflammatory bowel disease in order to assess predictive values found in the first patient group in an independent sample.

RESULTS

Multiple linear regression showed that N-telopeptides (P < 0.0001) and total white blood cell count (P = 0.006) correlated negatively with the bone mineral density of the lumbar spine and only N-telopeptides (P = 0.005) correlated negatively with the bone mineral density of the femoral neck. Using receiver operator characteristic curves N-telopeptide concentrations of > 40 (30) nmol N-telopeptides/mmol creatinine were chosen as best cut-off values to exclude osteoporosis at the lumbar spine (femoral neck). Using these cut-off values a negative predictive value of 100% (100%) and a positive predictive value of 37.5% (27.9%) were found in the first group, and a negative predictive value of 95.2% (96%) and a positive predictive value of 15.6% (23.3%) in the second, independent group of patients.

CONCLUSION

Our data suggest that N-telopeptide levels could be used as a tool for the screening of osteoporosis and for selecting those inflammatory bowel disease patients where bone mineral density measurement is indicated.

Pathogenesis of bone fragility in women and men

There is no one cause of bone fragility; genetic and environmental factors play a part in development of smaller bones, fewer or thinner trabeculae, and thin cortices, all of which result in low peak bone density. Material and structural strength is maintained in early adulthood by remodelling; the focal replacement of old with new bone. However, as age advances less new bone is formed than resorbed in each site remodelled, producing bone loss and structural damage. In women, menopause-related oestrogen deficiency increases remodelling, and at each remodelled site more bone is resorbed and less is formed, accelerating bone loss and causing trabecular thinning and disconnection, cortical thinning and porosity. There is no equivalent midlife event in men, though reduced bone formation and subsequent trabecular and cortical thinning do result in bone loss. Hypogonadism contributes to bone loss in 20-30% of elderly men, and in both sexes hyperparathyroidism secondary to calcium malabsorption increases remodelling, worsening the cortical thinning and porosity and predisposing to hip fractures. Concurrent bone formation on the outer (periosteal) cortical bone surface during ageing partly compensates for bone loss and is greater in men than in women, so internal bone loss is better offset in men. More women than men sustain fractures because their smaller skeleton incurs greater architectural damage and adapts less effectively by periosteal bone formation. The structural basis of bone fragility is determined before birth, takes root during growth, and gains full expression during ageing in both sexes.

Relationships among physical activity, metacarpal bone mass, and bone resorption marker in 70 healthy adult males

The purpose of the present study was to investigate the relationships among physical activity, metacarpal bone mineral density (BMD), and bone resorption marker in healthy active adult men. Seventy healthy men (mean age, 68.4 years, range, 48-85 years) were recruited. The metacarpal BMD of the nondominant hand was measured by computed X-ray densitometry, and the levels of urinary cross-linked N-telopeptides of type I collagen (NTx), as a marker of bone resorption, were measured with an enzyme-linked immunosorbent assay. The relationships among BMD, urinary NTx levels, and activities in leisure time and at work were examined. BMD was 2.77 +/-0.48 (mean+/- SD; range, 1.54-3.60) mmAl, and NTx levels were 44.9 +/-21.0 (range, 11.7 - 91.0) nmol BCE/mmol creatinine. Single regression analysis showed that BMD was significantly correlated with NTx levels and activity at work (r = - 0.331 and P < 0.01; r = 0.468 and P < 0.05, respectively), while NTx levels were significantly correlated with activities in leisure time and at work (r = -0.250 and P < 0.01; r = -0.325 and P < 0.01, respectively). NTx levels were decreased and BMD were increased with higher activity at work. The present study shows that increased physical activity as a result of hard work may have the potential to decrease bone resorption and increase BMD in healthy adult men.

Relationships between physical activity and metacarpal cortical bone mass and bone resorption in hemiplegic patients

The aim of the present study was to investigate the relationships between physical activity and metacarpal cortical bone mineral density (BMD) and bone resorption in hemiplegic patients. Seventy-two male hemiplegic patients with cerebrovascular disease (mean age, 67.0 years; range 48-83 years) were recruited. Metacarpal cortical BMD in bilateral hands was measured by computed X-ray densitometry, and the levels of urinary cross-linked N-telopeptides of type I collagen (NTx), as a bone resorption marker, were measured by an enzyme-linked immunosorbent assay (ELISA). BMD (mean +/- SD) in the paralyzed hand was significantly lower than that in the nonparalyzed hand (2.52 +/- 0.46 and 2.64 +/- 0.45 mmAl; P < 0.05). On multiple regression analysis, BMD was significantly positively correlated with Brunnstrom stage (assessment of degree of paralysis) in the hand (P < 0.05), whereas urinary NTx levels were significantly negatively correlated with Brunnstrom stage in the hand, arm, and leg, and with walking ability (P < 0.05, P < 0.05, P < 0.01, and P < 0.01, respectively). These findings suggest that, in male hemiplegic patients, although metacarpal cortical BMD may be affected by only local physical activity, urinary NTx appears to be responsive to local and general physical activity.

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.

Interlaboratory Variation of Biochemical Markers of Bone Turnover

Background: Biochemical markers of bone metabolism are used to assess skeletal turnover, but the variability of marker assays is still an issue of practical concern. We describe the results of an international proficiency testing program for biochemical bone markers among clinical laboratories.

Methods: Two serum and two urine pools (normal and increased marker concentrations) were sent on dry ice to 79 laboratories for analysis within 2 weeks of receipt.

Results: Data were submitted by 73 laboratories. The within-method interlaboratory CVs (CVILs) were as follows: serum bone-specific alkaline phosphatase (n = 47 laboratories), 16–48%; serum osteocalcin (n = 31), 16–42%; urinary free deoxypyridinoline (n = 30), 6.4–12%; urinary total deoxypyridinoline and pyridinoline (n = 29), 27–28%; urinary N-terminal cross-linked telopeptide of type I collagen (n = 10), 39%; serum C-terminal cross-linked telopeptide of type I collagen (ICTP; n = 8), 22–27%; urinary hydroxyproline (n = 13), 12%. Analytical results showed both systematic and nonsystematic deviations. In identical samples, results obtained for the same marker by the same method differed up to 7.3-fold. In urine-based assays, correction for urinary creatinine slightly increased CVs.

Conclusion: Even with identical assays and methods, results for most biochemical markers of bone turnover differ markedly among laboratories.

Unresolved issues in osteoporosis in men

Fragility fractures in men are a public health problem. The increasing longevity in men is likely to increase the public health burden of fractures in men. This problem remains unrecognized by doctors, the public and governments. About one third of all hip fractures occur in men but the incidence and gender ratio varies from country to country for reasons that are not understood. The prevalence of spine fractures is about half that of women in most studies, but similar to that of women in several other studies. The incidence of spine fractures is uncertain but is likely to be about half that of women except in 80+ year olds, when it appears to be similar. The causes of the higher mortality in men than in women following hip or spine fracture are not well defined. Areal bone mineral density (aBMD) predicts fracture risk in men; the relative risk for spine and hip fracture conferred by a 1 SD lower aBMD, or by a prevalent fracture, is similar in men and women. The age-specific absolute risk (number of cases per 1,000 per year) conferred by a given hip aBMD is similar in men and women. The age-specific absolute risk conferred by aBMD at the calcaneus or radius for spine fracture is similar for men and women. If the absolute and relative risks are similar then the lower incidence of fractures in men than women may reflect the lower proportion of the male population distribution below a given structural determinant of bone fragility. That is, at any age, there may be fewer men than women with smaller bones, lower volumetric bone mineral density (vBMD), thinner trabeculae or cortices, architectural disruption, or higher remodeling rates. Higher mortality and fewer falls may also contribute to the lower incidence of fractures in men. This tail end of the male population distribution (for traits like bone size, vBMD, architecture, and remodeling rates) is the likely source of fracture cases in males. Hypogonadism is a risk factor for osteoporosis. However, the definition, prevalence, causes and structural consequence of hypogonadism are inadequately defined. At what level of testosterone is bone balance negative? What structural determinants of axial and appendicular strength are regulated by testosterone, estrogen, growth hormone (GH), insulin like growth factor 1 (IGF-1) (or their interactions)? Is reduced bone size in men with spine or hip fractures due to failed growth-related or age-related periosteal expansion? If reduced vBMD is due to reduced accrual, is this due to reduced cortical thickness? What factors regulate and coregulate the periosteal and endocortical modeling and remodeling? Are reduced trabecular numbers due to failed formation at the growth plate, excess resorption of primary trabeculae or reduced formation of secondary trabeculae? Is reduced trabecular thickness due to failed prepubertal or pubertal bone formation? Is reduced cortical and trabecular thickness during aging due to excessive endosteal resorption or reduced bone formation? If the former, is this due to increased remodeling sites or increased resorption depth? Most evidence favors reduced bone formation as the cause of bone loss with trabecular bone loss occurring by reduced formation and thinning more than by increased resorption and loss of connectivity. Cortical bone loss is less than in women because endocortical resorption is less and periosteal apposition is greater. If the reduced bone formation is most important, is this due to reduced osteoprogenitors, reduced osteoblast matrix synthesis or early osteoblast apoptosis? Anti-spine-fracture efficacy has been demonstrated in only one randomized heated with alendronate drug in men. The gaps in our knowledge remain large.

Proteolysis of human bone collagen by cathepsin K: characterization of the cleavage sites generating by cross-linked N-telopeptide neoepitope

An immunoassay for cross-linked N-telopeptides of type I collagen (NTx) in urine or serum has proven to give a sensitive index of osteoclast-mediated bone resorption. We show that recombinant human cathepsin K is highly active in releasing the NTx neoepitope in 100% yield from bone type I collagen. Cathepsins S, L, and B were also active but at 57%, 36%, and 27% of the yield of K, respectively. The matrix metalloproteinases that were tested, stromelysin, collagenase 3, or matrilysin, did not produce any immunoreactivity. Cathepsin K also acted on demineralized bone matrix, releasing NTx epitope and completely dissolving the bone particles in 24-48 h. Proteolytic cleavage of a G-L peptide bond in the alpha2(I)N-telopeptide was shown to be required for recognition by monoclonal antibody 1H11. Peptide analysis identified bonds in the N-telopeptide and helical cross-linking domains adjacent to the cross-linking residues at which cathepsin K cleaved in bone collagen. The sites were consistent with the known substrate specificity of cathepsin K, which prefers a hydrophobic residue or proline in the critical P2 position. The NTx peptides generated by cathepsin K were of low molecular weight, in the range previously found in human urine. Because cathepsin K appears to be essential for the normal resorption of mineralized bone matrix by osteoclasts, these findings help explain the specificity and responsiveness of NTx as a marker of osteoclastic bone resorption in vivo.

Dietary change and stable isotopes: a model of growth and dormancy in cave bears

In order to discuss dietary change over time by the use of stable isotopes, it is necessary to sort out the underlying processes in isotopic variation. Together with the dietary signal other processes have been investigated, namely metabolic processes, collagen turnover and physical growth. However, growth and collagen turnover time have so far been neglected in dietary reconstruction based on stable isotopes. An earlier study suggested that cave bears (Ursus spelaeus) probably gave birth to cubs during dormancy. We provide an estimate of the effect on stable isotopes of growth and metabolism and discuss collagen turnover in a population of cave bears. Based on a quantitative model, we hypothesized that bear cubs lactated their mothers during their first and second winters, but were fed solid food together with lactation during their first summer. This demonstrates the need to include physical growth, metabolism and collagen turnover in dietary reconstruction. Whereas the effects of diet and metabolism are due to fractionation, growth and collagen turnover are dilution processes.

Osteoporosis in men. New insights into aetiology, pathogenesis, prevention and management

Osteoporosis is increasingly recognised in men. Low bone mass, risk factors for falling and factors causing fractures in women are likely to cause fractures in men. Bone mass is largely genetically determined, but environmental factors also contribute. Greater muscle strength and physical activity are associated with higher bone mass, while radial bone loss is greater in cigarette smokers or those with a moderate alcohol intake. Sex hormones have important effects on bone physiology. In men, there is no abrupt cessation of testicular function or 'andropause' comparable with the menopause in women; however, both total and free testosterone levels decline with age. A common secondary cause of osteoporosis in men is hypogonadism. There is increasing evidence that estrogens are important in skeletal maintenance in men as well as women. Peripheral aromatisation of androgens to estrogens occurs and osteoblast-like cells can aromatise androgens into estrogens. Human models exist for the effects of estrogens on the male skeleton. In men aged > 65 years, there is a positive association between bone mineral density (BMD) and greater serum estradiol levels at all skeletal sites and a negative association between BMD and testosterone at some sites. It is crucial to exclude pathological causes of osteoporosis, because 30 to 60% of men with vertebral fractures have another illness contributing to bone disease. Glucocorticoid excess (predominantly exogenous) is common. Gastrointestinal disease predisposes patients to bone disease as a result of intestinal malabsorption of calcium and colecalciferol (vitamin D). Hypercalciuria and nephrolithiasis, anticonvulsant drug use, thyrotoxicosis, immobilisation, liver and renal disease, multiple myeloma and systemic mastocytosis have all been associated with osteoporosis in men. It is possible that low-dose estrogen therapy or specific estrogen receptor-modulating drugs might increase BMD in men as well as in women. In the future, parathyroid hormone peptides may be an effective treatment for osteoporosis, particularly in patients in whom other treatments, such as bisphosphonates, have failed. Men with idiopathic osteoporosis have low circulating insulin-like growth factor-1 (IGF-1; somatomedin-1) concentrations, and IGF-1 administration to these men increases bone formation markers more than resorption markers. Studies of changes in BMD with IGF-1 treatment in osteoporotic men and women are underway. Osteoporosis in men will become an increasing worldwide public health problem over the next 20 years, so it is vital that safe and effective therapies for this disabling condition become available. Effective public health measures also need to be established and targeted to men at risk of developing the disease.

Serum B2-microglobulin concentration correlates with urinary concentrations of type 1 collagen cross-linked N-telopeptides and deoxypyridinoline in rheumatoid arthritis

BACKGROUND

Determination of serum ss2-microglobulin concentration, an invasive procedure, has been advocated for monitoring patientsA centAA response to treatment in rheumatoid arthritis. The object of this study was to find out if serum ss2-microglobulin concentration correlated with urinary excretions of type 1 collagen crosslinked N-telopeptides (NTx) and deoxypyridinoline (Pyrilinks-D) in rheumatoid arthritis (RA).

SUBJECTS AND METHODS

Using chemiluminiscent assay, serum ss2-microglobulin concentrations were estimated in 25 female patients with active RA, 25 female with inactive disease, and 25 age-matched healthy female controls. Concentrations of NTx and Pyrilinks-D were also determined by immunoabsorbent assays in spot urine samples from these subject groups.

RESULTS

The serum concentration of ss2-microglobulin in patients with RA (7.45+/-2.10 mg/L) was significantly higher (P<0.001) than the concentrations in patients with inactive disease (3.33+/-0.76 mg/L), or than in normal healthy controls (2.747plusmn;0.52 mg/L). Similarly, in patients with active RA, the spot urinary concentrations of NTx (123.08+/-25.53 nmol BCE/mmol creatinine) and Pyrilinks-D (15.087plusmn;3.29 nmol/mmol creatinine) were significantly higher (P<0.01) than those in patients with inactive disease (58.42AA+/-12.65 nmol BCE/mmol creatinine and 10.10+/-2.43 nmol/mmol creatinine, respectively). In patients with active RA, serum concentration of ss2-microglobulin correlated positively with spot urinary NTx concentrations (r=0.9910, P=0.0001), and Pyrilinks-D concentration (r=0.6177, P=0.001).

CONCLUSION

In patients with active RA, the spot urinary concentrations of NTx and Pyrilinks-D correlated positively with serum AA2-microglobulin. Therefore, the estimations of these urinary markers may take the place of serum ss2-microglobulin estimation in monitoring the patientA centAAs response to treatment in rheumatoid arthritis.

Biochemical markers in the assessment of bone disease

As the mean age of our population increases, increasing attention has been paid to the diseases associated with aging, including diseases of the skeleton such as osteoporosis. Effective means of treating and possibly preventing such skeletal disorders are emerging, making their early recognition an important goal for the primary care physician. Although bone density measurements and skeletal imaging studies remain of primary diagnostic importance in this regard, a large number of assays for biochemical markers of bone formation and resorption are being developed that promise to complement the densitometry measurements and imaging studies, providing an assessment of the rates of bone turnover and an earlier evaluation of the effects of therapy. In this review, emphasizing the recent literature, the major biochemical markers currently in use or under active investigation are described, and their application in a number of diseases of the skeleton including osteoporosis is evaluated.

Evidence that serum NTx (collagen-type I N-telopeptides) can act as an immunochemical marker of bone resorption

Previous studies have shown that immunoassay of urinary NTx (cross-linked N-telopeptides of type I collagen) provides a responsive index of human bone resorption. Here we report by a sensitive immunoassay that NTx is present in serum and is suppressed appropriately in patients with Paget disease of bone by bisphosphonate antiresorptive therapy. The monoclonal antibody (1H11) developed against urinary NTx was applied in a sensitive chemiluminescence format. Results for human serum and urine showed parallel inhibition curves. The NTx concentrations in paired serum and urine samples from individual patients correlated well when urinary concentrations were normalized to creatinine concentrations (in premenopausal and postmenopausal women and Paget disease patients, r = 0.90, n = 60). The percentage of NTx suppression from baseline values for Paget disease patients on bisphosphonate therapy was similar for serum and urine. Blood samples drawn from bone marrow at the site of Pagetic lesions in three patients with active disease had as much as 10-fold higher concentrations of NTx than did peripheral blood samples drawn at the same time. The latter finding is consistent with other evidence showing that immunoreactive NTx originates directly during the proteolytic cleavage of bone collagen by osteoclasts rather than, e.g., by degradative processes occurring later in the liver and kidney.

Osteoporosis in men

Hip fractures in men account for one third of all hip fractures and have a higher mortality than in women. The public health burden will increase as the increase in the numbers of elderly men in the community increases. In addition, the age-specific incidence of hip fractures may be increasing in some, but not all, countries. Vertebral fractures may be a public health problem as recent studies suggest that the prevalence in the community is 20-30%, similar to that reported in women. Forearm fractures should probably not be regarded as a public health problem. Peak bone mass is higher in men than women because men have bigger bones. Peak bone mineral density is the same. The amount of trabecular bone lost at the spine and iliac crest during ageing is similar in men and women. Cortical bone loss is less in men because endocortical resorption is less and periosteal formation is greater. Bone loss accelerates in elderly men because endocortical resorption and increasing cortical porosity increase the surface available for resorption. Bone fragility is less in men than women because: (a) the cross-sectional surface of the bone is larger; (b) trabecular bone loss is less as a percentage of the higher peak bone mass; (c) trabecular bone loss occurs by thinning rather than perforation; and (d) periosteal appositional growth compensates for endocortical resorption by maintaining the bending strength of bone. Reduced BMD in men with fractures may be due to reduced peak bone size and mass, and bone loss. Bone loss occurs by reduced bone formation. Whether men with fractures have increased bone fragility due to reduced periosteal appositional growth during ageing is unknown. The age-related decline in testosterone, adrenal androgens, growth hormone, and insulin-like growth factor 1 may contribute to reduced bone formation and bone loss. Men with vertebral fractures often have hypogonadism or illnesses with few clinical features that should be considered with a high index of suspicion (alcoholism, myeloma, malabsorption, primary hyperparathyroidism, haemochromatosis, Cushing's disease). Secondary hyperparathyroidism may contribute to bone loss by activating bone turnover and so increasing the number of bone remodelling units with impaired bone formation in each. There is no proven treatment for osteoporosis in men because there have been no trials using anti-fracture efficacy as an end point. Testosterone replacement should be considered in men with proven hypogonadism and vitamin D deficiency should be corrected if present. Calcium supplements and bisphosphonates are reasonable options given the lack of information.

Relationship of bone turnover to bone density and fractures

To assess the influence of bone turnover on bone density and fracture risk, we measured serum levels of osteocalcin (OC), bone alkaline phosphatase (BAP), and carboxy-terminal propeptide of type I procollagen (PICP), as well as 24-h urine levels of cross-linked N-telopeptides of type I collagen (NTx) and the free pyridinium cross-links, pyridinoline (Pyd) and deoxypyridinoline (Dpd), among 351 subjects recruited from an age-stratified random sample of Rochester, Minnesota women, PICP, NTx, and Dpd were negatively associated with age among the 138 premenopausal women. All of the biochemical markers were positively associated with age among the 213 postmenopausal women, and the prevalence of elevated turnover (> 1 standard deviation [SD] above the premenopausal mean) varied from 9% (PICP) to 42% (Pyd). After adjusting for age, most of the markers were negatively correlated with bone mineral density (BMD) of the hip, spine, or forearm as measured by dual-energy X-ray absorptiometry, and women with osteoporosis were more likely to have high bone turnover. A history of osteoporotic fractures of the hip, spine, or distal forearm was associated with reduced hip BMD and with elevated Pyd. After adjusting for lower BMD and increased bone resorption, reduced bone formation as assessed by OC was also associated with prior osteoporotic fractures. These data indicate that a substantial subset of elderly women has elevated bone turnover, which appears to adversely influence BMD and fracture risk. Combined biochemical and BMD screening may provide better prediction of future fracture risk than BMD alone.