The performance and utility of biochemical markers of bone turnover: do we know enough to use them in clinical practice?

Impact of Intestinal Urinary Diversion on the Risk of Fracture and Loss of Bone Mass: A Systematic Review

BACKGROUND

Patients undergoing intestinal urinary diversion (IUD) may have a higher risk of osteoporosis and risk of fractures due to metabolic acidosis and decrease of intestinal absorption surface.

OBJECTIVE

We performed a systematic review of the available literature on the impact of IUD on bone demineralization.

METHODS

We systematically searched PubMed®, for original articles published before April 2020. Primary end points were the risk of fracture and loss of bone density. Secondary outcomes were the metabolic changes in biochemical and urine parameters related to calcium metabolism and histological changes.

RESULTS

Our electronic search identified a total of 2417 articles. After a detailed review, we selected 11 studies that addressed the impact of IUD on bone health in 10369 patients. The risk of bone fracture was studied in 3 articles, showing a higher risk in the IUD population. Of the 9 articles evaluating the relation between intestinal urinary diversion and bone density, 5 did find a positive association. One article evaluated the bone metabolism at a cellular level after IUD showing a decrease in bone turnover in this population. Three of the eight studies reporting data on serum parameters related to calcium and phosphate metabolism showed differences. Finally, a correlation between concentration of pyridolines in urine and loss of bone density was found in two of the three studies.

CONCLUSIONS

Although published data on BMD are contradictory, patients undergoing IUD seem to be at higher risk of bone fractures. Our finding support the need to implement accessible strategies on osteoporosis screening and prevention in IUD patients.

Non-reproductive Effects of Anovulation: Bone Metabolism in the Luteal Phase of Premenopausal Women Differs between Ovulatory and Anovulatory Cycles

Introduction: Several authors have linked subclinical ovulatory disturbances in normal length menstrual cycles to premenopausal fracture risk and bone changes. This study systematically examined the influence of ovulation and anovulation on the bone metabolism of premenopausal women. Participants and Methods: In 176 cycles in healthy premenopausal women, FSH, 17β-estradiol (E2) and progesterone (P4) as well as bone alkalic phosphatase (BAP), pyridinoline (PYD) and C-terminal crosslinks (CTX) were measured during the follicular and during the luteal phase. The probability and timing of ovulation was self-assessed by a monitoring device. In addition, bone density of the lumbar spine was measured by quantitative computed tomography (QCT) at baseline and at the end of the study. Analysis was restricted to blood samples taken more than three days before the following menstruation. Results: 118 cycles out of the 176 collected cycles were complete with blood samples taken within the correct time interval. Of these, 56.8 % were ovulatory by two criteria (ovulation symbol shown on the monitor display and LP progesterone > 6 ng/ml), 33.1 % were possibly ovulatory by one criterion (ovulation symbol shown on the monitor display or LP progesterone > 6 ng/ml), and 10.2 % were anovulatory by both criteria). Ovulation in the previous cycle and in the same cycle did not significantly influence the mean absolute concentrations of the bone markers. However, bone formation (BAP) was higher in the luteal phase of ovulatory cycles than in anovulatory cycles (n. s.) and the relative changes within one cycle were significantly different for bone resorption (CTX) during ovulatory vs. anovulatory cycles (p < 0.01). In 68 pairs of cycles following each other directly, both ovulation in the previous cycle and ovulation in the present cycle influenced CTX, but not the differences of other bone markers. Conclusion: Ovulatory cycles reduce bone resorption in their luteal phase and that of the following cycle. The interaction between ovulation and bone metabolism is complex. Since anovulation may occur in low estrogen states such as pre-anorexic dietary restraint, as well as with high estrogenic circumstances e.g. from functional perimenopausal ovarian cysts, the association with bone changes has been variable in the literature. Accumulating physiological and clinical evidence however point towards a role for ovulation in enhancing bone formation and limiting bone resorption.

Effect of gender, season, and vitamin D status on bone biochemical markers in Saudi diabetes patients

Biochemical bone turnover markers (BTMs) provide important information on the diagnosis, therapy and monitoring of metabolic bone diseases. They are evident before measurable changes in bone mineral density (BMD) take place. A total of 35 adult Saudi patients (23 males; 12 females) with type 2 diabetes and diagnosed to be vitamin D deficient were recruited in this prospective study. Here we investigated the effects of gender, season, and vitamin D status on bone biochemical markers of bone remodeling. Anthropometry and blood samples were collected at different intervals. Metabolic parameters and bone biomarkers were measured routinely and by ELISA. Both males and females had a significant increase in their vitamin D status over time, but no significant changes in the bone biomarkers were observed in females. In males there was a significant increase in circulating levels of corrected calcium and OPN (p = 0.004 and 0.01 respectively) and a significant decrease in crosslaps (p = 0.005). In all subjects there was a modest but significant positive relationship between vitamin D status and OC (R = 0.34; p = 0.04). In conclusion, our study demonstrates that changes in bone remodeling markers are affected by season, gender, and possibly vitamin D status. This gender difference may well reflect the physiologic pathway responsible for the higher peak bone mass achieved in males compared to females.

Prolyl-hydroxyproline dipeptide in non-hydrolyzed morning urine and its value in postmenopausal osteoporosis

BACKGROUND

Owing to the high correlation between the level of prolyl-4-hydroxyproline dipeptide in non-hydrolyzed urine and that of 4-hydroxyproline in hydrolyzed urine, we examined whether the dipeptide might function as a valuable marker of bone turnover.

METHODS

Based on densitometric measurements, 68 postmenopausal women were divided into groups of non-osteopathic, osteopenic and osteoporotic subjects. The dipeptide and current urinary resorption markers were assayed in morning urine, the former using liquid chromatography, the others plus serum formation markers by means of immunoassay procedures. Together with the assay of basal levels, diet-related changes and healing effect of yearly alendronate therapy were assessed.

RESULTS

Concentration levels in controls and osteoporotic subjects differed significantly; receiver operating characteristics yielded sensitivity of 0.743, specificity of 0.908, area under curve of 0.903, and cut-off of 10.2 micromol/mmol of creatinine. Spearman rank correlation showed the highest pair coefficient between the dipeptide and osteocalcin. Diet-related changes were not found. Following therapy, a significant decline occurred already within a trimester, whilst with the other resorption markers not until 6 months.

CONCLUSIONS

The ease of the dipeptide assay in non-hydrolyzed urine surpasses that of hydroxyproline, and the results present the compound as a real competition to other commonly assessed markers in osteopathies.

[Biochemical bone resorption markers during the healing of osteoporotic fractures]

BACKGROUND

This study investigated the progression and clinical relevance of biochemical resorption marker values during fracture healing in osteoporosis.

PATIENTS AND METHODS

In 44 patients with distal radius fractures and 29 patients without fractures, the blood and urine concentrations of pyridinoline (PYD), deoxypyridinoline (DPD), N-telopeptides (NTx), and bone sialoprotein (BSP) were recorded on the day of trauma as well as during further progression. All postmenopausal patients underwent bone density measurement. Accordingly, patients were divided into premenopausal, postmenopausal osteoporotic, and postmenopausal nonosteoporotic groups.

RESULTS

Between the groups, PYD, DPD, and NTx showed significant differences in their initial values. However, their further relative progression was primarily affected by the chosen therapy.

CONCLUSION

Bone resorption markers can diagnostically point to osteoporosis and are significant parameters in fracture healing.

Alendronate prevents femoral periprosthetic bone loss following total hip arthroplasty: prospective randomized double-blind study

Following total hip arthroplasty (THA), femoral periprosthetic bone undergoes a remodeling process that results in bone loss in its proximal regions that may compromise the long-term outcome of THA. Periprosthetic bone loss mainly occurs during the first postoperative months. The question is whether a postoperative treatment with alendronate is effective in reducing periprosthetic bone loss and which doses and duration of treatment are required. In a 12-month prospective, randomized double-blind study, 51 patients undergoing cementless THA were treated postoperatively either with a daily dose of 20 mg alendronate for 2 months and 10 mg for 2 months thereafter (group I), with 20 mg of alendronate for 2 months and 10 mg for 4 months thereafter (group II), or treated with placebo (group III). Proximal femoral bone mineral density (BMD) was measured with dual-energy X-ray absorptiometry (DEXA) and serum biochemical markers of bone turnover bone specific alkaline phosphatase, osteocalcin, and C-terminal telopeptides (CTX-I) were assayed. Six months of alendronate treatment significantly reduced (p<0.001) bone loss in proximal medial region (-10%) compared with placebo (-26%). All biochemical markers of bone turnover were suppressed by alendronate. These data suggest that alendronate administered for the first 6 postoperative months following THA was effective in preventing early periprosthetic bone loss.

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.

Das gemeinsame Auftreten von Osteoporose und Arthrose und der Nutzen der Knochenstoffwechselmarker

OBJECTIVE

Increasing bone mineral density (BMD) has been found in several studies in patients with osteoarthritis. Therefore, many clinicians deny the simultaneous occurrence of osteoporosis (OP) and osteoarthritis (OA). Because of our clinical impression however, we suggested that we have to consider a common occurrence. Furthermore, the value of markers of bone turn over with a view to early diagnosis of OP and or as an assessment for bone metabolism in OA is still a matter debate and their clinical use has not been clearly defined in the management of the individual patient.

METHOD

The BMD of the lumbar spine and the proximal femur of 119 OA patients (83 postmenopausal female patients aged 50-83 and 35 male patients aged 36-86 years) who subsequently required hip or knee replacements, but were otherwise healthy, were measured by dual energy X-ray absorption (DXA), Hologic QDR-2000. We also measured biochemical markers of bone turn over, i. e., CICP, ICTP, DPD, PTH, estrogen, testosterone, bAP, hydroxy vitamin D and the normal blood count.

RESULTS

There was a high occurrence of a low BMD among the patients. A total of 28.9% of women were affected by OP and 52.9% by osteopoenie. This reflects the normal distribution of OP in the female population. Of the male patients 20% had OP and 38.8% osteopoenie. This is astonishing high. Age proved to be a significant factor in the degree of BMD. An association between disuse osteoporosis and degree of BMD in the OA affected joint could not be proven. The use of the biochemical markers for an earlier diagnosis or to assess bone metabolism in OP and OA was not possible.

CONCLUSION

We can not support the hypotheses that OA prevents OP. Moreover, the occurrence of OP in our study reflected the incidence of OP in the average female and the astonishingly high incidence in the male population; however does not mean that the two conditions are mutually exclusive. We did not find that the biochemical markers of bone turn over could deliver additional information with respect to bone metabolism and an earlier diagnosis of OP.

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).

Osseous complications of pediatric transplantation

Adult stature and peak bone mass are achieved through childhood growth and development. Multiple factors impair this process in children undergoing solid organ transplantation, including chronic illness, pretransplant osteodystrophy, use of medications with negative impact on bone, and post-transplant renal dysfunction. While growth delay and short stature remain common, the most severe forms of transplant-related bone disease, fracture and avascular necrosis, appear to have become less common in the pediatric age group. Osteopenia is very prevalent in adult transplant recipients and probably also in pediatrics, but its occurrence and sequelae are difficult to study in these groups due to methodological shortfalls of planar densitometry related to short stature and altered patterns of growth and development. Although the effect on lifetime peak bone mass is not clear, data from adult populations suggest an elevated long-term risk of bone disease in children receiving transplants. Optimal management of pretransplantation osteodystrophy, attention to post-transplant renal insufficiency among both renal and non-renal transplant patients, reduction of steroid dose in select patients, and supplementation with calcium plus vitamin D during expected periods of maximal bone loss may improve bone health. Careful research is required to determine the role of bisphosphonate therapy in pediatric transplantation.

Bone mineral density and markers of bone turnover in patients with glycogen storage disease types I, III and IX

Patients with glycogen storage disease (GSD) types I, III and IX show reduced bone mineral content, but there is scarce data on new serum and urine markers of bone turnover or their relationship to bone densitometry. Six GSD I, four GSD III and four GSD IX patients underwent bone mineral density (BMD) measurement by dual-energy X-ray absorptiometry. Free pyridinoline (fPYD):creatinine and free deoxypyridinoline (fDPD):creatinine ratios were analysed on random urines. Procollagen type I C-terminal propeptide, procollagen type I N-terminal propeptide (PINP), carboxyterminal telopeptide of type I collagen and bone-specific alkaline phosphatase were analysed in serum. Some GSD I and GSD III patients had low or very low BMD. There was no difference in total body BMD z-score between the GSD types after adjusting for height (p=0.110). Bone marker analysis showed no consistent pattern. Urine fPYD:creatinine ratio was raised in four GSD I and two GSD III patients, while serum PINP was inappropriately low in some of these patients. There was no clear correlation between any markers of bone destruction and total body z-score, but the patient with the lowest total body z-score showed the highest concentrations of both urinary fPYD:creatinine and fDPD:creatinine ratios. We conclude that some GSD I and GSD III patients have very low bone mineral density. There is no correlation between mineral density and bone markers in GSD patients. The inappropriately low concentration of PINP in association with the raised urinary fPYD:creatinine and fDPD:creatinine ratios seen in two GSD I patients reflect uncoupling of bone turnover. All these findings taken together suggest that some GSD I and GSD III patients may be at an increased risk of osteoporosis.

Bone remodeling markers: assessment of fracture risk and fracture risk reduction

There is an increasing repertoire of laboratory tests available for assessing the bone remodeling process. Biochemical markers of bone remodeling can be measured in serum or urine, and have a number of potential roles in the management of fracture risk. Differences in remodeling between individuals might be related to fracture risk and could be used to target therapy. Change in remodeling with therapy could be related to fracture risk reduction and the choice of therapy could be influenced by knowledge of bone remodeling. Biochemical therapeutic monitoring may improve patient understanding and therapeutic adherence. The rate of bone remodeling is weakly predictive of fracture risk in individuals who are not receiving therapy; however, it is not clear whether this is independent of other risk factors. There is increasing evidence that change in bone mineral density does not explain fracture risk reduction with antiresorptive therapies, and that therapeutic benefit might be explained by change in bone turnover. Additional studies and information are required to allow these scientific advances to be translated into cost-effective and validated clinical protocols. Optimizing the precision and accuracy of bone turnover assessment remains an important priority.

Vitamin C and bone markers: investigations in a Gambian population

Vitamin C is an essential micronutrient. Absence from the diet will result in the deficiency disease scurvy, typically characterised by weakening of collagenous structures. High intakes of vitamin C have been associated with decreased incidence or severity of a number of diseases, including cancer and cardiovascular disease. These beneficial effects may be attributed to its antioxidant properties, although the exact mechanisms of action remain elusive. It is also unclear what intake levels are required for optimal health benefits. The task of defining optimal intakes is hindered by the lack of a reliable functional marker of tissue vitamin C status in man. Many different pathways have been investigated, but none of them have measurable outcome variables relating directly to scorbutic changes. The bone-collagen formation pathway has the potential to provide a functional index of tissue vitamin C adequacy. Vitamin C acts as a cofactor for the enzyme lysyl hydroxylase, which is required for the hydroxylation of lysine residues in procollagen chains. Pyridinoline is a mature collagen cross-link formed from three hydroxylysine residues, deoxypyridinoline is formed from two hydroxylysine and one lysine residue. Guinea-pig studies have shown an alteration in the pyridinium cross-link ratios in response to graded vitamin C intakes (Tsuchiya & Bates, 1998). In order to investigate whether these changes can be seen in a human population group, a study was carried out in rural Gambia, where there is a marked seasonal variation in dietary vitamin C. The present review discusses the rationale behind the study and presents some preliminary results.

Bone metabolism and risk of secondary hyperparathyroidism 12 months after gastric banding in obese pre-menopausal women

OBJECTIVE

To evaluate, during the first postoperative year in obese pre-menopausal women, the effects of laparoscopic gastric banding on calcium and vitamin D metabolism, the potential modifications of bone mineral content and bone mineral density, and the risk of development of secondary hyperparathyroidism.

SUBJECTS

Thirty-one obese pre-menopausal women aged between 25 and 52 y with a mean body mass index (BMI) of 43.6 kg/m(2), scheduled for gastric banding were included. Patients with renal, hepatic, metabolic and bone disease were excluded.

METHODS

Body composition and bone mineral density (BMD) were measured at baseline, 6 and 12 months after gastric banding using dual-energy X-ray absorptiometry. Serum calcium, phosphate, alkaline phosphatase, aspartate aminotransferase, alanine aminotransferase, gamma-glutamyltransferase, bilirubin, urea, creatinine, uric acid, proteins, parathormone, vitamin D(3), IGF-1, IGF-BP3 and telopeptide, as well as urinary telopeptide, were measured at baseline and 1, 3, 6, 9 and 12 months after surgery.

RESULTS

After 1 y vitamin D3 remained stable and PTH decreased by 12%, but the difference was not significant. Serum telopeptide C increased significantly by 100% (P<0.001). There was an initial drop of the IGF-BP3 during the first 6 months (P<0.05), but the reduction was no longer significant after 1 y. The BMD of cortical bone (femoral neck) decreased significantly and showed a trend of a positive correlation with the increase of telopeptides (P<0.06). The BMD of trabecular bone, at the lumbar spine, increased proportionally to the reduction of hip circumference and of body fat.

CONCLUSION

There is no evidence of secondary hyperparathyroidism 1 y after gastric banding. Nevertheless biochemical bone markers show a negative remodelling balance, characterized by an increase of bone resorption. The serum telopeptide seems to be a reliable parameter, not affected by weight loss, to follow up bone turnover after gastroplasty.

Novel and traditional biomarkers of bone turnover in postmenopausal women

Urinary markers of bone collagen degradation such as N-terminal telopeptide, deoxypyridinoline, hydroxyproline and proline-hydroxyproline dipeptide as a novel marker were measured in both morning and daily urine samples collected from 40 postmenopausal women on 10 consecutive days. In addition, osteocalcin, bone alkaline phosphatase and procollagen C-terminal propeptide were analyzed in one serum sample from each of the women. DXA densitometry was employed to differentiate between osteopenic and osteoporotic women. Spearman rank correlation, factor analysis and receiver-operating characteristics were computed to evaluate the results. The highest correlation with a single common factor was found between telopeptide assayed in daily urine, followed by the dipeptide and hydroxyproline assayed in morning urine. These markers also showed high sensitivity for the diagnosis of osteoporosis, while osteocalcin had a high sensitivity for the diagnosis of bone disease. The concentrations of telopeptide, dipeptide and osteocalcin differed significantly between the osteopenic and osteoporotic subjects. Because of the ease of non-hydrolyzed urine processing, the speed of chromatographic analysis and the negligible costs, the dipeptide assay opens new possibilities in the field.

Marcadores Bioquímicos da Remodelação Óssea na Prática Clínica

Em situações fisiológicas os processos de reabsorção e formação ósseas são fenômenos acoplados e dependentes. O predomínio de um sobre o outro resulta em ganho ou perda de massa óssea. É esta capacidade de avaliação dinâmica que se deseja em um marcador de remodelação óssea. A osteocalcina sérica intacta e fosfatase alcalina óssea melhor representam o processo de formação óssea enquanto as piridinolinas e fragmentos telopeptídeos carboxi e amino-terminais do colágeno tipo I melhor refletem a reabsorção óssea. Na avaliação da resposta ao tratamento, marcadores de reabsorção têm grande sensibilidade e especificidade, sendo que a queda de seus valores após tratamento com anti-reabsortivos correlaciona-se com o ganho de massa óssea obtido. Os marcadores de remodelação, apesar de terem trazido grandes avanços no entendimento das doenças ósseas, ainda necessitam de melhor sensibilidade e especificidade para que sua larga utilização na clínica diária seja estimulada. Entretanto, podem auxiliar no diagnóstico e decisão terapêutica em casos difíceis e no acompanhamento do tratamento.

Changes of biochemical bone markers during the menopausal transition

We present data on the changes of the bone formation markers osteocalcin (OC), bone-specific alkaline phosphatase (bone ALP) and bone sialoprotein (BSP), as well as the resorption markers pyridinoline (PYD), deoxypyridinoline (DPD), C- and N-terminal telopeptide cross-linked collagen type I (CTX, NTX), and tartrate-resistant acid phosphatase type 5b (TRACP) at five time points during the course of two years in healthy premenopausal, perimenopausal and early postmenopausal women. The prospective study showed that CTX (p<0.001), NTX (p=0.001) and TRACP (p=0.001), as well as bone ALP (p=0.009) and OC (p=0.052), were significantly increased already in the transition period from peri- to postmenopause. The pyridinium crosslinks indicated an increased collagen degradation rate already in the perimenopause (PYD, p=0.017; DPD, p=0.054). Significant inverse correlations with the two years changes of the bone mineral density were found for bone ALP, CTX, OC and DPD in the perimenopausal group. The measurement of a comprehensive panel of biochemical bone markers clearly shows that metabolic changes in bone metabolism appear pronounced in the perimenopause, a period still presenting satisfactory estrogen supply. Thus, the perimenopause is an important phase for a contingent development of osteoporosis.

Association of vitamin D receptor and estrogen receptor gene polymorphisms with bone mass in postmenopausal Korean women

OBJECTIVE

To examine the relationship between vitamin D receptor (VDR) and estrogen receptor (ER) gene polymorphism and bone mineral density (BMD).

DESIGN

Polymorphisms at the VDR FokI and ER PvuII and XbaI gene sites, serum bone-specific alkaline phosphatase, urinary N-telopeptide of type I collagen, and BMD at the lumbar spine and proximal femur were analyzed in 229 postmenopausal Korean women.

RESULTS

The distribution of ER PvuII and XbaI and VDR FokI restriction fragment length polymorphisms was as follows: pp 39.3%, Pp 46.3%, PP 14.4%, xx 34.1%, Xx 61.1%, XX 4.8%. ff 17.0%, Ff 43.7%, and FF 39.3%, respectively (upper-case letters signify the absence, and lower-case letters signify the presence of the restriction site). After adjusting for potential confounding factors such as age, body mass index, and menopause duration, ER PvuII was independently associated with BMD at the lumbar spine and XbaI polymorphism BMD at the femoral neck. The lumbar spine BMD in the pp genotype was 7.5% lower than in the PP genotype, and the femoral neck BMD was 4.8% lower in the Xx genotype than in the xx genotype. By itself, the VDR FokI polymorphism was not related to BMD, but by combining the FokI genotype (FF) with ER genotypes, such as ppxx and the PpXx, the difference in the BMD at the Ward's triangle became significant. There were no significant differences in the levels of biochemical markers between the genotypes of three polymorphisms.

CONCLUSION

ER polymorphisms, singly and in relation to VDR FokI polymorphism, influence bone mass in Korean women.

The role of bone turnover markers and risk factors in the assessment of osteoporosis and fracture risk

The clinical evaluation of osteoporosis in individual patients involves confirmation of the diagnosis, the investigation of secondary causes of osteoporosis and the evaluation of subsequent fracture risk. Optimum clinical assessment involves bone mineral densitometry with the treatment thresholds modified by clinical risk factors for individual patients. Bone turnover markers and clinical risk factors can be used to identify patients at risk of osteoporotic fracture and those who have secondary osteoporosis. Risk assessment should involve the evaluation of absolute rather than relative risk. Further work is required to improve the integration of clinical risk factors, bone turnover markers and bone densitometry into appropriate models to enable the assessment of the absolute risk of fracture for individual patients.

The relationship among circulating insulin-like growth factor components, biochemical markers of bone turnover and bone mineral density in postmenopausal women under the age of 60

OBJECTIVES

The changes in circulating IGF components after the menopause and the potential role of new markers of bone turnover and circulating IGF components in predicting bone mass in postmenopausal women are still controversial and the relationship between these two systems has not been investigated. The aims of this study were to investigate the changes in circulating IGF components after the menopause, to evaluate whether new markers of bone turnover and circulating IGF components reflect bone mass in postmenopausal women under the age of 60 and to study the relationship between these two systems.

DESIGN, PATIENTS AND MEASUREMENTS

Serum IGF-I, IGF-II, IGFBP-1, IGFBP-2, IGFBP-3, osteocalcin (OST), bone specific alkaline phosphatase (BAP), urinary deoxypyridinoline (DPYD) and N-telopeptide of type I collagen (NTX) were measured in 31 premenopausal women aged 31-43 and 65 postmenopausal women aged 47-60: this latter group comprised 30 normal healthy women and 35 osteoporotic women.

RESULTS

Compared with premenopausal women or normal postmenopausal women, serum IGF-1 and IGFBP-3 levels were significantly lower in osteoporotic postmenopausal women while no significant differences in serum levels of IGF-II, IGFBP-1 and IGFBP-2 were observed. The correlations between bone turnover markers and circulating IGF components (except between serum BAP and IGF-II), and between bone turnover markers and bone mineral density (BMD) in postmenopausal women were not significant. However, serum IGF-I and IGFBP-3 correlated positively with BMD of the lumbar spine and/or Ward's triangle even if age, BMI and menopause duration were taken into account in a multiple regression analysis model.

CONCLUSIONS

Circulating IGF-I and IGFBP-3 may be involved in the mechanism of bone loss in postmenopausal women under the age of 60. They may also provide indirect information on the current bone microenvironment different from that provided by new markers of bone turnover.

Neural networks for the biochemical prediction of bone mass loss

Neural networks are specialized artificial intelligence techniques that have shown high efficiency in dealing with complex problems. Paradigms such as backpropagation have been successfully applied in a number of biomedical applications, but not in attempts to identify women at risk of postmenopausal osteoporotic complications. In this paper, several neural networks were trained using different combinations of biochemical variables as inputs. Bone densitometric measurements in Ward's triangle and in the spinal column were used as separate classification criteria (outputs) between slow and fast bone mass losers. The most parsimonious model with the best performance included plasma concentrations of estrone, estradiol, osteocalcin, parathyrin and urine concentrations of calcium and hydroxyproline (expressed as ratio to creatinine excretion) as input neurons; ten neurons in a single hidden layer; and one neuron in the output layer. Diagnostic efficiency was 76% in Ward's triangle and 74% in the spinal column; sensitivity was 70 and 81%, and specificity was 77 and 65%, respectively. Linear discriminant analysis showed a diagnostic efficiency of 66% in Ward's triangle and 64% in the spinal column, sensitivity was 55 and 86%, and specificity was 75 and 13%, respectively. We conclude that performance of the stepwise discriminant analysis was not superior to the neural networks.

Clinical usefulness of biochemical resorption markers in osteoporosis

We have evaluated three commercial assays for collagen cross-links, two urine assays and a recently developed serum assay, as markers of bone turnover in 30 postmenopausal women with osteoporosis during their first year of treatment with the anti-resorptive drug alendronate. Before treatment, urine free deoxypyridinoline crosslinks (Dpd), urine N-telopeptide crosslinks (NTx) and serum C-telopeptide (CTx) values were within postmenopausal reference ranges. After 3 months' treatment the decrease in NTx and CTx was greater than that of Dpd (-50%, P < 0.0001 and -48%, P < 0.0001, compared with -11%, NS), as it was after 6 months (-51%, P < 0.0001, and -57%, P < 0.0001, compared with -19%, P < 0.01). The decrease in resorption markers after 6 months was significant in 23% (Dpd), 66% (NTx) and 66% (CTx) of individuals. Neither baseline resorption marker values nor the per cent change after 6 months' therapy correlated with bone mineral density change (BMD) at either lumbar spine or femoral neck after one year's therapy, except baseline Dpd and lumbar spine BMD (P < 0.01). We conclude that NTx and serum CTx were more sensitive markers of bone turnover suppression by alendronate, but only baseline Dpd was useful in the prediction of individual bone density response after one year.

Serum Galactosyl Hydroxylysine as a Biochemical Marker of Bone Resorption

Background: Serum-based biochemical markers of bone resorption may provide better clinical information than urinary markers because direct comparison with serum markers of bone formation is possible and because the within-subject variability of serum markers may be lower. We describe a method for the measurement of free β-1-galactosyl-O-hydroxylysine (Gal-Hyl) in serum.

Methods: The assay used preliminary ultrafiltration of serum, dansylation, and separation by reversed-phase HPLC with fluorescence detection. Healthy subjects were recruited from population-based studies of bone turnover.

Results: The within-run (n = 15) and between-run (n = 15) CVs were 7% and 14%, respectively, at a mean value of 48 nmol/L. In women and pubertal girls, serum free Gal-Hyl correlated with urine free Gal-Hyl (r = 0.84; P &lt;0.001). Serum Gal-Hyl was higher during puberty and increased after menopause. The fractional renal clearance of free Gal-Hyl relative to that of creatinine was 0.90 (95% confidence interval, 0.82–0.98). Serum free Gal-Hyl decreased by 36% (SE = 4%) in 14 patients with mild Paget disease treated with an oral bisphosphonate, and this decrease was significantly (P &lt;0.001) greater than that seen for either serum tartrate-resistant acid phosphatase (9%; SE = 4%) or serum C-terminal telopeptide of collagen I (19%; SE = 8%).

Conclusion: Serum free Gal-Hyl may be useful as a serum marker of bone resorption.

Predicting bone loss following orthotopic liver transplantation

BACKGROUND

Hepatic osteodystrophy occurs in the majority of patients with advanced chronic liver disease with the abnormalities in bone metabolism accelerating following orthotopic liver transplantation (OLT).

AIMS

To examine changes in bone mineral density (BMD) following OLT and to investigate factors that lead to bone loss.

METHODS

Twelve patients had BMD (at both the lumbar spine (LS) and femoral neck (FN)) and biochemical markers measured preoperatively and for 24 months following OLT.

RESULTS

BMD was low in 75% of patients prior to OLT and decreased significantly from baseline at the LS at three months and the FN at six months. BMD began to increase thereafter at both sites, approaching baseline values at the LS by 12 months. Bone formation markers, osteocalcin and procollagen type I carboxy propeptide, decreased immediately post-OLT, with a concomitant increase seen in the resorption markers pyridinoline and deoxypyridinoline. This resulted in a negative uncoupling index early post-OLT, that rebounded to positive values after six months. There was a significant correlation between the change in the uncoupling index between six and three months which preceded the increase in BMD at 12 months. The decrease in BMD recorded early post-OLT correlated with vitamin D levels at three months.

CONCLUSIONS

Results suggest that increased resorption and inadequate formation are the major contributors to additional bone loss following OLT. Non-invasive biochemical markers precede later changes in BMD in this patient group following OLT and may have a role in investigating and planning intervention strategies to prevent bone loss in future studies.

Clinical usefulness of bone alkaline phosphatase in osteoporosis

We have evaluated two commercial assays for serum bone specific alkaline phosphatase (bALP) as a marker of bone turnover in a group of 35 postmenopausal women with osteoporosis during their first year of treatment with the anti-resorptive drug, alendronate. The immunoradiometric assay (bALP-I) measured protein mass, whereas the immunocapture assay (bALP-E) measured activity. Before treatment, bALP values with both methods were within the postmenopausal reference ranges. Treatment with alendronate produced a decrease in bALP after 3 months, reaching a plateau after 6 months: for bALP-I a mean change of -34%, (P < 0.0001), bALP-E, -19% (P < 0.001), and total ALP, -19% (P < 0.0001). The decrease was significant in 53% (bALP-I) and 31% (bALP-E) of patients. The ratio of serum bALP-E/bALP-I in patients was not constant but rose after therapy with alendronate. Neither baseline bALP, nor the per cent change in bALP after 6 months, correlated with bone mineral density (BMD) change after 1 year at either lumbar spine or femoral neck. We conclude that bALP-I appeared to be a more sensitive marker of the suppression of bone turnover by alendronate than did bALP-E, but that neither was useful in the detection of osteoporosis, nor the prediction of individual BMD response to alendronate therapy.

Serum collagen crosslinks as markers of bone turn-over during GH replacement therapy in growth hormone deficient adults

OBJECTIVES

Bone metabolism is an important target for GH replacement therapy. However, in adults, treatment periods exceeding 12 months are required for a positive effect of GH on bone mineral density. Thus, to detect an early effect of GH on bone, markers of bone turn-over are important. Pyridinoline (PYR) and deoxypyridinoline (DPYR) are well-defined sensitive markers of bone resorption, but to date only urinary assays have been available. We report the use of a novel assay to measure changes in serum PYR and DPYR in GH deficient (GHD) adults during GH replacement therapy.

STUDY DESIGN

The study consisted of a 6-month randomized, double-blind, placebo-controlled study of the administration of GH (Genotropin) (0.25 IU/Kg/week (0.125 IU/kg/week for the first four weeks)) followed by a 6-month open phase of GH therapy.

PATIENTS

Thirty-five GHD adults (17 women; mean age 39.8 years; range 21.1-59.9) on conventional hormone replacement therapy as required, were studied.

MEASUREMENTS

Bone formation was analysed using serum bone alkaline phosphatase (BAP) and serum osteocalcin (OC). Bone resorption was analysed using serum pyridinoline (PYR) and serum deoxypyridinoline (DPYR). Bone mineral density (BMD) was determined by dual energy X-ray absorptiometry (DEXA).

RESULTS

After 6 months placebo treatment there were no significant changes in any of the bone markers analysed, nor in BMD. In the active arm of the study there was a significant increase in serum OC, BAP, PYR and DPYR (P = 0.03, P = 0.004, P = 0.003 and P = 0.01, respectively), remaining significantly elevated over their baseline levels for the subsequent 6 months of treatment (P = 0.04, P = 0.009, P = 0.003 and P = 0.04, respectively). No changes were observed in BMD in any of the groups after 6 months GH treatment. In the active arm of the study, after 12 months GH treatment there was a significant increase in BMD at both the lumbar spine and femoral neck (P = 0.01 for both sites).

CONCLUSIONS

In summary, the present study confirms that administration of GH treatment to GHD adult patients significantly activates bone remodelling, with the effect of GH both in bone formation and bone resorption markers being maximal after 6 months of treatment. The serum assay for PYR and DPYR has a number of practical and theoretical advantages over the urine assay and gave similar results to those previously reported for the urine assay.