Novel serum markers of bone resorption: clinical assessment and comparison with established urinary indices

The amino- and carboxyterminal cross-linked telopeptides of collagen type I, NTX-I and CTX-I: a comparative review

Bone diseases such as osteoporosis or bone metastases are a continuously growing problem in the ageing populations across the world. In recent years, great efforts have been made to develop specific and sensitive biochemical markers of bone turnover that could help in the assessment and monitoring of bone turnover. The amino- and carboxyterminal cross-linked telopeptides of type I collagen (NTX-I and CTX-I, respectively) are two widely used bone resorption markers that attracted great attention due to their relatively high sensitivity and specificity for the degradation of type I collagen, and their rapid adaptation to automated analyzers. However, the clinical performance of both markers differs significantly depending on the clinical situation. These differences have caused considerable confusion and uncertainty. If used correctly, both markers have great potential to improve the management of many bone diseases. We here review the biochemistry, analytical background and clinical performance of NTX-I and CTX-I, as documented in the accessible literature until March 2008.

Higher efficacy of urinary bone resorption marker measurements in assessing response to treatment for osteoporosis in postmenopausal women

Osteoporosis has reached epidemic proportions. This situation has stimulated the development of biochemical markers to assist in assessing osteoporotic risk and monitoring treatment efficacy. Biochemical markers for assessing the level of bone resorption have been developed during the last few decades. One of the most widely used bone resorption markers is cross-linked N-terminal telopeptides (NTX). Measurements of urinary and serum NTX provide indications of the level of bone resorption during osteoporosis treatment. However, it remains unclear whether urinary or serum NTX measurements show better efficacy for assessing osteoporosis treatment effects during the early phase of treatment. Therefore, the primary aim of the present study was to compare the efficacies of urinary and serum NTX measurements for assessing the level of bone resorption during the early stage of osteoporosis treatment. We enrolled 43 postmenopausal Japanese women in an open-label randomized placebo-controlled trial. Overall, 21 women in the osteoporosis treatment group and 19 women in the placebo group completed the study. There was a significant reduction in urinary NTX in the treatment group, which was detectable as early as 4 weeks and maintained until 16 weeks, compared with the placebo group. On the other hand, serum NTX did not show a significant reduction in the treatment group compared with the placebo group until 16 weeks. These results indicate that urinary NTX measurements are more sensitive and show higher efficacy than serum NTX measurements for assessing treatment effect during the early phase of osteoporosis treatment in postmenopausal women.

Bortezomib inhibits osteoclast activity in patients with multiple myeloma

BACKGROUND

The antimyeloma agent bortezomib functions as an inhibitor of nuclear factor (NF)-kappaB. Although NF-kappaB inhibition is predicted to affect osteoclast function, preclinical and clinical studies have primarily reported an effect on osteoblasts.

PATIENTS AND METHODS

We examined parameters of bone turnover prospectively in patients with multiple myeloma treated with bortezomib before and after autologous transplantation. Thirty-nine patients received 2 cycles of bortezomib on days 1, 4, 8, and 11 of a 21-day cycle. After high-dose melphalan with autologous stem cell transplantation, bortezomib 1.3 mg/m2 on days 1, 8, 15, and 22 of a 5-week cycle was administered as maintenance therapy.

RESULTS

During posttransplantation bortezomib, decreases in the urinary excretion of collagen N-telopeptide indicated that bortezomib suppresses osteoclast function.

CONCLUSION

The effects on osteoclasts occurred in the absence of bisphosphonate treatment and independently of changes in monoclonal protein levels. Further studies exploring the role of bortezomib as a bone protective agent could be warranted.

Short-term effects of glucocorticoid therapy on biochemical markers of bone metabolism in Japanese patients: a prospective study

Glucocorticoid (GC) therapy induces rapid bone loss, but the early changes in calcium and bone metabolism in patients treated with GC have not been clarified. To investigate the changes in calcium and bone metabolism during the early stage of GC therapy, we analyzed various biochemical markers of bone metabolism. The serum levels of calcium (Ca), phosphorus, parathyroid hormone (PTH), osteocalcin (OC), bone alkaline phosphatase (BAP), and type I collagen cross-linked N-telopeptide (NTx), as well as the urinary levels of Ca, creatinine, and NTx, were measured on days 0, 3, 7, and 28 of GC therapy. The subjects were divided into the following four groups: 9 patients receiving pulse therapy (P), 18 patients receiving prednisolone (PSL) at doses > or =40 mg/day (H), 9 patients receiving PSL at doses > or =20 mg/day (M), and 11 patients receiving PSL at doses < or =10 mg/day (S). The serum OC level showed a marked decrease on day 3 of GC therapy (-41.2% +/- 6.6%, P < 0.01), while the BAP level decreased gradually. Both serum and urinary NTx levels significantly increased on day 7 of GC therapy (9.9% +/- 4.5%, P < 0.05, and 42.2% +/- 10.6%, P < 0.01, respectively). Urinary Ca excretion was increased on day 3 of GC therapy and continued to increase until 4 weeks, while intact PTH showed an increase on day 3 and then remained constant until 4 weeks. In groups P and H, there were significant early changes in OC, BAP, NTx, and intact PTH levels, as well as urinary Ca excretion. Even a PSL dose of <10 mg/day caused a decrease in the serum OC level. In conclusion, the biochemical markers of Ca and bone metabolism showed different kinetics depending on the dose of GC, and it is important for patients on high-dose GC therapy to receive prophylaxis for bone loss from the start of GC treatment.

The use of bone markers in a 6-week study to assess the efficacy of oral clodronate in patients with metastatic bone disease

Biochemical markers of bone metabolism are strongly associated with skeletal complications in metastatic bone disease. The bisphosphonate clodronate reduces skeletal morbidity by inhibiting bone resorption. This study investigated the use of bone markers to assess the efficacy of oral clodronate across a range of clinically relevant doses. There were 125 patients with metastatic bone disease randomized to daily oral clodronate (800, 1,600, 2,400 and 3,200 mg) or placebo in a double-blind, multicenter study. Urinary N-terminal telopeptide of type I collagen (U-NTX), serum C-terminal telopeptide of type I collagen (S-CTX), urinary calcium (U-Ca), and bone alkaline phosphatase were measured weekly for a 6-week treatment period. Doses of >or=1,600 mg clodronate produced mean reductions of >40% in U-NTX, S-CTX and U-Ca, all significantly different from placebo (P=0.0015, 0.001, 0.0036, respectively), after 6 weeks. Evaluation of least significant changes in markers suggested that the commonly used 1,600 mg dose was most appropriate for breast cancer patients. However, this dose was suboptimal for other (mainly prostate cancer) patients, who showed better response to 2,400 mg. The number of adverse events in the treatment arms was not significantly different from that in placebo, but a higher number of patients had diarrhea in the 3,200 mg arm and withdrew from the study. This trial is the first to explore the dose-response relationship of clodronate in oncology using specific markers of bone turnover. It has confirmed that the 1,600 mg dose is safe and effective for breast cancer patients but may be suboptimal for the other tumors studied.

Serial Markers of Bone Turnover in Men with Metastatic Prostate Cancer Treated with Zoledronic Acid for Detection of Bone Metastases Progression

OBJECTIVES

This study assessed the usefulness of serial measurements of bone turnover markers in men with metastatic prostate cancer treated with zoledronic acid to detect disease progression.

METHODS

Serum measurements of total alkaline phosphatase (tALP), bone-specific alkaline phosphatase (bALP), cross-linked N-terminal (NTx) and cross-linked C-terminal (CTx) telopeptides of type I collagen, amino-terminal procollagen propeptides of type I collagen (PINP), C-terminal telopeptides of type I collagen (ICTP), and prostate-specific antigen (PSA) were performed in 77 prostate cancer patients suffering from bone metastases and treated with zoledronic acid up to 15 mo. Fifty patients were with and 27 patients without objective evidence of metastatic bone progression during the administration of zoledronic acid.

RESULTS

The baseline bone marker concentrations were not significantly different between the groups. After administration of zoledronic acid all bone markers except of ICTP decreased compared with baseline. CTx showed the greatest decrease. In patients with metastatic bone progression PINP, tALP, bALP, and ICTP were significantly higher at weeks 24, 36, 48, and 60 after starting treatment with zoledronic acid compared with patients without progression. In addition to the information of prostate-specific antigen as a monitoring parameter, the bone formation marker showed a better distinction between patients with and without disease progression.

CONCLUSIONS

Selected bone turnover markers provide valuable information regarding progression of bone metastasis in men with metastatic prostate cancer under bisphosphonate therapy. The clinical impact should be confirmed in prospective randomised studies.

Assessment of osteoclast number and function: application in the development of new and improved treatment modalities for bone diseases

Numerous experimental and clinical observations suggest that overall changes in bone resorption during menopause or treatment with hormone replacement therapy (HRT) are combined effects of changes in osteoclast number and function. Moreover, due to a coupling between osteoclastic bone resorption and osteoblastic bone formation, pronounced alteration of osteoclast number will eventually lead to alteration of osteoblastic bone formation. Fragments of type I collagen, such as the C- and N-terminal telopeptides of collagen type I (CTX and NTX, respectively), are generated during bone resorption and hence can be used as surrogate markers of osteoclast function. Circulating levels of different enzymes in the serum, such as TRAP 5b and cathepsin K are proportional to the number of osteoclasts, and hence can be used as surrogate markers of osteoclast number. Since antiresorptive effects can be obtained in different ways, we felt it was timely to discuss the different scenarios, highlight differences specific to different pharmacological interventions with different mechanisms of action, and discuss how these bone markers can assist us in a deeper analysis of the pharmacodynamics and safety profile of existing and upcoming drug candidates.

A new method of monitoring osteomyelitis

Chronic infections of bone such as osteomyelitis are frequent events, especially in immunocompromised or diabetic patients, and costly on a national level. Incorrect treatment or delayed diagnosis may lead to loss of the affected extremity or mandible. The aim of this study was to assess the possible value of urinary lysylpyridinoline (LP) and hydroxylysylpyridinoline (HP) concentrations in the monitoring of mandibular osteomyelitis. Patients were assigned to the following groups: group 1 (n=85), control; group 2a (n=38), patients with active disease; group 2b (n=25), patients of group 2a 6 months after successful treatment; group 2c (n=7), patients of group 2a with ongoing osteomyelitis 6 months after treatment. The range and upper limit of normal values (HP(max) and LP(max)) were determined in group 1. Levels of LP and HP were measured by high-performance liquid chromatography and fluorescence detection. There was a significant decrease (mean 45.43% for HP and 32.12% for LP) in samples of group 2b compared to 2a (P<0.001 for HP and LP). There was a significant increase in HP values in samples from group 2c compared to 2a (P=0.018). The urinary concentrations of HP and LP appear to act as a marker of disease activity, with a decrease reflecting treatment success and an increase or stable values indicating persistent disease. An inexpensive tool (US$5 per analysis) for the monitoring of osteomyelitis is described.

Clinical Utility of Biochemical Markers of Bone Metabolism for Improving the Management of Patients with Advanced Multiple Myeloma

Osteolytic bone lesions from advanced multiple myeloma (MM) result in significant skeletal morbidity. Therefore, biochemical markers of bone metabolism, such as the N-terminal and C-terminal telopeptides of type I collagen, bone-specific alkaline phosphatase, and osteocalcin, have been investigated as tools for evaluating the extent of bone disease, risk of skeletal morbidity, and response to antiresorptive treatment. Several studies have shown that the majority of biochemical markers of bone metabolism are increased in patients with MM with osteolytic bone lesions, thus reflecting changes in bone metabolism associated with tumor growth. There is also a growing body of evidence that markers of bone metabolism correlate with the risk of skeletal complications, disease progression, and death. In addition, bone markers could potentially be used as a tool for early diagnosis of bone lesions. The aim of this review is to improve our understanding of bone markers as a clinical tool for the management of malignant bone disease in patients with MM.

Biochemical markers of bone turnover in patients with localized and metastasized prostate cancer

OBJECTIVE

To evaluate and compare the value of several markers of bone turnover in different stages of prostate cancer, as bone metastases are a common feature in this disease, and for assessing bone metastases both bone formation and bone resorption markers are diagnostic.

PATIENTS AND METHODS

The prospective study included 219 men, i.e. 129 undergoing radical retropubic prostatectomy (RRP) and 25 with bone metastases due to prostate cancer, and 65 with benign urological disorders who served as controls. Before any treatment the concentrations of alkaline phosphatase (ALP), osteocalcin, serum C-terminal telopeptide of type I collagen (S-CTX) and tartrate-resistant acid phosphatase type 5b (TRACP5b) were determined.

RESULTS

Men undergoing RRP were divided into those with lymph node-negative, localized (pT3, 101) and lymph node-positive (28) disease, after histological examination. The controls had the lowest marker levels while patients with bone metastases due to prostate cancer had the highest levels, with significance for ALP, osteocalcin and TRACP5b. Patients with lymph node-positive cancer had significantly high serum levels of TRACP5b and ALP but not for osteocalcin and S-CTX.

CONCLUSIONS

Bone turnover markers represent a new diagnostic tool in prostate cancer; the present data show that both bone resorption and bone formation are crucial for detecting bone metastases in prostate cancer. The value of bone turnover markers in high-risk patients should be evaluated in a longitudinal study.

Serum NTX is a practical marker for assessing antiresorptive therapy for glucocorticoid treated patients with chronic kidney disease

INTRODUCTION

In chronic kidney disease (CKD) patients, serum concentration of type I collagen N-telopeptide (S-NTX) increases as renal function declines because of perturbed bone metabolism by renal dysfunction itself and impaired urinary excretion of NTX. Glucocorticoid (GC), which is often used for the treatment of kidney disease, may enhance bone resorption. We studied the bone resorption state in GC-treated CKD patients and the effects of bisphosphonate on S-NTX.

METHODS

We measured S-NTX and creatinine clearance (Ccr) in 48 non-diabetic patients with declining renal function who had never received GC, vitamin D, calcium or bisphosphonate (reference group). Bone markers including S-NTX and BSAP (bone specific alkaline-phosphatase) in 144 patients receiving GC (prednisone equivalent of > or =2.5 mg/day) for more than 6 months (GC-treated group) were measured. We compared the GC-treated group to the reference group in a cross-sectional study. In a longitudinal study, we further followed 55 patients from the GC-treated group, whose Ccr was more than 60 mL/min (CKD stage 1 or 2) for 1 year after 2.5 mg/day of risedronate was commenced.

RESULTS

In the reference group, S-NTX was correlated with Ccr (S-NTX = 456.6/Ccr + 4.5, r = 0.797, P < 0.0001). S-NTX values in the GC-treated group were higher than those found in the reference group at any Ccr. We defined the resorption index (RI) as a ratio of measured S-NTX to estimated NTX given by the correlation curve. Whereas BSAP did not change significantly, S-NTX decreased significantly by risedronate treatment. RI decreased from 1.59 (baseline) to 1.54, 1.25 (P < 0.01, versus baseline) and 1.23 (P < 0.01) at 1, 3 and 6 months after the start of therapy, respectively, which means that S-NTX values approached the correlation curve. Percent changes of S-NTX at 3 months were larger in patients with higher pretreatment S-NTX.

CONCLUSION

Higher S-NTX in the GC-treated group suggests that bone resorption is enhanced by GC. In CKD patients with mild renal dysfunction, S-NTX is a practical and useful marker for monitoring bone resorption during GC treatment.

Biochemical markers of bone metabolism in multiple myeloma

Osteolytic bone disease is a major clinical feature of multiple myeloma (MM). Mechanisms of bone destruction are related to increased osteoclastic activity, which is not accompanied by a comparable increase in bone formation, as osteoblasts are functionally exhausted. Thus the lesions rarely heal and bone scans are often negative in myeloma patients with extensive lytic lesions, offering very little in the follow-up of bone disease. Biochemical markers of bone resorption, such as N- and C-terminal cross-linking telopeptide of type I collagen (NTX, CTX/ICTP, respectively), tartrate resistant acid phosphatase isoform-5b, bone formation (bone-specific alkaline phosphatase [BAP]), and osteocalcin provide useful information on bone dynamics. Several studies have shown that NTX, CTX, and ICTP are elevated in myeloma patients, reflect the extent of bone disease, and correlate with survival. Furthermore, they are useful in monitoring bone destruction during antimyeloma or bisphosphonate treatment. Markers of bone formation have produced conflicting results in trials. However, BAP correlates with bone pain, lytic lesions, and fractures in quite a few studies of MM. Novel markers, such as bone sialoprotein, receptor activator of nuclear factor-kappa B ligand (RANKL), osteoprotegerin, osteopontin, dickkopf-1, and soluble Frizzle-related protein-2 have been found of value in assessing bone lytic disease in MM, but their promising results must be confirmed in large trials. In conclusion, although no marker provides optimal analysis of MM or of MM treatments, combinations of markers have at times helped in assessing MM stages and lytic bone disease and in monitoring specific treatment modalities. The need for further research in this field is clear.

Changes of the biochemical markers of bone turnover and periprosthetic bone remodeling after cemented hip arthroplasty

Do periprosthetic bone loss and postoperative levels of the biochemical markers of bone turnover correlate? The femoral bone mineral density of 53 patients was measured by dual-energy x-ray absorptiometry 1 week and 2, 4, 6, and 12 months after cemented total hip arthroplasty (THA). Biochemical markers of bone turnover were assayed preoperatively and 3, 8, 16, and 24 weeks post-THA. Greatest bone loss was detected in the calcar region (region of interest 7), on average, 16% after 1 year. A marker of bone resorption, C-terminal telopeptides of type I collagen, increased 21% 3 weeks after THA. A significant correlation between periprosthetic bone loss in region of interest 7 after 1 year and type I collagen at 3 weeks was seen (r = -0.42, P = .003). Data suggest that periprosthetic bone loss is induced by an early postoperative high activity of osteoclasts. Counteracting this osteoclast activity with a limited and timely postoperative antiresorptive treatment may be concluded for clinical application.

Clinical use of markers of bone turnover in metastatic bone disease

Bone metastases profoundly perturb normal bone remodeling. Biochemical markers of bone turnover have been shown to reflect these tumor-induced changes in bone remodeling and might therefore be useful in the diagnosis and follow-up of patients with malignant bone disease. Most markers of bone turnover, particularly those of bone resorption, are elevated in patients with established bone metastases. While this might indicate a role for bone markers as diagnostic tools in cancer patients, the available evidence does not provide any final conclusions as to the accuracy and validity of the markers presently used in the early diagnosis of bone metastases. Markers of bone resorption respond promptly and profoundly to bisphosphonate and antineoplastic therapy, and this response is associated with a favorable clinical outcome. Most markers, however, have been more useful in groups of patients monitored in clinical studies than in studies of individuals. While this makes them a good tool for drug development, it remains unknown whether the use of bone markers in a routine clinical setting has any defined beneficial effects on overall outcome in cancer patients. In particular, no study has addressed the question of whether patients with bone metastases should be treated according to their rate of bone turnover and what the treatment goals are in this respect. While it is unlikely that bone-turnover markers have sufficient diagnostic or prognostic value when used in isolation, the combination of these markers with other diagnostic techniques might be the way forward to improve the clinical assessment of patients with cancers of the bone.

Serum tartrate-resistant acid phosphatase 5b in monitoring bisphosphonate treatment with clodronate: a comparison with urinary N-terminal telopeptide of type I collagen and serum type I procollagen amino-terminal propeptide

Osteoclastic tartrate-resistant acid phosphatase activity in serum (S-TRACP 5b) was measured in postmenopausal women ( n =59, mean age 56.1 years) with vertebral osteopenia before and during 2-year treatment with an 800-mg daily dose of clodronate, with a non-amino bisphosphonate. Changes in TRACP 5b were compared with those in urinary excretion of type I collagen amino-terminal telopeptide (U-NTX), corrected for creatinine excretion, a well-established marker of bone resorption, and to serum type I procollagen amino-terminal propeptide (S-PINP), a marker of bone formation. Marker changes 1 year after start of treatment were correlated with changes in bone mineral density (BMD). The least significant change (LSC) for each marker and BMD was calculated from values for subjects receiving placebo. Responders to treatment were those exhibiting a change larger than LSC. In response to clodronate treatment S-TRACP 5b (mean change up to -18%) decreased less than did U-NTX (up to -51%) or S-PINP (up to -46%). Marker changes correlated with changes in lumbar spine and trochanter BMD. The most efficient marker for finding responders to treatment was S-PINP, which changed more than the LSC (32%) in 72% of the subjects at the 1-year time point and in 79% at the 2-year time point. S-TRACP 5b change exceeded the LSC (27%) in 40% and 34% of the subjects at each time point, while U-NTX change exceeded the LSC (55%) in 55% and 40%, respectively. We conclude that, in terms of the proportion of subjects exhibiting any change exceeding the LSC, S-TRACP 5b did not appear to be superior to U-NTX and S-PINP in the follow-up of clodronate treatment. The reason may lie in the mechanism of action of clodronate, which rather than reducing the number of TRACP 5b-secreting osteoclasts, reduces the activity of bone proteolytic enzymes and thus the rate of bone organic matrix degradation. This is seen in decreased amounts of type I collagen breakdown products (U-NTX), and through coupling of bone resorption with bone formation, in a decrease in circulating levels of the marker that reflects new collagen formation (S-PINP).

Prevention and treatment of postmenopausal osteoporosis

Osteoporosis is a systemic disease characterized by low bone mass and microarchitectural deterioration of the skeleton leading to enhanced bone fragility and an increased risk of fracture. Prior to fracture, diagnosis is established by documenting low bone mass. In the first section of this article we review the clinical use of bone mass measurements and biochemical markers of bone remodeling in selecting patients most in need of preventive therapy at menopause. Women with high bone turnover lose bone at menopause more rapidly than those with normal bone turnover and are more likely to derive benefit from the several preventive therapies available. The second section addresses the available technologies used to diagnose osteoporosis and/or establish fragility fracture risk using noninvasive bone mass measurement and biochemical markers of bone remodeling separately or in combination. In the third section we review the several treatment options available for patients with osteoporosis, including alendronate (alendronic acid), risendronate (risedronic acid), calcitonin, teriparatide, and raloxifene, and the approaches to monitoring the therapeutic response. The final section deals with fall protection--an often forgotten aspect of management of the patient at risk for sustaining and osteoporotic fragility fracture.

The role of markers of bone remodeling in multiple myeloma

Osteolytic bone disease is a frequent complication of multiple myeloma, resulting in skeletal complications that are a significant cause of morbidity and mortality. A characteristic feature of myeloma bone disease is that the lesions rarely heal and bone scans are often negative in myeloma patients who have extensive lytic lesions, offering very little in the follow-up of bone disease. X-rays are also of limited value in monitoring bone destruction during anti-myeloma or anti-resorptive treatment. Biochemical markers of bone turnover, such as N- and C-terminal cross-linking telopeptide of type I collagen (NTX, CTX/ICTP, respectively), and newer ones such as the tartrate resistant acid phosphatase isoform 5b, provide information on bone dynamics that in turn may reflect disease activity in bone. Several studies have shown bone markers to be elevated in myeloma patients and reflect the extent of bone disease, while in some of them bone resorption markers correlate with survival. These markers may also be helpful in identifying those patients likely to respond to bisphosphonate treatment, and monitoring the effectiveness of bisphosphonate therapy in the management of myeloma bone disease. This review attempts to summarize the existing data for the role of markers of bone remodeling in assessing the extent of bone destruction in myeloma and monitoring bone turnover during specific anti-myeloma treatment. We also discuss some novel markers that may be of particular interest in the near future.

Diagnostic value of bone remodeling markers in the diagnosis of bone metastases in patients with breast cancer

Metastatic spread to bone is common in patients with breast cancer and its early detection is required for the better management of these patients. Several biochemical markers of bone remodeling have been recently developed, in order to assess metastatic bone disease with non radiologic methods. The pyridinolin cross-linked amino-terminal telopeptide of type I collagen (NTx) has been measured in serum and urine as a specific marker of bone collagen breakdown, while the bone-isoform of alkaline phosphatase (BAP) has been used to determine bone formation activity. Thirty-three consecutive ambulatory patients with metastatic breast cancer and bone metastases and 31 with extraskeletal metastases only, matched for age and menopausal status, were studied. Serum levels of NTx and BAP were measured by enzyme-linked immunosorbent assays. The diagnostic accuracy of both markers was evaluated by receiver operating characteristic (ROC) analysis. Patients with bone metastases had significantly higher levels of NTx (37.0+/-36.9 nM BCE versus 23.5+/-21.0 nM BCE, P<0.05) and BAP (57.8+/-31.7 U/L versus 36.5+/-28.5 U/L, P<0.01) compared to those without bone metastases. NTx was positively correlated with BAP (R=0.340, P<0.01). The area under the ROC curve was 0.671 for NTx and 0.755 for BAP. Using a cut-off value of 29.7 nM BCE for NTx, specificity and sensitivity were 87.1% and 45.5%, respectively; in the case of BAP, using a cut-off value of 50.6 U/L, the specificity and sensitivity were 90.3% and 54.5%, respectively. In patients not receiving concomitant hormonal treatment, the area under the ROC curve was 0.724 for NTx and 0.822 for BAP; in this subgroup of patients, using a cut-off value of 30.0 nM BCE for NTx, the specificity and sensitivity were 96.2% and 47.1%, respectively, while using a cut-off value of 50.0 U/L for BAP, the corresponding percentages were 92.3% and 70.6%. Although serum NTx and BAP are quite specific, they are not sensitive enough to diagnose bone metastases in patients with advanced breast cancer. Their diagnostic accuracy, however, is considerably enhanced in patients not receiving hormonal therapy.

Detection of mature collagen in human dental enamel

Mature dental enamel is the most mineralized of all mammalian tissues and considered to be free of collagen. Hydroxylysylpyridinoline (HP) and lysylpyridinoline (LP) are two nonreducible cross-links of mature collagen. Hydroxyproline (Hyp) is an amino acid that is believed to be indicative of the presence of collagen. We set out to assess the concentrations of Hyp, HP, and LP in dental enamel and dentin (control) to clarify whether there was minor collagen content in dental enamel. We studied 17.53 g of enamel and 22.12 g of dentin gained from 120 extracted human teeth. Enamel and dentin (control) were separated with a diamond dental drill under microscopic control by wasting a margin of enamel (Ca. 2 mm) at the dentin-enamel border. Collagen alpha-chains were analyzed by Sodium dodecylsulfate-polyacrylamide gel (SDS-PAGE) after decalcification and collagen extraction. Concentrations of HP and LP where measured by using high-performance liquid chromatography (HPLC). Hyp was analyzed by a spectrophotometric method. The pooled probe of enamel contained 0.23 mug/g of Hyp. This concentration was 49 times lower than that in dentin. Concentrations of HP and LP in enamel were 0.07 nmol/g and 0.02 nmol/g, respectively being 605.57 (HP) and 251.50 (LP) times lower in enamel as compared to dentin. Collagen type I was found in enamel; collagen types I and V were found in dentin samples. In reports of many studies and textbooks, collagen is considered to be completely absorbed in the course of the mineralization and maturation of dental enamel. We show that this is not the case. However, the concentration of collagen in enamel was considerably lower as compared to that in dentin.

Comparison of 10 serum bone turnover markers in prostate carcinoma patients with bone metastatic spread: diagnostic and prognostic implications

Our aim was to assess the diagnostic accuracy of bone markers in serum of patients with prostate cancer (PCa) for early detection of bone metastases and their usefulness as predictors of PCa-caused mortality. In sera of 117 PCa patients (pN0M0, n = 39; pN1M0, n = 34; M1, n = 44), 35 healthy men and 35 patients with benign prostatic hyperplasia, bone formation markers [total and bone-specific alkaline phosphatase (tALP, bALP), amino-terminal procollagen propeptides of type I collagen (P1NP), osteocalcin (OC)], bone resorption markers [bone sialoprotein (BSP), cross-linked C-terminal (CTX) and cross-linked N-terminal (NTX) telopeptides of type I collagen, tartrate-resistant acid phosphatase isoenzyme 5b (TRAP)] and osteoclastogenesis markers [osteoprotegerin (OPG), receptor activator of nuclear factor kappaB ligand (RANKL)] were measured. tALP, bALP, BSP, P1NP, TRAP, NTX and OPG were significantly increased in PCa patients with bone metastases compared to patients without metastases. OPG showed the best discriminatory power to differentiate between these patients. Logistic regression analysis resulted in a model with OPG and TRAP as variables that predicted bone metastasis with an overall correct classification of 93%. Patients with concentrations of OPG, P1NP, tALP, bALP, BSP, NTX, TRAP and CTX above cut-off levels showed significantly shorter survival than patients with low marker concentrations. Multivariate Cox proportional hazards regression revealed that only OPG and BSP were independent prognostic factors for PCa-related death. Thus, the importance of serum OPG in detecting bone metastatic spread, alone or in combination with other bone markers, and predicting survival in PCa patients has been clearly demonstrated.

An update from the latest workshop on asymptomatic primary hyperparathyroidism

Considerable data have accumulated since 1990 concerning the natural history of asymptomatic primary hyperparathyroidism,the extent of target organ involvement, techniques for preoperative localization of parathyroid glands, and new surgical approaches for parathyroidectomy. Therefore a Workshop on Asymptomatic Primary Hyperparathyroidism: a Perspective for the Twenty-first Century was held in April 2002 with a goal of reevaluating the conclusions from the 1990 National Institutes of Health (NIH)Consensus Development Conference. This article presents the recommendations of the workshop panel and discusses the evidence leading to the changes in the recommendations of the 1990 NIH conference.

Comparative responses of bone turnover markers to bisphosphonate therapy in Paget's disease of bone

The measurement of biochemical markers of bone turnover is integral to the diagnosis and management of Paget's disease. Recently, there has been a proliferation of new markers and a move to carry out existing assays on automated platforms. We have assessed the performance of seven currently available markers in 20 patients with Paget's disease undergoing ibandronate therapy (6 or 12 mg) and in nine placebo-treated controls. Samples were collected at baseline and 6 months following intervention. The mean reductions in serum markers following treatment with either dose of ibandronate were: total alkaline phosphatase (AP; Roche Modular) 70%, bone AP (Beckman Access, Ostase) 80%, osteocalcin (Roche Elecsys 2010) 33%, beta-C-terminal telopeptide of type I collagen (betaCTX; Roche Elecsys 2010) 50%, and procollagen-N-terminal peptide (P1NP; Roche Elecsys 2010) 80%. For urine markers the reductions were: free deoxypyridinoline/creatinine (fDPD/creat) (DPC Immulite 2000) 36%, and N-telopeptide/creatinine (NTX/creat) (Osteomark) 81%. Total AP, bone AP, P1NP, and NTX all showed >95% of subjects to have abnormal values at baseline, reducing to 15-30% following treatment, and these treatment effects were highly significant (P < or = 0.0005), except for NTX (P = 0.02). The poorer precision of NTX reduced its utility. Baseline sensitivity was lower for the other markers (osteocalcin 68% of subjects abnormal, fDPD 22%, betaCTX 50%). Total AP, bone AP, and P1NP are suitable osteoblast markers for monitoring bisphosphonate therapy in Paget's disease, with performance approaching that of bone scintigraphy. NTX is less sensitive in detecting the effects of therapy, but is the best performing bone resorption marker. There is no clear evidence from this study that any of these newer markers are superior to total AP in assessing patients with this severity of Paget's disease.

Age-dependent effects of atorvastatin on biochemical bone turnover markers: a randomized controlled trial in postmenopausal women

The use of HMG-CoA-reductase inhibitors (statins) has been associated with decreased risk of bone fractures in epidemiological studies. In vitro evidence suggests that statins may stimulate bone formation, but the data are still preliminary. We assessed the effects of the HMG-CoA-reductase inhibitor atorvastatin on biochemical parameters of bone metabolism in a multicenter, randomized, double-blind, placebo-controlled trial conducted between October 2001 and October 2002 in three hospital-based outpatient metabolism clinics. Forty-nine postmenopausal women, mean age 61 +/- 5 years, mean time postmenopause 12.6 +/- 8.8 years, were treated with atorvastatin, 20 mg per day ( n=24) or matching placebos ( n=25) for 8 weeks. Comparing the differences to baseline between the groups, there were no statistically significant effects of atorvastatin either on the bone formation markers intact osteocalcin and bone-specific alkaline phosphatase or on the bone resorption markers C-telopeptide and intact parathyroid hormone. The marker of bone fractures, undercarboxylated osteocalcin, was also unchanged. When analyzed in dependence of age, atorvastatin increased C-telopeptide and osteocalcin in the younger subjects, while it decreased them in older subjects. Most interestingly, in older subjects, atorvastatin caused a significant decrease in the ratio of C-telopeptide to osteocalcin, an indicator of bone remodeling, while the ratio was increased in younger subjects, suggesting beneficial effects on bone turnover exclusively in older individuals (approx. >63 years). In summary, the present data suggest that short-term treatment with atorvastatin may have age-dependent effects on biochemical markers of bone turnover in postmenopausal women.

Follow-up of collagen crosslink excretion in patients with oral squamous cell carcinoma and analysis of tissue samples

The presence of an oral squamous cell carcinoma (OSCC) may be associated with increased urinary excretion of the markers of collagen degradation, hydroxylysylpyridinoline (HP) and lysylpyridinoline (LP). We investigated the possibility of these markers predicting the presence of active disease. Patients from a current study on HP and LP were included as follows: Group 1a (OSCC with confirmed mandibular bony infiltration, n=12), group 1b (group 1a patients >6 months after successful treatment), group 2a (OSCC without evidence of mandibular bone infiltration, n=8), group 2b (group 2a patients >6 months after successful treatment), group 3a (recurrent OSCC, n=8), group 3b (group 3a patients >6 weeks later, symptoms unchanged) and group 4 (control group, n=74). Tissue samples from tumour tissue and adjacent healthy mucosa were additionally investigated for HP and LP concentrations (n=8). The decrease in the urinary concentrations of HP and LP was statistically significant between groups 1a and 1b (P<0.001 for HP and LP), but not between groups 2a and 2b (P=0.07 for HP and LP), while values in groups 1b and 2b were within the normal range. When comparing groups 3a and 3b, a significant increase was observed for LP (P=0.050), but not HP (P=0.208). In conclusion, successful treatment of OSCC with bony involvement may be associated with a reduction of urinary HP and LP, whereas ongoing disease may result in an increase of LP. HP and LP may both be useful markers of tumour progression in patients with OSCC.

Clinical review 165: Markers of bone remodeling in metastatic bone disease

Many cancers have a strong propensity to spread to bone. The processes involved in cancer dissemination to bone are complex and variable, and the changes in bone metabolism, once bony metastases have occurred, are usually profound. This review surveys the usefulness of bone markers in the diagnosis and follow-up of patients with malignant bone disease. In patients with established bone metastases, most markers of bone remodeling are abnormal compared with healthy controls or cancer patients without bone lesions. Although bone markers may have a potential as diagnostic tools in cancer patients, the available data do not allow final conclusions regarding the accuracy and validity of any of the presently used markers in the diagnosis of bone metastases. As regards monitoring of anticancer therapy, most markers of bone remodeling respond to active treatments. These indices therefore may have the potential to be used in the monitoring of antitumor therapies. However, most if not all of the available evidence on the use of bone markers in monitoring anticancer therapy is observational, and it remains unclear whether they have any beneficial effects on overall outcome. The same is true for their prognostic value, although evidence suggests that suppressed levels of bone formation or high rates of bone resorption are independent predictors of poor survival.

Differential enhancement of collagen crosslink excretion in cases of osteosarcoma and chondrosarcoma

Hydroxylysylpyridinoline (HP) and lysylpyridinoline (LP) are markers of collagen absorption and LP is specific for collagen type I in bone. In the present study we evaluated the concentration of HP and LP in urine of patients with osteosarcoma ( n=20; age range 16-49 years) and chondrosarcoma ( n=15; age range 18-70 years). The values were compared with those obtained from 74 healthy controls (age range 16-83 years). The range and upper limit of normal values (HP(max) and LP(max)) were measured in our control group. High performance liquid chromatography (HPLC) was used to determine concentrations of HP and LP (nmol/mmol creatinine). The average urinary HP concentrations were significantly increased in patients with osteosarcoma ( p=0.001) and chondrosarcoma ( p<0.001), whereas HP remained within the normal range in approximately half of the patients. The average urinary LP concentrations were not increased in osteosarcoma and chondrosarcoma patients as compared with the control group. Further studies in a large group of patients are necessary to evaluate whether HP might be a valuable marker of prognosis, and if its urinary concentration can be correlated to tumour burden.

A new serum assay to measure N-terminal fragment of telopeptide of type I collagen in patients with renal osteodystrophy

BACKGROUND: Up until now, there was little known about the use of bone resorption markers in the assessment of bone status in patients with chronic renal failure (CRF). The present study evaluated the ability of a new immunoassay for N-terminal telopeptide of type I collagen to assess bone turnover in a group of hemodialyzed patients. METHODS: The following parameters were measured in a fasting blood sample from 111 patients on maintenance hemodialysis for at least 2 years and in 120 healthy subjects: calcium, phosphorus, magnesium, BALP, PTH, and N-terminal telopeptide of type I collagen (NTx-ELISA, OSTEOMARK NTx Siero-Ostex International). RESULTS: Serum PTH, BALP, and NTx were significantly higher (P<0.001) in hemodialyzed (HD) patients than in healthy subjects. In HD patients, PTH was correlated to BALP and NTx (r=0.40 and 0.55, respectively). When combining PTH and BALP serum levels, 17 patients showed high turnover (HT) and 65 were found to have a normal to low turnover (N-LT). In HT patients, serum NTx and dialytic age were significantly (P<0.01) higher than in N-LT patients. Moreover, even after adjusting for age, body mass index, dialytic age, and calcium-vitamin D treatment, serum NTx discriminated between HT and N-LT with a sensitivity of 97.6% and a specificity of 90.9%. CONCLUSION: Although bone biopsy remains the reference method for the diagnosis of renal osteodystrophy, the combined use of markers of bone resorption and bone formation could improve the clinical management of renal bone diseases.

Collagen crosslink excretion and staging of oral cancer

Lysylpyridinoline (LP) and hydroxylysylpyridinoline (HP) are collagen crosslink residues of which the urinary concentration reflects the level of connective-tissue turnover. HP is ubiquitous in tissue, whereas LP is specific for bone. The purpose of this investigation was to assess the sensitivity and specificity of an increased urinary concentration of both HP and LP in indicating infiltration of mandibular bone by an oral squamous cell carcinoma (OSCC) or recurrence of the disease after successful therapy. We investigated the history and urine levels in 116 adult patients, who were divided into the following groups. Group 1: patients with OSCC with bone infiltration (n=17); group 2: patients with confirmed OSCC (n=12) without evidence of bone infiltration; group 3: patients with recurrence of an OSCC (n=13); group 4: patients without clinical evidence of disease (n=74). The range and upper limit of normal values (HP(max) and LP(max)) were measured from the normal controls in group 4. Levels of LP and HP were measured by HPLC and fluorescence detection. There was a significant difference in the average urinary levels of LP and HP between groups 1-4 (P<0.001). The presence of mandibular bone infiltration could be detected with a sensitivity and specificity of 100% when comparing groups 1 and 2. Presence of tumour tissue could be detected with a sensitivity of 90%. In conclusion, a normal LP concentration in patients with an OSCC strongly suggests that bone invasion by the disease has not taken place. If both urinary HP and LP are elevated, disease recurrence is highly likely.

The renal clearance of free and peptide-bound deoxypyridinoline: response to pamidronate treatment of Paget's disease

Bisphosphonate treatment of Paget's disease results in a large decrease in urinary peptide-bound pyridinolines but a smaller decrease in urinary free pyridinolines. This discrepancy could be explained by changes in renal handling of pyridinoline forms. We studied eight patients with Paget's disease treated with pamidronate. We collected blood and urine at baseline and at 3 and 14 days after treatment. We measured free and total deoxypyridinoline (DPD) in serum (S) and urine (U) by high-performance liquid chromatography (HPLC). The ratio of free to total DPD at baseline was (mean +/- SE) 13 +/- 1% in serum and 37 +/- 3% in urine; at 3 days, this had increased to 25 +/- 3% in serum and 62 +/- 7% in urine. Peptide-bound (pb) DPD decreased significantly 3 days after treatment: UpbDPD -63 +/- 11%, p < 0.001; SpbDPD -51 +/- 8%, p < 0.01. Free DPD decreased in the urine after 14 days: UfDPD -48 +/- 5%, p < 0.01; there was no significant change in SfDPD. The fractional excretion of pbDPD relative to creatinine was less than one at all time-points; however, the fractional excretion of fDPD was significantly greater than one throughout the study. As a consequence, the proportion of free DPD in the urine increased as bone turnover decreased. This resulted in a smaller decrease in urine free compared with peptide-bound DPD in response to bisphosphonate therapy. Thus, the conversion of peptide-bound to free DPD in the kidney may become more efficient as bone turnover decreases as a consequence of pamidronate treatment.

The use of zoledronic acid, a novel, highly potent bisphosphonate, for the treatment of hypercalcemia of malignancy

BACKGROUND

Hypercalcemia of malignancy is a serious complication of cancer that affects patients with and without bone metastases. A single infusion of pamidronate disodium, a nitrogen-containing bisphosphonate, effectively normalizes serum calcium in the majority of patients treated for up to 1 month. Zoledronic acid is a new-generation, heterocyclic nitrogen-containing bisphosphonate and the most potent inhibitor of bone resorption identified to date.

METHODS

The natural history, clinical presentation, and treatment of hypercalcemia of malignancy are reviewed, with a focus on the mechanisms of action and relative efficacy and safety of bisphosphonate therapies.

RESULTS

The improved efficacy of zoledronic acid compared with pamidronate disodium has been demonstrated in a pooled analysis of two randomized clinical trials in patients with hypercalcemia of malignancy. In these trials, both zoledronic acid and pamidronate disodium were safe and well tolerated; however, zoledronic acid treatment resulted in a significantly higher number of complete responses, more rapid calcium normalization, and more durable responses compared with pamidronate disodium.

CONCLUSIONS

Given the superior efficacy and comparable safety profile of zoledronic acid compared with pamidronate disodium, zoledronic acid is likely to become the treatment of choice for hypercalcemia of malignancy.

Association between changes in plasma calcium concentration and plasma tartrate-resistant acid phosphatase activity in periparturient cows

Eight periparturient Holstein Friesian cows were examined for plasma tartrate-resistant acid phosphatase (TRAP) activity to assess the degree of bone metabolic activity and to evaluate the association between the change in calcium (Ca) concentration and bone metabolism during the periparturient period. Milk fever occurred in 1 of 8 cows just after parturition. Plasma TRAP activities did not markedly change in 5 of 8 cows during the experimental period. The changing rate of Ca between preparturition and just after parturition was under -20% in 3 of 8 cows, and low TRAP activities were observed in 2 of these 3 cows. This study suggests that cows with a low TRAP activity are at risk of developing milk fever in comparison to cows with high TRAP activity. Temporary increases of parathyroid hormone were observed in 7 cows, but not in the cow with milk fever.

Skeletal aspects of Gaucher disease: a review

In Gaucher disease, a genetic deficiency in the activity of the lysosomal enzyme beta-glucocerebrosidase (acid beta-glucosidase) causes monocytes and macrophages to store excessive amounts of glucocerebroside in lysosomes. The resulting distended cells are called Gaucher cells, and the pathology associated with this condition stems from the accumulation of Gaucher cells in organ systems. The skeletal manifestations are probably the most disabling aspect of the disease. Patients commonly experience bone pain, some suffer bone crises, and up to 20% have impaired mobility. Radiological findings include Erlenmeyer flask deformity, osteopenia, osteosclerosis, osteonecrosis, fractures and bone marrow infiltration. Findings from the Gaucher Registry show that nearly all patients with Gaucher disease have radiological evidence of skeletal involvement, and the majority have a history of serious skeletal complications. Skeletal involvement follows three basic processes: focal disease (irreversible lesions such as osteonecrosis and osteosclerosis), local disease (reversible abnormalities adjacent to heavily involved marrow such as cortical thinning and long bone deformity) and generalized osteopenia. Infarctions are involved in some of the skeletal manifestations, but the mechanisms causing high rates of bone turnover and failure of remodelling are not known. The availability of a beta-glucocerebrosidase-deficient mouse model of Gaucher disease with long-term survival should help elucidate the skeletal pathology in Gaucher disease and may ultimately lead to improved management of skeletal complications.

Instability and variability of urinary telopeptides and free crosslinks

BACKGROUND

The use of the urinary bone degradation markers, NTx and free Dpd, in the diagnosis and monitoring of pathological bone resorption has been studied intensely. Urinary NTx and Dpd are normalized by creatinine to account for differences in diuresis.

METHODS

We investigated the effects of storage (-20 degrees C for 119 days) on concentrations of NTx, Dpd and creatinine in the urine of 40 subjects. Precipitates (visible upon thawing) were resuspended, but specimens were not recentrifuged (in contrast to previous experiments).

RESULTS

After storage at -20 degrees C, the NTx and creatinine concentrations in urine specimens were significantly decreased by about 18% and 22% (p < 0.01 and p < 0.0001), respectively. Thus, the quotient of NTx/creatinine was slightly increased after storage (p < 0.05). Free Dpd and free Dpd/creatinine were both significantly increased after storage (p < 0.0001)--by about 20% and 60%, respectively.

CONCLUSIONS

We suggest that storage at -20 degrees C frees Dpd and denatures the epitope used in NTx quantification, and that these changes are usually masked by the removal of free Dpd via recentrifugation and by the decrease in creatinine in NTx/creatinine. Additionally, we suggest that the quotient Dpd/NTx should be evaluated as an alternative to normalizing via creatinine excretion.

Measurement of serum beta-crosslaps is influenced by proteolytic conditions

Serum beta-crosslaps are an established laboratory test to investigate bone metabolism. However, lytic conditions may affect the measurement of serum beta-crosslaps. Therefore, we investigated the effect of cathepsin C and human leukocyte lysate on serum beta-crosslaps in relation to temperature and time. We divided eight serum samples with elevated beta-crosslaps levels into three aliquots and stored them at 4, 21 and 37 degrees C. Another five serum samples were divided into three aliquots and adjusted to contain different cathepsin C concentrations (50, 250, 500 IU/l). These aliquots were divided again and stored at 4, 21 and 37 degrees C. Finally, three aliquots from three additional serum samples were treated with human leukocyte lysate (100, 300, 500 microl), divided again and stored at 4, 21 and 37 degrees C. Measurements of serum beta-crosslaps were then carried out before and immediately after manipulation, and after 2 and 5 days of storage. When stored at 21 degrees C, serum beta-crosslaps diminished significantly (25% after 5 days), but no significant change was detectable when they were stored at 4 degrees C. Cathepsin C induced up to a 14% increase in beta-crosslaps while human leukocyte lysate caused up to a 17% decrease. This study demonstrates that the influence of proteolytic conditions on the serum concentration of beta-crosslaps is not uniform. Leukocyte lysate decreased serum beta-crosslaps while the addition of cathepsin C increased their concentration. Therefore, serum should be separated from the whole blood immediately after coagulation and stored until analysis in a deep freezer.

The management of primary hyperparathyroidism

Recent improvements in parathyroid imaging have led to renewed interest in the criteria for, and the surgical approach to, parathyroidectomy. It therefore seemed appropriate to review current evidence relating to the evaluation and management of primary hyperparathyroidism for those working within a general endocrine service. The recommendations are based on an electronic search spanning the past decade using the search terms hyperparathyroidism, management and parathyroidectomy/surgery, but we have also included key publications outside this period. The findings have been graded systematically (Appendix), according to the quality of the information available, to indicate the level of evidence on which they are based.

The clinical use of bone resorption markers in patients with malignant bone disease

BACKGROUND

Advanced tumors often metastasize to bone, resulting in a variety of skeletal complications. Bisphosphonates are potent inhibitors of osteoclast-mediated bone resorption that reduce the incidence and delay the onset of skeletal complications and reduce the need for radiation and surgery. Biochemical markers of bone resorption have been identified that can augment the imaging techniques used to diagnose bone metastases and assess response to bisphosphonate therapy.

METHODS

In the current study, the available literature regarding bone resorption markers is reviewed and the clinical relevance of these data with respect to the treatment of bone metastases discussed.

RESULTS

Urinary calcium and hydroxyproline have been widely used to assess bone metabolism, but do not appear to be well correlated with clinical outcome in patients with bone metastases. Several unique breakdown products of Type I collagen (including pyridinium crosslinks, pyridinoline, and deoxypyridinoline) and peptide-bound crosslinks (N-telopeptide and C-telopeptide) are more specific and sensitive markers of bone resorption. N-telopeptide and C-telopeptide have been identified as the most sensitive biochemical markers currently available for detecting bone metastases and for assessing response to therapy or disease progression.

CONCLUSIONS

To the author's knowledge markers of bone resorption have not yet been recommended for routine clinical use. However, further research is needed to define their potential role in the diagnosis of bone metastases, the assessment of disease progression and response to bisphosphonate therapy, and predict the rate of bone loss and the potential for fracture. Suppression of bone resorption markers in response to bisphosphonate therapy appears to correlate with clinical outcome in patients with both osteolytic and blastic bone lesions; therefore, the goal of bisphosphonate therapy should be to suppress markers of bone resorption.

Bone turnover following autologous transplantation in multiple myeloma

Most patients with multiple myeloma have lytic lesions at multiple sites in the axial skeleton. These lesions commonly give pain and are at risk of pathological fracture, and bony disease is therefore a cause of much morbidity in myeloma. Recent data indicates that the Receptor Activator of NF-kappaB ligand (RANKL) and Osteoprotegerin (OPG) may be central to the local pathogenesis of these lytic lesions. Bisphosphonates may ameliorate some of these abnormalities, and clinically these agents improve the skeletal prognosis in myeloma patients. High dose chemotherapy with autologous stem cell rescue is currently under evaluation in the management of myeloma, though little is known of the effect of this therapeutic modality on the skeleton. Studies using biochemical markers of bone turnover suggest that increased osteoclast activity may be present even in apparent plateau phase of myeloma. High dose chemotherapy with autografting may normalise abnormal bone resorption, though the effect may take several weeks to emerge, and may be paralleled by increased osteoblast activity. The findings provide biochemical evidence that autografting may help normalise the abnormal bone turnover characteristic of myeloma.

Assessment and Recommendations on Factors Contributing to Preanalytical Variability of Urinary Pyridinoline and Deoxypyridinoline

Background: Pyridinoline (PYD) and deoxypyridinoline (DPD) are two of the most extensively characterized biochemical bone markers, but the interpretation of results is hampered by biologic and other preanalytical variability. We reviewed factors contributing to preanalytical variation of pyridinium cross-links in urine.

Methods: We searched four databases for English-language reports on PYD and/or DPD in urine. Searches were restricted to humans, except for studies of stability, when the search was expanded to other species. The 599 identified articles were supplemented with references from those articles and with articles known to the authors.

Results: The mean reported within-day variability was 71% for PYD (range, 57–78%) and 67% for DPD (range, 53–75%). The mean interday variability was 16% for both DPD and PYD (range for PYD, 12–21%; range for DPD, 5–24%). The mean intersubject variabilities across studies were 26% for PYD (range, 12–63%) and 34% for DPD (range, 8–98%) for healthy premenopausal women and 36% (range, 22–61%) and 40%, (range, 27–54%) for postmenopausal women, respectively. Specimen instability and errors in creatinine measurements were additional sources of variability.

Conclusions: Intra- and intersubject variability can be reduced by collecting specimens at a specific time of the day and by maintaining similar patient status at each specimen collection regarding factors such as medications and dietary supplements.

Critical differences in the serial measurement of three biochemical markers of bone turnover in the sera of pre- and postmenopausal women

OBJECTIVES

The purpose of this investigation was to quantify the biologic, day-to-day variability and critical differences in serum levels of crosslinked collagen N-telopeptides (NTx), procollagen aminoterminal extension propeptides (PINP) and bone specific alkaline phosphatase (bAP) in healthy women.

DESIGN AND METHODS

Seven blood samples were collected from 12 pre- and 15 postmenopausal women over 4 to 6 months. NTx, PINP and bAP levels were determined utilizing enzyme- and radioimmunoassay techniques.

RESULTS

The within-subject coefficient of variation (C.V.) in serum bAP, NTx and PINP levels was 7.1, 10.6 and 12.4% respectively. These variances did not differ significantly among premenopausal women when compared with postmenopausal subjects. Combining terms for analytical and biologic variability revealed that a critical difference between 2 successive serial measurements is 24% for bAP, 34% for NTx and 38% for PINP.

CONCLUSION

Circulating levels of NTx, PINP and bAP are stable over time periods of several months, allowing for the determination of significant changes in skeletal metabolism of women.

Biomarkers in disease and health

Biomarkers have considerable potential in aiding the understanding of the relationship between diet and disease or health. However, to assess the role, relevance and importance of biomarkers on a case by case basis it is essential to understand and prioritise the principal diet and health issues. In the majority of cases, dietary compounds are only weakly biologically active in the short term, have multiple targets and can be both beneficial and deleterious. This poses particular problems in determining the net effect of types of foods on health. In principle, a biomarker should be able to contribute to this debate by allowing the measurement of exposure and by acting as an indicator either of a deleterious or of an enhanced health effect prior to the final outcome. In this review, the examples chosen - cancer (stomach, colon/rectal, breast); coronary heart disease and osteoporosis - reflect three major diet-related disease issues. In each case the onset of the disease has a genetic determinant which may be exacerbated or delayed by diet. Perhaps the most important factor is that in each case the disease, once manifest, is difficult to influence in a positive way by diet alone. This then suggests that the emphasis for biomarker studies should focus on predictive biomarkers which can be used to help in the development of dietary strategies which will minimise the risk and be of greater benefit.

Bone turnover markers and sex hormones in men with idiopathic osteoporosis

BACKGROUND

In contrast to osteoporosis in postmenopausal women, osteoporosis in men has received much less attention.

PATIENTS AND METHODS

We determined various biochemical parameters of bone metabolism and sex hormones in 31 men with idiopathic osteoporosis and 35 age matched control subjects.

RESULTS

In the men with osteoporosis, a significantly increased urinary excretion of deoxypyridinoline (5.3 +/- 0.2 vs. 4.6 +/- 0.2 nmol mmol-1 creatinine; P = 0.033) in addition to increased serum levels of the c-terminal telopeptide of type I collagen (2677 +/- 230 vs. 2058 +/- 153 pmol; P = 0.037) were found. While parameters of bone formation were not significantly different in the patients and controls, serum bone sialoprotein levels were significantly decreased in the patients (3.7 +/- 0.8 vs. 12.4 +/- 4.0 ng mL-1; P = 0.021). Moreover, in men with idiopathic osteoporosis, lower levels of estradiol (91.3 +/- 5.8 vs. 114.6 +/- 7.8 pmol L-1; P = 0.044), higher levels of sex hormone binding globulin (31.5 +/- 3.1 vs. 24.2 +/- 1.4 nmol L-1; P = 0.034) and a decreased free androgen index (42.6 +/- 5.2 vs. 56.4 +/- 5.9; P = 0.016) were seen. Serum estradiol levels correlated negatively with several parameters of bone resorption.

CONCLUSIONS

In men with idiopathic osteoporosis, bone resorption is increased and exceeds bone formation. The excessive bone resorption seen in idiopathic male osteoporosis may be due to decreased estradiol levels and low levels of bioavailable testosterone.

Biochemical Markers of Bone Formation in Patients with Plasma Cell Dyscrasias and Benign Osteoporosis

Background: Myeloma-induced bone loss is related to an uncoupling of bone formation and bone resorption. The aim of the present study was to assess the potential clinical value of biochemical markers of bone formation in the work up of patients with plasma cell dyscrasias.

Methods: Serum total alkaline phosphatase, bone-specific alkaline phosphatase (BAP), and osteocalcin (OC) were measured in 43 patients with newly diagnosed multiple myeloma (MM), in 40 patients with monoclonal gammopathy of undetermined significance (MGUS), in 40 patients with untreated benign vertebral osteoporosis (OPO), and in 48 healthy adults.

Results: In MM and MGUS patients, serum BAP, but not serum OC, was lower than in healthy controls (P &lt;0.05). Serum OC was higher in patients with OPO than in healthy controls (P &lt;0.05). The strongest associations between markers were found in OPO patients and in healthy adults. MM patients with early-stage disease or without detectable osteolysis had decreased serum BAP values (P &lt;0.05). Serum OC was higher in MM patients with stage III disease (P &lt;0.05) than in healthy controls. MM patients with OPO-like bone involvement had lower BAP values than sex- and age-matched MGUS patients with OPO-like bone involvement and patients with benign OPO (P &lt;0.05).

Conclusions: In patients with plasma cell dyscrasias, serum BAP, rather than serum OC, appears to reflect a suppressed bone formation rate and may be helpful in the differentiation between benign and myeloma-induced OPO. However, the overall clinical use of biochemical markers of bone formation in patients with plasma cell dyscrasia appears limited.

Suppressive levothyroxine therapy has no significant influence on bone degradation in women with thyroid carcinoma: a comparison with other disorders affecting bone metabolism

The aim of this study was to examine different influences on bone degradation (estrogen status, thyroid function, parathyroid function, bone metastases) with special interest focusing on the significance of suppressive levothyroxine therapy (LT4) on bone degradation in patients with differentiated thyroid carcinoma (DTC). Two markers of bone degradation (ELItest NTx = U-NTx; Serum CrossLaps = S-CTx) were used (1) to quantify the influence of different metabolic influences on bone degradation and (2) to compare these two markers with each other. One hundred forty samples of 98 female patients ages 23-86 years were analyzed. The correlation between the two assays of bone degradation was high (r = 0.825; p < 0.001). Both assays demonstrated that estrogen deficiency, hyperparathyroidism, and bone metastases caused significant increases of bone degradation. A suppressive LT4 therapy, as used for patients with DTC, led to no significant increases of S-CTx and U-NTx. The study indicates that a well-controlled suppressive LT4 therapy has only a minor effect on the degree of bone degradation and that a possible estrogen deficiency in patients with DTC has a greater impact on bone degradation. Thus, female patients with DTC on suppressive LT4 therapy and estrogen deficiency may benefit from hormone replacement therapy, as patients with DTC and normal estrogen levels presented similar results to euthyroid controls.

Biochemical markers to survey bone turnover

Molecular markers of bone turnover have gained increasing relevance in the evaluation of patients with metabolic bone diseases. Their clinical applications include the assessment of future osteoporotic fracture risk, complementation of bone density measurements, diagnosis of certain metabolic osteopathies, therapeutic decision making, and monitoring of therapeutic efficacy and patient compliance. One should be aware, however, that the results from large epidemiologic or clinical trials are sometimes difficult to translate into the everyday clinical situation. The individual patient often has more than one disease that might affect either bone turnover or the handling of the parameters mentioned (or both). Analytic and biologic variability of bone markers can be significant and also needs to be considered when using these indices. In the scientific setting, conventional and new markers of bone turnover can help to elucidate formerly unknown mechanisms and pathways. Because the development of ever more specific and sensitive markers of bone metabolism is progressing rapidly, we are likely to witness new insights into the pathophysiology of bone diseases in the near future.