Dynamic pattern of IGF-I and chosen biochemical markers of bone metabolism in a rat model of postmenopausal osteoporosis

OBJECTIVE

To assess the relationship between the dynamic pattern of IGF-I levels and chosen biochemical markers of bone metabolism in ovariectomized rats - a model of postmenopausal osteoporosis.

METHODS

Six-month-old rats were randomized to sham operation (control group) or ovariectomy. Serum levels of insulin-like growth factor (IGF-I) and chosen biochemical markers of bone metabolism (alkaline phosphatase - ALP, carboxyterminal propeptide of type I procollagen - PICP, cross-linked carboxyterminal telopeptide of type I collagen - ICTP in serum as well as urinary excretion of hydroxyproline - HYP and total calcium - Ca) were measured before (group 0) and 1, 2, 3, 4, 6, 8, 12, 16, 20, 24 and 28 weeks after the operation.

RESULTS

In a model of experimental osteoporosis induced by ovariectomy in female rats a distinct tendency to decrease the IGF-I concentrations was shown. Differences were significant in relation to the control group in a period from 2 to 28 weeks after operation. Ovariectomy stimulated the values of studied markers of bone metabolism; it was more intensified in regard to resorption markers. Significant ICTP and HYP concentrations' changes, in relation to the control group, were shown in the some period and total calcium - from 2 to 16 weeks after ovariectomy. However, the values of studied markers of bone formation were generally changing to a slight degree. Significant differences of ALP activity, in relation to the control group, were observed only at 8 and 20 weeks, while those of PICP concentrations were found at in 4, 8 and 12 weeks after the operation. The alterations in the levels of IGF-I correlated significantly and negatively with the changes in ALP activity as well as in PICP, ICTP, HYP and Ca concentrations both in ovariectomized and control rats. This relation was more expressed in the ovariectomized group.

CONCLUSIONS

Our findings suggest that secondary changes in IGF-I concentration, due to the deficiency of sex hormones, results in altered bone metabolism in ovariectomized rats.

Comparison of serum and urinary C-terminal telopeptide of type I collagen in aging, menopause and osteoporosis

BACKGROUND

Urinary C-terminal telopeptide of type I collagen (u-CTx) has been reported to be a sensitive biochemical marker of bone turnover. There have been two assays for urinary CTx, which are alpha-CTx and beta-CTx. A newly developed immunoassay for serum CTx (s-CTx) is now available for assessment of bone resorption. We evaluated the effects of aging, menopause, and osteoporosis on the measurements of serum CTx and compared them to urinary CTx assays.

METHODS

In 79 premenopausal healthy women, 80 postmenopausal healthy women, 61 osteoporotic patients with vertebral fractures and 34 osteoporotic patients with hip fractures, s-CTx and urinary beta-CTx (u-betaCTx) were measured by ELISAs, and urinary alpha-CTx (u-alphaCTx) was measured by an RIA.

RESULTS

In all subjects, s-CTx significantly correlated with both u-alphaCTx (r=0.54) and u-betaCTx (r=0.51). There was no significant difference among s-CTx, u-alphaCTx and u-betaCTx in the T-scores of the postmenopausal group over the premenopausal group. These findings indicate that the value of s-CTx, as well as urinary CTxs, reflected the increase of bone resorption associated with menopause with a high degree of sensitivity. Patients with vertebral fractures had moderately increased concentrations of bone resorption markers compared to age-matched healthy postmenopausal women (T-score; s-CTx: 0.8, u-alphaCTx: 0.9, u-betaCTx: 0.7), whereas bone resorption markers in hip fracture patients were greatly increased compared to healthy postmenopausal women (T-score; s-CTx: 1.1, u-alphaCTx: 1.3 u-betaCTx: 1.3). The T-scores of u-CTxs against the postmenopausal group in vertebral fracture group and in hip fracture group were not significantly different from those of s-CTx.

CONCLUSIONS

s-CTx, as well as urinary CTxs, reflects the increase of bone resorption in patients with vertebral fractures and hip fractures.

Determination of NTx in second-morning urine: a proposal for the standardization of morning urine collection

According to the instruction manual from the producer of kits for determining the levels of aminoterminal telopeptide of type I collagen of organic bone matrix (NTx), the time of the collection of second-morning urine is arbitrary, i.e., a patient can urinate anytime within the period from about 6 to 8:30 a.m. This time interval is within the period of change in the circadian rhythm of the NTx excretion (maximum excretion with transition into fast decrease of excretion). Therefore, we considered it appropriate to standardize the conditions for the collection of second-morning urine and proposed applying the so-called 2-hour morning urine NTx2 (from 6 to 8.00 a.m. after an overnight fast). We examined 48 female patients aged 33-65 years with primary or secondary osteopenia or osteoporosis (all patients had normal renal functions). In these patients we determined NTx (Osteomark, OSTEX, USA) in standardly used 24-hour urine (NTx24) and in the proposed 2-hour morning urine (NTx2).

AIM OF THE STUDY

1) To find a mathematical character for the dependence of values of dependent variable NTx2 on independent variable NTx24 and to evaluate the statistical significance of this dependence; 2) to compare the ratio of the widths of 95% confidence intervals (C. I.) for NTx2 and NTx24 in patients (index: IO) with the ratio of the widths of reference limits for NTx in arbitrary second-morning urine (NTx2ostex) and in 24-hour urine (NTx24ostex) in healthy women (index: IR); 3) to evaluate the proposed 2-hour urine for the determination of NTx.

STATISTICAL ANALYSIS

Stochastic and deterministic linear regressive analysis. Index of 95% C. I., index of reference limits.

RESULTS

A statistically significant (P < 0.01) regressive dependence (r2 = 0.781) was found between the values of NTx24 and NTx2. The index for the widths of reference limits (IR) was 1.5 times greater than the index for osteopenic and osteoporotic patients (IO), meaning that the scatter of the NTx2ostex values was greater than NTx2 in the proposed 2-hour urine.

CONCLUSION

Based on the statistically significant linear regressive dependence between NTx24 and NTx2 values, it is possible to use the proposed 2-hour morning urine to determine NTx levels in women. The introduction of 2-hour morning urine NTx2 could decrease the fluctuation range of NTx values in repeated examinations and in comparison with the determination of NTx2ostex in a random second-morning urine sample could make its values more accurate.

Bone metabolism during the perimenopausal transition: a prospective study

OBJECTIVE

Changes in biochemical markers of bone formation and resorption were followed over the course of 1 year in premenopausal, perimenopausal and early postmenopausal women.

METHODS

Sixty-four subjects were analyzed, grouped according to their menstrual pattern, menopausal complaints and endocrinological parameters to be premenopausal (n=20), perimenopausal (n=24) or early postmenopausal (n=20). The parameters studied at four visits during the 12-month study period were the urinary pyridinium cross-links pyridinoline (PYD) and deoxypyridinoline (DPD), and N-terminal telopeptide (NTX) as bone resorption markers, as well as osteocalcin (OC) and bone-specific alkaline phosphatase (BAP) in serum, representing bone formation. The longitudinal changes over time as well as intergroup differences were analyzed using generalized estimating equations (GEE) in connection with Wald statistics.

RESULTS

Over the course of 1 year BAP levels decreased in the late premenopausal group (P<0.05). The perimenopausal group exhibited significant changes of PYD, DPD and OC (P<0.01), NTX levels were higher than in premenopause. Postmenopausal subjects had elevated NTX values, while PYD and DPD levels remained close to the perimenopausal range. Only for OC a time effect was seen during postmenopause.

CONCLUSIONS

Changes in bone turnover already begin in late premenopause, when decreased bone formation may precede increased bone resorption. The rise of NTX from late premenopause through early postmenopause indicates diagnostic sensitivity of this parameter to changes in bone metabolism induced by estrogen withdrawal. PYD and DPD do not follow this pattern, but change significantly with time during perimenopause to then remain largely unchanged in early postmenopause.

A new monoclonal antibody ELISA for detection and characterization of C-telopeptide fragments of type I collagen in urine

Clinical studies have shown that measurements of urine concentration of degradation products of C-terminal telopeptides of type I collagen provide a selective marker to assess bone resorption. Assays for C-telopeptide fragments have been described using antibodies generated against an eight amino acid synthetic peptide EKAHDGGR. In this study, we describe development of a rat monoclonal antibody against a synthetic linear peptide, DFSFLPQPPQEKAHDGGR, which we isolated and characterized from Paget's urine by chromatographic methods. An ELISA procedure was developed to evaluate the efficacy of this monoclonal to measure bone resorption and characterize urinary degradation products of C-terminal type I collagen. The measuring range of ELISA was 10-1,000 ng/ml with a detection limit of 10 ng/ml. Averaged intraassay and interassay CVs were <7% (n = 8) and <11% (n = 3), respectively. Mean spike and dilution recoveries range between 90 and 116%. In assessing the clinical performance, we observed approximately 48% higher values for postmenopausal patients (n = 20) compared with premenopausal women (n= 19), Z score = 2.7 (P = 0.0091). The discriminatory power to assess subtle changes in bone turnover between pre- and postmenopausal women compares well with the commercially available markers of bone resorption. Comparison of C-telopeptide concentration in a population including normal and osteoporotic patients (n = 74) shows a strong correlation with DPYR r = 0.95 (P < 0.001). In addition, in postmenopausal osteoporotic patients, a 44% (P < 0.05) decrease in C-telopeptide concentration was observed after 3 months of treatment with Alendronate, as compared with basal values. The antibody developed in this study displays a slightly different epitope than that reported previously using eight amino acid residues EKAHDGGR. In addition, isolation and characterization of circulating forms of C-telopeptide from healthy children by immunoaffinity purification revealed the presence of two novel urinary fragments corresponding to amino acid sequence EKAHDGGR and EKAHDG, in addition to the previously known two fragments composed of two alpha-1 chains linked together by a pyridinium crosslinks. The origin of the fragment EKAHDG could not be explained by the known mechanisms involved in collagen degradation, indicating that it could be a product of renal handling of C-telopeptide fragments generated from bone. The preliminary clinical data suggest that the new assay may be useful for further investigation of the clinical importance of measurement of these type I collagen degradation products.

Serum bone specific alkaline phosphatase and urinary deoxypyridinoline in postmenopausal osteoporosis

The objectives of this study were to: (i) evaluate the diagnostic sensitivity and specificity of the biochemical bone markers: serum total alkaline phosphatase (TALP), bone specific alkaline phosphatase (BSALP) and urinary deoxypyridinoline (Dpyr) in postmenopausal osteoporosis, (ii) compare the bone turnover of postmenopausal osteoporotic patients without and with hormone replacement therapy (HRT) against controls and (iii) identify the correlation between these bone markers and bone mineral density (BMD). We examined 42 postmenopausal women with BMD proven osteoporosis and 35 control subjects. Serum TALP, BSALP and urinary Dpyr were measured. All three biochemical bone markers showed comparable moderate diagnostic sensitivity but Dpyr had the highest diagnostic specificity. There were significantly higher serum TALP, BSALP and urinary Dpyr levels in non-HRT treated patients compared to controls (p<0.005, <0.0001 and <0.005 respectively). There were no significant differences in the levels of all three bone markers between HRT treated patients and control subjects. There was no significant correlation between TALP, BSALP or Dpyr and BMD in both controls and patients. In conclusion, the biochemical bone markers are not useful in diagnosis of postmenopausal osteoporosis but may have a role in monitoring progress and response to treatment. HRT treatment reduces bone turnover of postmenopausal osteoporosis.

Effect of intramuscular clodronate on bone mass and metabolism in osteoporotic women

Bisphosphonates have significantly improved the treatment of postmenopausal osteoporosis. However, when administered orally, gastric intolerance is their main adverse effect. This makes patients reluctant to undergo treatment. As an alternative, intramuscular (i.m.) administration may be more acceptable to patients undergoing long-term treatment. Since clodronate has been easily available in Italy for many years, we carried out this study to evaluate its effect on bone mineral density (BMD) in 36 osteoporotic postmenopausal women who were intolerant to oral administration of bisphosphonates. Patients received 100 mg of clodronate i.m. every 10 days together with 500 mg/day of calcium orally for 2 years. A control group of 32 women received only oral calcium at the same dose and for the same length of time. In the control group a progressive but not statistically significant decrease in BMD was observed in the spine and femoral neck over the 2-year follow-up. In contrast, patients treated with clodronate had a statistically significant increase in BMD in the spine at the first yearly check-up (+2.63%) and a further but not statistically significant increase during the second year of treatment (+0.59%). The increase in BMD at the femoral neck was not statistically significant during the first and second years of treatment, being 1.21% and 0.37% respectively. In the women treated with clodronate, hydroxyproline was significantly suppressed. All the patients reported local pain at the injection site. This led 11.11% of the subjects to withdraw from treatment.

Ibandronate: a comparison of oral daily dosing versus intermittent dosing in postmenopausal osteoporosis

The objective of this study was to compare efficacy and safety of continuous versus intermittent oral dosing of ibandronate. Two hundred forty women aged 55-75 years with postmenopausal osteoporosis were randomized to active treatment or placebo. Similar total doses of ibandronate were provided by treatment regimens with either continuous 2.5 mg of ibandronate daily (n = 81) or intermittent 20 mg of ibandronate every other day for the first 24 days, followed by 9 weeks without active drug (n = 78). The placebo group (total, n = 81) was crossed over after 12 months to receive either continuous (n = 37) or intermittent ibandronate (n = 35). By 24 months, bone mineral density (BMD) had increased significantly relative to baseline in both active treatment groups. The continuous and intermittent groups showed statistically equivalent increases in lumbar spine BMD of +5.64% (+/-0.53) and +5.54% (+/-0.53) and in total hip of +3.35% (+/-0.40) and +3.41% (+/-0.40), respectively (per protocol population). Biochemical markers of bone turnover decreased significantly in both treatment groups. The level of marker suppression was similar, although the intermittent group displayed, as expected, more fluctuation over the treatment period. The frequency of adverse events was similar in the treatment groups. In conclusion, the intermittent and continuous regimens showed equivalent changes in BMD and bone turnover. These results confirm previous preclinical findings indicating that the efficacy of ibandronate depends on the total oral dose given rather than on the dosing schedule. This supports development of new flexible dosing regimens targeted to minimize the frequency of dosing, which are expected to improve convenience and lead to enhanced long-term patient compliance.

[Laboratory diagnosis of osteoporosis]

Bone is biologically a highly active tissue whose cells are embedded in a complex network of systemically acting hormones and local mediators. The mechanisms of action involved are as yet only partially understood. With the increase in life expectancy and the resultant change of the population's age structure, diseases of the musculoskeletal system and bones have increased in importance. Thus, research is directed to a greater extent toward bone metabolism and the most frequent bone disease, osteoporosis. Until a few decades ago, the diagnosis of a bone disease was based principally on clinical and radiological methods. Laboratory methods only included the measurement of total alkaline phosphatase activity and calcium and phosphate balance. The development and introduction of new biochemical markers of bone metabolism in recent years led to a considerable increase in available laboratory methods. To evaluate the activity of osteoblastic synthesis, alkaline phosphatase and other bone-forming markers with higher tissue specificity such as bone alkaline phosphatase, osteocalcin, and several collagen propeptides are used. Bone degradation (calcium and hydroxyproline were the only markers until several years ago) can now be detected quickly and reliably with many new serological and urinary markers. Pyridinium derivatives and telopeptides as products of the metabolic activity of osteoclasts have been proved efficacious in diagnosis and therapy control.

Markers of bone turnover in postmenopausal women receiving hormone replacement therapy

We investigated the effects of hormone replacement therapy (n = 27) on biochemical markers of bone turnover in a cross-sectional study of 127 postmenopausal women (according to WHO guidelines 18 patients had normal bone mineral density and 109 suffered from bone loss). Urinary excretion of free deoxypyridinoline and C- or N-telopeptide fragments of type I collagen served as bone resorption markers, serum osteocalcin as a bone formation marker. In women with no hormone replacement therapy, only C- and N-telopeptides correlated significantly with the lumbal T-score as an index for bone mineral density. Patients with bone loss receiving hormone replacement therapy exhibited significantly lower C-telopeptide, N-telopeptide and osteocalcin levels than those with no therapy (mean -45%, -43% and -26%, respectively), while deoxypyridinoline showed no significant differences. Among the markers investigated, C- and N-telopeptides seemed to be more reliable to detect therapeutic effects on bone metabolism. We present a preliminary model to evaluate bone turnover and resorption/formation rate.

Inhaled corticosteroids reduce bone mineral density in early postmenopausal but not premenopausal asthmatic women

Inhaled corticosteroids are widely used in the treatment of bronchial asthma, but it is still uncertain whether long-term use of the inhaled corticosteroids affects bone metabolism in asthmatic patients. In this study, we examined the effect of inhaled beclomethasone dipropionate (BDP) on bone mineral density (BMD) and biochemical markers of bone metabolism in pre- and early postmenopausal asthmatic women. Thirty-six (17 premenopausal and 19 early postmenopausal) asthmatic women and 45 healthy control (24 premenopausal and 21 early postmenopausal) women were investigated. All the asthmatic patients were treated with BDP (542 +/- 298 microg/day; 100-1200 microg/day) without any systemic administration of corticosteroids for at least 1 year. In premenopausal women, BMD as well as the biochemical markers of bone metabolism did not differ between control subjects and BDP-treated asthmatic patients. By contrast, in early postmenopausal women, BMD was significantly lower in BDP-treated asthmatic patients than in control subjects. In these early postmenopausal women, serum intact osteocalcin concentration was lower in the BDP-treated asthmatic patients than in the control subjects whereas urinary free pyridinoline (F-PYD) and free deoxypyridinoline (F-DPD) concentrations did not differ between the groups. Thus, early postmenopausal, but not premenopausal, asthmatic patients who were treated with inhaled BDP had reduced BMD, which was associated with a decreased level of the bone formation marker. Ovarian hormones may be protective against the adverse effect of inhaled BDP on bone metabolism in the premenopausal patients.

Effect of high doses of oral risedronate (20 mg/day) on serum parathyroid hormone levels and urinary collagen cross-link excretion in postmenopausal women with spinal osteoporosis

The present study describes the biological effects of risedronate, a pyridinyl bisphosphonate, on bone and assesses the safety and tolerability of risedronate when given at high doses, with or without calcium, to postmenopausal women with spinal osteoporosis. This single-center descriptive, double-blind, placebo-controlled, randomized, parallel group study included 32 postmenopausal white women with at least one radiographically confirmed vertebral compression fracture. Patients were randomized to one of four different dose regimen groups: (i) R-P, risedronate 20 mg/day for 14 days, followed by placebo for 42 days; (ii) R-CP-P, risedronate 20 mg/day for 14 days, followed by elemental calcium 1000 mg/day and placebo for 14 days, then by placebo for 28 days; (iii) R-CP-R-CP, risedronate 20 mg/day for 7 days, followed by elemental calcium 1000 mg/day and placebo for 21 days, then risedronate 20 mg/day for 7 days, and finally elemental calcium 1000 mg/day and placebo for 21 days; and (iv) P, placebo for 56 days. The biological response was investigated by measuring serum calcium, parathyroid hormone (PTH), and 2 h urinary pyridinoline/creatinine (Pyr/Cr) and deoxypyridinoline/creatinine (DPyr/Cr) ratios at baseline and at days 3, 7, 14, 21, 28, 35, 42, 49, 56, and 84. Overall, there were no consistent trends observed between the active group and placebo for serum calcium. In groups R-P, R-CP-P, and R-CP-R-CP, mean serum PTH levels were elevated above baseline values for the entire 56 day treatment period and remained elevated, although to a lesser extent, at the day 84 follow-up visit. The effect of calcium supplementation on PTH was variable. Urinary Pyr/Cr and DPyr/Cr ratios were decreased from baseline over the entire study period in all groups receiving risedronate. The maximum observed percent decreases from baseline for Pyr/Cr and DPyr/Cr were -46.9% and -58.8%, respectively, at day 49 in the R-CP-R-CP group. In conclusion, risedronate given orally at a dose of 20 mg/day, continuously for 7 or 14 days, resulted in the expected biological response in osteoporotic women. The time course of changes in PTH levels following cessation of dosing was unaffected by calcium supplementation. There was no evidence of a PTH-mediated rebound in bone resorption following cessation of therapy. Furthermore, based on collagen cross-link data, patients did not show an excessive reduction in bone turnover.

Inhibition of bone resorption by divided-dose calcium supplementation in early postmenopausal women

We have previously shown that a calcium (Ca) supplement of 1000 mg given in the evening reduces the overnight and early morning, but not the daytime, excretion of bone resorption markers in postmenopausal women within five years of the menopause. In the present study, we have looked at the effect of splitting the Ca into two doses of 500 mg each given in the morning and evening. We studied 19 healthy women (median age 53 years) who were all within 5 years of the menopause. On the 2 study days, urine was collected from 9 a.m. to 9 p.m. (day collection), and from 9 p.m. to 9 a.m. (night collection); a further fasting (spot) urine sample was obtained at 9 a.m. at the end of the night collection. The first day was a control day; on the second day the subjects ingested 500 mg Ca as the carbonate at 9 a.m. and 9 p.m. We measured pyridinoline cross-links excretion in all the samples, as well as hydroxyproline in the fasting urine. The Ca supplements lowered urinary excretion of the markers during the day (P < 0.01), had only a marginal effect during the night, but reduced excretion significantly in the fasting urine (P < 0.001). In the whole 24-hour period, the falls in resorption markers were small but comparable to those seen after the ingestion of 1 g of Ca in the evening. We conclude that the acute administration of 0.5 g Ca in the morning and evening reduced the markers of bone resorption in early postmenopausal women during the day but not during the following night, whereas the single 1 g supplement had the reverse effect. Over the 24-hour period, there was nothing to choose between the two regimes. Women at this stage in their life cycle probably require a larger Ca supplement if they are not taking estrogen.

Impact of calcitonin on urinary excretion of prostaglandins during menopause

The aim of this study was to investigate the effects of calcitonin as an antiresorptive agent in postmenopausal osteoporosis in prostaglandin metabolism. Urinary prostaglandin E2 (PGE2) concentrations were determined by PGE2 (125I) RIA kit in a total number of 37 patients in postmenopause; 27 in study group with established osteoporosis (WEO) and 10 in another group without osteoporosis (WO). An additional group of 12 patients in the premenopausal period were selected as controls (PreM). Data were given as mean +/- SD and statistical analysis was performed by Student's t test for paired and unpaired values. A significant decrease in urinary PGE2 concentrations was observed in WEO (7.91 +/- 3.08 vs. 3.79 +/- 3.01 ng/l) (p < 0.001), WO (9.06 +/- 6.76 vs. 6.06 +/- 3.90 ng/l) (p < 0.05) and PreM (7.14 +/- 1.68 vs. 5.16 +/- 1.91 ng/l) (p < 0.01). As a conclusion, calcitonin seems to exert a negative effect on prostaglandin metabolism resulting in reduced new prostaglandin formation.

The predictive value of biochemical markers of bone turnover for bone mineral density in postmenopausal Japanese women

To examine the predictive value of biochemical markers of bone turnover for bone loss pre- and postmenopausally, we measured two markers of bone formation, bone-specific alkaline phosphatase (BALP) and intact osteocalcin (OC); four markers of bone resorption, urinary cross-linked N-telopeptides of type I collagen (NTx), type I collagen C-telopeptide breakdown products (CTx), hydroxylysylpyridinoline (HP) and lysylpyridinoline (LP); serum OC N-terminal (OC-N); and two serum cytokines, soluble interleukin-6 receptor (sIL-6R) and IL-1r antagonist at baseline and 1 year, as well as lumbar spine bone mineral density (BMD) at baseline and 1, 2, 3, 4, and 5 years after trial in 82 premenopausal (44.8 +/- 5.4 years old) and 325 postmenopausal (60.2 +/- 6.1 years old) healthy Japanese women. In premenopausal women, stratification of the baseline value of each biochemical marker into quartiles did not cause any significant difference in the change in BMD. Stratification of the NTx baseline value in postmenopausal women showed significant differences in rate of bone loss to the first year among those subjects with each quartile (Q1 [0.28 +/- 0.28%], Q2 [-0.32 +/- 0.34%], Q3 [-1.50 +/- 0.31%], and Q4 [-2.43 +/- 0.35%]) except for the difference between Q1 and Q2. The predictive value of NTx for BMD was greater in early postmenopausal women within 5 years after menopause than in late postmenopausal women with more than 5 years since menopause (YSM). Quartile analysis of the other biochemical markers and serum cytokines did not show any significant capacity for differentiating between bone loss rates. Moreover, when the changes in the lumbar spine BMD to the second and third years were stratified into quartiles by the baseline NTx, the ratios of bone loss to the second and the third years were significantly higher in those women with higher NTx (Q4; -3.15 +/- 0.56% and -4.06 +/- 0.57%, respectively) than in those with lower NTx (Q1; -0.74 +/- 0.44% and -1.03 +/- 0.51%, respectively). In conclusion, baseline urinary NTx was the most sensitive predictor of bone loss in the lumbar spine after 1, 2, and 3 years. Markers of bone resorption can be used clinically to predict future BMD in postmenopausal women.

Biochemical markers of bone turnover, endogenous hormones and the risk of fractures in postmenopausal women: the OFELY study

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

Biochemical markers as predictors of rates of bone loss after menopause

Biochemical markers of bone turnover may correlate with rates of bone loss in a group of postmenopausal women, but it is uncertain how useful they are in predicting rates of bone loss in the individual. The aim of this study was to determine the value of measurements of biochemical markers for the prediction of rates of bone loss in the individual. We studied 60 postmenopausal women (ages, 49-62 years), 43 of whom had gone through a natural menopause 1-20 years previously and 17 of whom had undergone hysterectomy 3-22 years ago. Lumbar spine bone mineral density (BMD) was measured using dual-energy X-ray absorptiometry (DXA) over 2-4 years. Bone formation markers (bone-specific alkaline phosphatase [ibAP] and amino terminal of type I collagen [PINP] and osteocalcin [OC]) were measured in serum. Bone resorption markers (N-telopeptide of type 1 collagen [NTx] and immunoreactive free deoxypyridinoline [iFDpd]) were measured in urine and corrected for creatinine (Cr). Rates of bone loss were calculated as percent change per year. We found significant negative correlations (Spearman rank) between all measured biochemical markers and rate of change in bone density with r values ranging from -0.35 to -0.52. When markers and rates of bone loss were divided into tertiles, prediction of bone loss in an individual was poor (kappa < 0.2). There was an exponential relationship between rate of bone loss and years since menopause (YSM) in the 43 women having a natural menopause (r2 = 0.44; p = 0.008) indicating higher rates of loss in the early postmenopausal period. Levels of NTx, iFDpd, and PINP also showed a significant negative correlation with YSM. We conclude that there is a strong relationship between rates of spinal bone loss and levels of bone turnover markers. Although this is a small study, the results also suggest that using DXA measurements of the lumbar spine as the "gold standard," it is not possible to use biochemical markers to predict rate of bone loss in the individual.

[Effect of low calcitonin doses on bone remodeling in postmenopausal women with high bone turnover rate]

BACKGROUND

Calcitonin is specially indicated for the treatment of osteoporosis in women that cannot receive estrogen replacement therapy or that have a high bone turnover rate.

AIM

To study the effects of low intranasal calcitonin doses on bone remodeling in postmenopausal women with a high bone turnover.

PATIENTS AND METHODS

Forty one healthy women aged 56 +/- 6 years old, with a mean lapse after menopause of 7.6 +/- 6.5 years and with a high bone turnover rate, evidenced by an urinary hydroxyproline (mg/dl)/creatinine (g/dl) ratio of 52.4 +/- 7.2, were studied. They were randomly assigned to receive 100 or 50 U/calcitonin thrice a week during 3 months or to a control group that received placebo. All received 500 mg/day calcium carbonate. Urinary hydroxyproline/creatinine ratio was measured a 0, 15, 30, 60 and 90 days. Plasma bone fraction of alkanine phosphatases was measured at 0, 30 and 90 days.

RESULTS

Initial urinary hydroxyproline/creatinine ratio and plasma bone fraction of alkanine phosphatases were similar in all study groups and there was no change in these parameters during the study period.

CONCLUSIONS

Intranasal calcitonin in doses of 100 U thrice a week or less, does not modify accelerated bone turnover in postmenopausal women.

Chronic intravenous aminobisphosphonate therapy increases high-density lipoprotein cholesterol and decreases low-density lipoprotein cholesterol

Nowadays, bisphosphonates are considered the drugs of choice for the treatment of several bone disorders. Their exact mechanism of action is not clear but recently it has been reported that the aminobisphosphonates inhibit cholesterol biosynthesis and that this might be relevant for their actions on bone osteoclasts. The study includes 87 postmenopausal women with moderate to severe osteoporosis. The patients were randomly assigned to intravenous (iv) infusion of 50 mg of the aminobisphosphonate Neridronate dissolved in 100 ml of saline solution every 2 months for a year (44 patients). The remaining 43 served as controls. At the time of each infusion blood samples were obtained for the evaluation of total cholesterol, triglycerides, high-density lipoprotein cholesterol (HDL-C) and low-density lipoprotein cholesterol (LDL-C), apolipoprotein A-I (Apo A-I), apolipoprotein B (Apo B), and total and bone alkaline phosphatase (AP). Free deoxypyridinoline (f-DPD) was measured in fasting urine specimens. In the control group no significant changes were observed throughout the study period for any of the biochemical variables. In the Neridronate-treated patients both bone AP and f-DPD excretion fell significantly by 15-20%. In these patients serum total cholesterol and serum triglycerides showed marginal decreases, which were occasionally significant. LDL-C and Apo B fell by 5-6% and these changes were statistically significant at most time points. Apo A-I and HDL-C rose progressively with time. At the 12th month, HDL-C rose 17-18% (p < 0.0001) above the baseline values. Similar findings were obtained in four postmenopausal women given high iv doses of Pamidronate or Alendronate. In conclusion aminobisphophonates, at least when given iv, induce remarkable and unexpected effects on lipid metabolism with a final profile that might be clinically relevant.

Comparison of serum and urine assays for biochemical markers of bone resorption in postmenopausal women with and without hormone replacement therapy and in men

Biochemical markers of bone resorption have been used to characterize metabolic bone disease and assess therapeutic response. Most studies have used the urinary measurement of collagen crosslinks, but serum assays have recently been developed that may have less analytic and biologic variability. In the present study, we measured urine and serum N- and C-terminal crosslinked telopeptides of type I collagen (NTX and CTX) and serum bone sialoprotein (BSP) in postmenopausal women with or without hormone replacement therapy (HRT) and in men of similar age. In these populations, the variability of serum and urine markers was similar, except that serum NTX showed somewhat lower variability in postmenopausal women. Urine and serum assays correlated well with one another and were significantly lower in postmenopausal women on HRT compared with untreated women. The difference in women on HRT was similar for sNTX, uNTX and BSP (35-40%) and greater for sCTX and uCTX (52-53%). There was an inverse correlation between markers and bone mineral density, largely attributable to the high correlation in women not on HRT. Fractional excretion of NTX and CTX were estimated at 0.20+/-0.07 and 0.44+/-0.11, respectively. These values were independent of the concentration of the marker or of creatinine in the urine. We conclude that serum markers are useful measures of bone resorption in these populations, in whom the use of such markers is likely to be helpful in the management of osteoporosis.

Longitudinal study of bone loss in pre- and perimenopausal women: evidence for bone loss in perimenopausal women

Bone loss before and around the time of menopause is not well characterized by longitudinal studies. We measured bone mineral density at various skeletal sites--total body, femoral neck, trochanter, anteroposterior (AP) and lateral spine, and forearm--with dual-energy X-ray absorptiometry in a large prospective cohort of 272 untreated pre- and perimenopausal women aged 31-59 years, at 1 year intervals for 3 years. Sex steroids and the following markers of bone remodeling were measured: serum osteocalcin (OC), procollagen I carboxyterminal extension peptide, bone alkaline phosphatase (BAP) and urinary crosslinks (CTX and NTX). Seventy-six women were classified as perimenopausal and 196 as premenopausal. Over the 3 years, premenopausal women had no significant bone loss at any site and a small but significant increase in bone mineral density at the trochanter, total hip, AP spine and radius. Perimenopausal women significantly lost bone from cancellous and cortical sites, i.e., the femoral neck, trochanter and lumbar spine. In perimenopausal women with increased follicle stimulating hormone, the rate of bone loss at the femoral neck correlated negatively with OC and BAP. In perimenopausal women, serum estradiol levels decreased during the 3 years of follow-up and bone loss from the trochanter and the AP spine was correlated with serum estradiol after 3 years. In conclusion, among premenopausal women there is no bone loss. In contrast, there is a rapid and diffuse bone loss in perimenopausal women, related to decreased estrogen secretion. Bone markers may be useful to identify these women losing bone.

The effect of calcium citrate on bone density in the early and mid-postmenopausal period: a randomized placebo-controlled study

This placebo-controlled randomized trial was conducted to ascertain the value of calcium citrate supplementation in averting bone loss in 63 postmenopausal women, 57 of whom were early postmenopausal (five years after menopause) and six of whom were mid-postmenopausal (five to ten years after menopause). Bone density data were available for 25 women who took 800 mg of calcium citrate daily and 31 women who received placebo for one to two years. The two groups were similar in baseline age, years postmenopause (3.3 in the calcium citrate group vs 2.7 in the placebo group), height, weight, calcium intake, and L2-L4 bone density. L2-L4 bone density did not change during calcium citrate treatment (+ 1.03% after two years), whereas it declined significantly by -2.38% after two years on placebo (P < .001). Femoral neck bone density did not change in either group. Radial shaft bone density did not change in the calcium citrate group (-0.02% after two years), but it declined significantly in the placebo group (-1.79% after one year and -3.03% after two years, P < .01). The difference in bone density of the L2-L4 vertebrae and radial shaft after two years of treatment was significant between the two groups. An analysis of covariance disclosed no significant effect of calcium citrate on L2-L4 bone density during the first three years after menopause, but a protective effect after three years. Although serum PTH did not change, serum and urinary calcium increased and serum calcitriol and urinary phosphorus decreased in the calcium citrate group, indicative of parathyroid suppression. Serum bone-specific alkaline phosphatase and osteocalcin, and urinary hydroxyproline and N-telopeptide decreased during some calcium citrate treatment periods, indicative of a reduction in bone turnover. Thus, calcium citrate supplementation (400 mg of calcium twice daily) averted bone loss and stabilized bone density in the spine, femoral neck, and radial shaft in women relatively soon after menopause. This bone-sparing action was probably due to the inhibition of bone resorption from parathyroid suppression.

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.

Urinary galactosyl-hydroxylysine in postmenopausal osteoporotic women: A potential marker of bone fragility

Alterations of the collagen matrix, e.g., increased hydroxylation and glycosylation of lysyl residues in collagen I, were found in human osteoporotic bone, and it was suggested that they could alter the mechanical properties of skeleton. To test this hypothesis, we evaluated the content of galactosyl-hydroxylysine (GHYL) in bone collagen, as assessed by its urinary excretion, and related it to the occurrence of fracture. Two hundred and fifteen unselected postmenopausal women with osteoporosis were divided in two subgroups (comparable for age, age of menopause, bone mineral density, and biochemical parameters of bone turnover) on the basis of the history of fragility fracture; 115 patients had suffered no fracture and 100 patients had suffered one or more fractures 3 or more years before. Four urinary markers of bone turnover (hydroxyproline, cross-linked N-telopeptide, free deoxypyridoline, and GHYL) were evaluated in all patients. There was no difference between the two groups with regard to all the parameters studied except for GHYL, which was significantly higher in the group with a history of fracture (1.35 +/- 0.82 mmol/mol of creatinine [Cr] versus 1.03 +/- <0.48 mmol/mol Cr, p < 0.001); this marker did not correlate with other markers of bone remodeling in the fracture group, indicating a possible defect in bone collagen. In conclusion, provided that increased levels of urinary GHYL do reflect overglycosylation of hydroxylysine in bone collagen, the GHYL may be considered a marker of bone collagen quality. Our results, showing higher urinary GHYL in osteoporosis patients with fracture, seem to confirm this suggestion.

The effect of modifying dietary calcium intake pattern on the circadian rhythm of bone resorption

In order to assess day-to-day variations of the circadian rhythm of biochemical bone resorption markers, urinary morning (6-8 a.m.) and evening (7-10 p.m.) samples from 35 individuals were monitored during 3 subsequent days. The bone-specific deoxypyridinoline (DPD) crosslinks of type I collagen followed a circadian rhythm in all individuals. In contrast, no such pattern was observed in the urinary hydroxyproline/creatinine and calcium/creatinine measurements. The DPD crosslink measurements showed a much larger difference between the morning and evening samples collected within 1 day compared with the variation between the samples collected in the morning or evening on subsequent days, indicating the importance of adequate timing of urine sampling for clinical trials aiming to monitor effects on bone resorption. The analysis of DPD crosslinks was then used to evaluate the effects of different patterns of dietary calcium intake on the circadian rhythm of bone resorption in osteoporotic patients. No significant effect on the circadian rhythm of the DPD crosslinks was found after concentrating the normal daily calcium intake to the evening (6-10 p.m.) during 8 days (n = 7). Ingestion of a dietary calcium supplement (600 mg) at 10 p.m. during 8 days (n = 7) resulted in an increased urinary calcium excretion in the morning, and a flattening of the circadian peak and nadir concentrations of urinary DPD/creatinine. The absolute levels of DPD/creatinine in the morning and evening urine samples, respectively, were not significantly altered compared with the control day. We conclude that dietary calcium supplementation in the evening only marginally affects the circadian rhythm of urinary DPD crosslinks in established osteoporosis patients.

The effectiveness of cyclic and continuous oral clodronate therapy on bone density and markers in osteopenic postmenopausal women

Bisphosphonates have been used effectively to treat established osteoporosis and prevent postmenopausal bone loss. However, the optimal manner of its administration-whether cyclic or continuous-has not been well established. This study investigated the efficacy of cyclic and continuous oral administration of clodronate in 54 newly identified osteopenic postmenopausal women in a randomized, double-blind, crossover fashion. The participants were randomly separated into two groups. The cyclic group (n = 29) received 800 mg twice daily of oral clodronate for 2 weeks every 3 months for the first 12 months followed by placebo for the second 12 months. The continuous group (n = 25) received placebo in the first 12 months and ingested 400 mg of clodronate once daily for the second 12 months. The urinary amino-terminal (NTXtrade mark) and carboxy-terminal (CrossLapstrade mark) cross-linked fragments of type I collagen, both markers of bone resorption, showed a marked decrease (25-50%) with both regimens during the period of active treatment. In the cyclic group, the levels of these two markers increased in the second 12 months with placebo, but did not return to the baseline completely. However, bone mineral density (BMD), determined by dual-energy X-ray absorptiometry (DXA), showed no significant change of BMD at various sites after 1 year of active treatment in both groups. Thoracic and lumbar spine X-ray showed no new vertebral fracture in either group after 2 years of treatment. With the two treatment protocols in this study, oral clodronate was effective in decreasing postmenopausal bone resorption, causing no significant changes in BMD at various sites.

Determinants of the first decade of bone loss after menopause at spine, hip and radius

This study documented bone loss at three different sites in the early postmenopausal period, and examined potential predictors. Forty-three women underwent repeated measurements of bone density at the lumbar spine, proximal femur and distal radius for up to 14 years. Individual rates of bone loss were calculated for the spine and hip; for radial trabecular bone, rates were calculated separately for two time periods, earlier and later after menopause. In the spine and radius, initially high rates of loss diminished with time after menopause. No positive correlations for bone loss were found between the three sites, suggesting that faster than average bone loss was specific to individual bones. High body mass index (BMI) was significantly protective against fast bone loss at the spine and radius; in the spine, each unit increase in BMI was associated with a approximately 5% reduction in the rate of bone loss. Of the other variables measured (maximum oxygen consumption, lean body mass, fat mass, mean psoas muscle area at the L3 level, hand grip strength as well as anthropometry) only bone densitometry was sufficiently predictive to help guidance on hormone replacement or other prophylactic therapy. The data suggest that the known relationship between excessive leanness and risk of osteoporosis and vertebral fracture after menopause might in part be due to fast post-menopausal bone loss. Because bulk of psoas muscle was associated with low spine loss rates, the data also support a role for applied muscular loading in local maintenance of bone density.

Hormone replacement therapy in perimenopause: effect of a low dose oral contraceptive preparation on bone quantitative ultrasound characteristics

OBJECTIVES

Our aim was to assess the effects of a combined oral contraceptive (OC) preparation on bone quantitative ultrasound and biochemical markers of bone metabolism in perimenopausal women.

DESIGN

Bone biochemical markers and bone quantitative ultrasound were evaluated in a longitudinal 2-year follow-up study conducted in healthy, normally menstruating perimenopausal women, perimenopausal oligomenorrheic women, and age-matched oral contraceptive-treated women (20 micrograms of ethinyl estradiol plus 0.15 mg desogestrel). The results were analyzed by factorial or repeated-measures analysis of variance, as appropriate.

RESULTS

In normal women, there were no significant modifications in menstrual cycle, plasma FSH and estradiol levels, biochemical markers of bone turnover, and bone quantitative ultrasound. Conversely, in oligomenorrheic women, an increase in the cycle length with a concomitant rise in circulating plasma FSH and parallel decrease of plasma estradiol levels was evident. In this group, an increase in both urinary excretion of hydroxyproline and plasma osteocalcin levels paralleled a decrease in bone quantitative ultrasound. In perimenopausal OC-treated women, the pattern of osteocalcin and urinary excretion of hydroxyproline showed a slight decrease, whereas bone quantitative ultrasound did not show any significant modification.

CONCLUSION

Perimenopausal OC administration can prevent the increase in bone turnover and the decrease in bone quantitative ultrasound that follow the perimenopausal impairment of ovarian function.

Early effects of hormone replacement therapy on bone

Estrogen replacement is currently the preferred therapy for postmenopausal osteoporosis, although its mechanism of action remains poorly understood. Its primary action on bone is generally considered to be antiresorptive, but there is evidence in animals to suggest a stimulatory effect on bone formation. We have now attempted to detect a similar effect in humans by administering hormone replacement therapy (estradiol valerate 2 mg/day and dydrogesterone 5 mg/day given in a continuous, combined manner) to ten postmenopausal women. We carried out histomorphometric analyses of transiliac bone biopsies after quadruple tetracycline labeling, which was commenced before and continued during the first 4 weeks of hormone replacement therapy. Biochemical markers of bone turnover suggested that bone resorption decreased, but no significant effects on histomorphometric parameters of bone formation were detected. We conclude that hormone replacement therapy at the dose given does not stimulate bone formation in the iliac crest as assessed by histomorphometry.

Association of polymorphism at the type I collagen (COL1A1) locus with reduced bone mineral density, increased fracture risk, and increased collagen turnover

OBJECTIVE

To examine the relationship between a common polymorphism within intron 1 of the COL1A1 gene and osteoporosis in a nested case-control study.

METHODS

We studied 185 healthy women (mean +/- SD age 54.3+/-4.6 years). Bone mineral density (BMD) was measured using dual x-ray absorptiometry, and fractures were determined radiographically. The COL1A1 genotype was assessed using the polymerase chain reaction and Bal I endonuclease digestion.

RESULTS

Genotype frequencies were similar to those previously observed and in Hardy-Weinberg equilibrium: SS 61.1%, Ss 36.2%, and ss 2.7%. Carriage of at least one copy of the "s" allele was associated with a significant reduction in lumbar spine BMD (P = 0.02) and an increased risk of total fracture (P = 0.04). Urinary pyridinoline levels were significantly elevated in those with the risk allele (P < 0.05).

CONCLUSION

These data support the findings that the COL1A1 gene polymorphism is associated with low BMD and fracture risk, and suggest a possible physiologic effect on total body turnover of type I collagen.

Urinary bone resorption markers in monitoring treatment of symptomatic osteoporosis

We have studied the clinical usefulness of urinary bone resorption markers in postmenopausal women with symptomatic osteoporosis. The study design is a randomised double-blind placebo controlled study, in which the subjects were daily treated for 24 months either with a hormone analogue (2.5 mg Livial, generic name Tibolone, Organon, Amsterdam, Holland) plus 800 mg calcium (n = 14, age 63+/-5 years, range 52-68 years), or with placebo plus 800 mg calcium (n = 19, age 66+/-7 years, range 50-75 years). The laboratory methods for urinary bone resorption markers were enzyme immunoassays (EIA) for urinary pyridoline (PYD) and deoxypyridoline crosslinks (DPD), and for cross-linked N-telopeptides of Type I Collagen (NTx), and an HPLC assay for urinary hydroxyproline (HOP). All the urine assay results were calculated per mmol creatinine. All the resorption markers decreased during the two-year study period in both groups. The Z scores (discriminating power, i.e. ability of the different tests to distinguish the hormone treated subjects from the placebo treated subjects) for HOP and PYD were rather low: 0.06-1.52 for HOP and 0.68-1.47 for PYD. The differences between the two treatment groups were statistically significant for DPD at 12 and 24 months of treatment (P = 0.0471 and P = 0.0466, respectively), the Z scores ranging 0.45-1.90. NTx showed the most prominent decrease from the beginning of the study especially in the hormone treatment group: the differences between the two treatment groups were statistically highly significant for NTx already at 6 months of treatment (P = 0.0015), and the Z scores remained high ranging 2.11-3.82 throughout the two-year study period. Dual X-ray absorptiometry (DXA) of the lumbar spine and femoral neck did not show statistically significant differences between the two treatment groups throughout the two-year study period. After 2 years there was, however, a significant increase in bone density both in the spine (+ 6.6%, P = 0.0002) and in the femoral neck (+ 3.4%, P = 0.0389) in the women with hormone treatment. In the control group a significant increase (+ 5.1%, P = 0.0012) in the spine, whereas a non-significant decrease (-1.5%, n.s.) in the femoral neck was observed. We suggest that measurement of urinary cross-linked peptides derived from Type I collagen (NTx and DPD) might be a useful biochemical method of observing the positive clinical effect (i.e. reduction in bone resorption) following hormone replacement therapy in postmenopausal fracture patients.

Effects of age, menopause and osteoporosis on free, peptide-bound and total pyridinium crosslink excretion

We evaluated urinary excretion of free pyridinoline (PYD)-deoxypyridinoline (DPD) by an enzymelinked immunosorbent assay (ELISA) method, free and total PYD by high-performance liquid chromatography (HPLC), free DPD by ELISA, chemiluminiscent immunoassay (CLEIA) and HPLC, total DPD by HPLC, and N-telopeptides (NTX) and C-telopeptides (CTX) by ELISA in 234 women distributed into three groups: 43 healthy young women (aged 26.2 +/- 2.5 years), 56 control postmenopausal women (aged 55.9 +/- 4.5 years) and 133 untreated osteoporotic women (aged 55.1 +/- 4.0 years). The control postmenopausal women had increased values of all markers considered, except NTX, compared with healthy young women. The osteoporotic postmenopausal women had significantly increased values compared with control postmenopausal women for free DPD by HPLC and free DPD by ELISA or CLEIA. HPLC, ELISA and CLEIA showed adequate correlation to measure free PYD and DPD. Control postmenopausal women had significantly decreased values of the fraction of free PYD and DPD (48.4% and 32.0%, respectively), as did the osteoporotic postmenopausal women (48.0% and 46.1%), compared with healthy young women (55.3% and 57.0%). We found a significant negative correlation comparing age with fraction of free PYD and DPD, but a positive correlation with total PYD and DPD, considering or not the osteoporotic postmenopausal women. T-score and Z-score values derived from healthy young women and control postmenopausal women for PYD, DPD, NTX and CTX measured by immunoassays were calculated to detect changes in bone turnover, DPD by ELISA or CLEIA showing the highest Z-score. The sensitivity and specificity of the different assays were evaluated using a receiver operating characteristic (ROC) curve. With a specificity of 90% the sensitivity of the markers considered was low (from 33% for DPD by CLEIA to 11% for PYD-DPD by ELISA), but increased considerably with a specificity of 75%. In conclusion, urinary pyridinium crosslink derivatives increase with age and after the menopause, and rise slightly in women with osteoporosis, there being a negative correlation among age and the fraction of free PYD and DPD of the total urinary excretion. Among the resorption markers most often available in clinical laboratories, free DPD by ELISA or CLEIA was the best at discriminating osteoporotic postmenopausal women from aged-matched control postmenopausal women.

The relationships between the degree of beta-isomerization of type I collagen degradation products in the urine and aging, menopause and osteoporosis with fractures

We have evaluated the effect of aging, menopause and osteoporosis on the measurements of both nonisomerized type I collagen C-telopeptide breakdown products (alpha-CTx) by radioimmunoassay (RIA) and beta-isomerized type I collagen C-telopeptide breakdown products (beta-CTx) by enzyme-linked immunosorbent assay (ELISA). In 86 premenopausal healthy women (PRE), 144 postmenopausal healthy women (POST), 74 patients with vertebral fractures (VX) and 61 patients with hip fractures (HX), urinary CTx excretion was measured by both ELISA and RIA assays. Samples were collected more than 6 months after fracture in the VX group and within 48 h after fracture in the HX group. In all subjects a highly significant correlation was found between alpha-CTx and beta-CTx (r = 0.85). The values of beta-CTx in the POST group greatly increased compared with those in the PRE group (% mean increase: 82%), while the values of alpha-CTx in the POST group moderately increased compared with those in the PRE group (% mean increase: 47%). The values of both alpha-CTx and beta-CTx in the HX group were significantly higher than those in the other groups, but particularly the increase in mean alpha-CTx (211% for HX versus POST) was very high compared with the increase in mean beta-CTx (68% for HX versus POST). Moreover, the alpha-CTx/beta-CTx ratio in the HX group was significantly higher than in the other groups. These results suggest that both assays well reflect the increase in bone resorption associated with high bone turnover, especially, in osteoporotic patients with hip fracture. However, there was a difference between the urinary excretion of alpha-CTx and beta-CTx in patients with hip fracture, so the alpha-CTx/beta-CTx radio might be a good indicator reflecting the characteristics of bone metabolism for osteoporosis with hip fracture.

The effects of low dose norethisterone on biochemical variables in postmenopausal women

Norethisterone 2.5 mg/day was administered to 26 postmenopausal women (aged 54-79 years) with varying degrees of osteoporosis and with a forearm bone mineral density value more than 2 SD below the young normal mean. Fasting blood and urine samples were collected and radiocalcium absorption measured at baseline and after treatment for a median period of 4 months. There were significant falls in serum calcium and its fractions, phosphate, alkaline phosphatase and cholesterol (HDL and LDL), and significant rises in serum chloride and parathyroid hormone. In the urine, there were significant falls in calcium, sodium and hydroxyproline. These changes were in close agreement with our previously reported responses to norethisterone 5 mg/day. We conclude that norethisterone in a dose of 2.5 mg/day is probably as effective as 5 mg/day in reducing bone resorption in postmenopausal women with low bone density.

Comparison of urinary bone resorption markers in women of 40-70 years; day-to-day and long-term variation in individual subjects

OBJECTIVES

Bone resorption can be judged using biochemical markers in urine and blood. Our aim was to study the patterns of markers in the postmenopausal period.

METHODS

The urinary excretion of bone resorption markers was tested using different assays. The study was undertaken to determine the day-to-day and the long-term variation, over 8 years, of these markers in individual women.

RESULTS

Over a period of 2 weeks, the median of the day-to-day variation of the pyridinium crosslink markers varied between 12 and 23%, the median value of the long-term variation over 8 years between 10 and 21%, for the telopeptide markers median day-to-day variation was 18 and 20% and the long-term variation was 17 and 19%. The correlations between the different crosslink markers varied between 0.63 and 0.92, depending on the kind of the crosslink and on the method of determination. The two telopeptide markers showed an excellent correlation with r of 0.95. The excretion of all bone resorption markers varied with postmenopausal age, some differences were found between the crosslink and the telopeptide excretions with age, in women more than 20 years postmenopausal the telopeptides decrease whereas the crosslinks show an increase.

CONCLUSIONS

This study shows that crosslinks and telopeptides give similar information on the rate of bone resorption: an increase during the first 5 years and a slight decrease in the next 5 years after menopause, discrepancies were found after 10 or more postmenopausal years.

Development of an immunoassay for urinary galactosylhydroxylysine

Galactosylhydroxylysine (GHL) is released during bone resorption and has been shown to be elevated in subjects with metabolic bone loss. GHL is relatively specific for bone, it is not recycled or significantly metabolized during collagen turnover, and the levels are not influenced by diet. Previous measurements of GHL levels in urine have been performed using reverse-phase high performance liquid chromatography following pre-column derivatization. We produced polyclonal antibodies to GHL using GHL purified from sea sponges and developed an immunoassay that can recognize GHL in urine. The antibodies have minimal cross-reactivity with a physiological mixture of amino acids (< 1%), galactose (< 0.2%), lactose (< 0.3%), and glucosylgalactosylhydroxylysine (< 1%). This competitive immunoassay requires no dilution or pretreatment of the samples and provides a rapid and easy method for the evaluation of GHL in urine. Analysis of clinical samples from normal individuals, post-menopausal women, osteoporotic patients and individuals with Paget's disease show that the assay can discriminate between groups with differing levels of bone resorption as well as deoxypyridinoline (Dpd).

Clinical evaluation of the Serum CrossLaps One Step ELISA, a new assay measuring the serum concentration of bone-derived degradation products of type I collagen C-telopeptides

The Serum CrossLaps One Step ELISA is a sandwich assay using two monoclonal antibodies specific for a beta-aspartate form of the epitope EKAHDGGR derived from the carboxy-terminal telopeptide region of type I collagen alpha1-chain. Our objective was to assess the clinical value of the Serum CrossLaps assay for monitoring antiresorptive therapy in osteoporosis treatment. Samples obtained from postmenopausal women treated with different doses of cyclic or continuous hormone replacement therapy (HRT) with an estrogen analog (tibolone) or with a bisphosphonate (ibandronate) were measured in the Serum CrossLaps One Step ELISA at baseline and at various time points during therapy. The corresponding urine samples were measured in the urine CrossLaps ELISA and corrected for creatinine excretion. The serum CrossLaps measurements and corresponding urinary CrossLaps measurements were highly correlated (r >0.8 for all studies). The serum and urine CrossLaps measurements showed a significant decrease among the women treated with clinically relevant doses of either of the antiresorptive agents. Furthermore, the annual percentage change in bone mineral density (BMD) correlated with the measured changes in CrossLaps concentration. The serum CrossLaps assay showed a specificity of 83-100% and a sensitivity of 59-83% for assessing BMD changes. The corresponding values for the creatinine-corrected urinary measurements were 83-92% specificity and 68-79% sensitivity. We conclude that performance of the convenient Serum CrossLaps One Step ELISA is at least equivalent to that of the urine text for follow up of antiresorptive treatment in osteoporosis. Further studies are needed to optimize its use in this and other clinical applications.

Phyto-oestrogen excretion and rate of bone loss in postmenopausal women

OBJECTIVE

The hypothesis was tested that the rate of postmenopausal bone loss is inversely associated with long-term urinary excretion of phyto-oestrogens, as a marker of habitual dietary intake.

DESIGN

Secondary analysis of a 10-year follow-up study (1979 1989) among postmenopausal women in the Netherlands.

SUBJECTS

From the original population of 154 women, 32 women were selected with an annual rate of radial bone loss of < or = 0.5% over the first 5 years of the study and 35 women with a rate of > or = 2.5% per year.

METHODS

The isoflavonoids genistein, daidzein and equol, and the lignan enterolactone were determined by gas chromatography mass spectrometry in aggregate samples from annually collected urine samples. Cortical bone density of the radius had previously been measured annually by single-photon absorptiometry.

RESULTS

Excretion of isoflavonoids did not differ between both groups, although in multivariate analysis equol excretion was weakly positively associated with rate of bone loss in the 5 years after the menopause. Enterolactone excretion was significantly higher in the group with high rate of bone loss. This positive association remained in multivariate linear regression analysis after adjustment for age, years since menopause, body mass index and intake of calcium, vegetable protein and dietary fibre.

CONCLUSIONS

Enterolactone excretion is likely to be an indicator of consumption of grains and legumes; it is not clear whether the observed positive association with rate of bone loss is a causal one. Our results do not support a preventive effect of low, unsupplemented dietary intake of phyto-oestrogens on postmenopausal cortical bone loss. However, no conclusions can be drawn about effects of higher doses of phyto-oestrogens.

Geographic differences in bone turnover: data from a multinational study in healthy postmenopausal women

Biochemical markers of bone metabolism (bone markers) are used increasingly to monitor response to therapy and may be predictors of bone loss and fractures. The relationship between fracture rates, which differ between countries, and the rate of bone turnover has not been examined. Therefore, we explored the geographic variability of bone turnover in a selected, healthy study population of 619 postmenopausal women, ages 40-61, participating in a clinical trial of raloxifene hydrochloride for osteoporosis prevention. The subjects were distributed among 38 investigative sites in 10 countries (9-211 subjects/country) on four continents (North America, n = 277, Europe, n = 168, Australia, n = 125, and Africa, n = 49). Specimens for serum osteocalcin (OC), bone-specific alkaline phosphatase (BSAP), and urine type I collagen fragment/urinary creatinine ratio (CTX) were handled in a uniform fashion and assayed in a central laboratory. Mean levels of OC (P < 0.001), BSAP (P = 0. 006), and CTX (P < 0.001) varied significantly by country (ANOVA), with the lowest values typically in German and Spanish subjects and the highest in American and Canadian subjects. The consistent pattern and wide ranges of mean bone marker values (OC 1.6-fold, BSAP 1.7-fold, CTX 3.1-fold) between countries suggest clinically significant differences in bone turnover. Geographic differences in bone markers were not explained by the determined potential confounders of age, years posthysterectomy, total serum cholesterol, and serum follicle stimulating hormone (FSH). We conclude that bone marker values vary substantially by country in this selected study population, suggesting systematic geographic differences in bone metabolism that potentially relate to osteoporotic fracture rates.

Markers of bone remodelling in metabolic bone disease

New specific markers of bone remodelling have been developed that allow the evaluation of bone formation (plasma levels of osteocalcin and bone alkaline phosphatases) or bone resorption (collagen crosslink levels in urine). These markers can be used to evaluate bone disease. Their best application is currently in renal osteodystrophy, where there is a broad spectrum of bone abnormalities. In patients with this disease, bone markers can obviate the need for bone biopsy. So far, bone alkaline phosphatase is the most sensitive and specific marker for predicting the type of bone disease and therefore for deciding treatment in dialysed patients, although it is not ideal. Bone markers have also allowed a dramatic improvement in the comprehensive approach to bone loss with aging in women. Monitoring of the marked increase in bone turnover, and its persistence, in older women after menopause may help in the design of treatment strategies for osteoporosis. There is some hope that the measurement of urinary levels of collagen crosslinks will help to predict the clinical outcome of osteoporosis with respect to fractures in postmenopausal women. Bone markers could, besides being a measurement of bone density, help to determine the optimal treatment of postmenopausal women. Bone markers could also be used to predict or ascertain the response to treatment of osteoporosis, but few data are currently available to judge the routine usefulness of these new applications.

Response of biochemical markers of bone turnover to hormone replacement therapy: impact of biological variability

Biochemical markers of bone turnover may be useful to monitor patients taking hormone replacement therapy (HRT). The aim of this study was to assess the utility of markers in monitoring HRT by comparing the response of a large panel of markers to HRT with their within subject variability. We measured the response of markers to transdermal estradiol in 11 postmenopausal women over 24 weeks. We measured the within subject variability of markers in 11 untreated healthy postmenopausal women over the same period. The mean decrease in markers of bone formation after 24 weeks treatment ranged from 19% for procollagen type I C-terminal propeptide (PICP) to 40% for procollagen type I N-terminal propeptide (PINP). The mean decrease in markers of bone resorption ranged from 10% for tartrate-resistant acid phosphatase (TRAP) to 67% for C-terminal cross-linked telopeptide The least significant change (LSC at p < 0.05), calculated from the within subject variability in the untreated group, was used to define response. LSC for osteocalcin was 21%, bone alkaline phosphatase 28%, PICP 24%, PINP 21%, type I collagen telopeptide 28%, TRAP 17%, urinary calcium 90%, hydroxyproline 75%, total deoxypyridinoline 47%, free pyridinoline 36%, free deoxypyridinoline 26%, N-terminal cross-linked telopeptide 70%, and C-terminal cross-linked telopeptide 132%. The greatest number of responders after 24 weeks of treatment were found using PINP and osteocalcin (9 each), and free deoxypyridinoline (8 each) and total deoxypyridinoline (8 each) and total deoxypyridinoline (7 each). Lumbar spine bone mineral density defined four patients as responders. The ability to detect a response differs between markers and is not dependent on the magnitude of response to therapy.

Urinary deoxypyridinoline is a useful biochemical bone marker for the management of postmenopausal osteoporosis

Most medical treatment of postmenopausal osteoporosis are inhibitors of bone resorption and urinary deoxypyridinoline (D-Pyr) has been shown to be a reliable indicator of bone resorption. Fifty-one healthy women were divided into four groups. Group A: premenopausal women (n = 10), Group B: postmenopausal women, no osteoporosis, not on hormone replacement therapy (HRT) (n = 14), Group C: postmenopausal women, osteoporotic, not on HRT (n = 12), and Group D: postmenopausal women on HRT (n = 15). Fasting urine was collected and sampled for D-Pyr using Pyrilinks-D Kit-(Metra Biosystems). Urinary D-Pyr was calculated in nM/creatinine mM. There was a significant difference between premenopausal and postmenopausal urinary D-Pyr showing a higher value of D-Pyr during menopause. Urinary D-Pyr results of postmenopausal women on HRT and premenopausal women showed no difference. Hence D-Pyr may be useful for the monitoring of hormonal treatment of postmenopausal bone loss.

Differences in bone resorption after menopause in Japanese women with normal or low bone mineral density: quantitation of urinary cross-linked N-telopeptides

The objective of this study was to examine the value of NTx, a urinary cross-linked N-telopeptides of type I collagen, as a marker of bone resorption. We assessed changes in pre- and postmenopausal bone resorption by evaluating the correlation of NTx with L2-4 bone mineral density (BMD) in a total of 1100 Japanese women, aged 19-80 years [272 premenopausal (45.2 +/- 6.2 years) and 828 postmenopausal (59.5 +/- 6.2 years)]. Postmenopausal women were divided into three groups based on the range of BMD (normal, osteopenic, and osteoporotic). Within each group, subjects were further segregated according to years since menopause (YSM). NTx values were then evaluated for each group. Our results showed that BMD was significantly decreased (P < 0.05) and NTx was significantly increased (P < 0.01) after menopause in age-matched analysis. Consistent with a previous report, NTx was inversely correlated with BMD for the entire cohort of study subjects (r = -0.299), although NTx correlated better with premenopausal than postmenopausal BMD (r = -0.240 versus r = -0.086). This may have been due to the fact that elevated values of NTx were exhibited over the entire range of BMD present in the postmenopausal women, suggesting that NTx might respond faster to the estrogen withdrawal than BMD. In all postmenopausal women, regardless of the range of BMD, the increase in NTx reached a peak within 5 YSM. After 11 YSM, however, NTx remained elevated in the osteoporotic group but it decreased in the osteopenic group, and showed no significant change in the group of postmenopausal women with normal BMD. These findings suggest that bone resorption is dramatically increased within 5 years after menopause but remains increased only in osteoporotic women.

Rapid bone loss is associated with increased levels of biochemical markers

We examined associations of biochemical markers of bone turnover with rapid bone loss, as measured by changes in bone mineral density (BMD). To improve the precision of bone loss estimates, calcaneal BMD was measured up to eight times over a long interval (13 years) among postmenopausal women (mean age = 62 years at baseline). Women with fractures during the previous year, and users of corticosteroids, active vitamin D, bisphosphonates or calcitonin were excluded to avoid potential transient effects on marker levels. Among the remaining 354 women, markers were measured for 100 women with the fastest BMD loss (rapid loss group; mean = 2.2%/year) and 100 with the slowest loss (mean = 0.4%/year). Two markers of bone formation, serum bone alkaline phosphatase (Alkphase-B; BAP) and osteocalcin (NovoCalcin; OC), and two markers of bone resorption, urinary creatinine-corrected free deoxypyridinoline (Pyrilinks-D; DPD) and free pyridinolines (Pyrilinks; PYD), were measured. In separate logistic regression models, each of the markers was strongly associated with rapid loss: the odds of rapid loss increased by 1.8 to 2.0 times for each 1.0 standard deviation (SD) increase of the marker. For BAP levels 2 SD above the mean, the probability of rapid bone loss was 80%; in contrast, the probability was only 20% at 2 SD below the mean. The other markers yielded similar results. We conclude that these markers are associated with rapid bone loss; this relationship appears to be continuous, with progressively greater risk of rapid bone loss with increasing levels of biomarkers. Prospective studies that include the entire distribution of bone loss rates are warranted to confirm these findings.

Three monthly intravenous injections of ibandronate in the treatment of postmenopausal osteoporosis

PURPOSE

Oral treatment of osteoporosis with bisphosphonates relies on compliance, the absorption being low and suppressed by simultaneous food intake. Intravenous (IV) treatment with an aminobisphosphonate, pamidronate (once every 3 months) was effective, but required infusions. Ibandronate, a new very potent aminobisphosphonate, can be administered safely as an IV bolus injection, and therefore offers an interesting alternative suitable for outpatient treatment.

PATIENTS AND METHODS

To test the efficacy of this bolus IV treatment in postmenopausal osteoporosis in randomized partly double-blind, placebo controlled study, 125 postmenopausal women (mean age, 64 years) with osteoporosis (bone mineral density [BMD] < -2.5 SD T score) received a placebo or ibandronate (0.25, 0.5, 1, or 2 mg) every 3 months. All patients received 1 g calcium/day. BMD, in g/cm2, was measured by dual-energy x-ray absorptiometry at all standard sites.

RESULTS

Lumbar spine BMD (L2 to L4) did not change (0.85%) in the placebo group, but increased by 2.4%, 3.5%, 3.7%, and 5.2% at 12 months for dose-ranging groups (no significant differences among ibandronate groups). The increase was statistically significantly different from placebo for the 0.5 mg (P < 0.006), 1 mg (P < 0.004), and 2 mg (P < 0.001) group, whereas with 0.25 mg no significant differences occured. After 1 year there were no significant changes in BMD compared with placebo at the femoral neck, Ward's triangle, and distal forearm. Total hip and trochanter BMD increased significantly, by 1.8% and 2.9% for total hip and by 2.7% and 4.2% for trochanter in the 1 and 2 mg group, respectively. Urinary excretion of C-telopeptide and N-telopeptide decreased after 1 month in all ibandronate groups, with a clear dose dependency. Three months after the first injection of 2 mg ibandronate there was still a significant reduction in these markers of bone resorption. Osteocalcin decreased progressively and dose dependently over time. There was a correlation between the decrease in C-telopeptide measured after 1 month and the increase in lumbar spine BMD after 1 year (n = 115, r = -0.26, P < 0.012). Ibandronate therapy proved to be safe. There was no significant difference in the overall number of adverse events in the ibandronate groups compared with the placebo group. Considering specific adverse events, no dose dependency and difference to placebo could be observed apart from acute reactions that occurred in 7% of the patients.

CONCLUSION

Treatment of postmenopausal osteoporosis by interval IV bolus injections of the bisphosphonate ibandronate was safe and effective in increasing BMD through a dose-dependent inhibition of bone resorption. The high potency of ibandronate allows 3-month interval bolus IV injections as a new therapeutic approach with optimal compliance.

Serum levels of pyridinium crosslinks in postmenopausal women and in Paget's disease of bone

The purpose of this study was to measure pyridinium crosslinks in serum by high performance liquid chromatography (HPLC) and to correlate levels with urinary excretion in patients with different osteometabolic conditions. Blood and spot urine samples were collected between 9 and 11 A.M. in 92 early postmenopausal, untreated women (age 52.3 +/- 2.6 years, months since menopause 20.4 +/- 9.6), 17 patients with active Paget's disease (10 males, aged 65. 1 +/- 12.6) and 24 healthy premenopausal women (aged 28.4 +/- 4.2). Urinary excretion of the total fraction (free + peptide bound) of pyridinolines (Pyr, Dpyr) was measured by HPLC. Before HPLC analysis, serum samples were submitted to a clean-up procedure by ultrafiltration. In 42 postmenopausal women, bone loss was calculated from two bone mass measurements (L2-L4, DXA), performed at study entry and after 12 months. Statistical analysis was performed by Student's t test for independent samples and linear regression analysis. In pagetic patients' serum levels of Pyr and Dpyr were more than threefold increased over the mean observed in healthy controls and were closely correlated with total alkaline phosphatase levels (Pyr: r = 0.73; Dpyr: r = 0.72, P < 0.0005). Compared with controls, postmenopausal women had significantly increased levels of both urinary and serum Pyr and Dpyr (P < 0.003). In pagetic patients and postmenopausal women, crosslinks serum levels were correlated with their urinary excretion with r values ranging from 0.46 to 0.84. In postmenopausal women, only serum Dpyr correlated with the rate of bone loss (r = -0.36, P = 0.02). The data suggest that serum levels of pyridinium cross-links are correlated with urinary excretion in patients with different osteometabolic conditions. The determination of serum levels prevents limitations related to urinary specimen collection and may be a more practical method for routine application, avoiding corrections for urinary creatinine which could be misleading.

Increments in bone mineral density of the lumbar spine and hip and suppression of bone turnover are maintained after discontinuation of alendronate in postmenopausal women

PURPOSE

Previously we have reported a significant increase in bone mineral density (BMD) of the spine and the hip and reductions in biochemical indices of bone turnover in postmenopausal women with osteoporosis treated with alendronate at various doses over 1 to 2 years. We have followed BMD and biochemical parameters in these patients for 1 or 2 years after discontinuation of alendronate to determine resolution of alendronate effects.

PATIENTS AND METHODS

Participants received daily oral doses of placebo, 5 or 10 mg of alendronate for 2 years, or 20 or 40 mg of alendronate for 1 year followed by 1 year of placebo. No treatment was given in the third year of study.

RESULTS

Lumbar spine BMD changes in the 5- and 10-mg groups (-1.4 and -0.4%) were similar to those in the placebo group (-1.2%) 1 year after discontinuation of drug and lumbar spine BMD changes in the 20- and 40-mg groups (-1.2% and 0.8%) were similar to those in the placebo group (-0.9%) 2 years after discontinuation of drug. BMD of the total hip followed the same pattern of resolution. The difference in BMD between alendronate and placebo groups at the end of alendronate treatment was maintained up to 2 years. Residual reductions in the bone resorption markers urinary deoxypyridinoline (D-Pyr) and collagen type 1 cross-linked N telopeptides and the bone formation markers serum bone-specific alkaline phosphatase and osteocalcin remained for 1 year after discontinuation of 5 and 10 mg of alendronate and for 2 years after discontinuation of 20 and 40 mg of alendronate, other than return of D-Pyr to baseline 1 year after cessation of treatment with the 5- and 10-mg doses.

CONCLUSIONS

A residual decrease in bone turnover may be found up to 2 years after discontinuation of alendronate. Accelerated bone loss is not observed when treatment is discontinued. However, continuous therapy with alendronate is required to achieve a continuous gain in BMD.

Elimination and biochemical responses to intravenous alendronate in postmenopausal osteoporosis

Postmenopausal women with established vertebral osteoporosis were studied for 2 years to determine the terminal elimination half-life and the duration of response to treatment with intravenous alendronate (30 mg) given over 4 days. The urinary excretion of alendronate followed a multiexponential decline. Approximately 50% of the total dose was excreted over the first 5 days, and a further 17% was excreted in the succeeding 6 months. Thereafter, there was a much slower elimination phase with an estimated mean terminal half-life of greater than 10 years (n = 11). Urinary excretion of hydroxyproline and calcium decreased significantly from pretreatment values by day 3, reaching a nadir by 1 week (40% and 67% decrease, respectively). Thereafter, hydroxyproline remained suppressed for the following 2 years. In contrast, urinary calcium excretion returned gradually toward pretreatment values over the first year and during the second year was comparable to pretreatment values. Serum activity of alkaline phosphatase activity decreased over 3 months (23% reduction), increased gradually thereafter, and returned to pretreatment values at month 24. Bone mineral density measured at the spine increased by approximately 5% during the first year and remained significantly higher than pretreatment values at 2 years. We conclude that a short course of high doses of intravenous alendronate is associated with a prolonged skeletal retention of the agent. This open study also suggests that this regimen has a sustained effect on bone turnover persisting for at least 1 year.

New biochemical markers of bone resorption in the study of postmenopausal osteoporosis

We performed a comparative study on the sensitivity of the determination of several biochemical markers of bone resorption: urinary calcium/creatinine, free pyridinolines (F-Pyr), free deoxypyridinoline (F-Dpyr), carboxyterminal telopeptide of collagen I (CTX) and aminoterminal crosslinked telopeptides of collagen I (NTX) in the study of postmenopausal osteoporosis. The study included 19 untreated osteoporotic postmenopausal women, aged 59 +/- 6 years, range 46-70 and 16 healthy control postmenopausal women, aged 56 +/- 7 years, range 48-70 years. The following bone markers were determined in 2-h fasting urine samples: calcium/creatinine (atomic absorptiometry), F-Pyr (ELISA, Metra), F-Dpyr (ELISA, Metra), CTX (Crosslaps, Cis bio International) and NTX (ELISA, Osteomark, OSTEX). Values of all markers were expressed as urinary creatinine (Cr) ratios. We found a significant increase in all the studied biochemical markers of bone resorption in osteoporotic patients with respect to control women. Areas under receiver operating characteristic (ROC) curves corresponding to F-Pyr/Cr, Calcium/ Cr, NTX/Cr, CTX/Cr and F-Dpyr/Cr were 74%, 75%, 93.4%, 95.7% and 96% respectively. There were no significant differences among the areas of the ROC curves corresponding to NTX, CTX and F-Dpyr, but areas under urinary calcium and F-Pyr were significantly lower. Among the biochemical markers of bone resorption studied, F-Dpyr, CTX and NTX presented the best discrimination between osteoporotic and control women. F-Dpyr/Cr sensitivity was 79% with a specificity of 100%, CTX/Cr sensitivity was also 79% with a specificity of 100% and NTX/Cr sensitivity was 52% with a specificity of 100%.