Urinary N-telopeptide levels discriminate normal, osteopenic, and osteoporotic bone mineral density

BACKGROUND

The level of urinary, type I collagen, crosslinked N-telopeptides (NTX) is a new marker of bone resorption. To our knowledge, no population-based studies of older adults have determined whether this measure can identify individuals with osteoporosis.

OBJECTIVES

To measure the levels of NTX in a cross-sectional study of ambulatory, older, white adults and to evaluate whether this measure of bone resorption could identify individuals with osteoporosis.

PATIENTS AND METHODS

The subjects, aged 50 to 98 years, formed 3 groups: 374 men, 223 women currently using estrogen, and 364 women not currently using estrogen. A standard medical history and validated record of medication use were obtained. Height and weight were measured. Bone mineral density (BMD) was measured at the hip and lumbar spine using dual energy x-ray absorptiometry. The levels of NTX were measured by enzyme-linked immunosorbent assay.

RESULTS

Overall, the levels of NTX increased slightly with age in men and in estrogen users and more dramatically in nonestrogen users. In a model adjusted for all major risk factors for osteoporosis, there was a significant decrease in BMD levels by increasing quintiles of NTX levels at the hip and spine in women with and without estrogen use and at the hip in men. Using sex-specific, peak bone mass criteria and age-adjusted analyses, the levels of NTX discriminated between normal (< or = -1.0 SD), osteopenic (> -1.0 and < -2.5 SD), and osteoporotic (> or = -2.5 SD) BMD levels in all groups except the spine in men.

CONCLUSIONS

The levels of NTX uniquely discriminated between older adults with normal, osteopenic, or osteoporotic BMD levels. If confirmed, these data suggest that NTX levels could be used to predict current osteoporosis in older men and women.

Specific changes of urinary excretion of cross-linked N-telopeptides of type I collagen in pre- and postmenopausal women: correlation with other markers of bone turnover

Urinary excretion of cross-linked N-telopeptide of type I collagen (NTx) has been reported to be a specific marker of bone resorption [18]. We assessed a new immunoassay for NTx as an indicator of changes in bone resorption caused by spontaneous menopause and compared cross-sectionally the levels of urinary NTx, hydroxylysylpyridinoline (HP), lysylpyridinoline (LP), hydroxyproline (OH-Pr), other serum biochemical indices, and lumbar spine and proximal femur bone mineral density (BMD). Eighty-one Japanese women aged 22-77 participated in this study; 36 were premenopausal and 45 were postmenopausal. Urinary HP, LP, and NTx stayed at low levels in the premenopausal period and rose 21%, 30%, and 67% in the postmenopausal period, respectively. The rise in LP and NTx was statistically significant (P < 0.01), suggesting that NTx is mostly released from bone matrix when bone resorption is accelerated. When premenopausal women were divided into two age groups and postmenopausal women were divided into two groups according to years since menopause (YSM) there were significant differences in LP and NTx between women <4 YSM and women aged <40 and those women aged 41+ (P < 0.01 and P < 0.05, respectively). A significant 110% increase in urinary NTx and a 48% increase in urinary LP were observed in postmenopausal women compared with age-matched premenopausal women aged 45-55. All biochemical markers other than serum PTH correlated significantly with each other (r = 0. 243-0.858, P < 0.05-0.0001). Urinary NTx inversely correlated with lumbar spine BMD. When postmenopausal women were divided into three groups, the correlation between bone resorption and formation markers in women 0-1 YSM was greater than in women 2-10 YSM and in women 11 + YSM, indicating that resorption and formation are coupled at the early postmenopausal period. We conclude that urinary NTx is responsive to changes in bone metabolism caused by estrogen deficiency and may be a more sensitive and specific marker than HP, LP, or OH-Pr in the early postmenopausal years.

Intraindividual variability in bone markers in the urine

The biological variability of urinary bone resorption markers was measured in 30 healthy and 20 postmenopausal osteoporotic women. The second spot urines were collected at weekly intervals for 5 weeks and urinary pyridinium crosslinks, hydroxyproline, calcium and Ntx were evaluated. Results are discussed in relation to analytical variability, critical difference values and index of individuality. In conclusion monitoring and classifying bone turnover in groups of persons are well established, but the routine use of urinary biochemical bone markers in the individual patient is of limited use.

Biochemical markers of bone resorption compared with estimates of bone resorption from radiotracer kinetic studies in osteoporosis

The pyridinium cross-links of collagen pyridinoline (Pyd) and deoxypyridinoline (Dpd) are released during bone resorption and are neither metabolized nor absorbed from the diet. The aim of this study was to validate their use in osteoporosis. We studied 19 women with osteoporosis and estimated the bone resorption rate from a combined calcium balance/kinetics technique without (R) and with partial (R(H)) and "complete" (Res) correction for long-term exchange. The strongest correlation was observed between the bone-specific marker (Dpd) and with complete correction for long-term exchange (Res) (r = 0.71, p < 0.001). The intercept was not different from zero, suggesting that bone was the major source for Dpd. The crude ratio of Dpd to Res in the 19 women was 54.5; but the regression coefficient relating Dpd as the dependent variable to Res was 31.8 (95% CI 15.6-48.0), which was higher, but not significantly, than the ratio between Dpd and calcium (16.4) in 10 bone samples (cortical and trabecular bone). The weakest correlations between a biochemical marker and a kinetic index were those between hydroxyproline (a nonspecific marker of bone resorption) and R or R(H). Treatment with hormone replacement therapy (HRT) or HRT and parathyroid hormone peptide 1-38 in seven women over 1 year resulted in similar percent changes in the biochemical markers and estimates of bone resorption. We conclude that the measurement of Dpd provides a reasonably accurate assessment of bone resorption in osteoporosis, and in the context of several repeat 24-h collections of urine offers measurement precision that is similar to that obtainable with methods depending on the use of radioisotopic tracers and the assessment of metabolic calcium balance.

Effects of cyclical etidronate therapy on bone loss in early postmenopausal women who are not undergoing hormonal replacement therapy

This study was carried out to investigate the effectiveness and tolerability of cyclical etidronate therapy in the prevention of bone loss occurring in early postmenopausal women who are not undergoing hormone replacement therapy (HRT). A total of 109 Caucasian women aged 45-60 years were treated with etidronate 400 mg/day or placebo for 14 days followed by calcium supplementation 500 mg/day for 77 days. Ninety-one women completed the 2 years of the study. After 2 years, the estimated difference between the two groups as regards lumbar spine bone mineral density (BMD) was 2.53% (SEM 1.07%; p = 0.01); BMD of the hip and wrist were not significantly different between treatment groups. A clear reduction in bone turnover was obtained as evidenced by a significant decrease in serum alkaline phosphatase level and in urinary N-telopeptide/ creatinine ratio in the etidronate group; the difference between the two groups was -12% +/- 3.2% for serum alkaline phosphatase level (p = 0.019) and -22.9% +/- 13.7% for the urinary N-telopeptide/creatinine ratio (p = 0.047). There was no statistically significant difference between the two groups in terms of the serum osteocalcin levels and urinary hydroxyproline/ creatinine and calcium/creatinine ratios. Etidronate was generally well tolerated and its adverse event profile was similar to that of placebo. The results of this study indicate that cyclic etidronate therapy can prevent trabecular bone loss, with no deleterious effect on cortical bone, in the first 5 years of menopause and that it has a very high safety margin.

Neridronate preferentially suppresses the urinary excretion of peptide-bound deoxypyridinoline in postmenopausal women

ELISAs for measuring the urinary excretion of collagen crosslinks and related peptides appear to show marked differences in sensitivity to anti-resorptive therapy. This presumably reflects variations in specificity of the anylate being detected in these assays, and the way in which they respond to treatment. To clarify these points, we used HPLC analysis to assess the effect of four weeks treatment with the amino-bisphosphonate, neridronate, on free and peptide-bound fractions of the collagen cross-links deoxypyridinoline (Dpd) and pyridinoline (Pyd). Six postmenopausal women, in whom two hour morning urine samples were obtained at baseline (x2), and one, two and four weeks after commencing treatment, were included. We found that neridronate had relatively little effect on peptide-bound or free urinary Pyd. but markedly reduced peptide-bound urinary Dpd. However, urinary excretion of free Dpd was not significantly affected. As a consequence of these differential effects on collagen cross-link excretion, neridronate led to a striking increase in the free/total Dpd ratio, and in the peptide-bound Pyd/Dpd ratio. We conclude that neridronate, and presumably other bisphosphonates, selectively suppresses peptide-bound Dpd excretion, possibly reflecting altered processing of collagen crosslinks released during bone resorption.

The effect of estrogen replacement therapy on zinc in serum and urine

OBJECTIVE

To ascertain the influence of estrogen replacement therapy (ERT) on blood and urinary zinc in postmenopausal women.

METHODS

Thirty-seven postmenopausal women aged 53.2 +/- 3.7 years were examined. All were treated with conjugated estrogens 0.625 mg and medroxyprogesterone acetate 5 mg. Zinc, magnesium, calcium, phosphate, and alkaline phosphatase levels in blood were measured before and after 6 and 12 months of treatment. Urinary excretion of zinc, magnesium, calcium, phosphate, and hydroxyproline were evaluated before and after 3, 6, and 12 months of therapy. Bone mineral density was examined before treatment and after 1.7 +/- 0.3 years of ERT. Subjects were classified by 1) initial bone mineral density values (osteoporotics less than 0.850 g/cm2) and 2) zinc excretion as elevated (greater than 600 micrograms/g creatinine).

RESULTS

At baseline, the values of most markers of bone turnover were higher in the osteoporotic women (Hotelling test, P = .06). After 1 year of treatment, a higher decrease of most indices was observed in the osteoporotic patients, and no statistical difference was found between the osteoporotic and the normal groups (Hotelling test, P = .31). A consistent negative association was observed between changes in bone mineral density and urinary zinc excretion in the osteoporosis group. Estrogen replacement therapy reduced excretion of zinc, magnesium, and hydroxyproline in the elevated zinc excretion group. Zinc excretion decreased 35% after 3 months and 26% after 1 year of treatment. The serum tests, with the exception of alkaline phosphatase, showed only negligible changes during ERT.

CONCLUSION

A significant decrease in zinc excretion was observed after 3 months of ERT. This change was more pronounced in women with osteoporosis and elevated zinc excretion. Because zinc excretion is almost uninfluenced by variation in diet, it may be used as an additional marker of changes in bone metabolism.

A controlled trial of raloxifene (LY139481) HCl: impact on bone turnover and serum lipid profile in healthy postmenopausal women

This randomized, double-blind, placebo-controlled, multicenter, 8-week study evaluated short-term effects of raloxifene on bone turnover, serum lipids, and endometrium in healthy, postmenopausal women. A total of 251 women received either placebo, raloxifene HCl 200 or 600 mg/day, or conjugated estrogens (Premarin, 0.625 mg/day). Bone turnover (serum alkaline phosphatase, serum osteocalcin, urinary pyridinoline cross-links, urinary calcium excretion, urinary hydroxyproline) and serum lipids (total serum cholesterol, high- and low-density lipoprotein cholesterol [HDL-C and LDL-C]) were evaluated at weeks 0, 2, 4, and 8. Endometrial biopsies were performed at weeks 0 and 8. Treatment groups were compared for each parameter for baseline-to-endpoint changes. The estrogen and raloxifene groups experienced similar decreases in serum alkaline phosphatase (range 10-11%), serum osteocalcin (range 21-26%), urinary pyridinoline cross-links (range 20-26%), and urinary calcium excretion (range 45-72%). These decreases differed significantly compared with placebo-treated subjects for all markers except serum osteocalcin, the raloxifene HCl 200 mg group. LDL-C decreased significantly in the estrogen and both raloxifene groups (range 5-9%) compared with placebo-treated subjects. HDL-C increased significantly in the estrogen group (16%) but was unchanged in the raloxifene groups. HDL-C:LDL-C ratios increased significantly in the estrogen and raloxifene groups (range 9-29%). Serum cholesterol decreased significantly in both raloxifene groups (range 4-8%) but was unchanged in the estrogen group. Uterine biopsies of raloxifene-treated subjects showed no change in the endometrium during this short-term treatment. Biopsies of the estrogen group showed significant endometrial stimulation. The only adverse event possibly related to raloxifene was vasodilatation (hot flashes) which was most common in the raloxifene HCl 600 mg group. Study results indicate that raloxifene may provide beneficial effects to bone and serum lipids in humans without uterine stimulatory effects.

Clinical performances of galactosyl hydroxylysine, pyridinoline, and deoxypyridinoline in postmenopausal osteoporosis

We have previously shown that galactosyl hydroxylysine (GHYL), pyridinoline (PYD), and deoxypyridinoline (DPD) have a better accuracy and discriminate power than hydroxyproline in distinguishing postmenopausal osteoporotic women from premenopausal controls. In this study, we evaluated the clinical performances of GHYL, PYD, and DPD, alone or in combination, in distinguishing postmenopausal osteoporotic women (OPBD, n = 26) from age-matched controls (CBD, n = 19). The diagnosis of osteoporosis was based upon the bone density (BD) of the lumbar spine measured by quantitative computed tomography (CBD: BD > 108 mg/cm3; OPBD: BD < 70 mg/cm3). Urinary excretion of GHYL, PYD, and DPD were measured by HPLC, and all data were expressed as the molar ratio with the creatinine excretion (GHYL/CR, PYD/CR, and DPD/CR). The clinical performances were tested by: Z score analysis (Z), Receiver Operated Characteristic curve analysis (%Acc) and logistic-regression analysis of the posterior probabilities for prediction from a logistic model (LOGIST). GHYL/CR, PYD/CR, and DPD/CR were significantly increased in OPBD compared with CBD. The clinical performances were similar for the three assays, with slightly better performances for GHYL/CR (GHYL/CR: Z = 3.14, %Acc = 70 +/- 8, LOGIST P = 0.01; PYD/CR: Z = 2.19, %Acc = 67 +/- 8, LOGIST P = 0.051; DPD/CR: Z = 2.13, %Acc = 65 +/- 8, LOGIST P = 0.06). None of the possible combinations of the three assays yielded better clinical performances than GHYL/CR alone. In conclusion, this study further confirms the validity of GHYL, PYD, and DPD as markers of bone resorption.

Osteoporosis: diagnosis and management today and tomorrow

Osteoporosis is a disease in which low bone mass and microarchitectural deterioration of bone tissue lead to increased bone fragility and a consequent increase in fracture risk. The risk of developing osteoporosis can be assessed by determining the maximum density and strength achieved at maturity (peak bone mass) and the rate and duration of age-associated bone loss. The major cause of osteoporosis is estrogen withdrawal in women, most commonly associated with the menopause, but also with other causes of ovarian failure. Androgen insufficiency in men, although much less common, can also lead to osteoporosis. Measurements of bone mineral density (BMD) have been used to predict fractures, and current evidence suggests that fractures at any site can be predicted by taking measurements of BMD at any other site in the skeleton, using noninvasive techniques such as single or dual energy absorptiometry, quantitative computed tomography and ultrasound, a promising but experimental approach. Rapid bone loss at the start of the menopause is also an important contributing factor to the development of osteoporosis. Levels of biochemical markers of bone turnover in plasma and urine have been found to correlate with rapid and prolonged bone loss. Powerful new assays for estimating bone turnover have emerged and more are being developed. Various combinations of these biochemical tests may be used in conjunction with bone densitometry to predict future risk of osteoporosis and osteoporosis-related fractures. Furthermore, biochemical tests can also be useful in assessing response to therapy. Although many factors, including sex, race, heredity and lifestyle (e.g., calcium intake, minerals, nutrition and exercise), influence the risk of osteoporosis, i.e., they affect peak bone mass and subsequent bone loss, and are of little use in predicting future occurrence.

Tiludronate: development as an osteoporosis therapy

The clinical development of tiludronate (tiludronic acid, disodium salt) for the treatment of Paget's disease of bone is now being complemented by another clinical trials program to investigate its use in osteoporosis. It is expected that osteoporosis will become a major indication for tiludronate, and this paper describes the trial design and treatment goals that will be employed in these new studies. In studies to assess the incidence of fracture, the primary efficacy end point is the occurrence of vertebral fractures after 3 years of therapy. Secondary end-points include changes in lumbar bone mineral density, spinal deformity index, and height. Changes in biochemical markers and quality of life will also be assessed. Safety evaluations include clinical laboratory parameters, adverse events and, in selected patients, histomorphometry of the iliac crest bone. For the nonfracture studies, the primary efficacy end-point is the effect on bone mineral density after 2 years of therapy. Secondary end-points include vertebral fracture rate, spinal deformity index, and height. Biochemical markers, quality of life, and safety (including bone biopsies in selected patients) will be evaluated as in the fracture studies. The studies are expected to be completed in early 1997, followed by worldwide regulatory applications in late 1997.

Effects of oral alendronate and intranasal salmon calcitonin on bone mass and biochemical markers of bone turnover in postmenopausal women with osteoporosis

The main objective of this study was to determine the effect of daily oral alendronate treatment on bone mass in postmenopausal women affected by osteoporosis. The efficacy of intranasal salmon calcitonin was also examined. Nine centers in Italy enrolled 286 postmenopausal women between the ages of 48 and 76 with spinal bone mineral density > or = 2 SD below adult mean peak in the two-year, double-blind, randomized, placebo-controlled trial. Patients were randomized to one of four treatment arms: double-blind placebo, alendronate 10 mg/day, alendronate 20 mg/day, or open-label intranasal salmon calcitonin 100 IU/day; all patients received 500 mg Ca++ supplements. Bone mass was measured by dual-energy x-ray absorptiometry every six months for two years. Patients who received alendronate 10 or 20 mg experienced significant increases in bone mass at all sites measured. At the end of the second year, the mean percent changes, for alendronate 10 and 20 mg relative to placebo, were 5.2% and 7.3% at the lumbar spine, 3.8% and 4.6% at the femoral neck, and 7.1% and 7.5% at the trochanter, respectively. In contrast, intranasal salmon calcitonin failed to increase bone mineral mass significantly at any site. Both alendronate doses significantly decreased serum alkaline phosphatase, serum osteocalcin, and urinary pyridinolines, markers of bone turnover, whereas placebo and intranasal calcitonin did not. Alendronate was generally well tolerated and no serious adverse events were attributed to its use.(ABSTRACT TRUNCATED AT 250 WORDS)

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

A new immunoassay for measuring urinary excretion of type I collagen crosslinked N-telopeptides (NTx) has been reported to be a specific and sensitive method for assessing bone resorption. We have studied factors affecting biological variations in urinary NTx excretion in a population of 452 healthy Japanese adults, comprising 238 men and 214 women, 20-79 years of age. Urinary NTx excretion increased significantly with age in women (> or = 25 years of age) (r = 0.55, p < 0.0001) and modestly correlated with lumbar bone mineral density (L-BMD) in both sexes (> or = 25 years of age) (r = 0.31, p < 0.0001 for men; r = 0.50, p < 0.0001 for women). Urinary NTx levels in women were significantly higher than in the corresponding male age groups after the fifth decade (p < 0.0001). None of the anthropometric variables (weight, height, and body mass index) showed a linear effect on the urinary NTx excretion independent of age and L-BMD. In women, menopause was reflected by a twofold increase in urinary NTx excretion, from a mean of 28-59 pmol bone collagen equivalents (BCE)/mumol creatinine, and this menopause-related increase persisted for the entire postmenopausal period. In postmenopausal women, the interindividual variations of urinary NTx excretion were much more marked than in men and in premenopausal women. Moreover, in the subgroups of pre- and postmenopausal women, urinary NTx excretion correlated with neither age nor L-BMD. These data show that the major biological factor that modifies urinary NTx level is menopause and suggest that the bone turnover rates in the elderly women are increased, on average, irrespective of bone mineral density.

Evolution of spinal bone loss and biochemical markers of bone remodeling after menopause in normal women

The main objective of this study was to describe longitudinal patterns of spinal bone loss in normal women who undergo a natural menopause. The second objective was to determine if a proportion of women suffer excessively rapid postmenopausal bone loss from the spine. If this was the case it was the aim to devise a means of predicting the woman at excess risk; but if all women lost bone at similar rates, the aim was to document changing loss rates over the first 5-8 postmenopausal years. Responding women in six suburban general practices recalled for cervical smears who had their last menstrual period 9- 36 months previously were invited to participate in a longitudinal study of bone loss and the biochemical markers plasma osteocalcin and urinary hydroxyproline. Sixty-four subjects agreed to participate, a response rate of 80%. In the ensuing 5 years, six received hormone replacement therapy and are not reported on. The main outcome measures were rates of spinal bone loss over 5 years, measured by dual photon absorptiometry, and radial bone loss over the first 2 years measured to quantitative computed tomography. Spinal bone loss was similar between individuals, with 94% of the variability in the data being accounted for by a statistical model that assumed parallel rates of bone loss. A less restrictive model allowing women to have different rates of spinal bone loss accounted for 12% more of the remaining variance in the data than the previous model. However, rates of radial bone loss were more dissimilar between women than rates of spinal loss. The results of the biochemical data collected serially showed that the plasma osteocalcin rose slowly to a plateau at 5 years postmenopause; in contrast, the hydroxyproline fell progressively with time over the whole period of study. These results were interpreted as being consistent with diminishing rates of bone destruction which gradually reequilibrated with bone formation as time passed after menopause.

Zinc, biochemical markers of nutrition, and type I osteoporosis

Having observed previously that the reduction of levels of biological markers of nutrition in postmenopausal osteoporosis may be related to zinc deficiency, we measured plasma and urinary zinc concentrations in 30 women with postmenopausal osteoporosis and in 30 healthy postmenopausal women who served as controls. Plasma zinc levels did not differ between groups, but urinary zinc excretion was significantly higher in the women with postmenopausal osteoporosis (p = 0.002). The relation between total body bone mineral content corrected for body weight (TBBMC/W) and markers of nutrition was significant (multiple regression analysis: p < 0.0001) in the women with postmenopausal osteoporosis but not in the healthy postmenopausal controls. Likewise, the relation between TBBMC/W and plasma and urinary zinc levels also was significant in the women with postmenopausal osteoporosis but not in the controls (multiple regression analysis: p = 0.0022). Neither group showed any correlation between plasma or urinary zinc concentrations and levels of biological markers of nutrition. Urinary zinc concentration correlated significantly with serum tartrate-resistant acid phosphatase level (simple linear regression analysis: r = 0.583, p < 0.001) in the women with postmenopausal osteoporosis but not in controls. TBBMC correlated with urinary zinc concentration significantly in the women with postmenopausal osteoporosis (simple linear regression: r = 0.567, p = 0.0015), but the correlation was nonsignificant in healthy postmenopausal controls. These findings indicate that the elevation of urinary zinc elimination in osteoporosis is dependent on bone resorption.

Urinary concentration of a specific peptide of type I collagen of bone (CrossLaps): correlation to hydroxyproline

Urinary bone resorption markers, CrossLaps and hydroxyproline are compared in a non-selected group of 93 women. The correlation between CrossLaps and hydroxyproline is satisfactory. The r value is 0.79. Furthermore, it is investigated whether CrossLaps can substitute for hydroxyproline in the estimation of bone loss, using a model based on the combination of several biochemical markers. The results indicate that the two systems reflect related or parallel events, and show that CrossLaps is suitable for use in a normal clinical chemistry laboratory.

Nocturnal rise in markers of bone resorption is not abolished by bedtime calcium or calcitonin

As assessed by urine pyridinium cross-links, bone resorption increases at night. This has been ascribed to either the nocturnal rise of serum parathyroid hormone (PTH) or immobilization. ICTP is the carboxyterminal telopeptide region of type I collagen in bone, cross-linked via pyridinium cross-links and liberated during the degradation of type I collagen. To study whether the nocturnal rise in bone resorption is seen also in serum type I collagen carboxyterminal telopeptide (ICTP) and whether this rise is abolished by bedtime calcium or calcitonin, nine healthy postmenopausal women participated in three 24 hour sessions. At 2200 hours, either 1 g of oral calcium or 200 IU of intranasal calcitonin or no treatment (control session) were given. The participants were recumbent from 2200 hours to 0600 hours. Like urinary pyridinolines, serum ICTP showed a clearcut nocturnal rise during the control session, increasing from 3.7 +/- 0.3 micrograms/liter (mean +/- SE) at 2000 hours to 4.9 +/- 0.4 micrograms/liter at 0600 hours (P < 0.001). Administration of calcium did not affect either serum ICTP or urinary pyridinolines, although it decreased serum intact PTH by 18% (P < 0.001) as assessed by areas under curve (AUC) after 2200 hours. Serum ICTP and urinary pyridinolines remained unchanged also after administration of calcitonin which increased the AUC for serum intact PTH by 9% (P < 0.05). In conclusion, serum ICTP follows a circadian rhythm in healthy postmenopausal women. The nocturnal rise in markers of bone resorption is not due to PTH, and its dependency on the function of osteoclasts is open to question.

Comparison of immuno- and HPLC-assays for the measurement of urinary collagen cross-links

Pyridinoline (Pyr) and deoxypyridinoline (D-Pyr) are two cross-links of collagen molecules, that are present in the extracellular matrix and released during its degradation. Pyr is present in bone and cartilage, but not in significant amounts in other connective tissues and D-Pyr appears to be specific for bone tissue. Therefore, the urinary excretion of Pyr and D-Pyr might be a sensitive marker of bone matrix degradation. For the determination of urinary Pyr and D-Pyr two methods are available: a chromatographic method (HPLC) by which it is possible to measure separately Pyr and D-Pyr, and a new immunoassay which measures total free and low molecular weight pyridinoline released in the urine. We compared the results obtained by HPLC analysis of 205 urinary samples from normal subjects and patients affected by various bone disorders with those obtained by the immunoassay. The overall correlation coefficient between the results obtained by the two methods was 0.34. When calculated in a range of pyridinoline concentrations from 0 to 30, 30 to 60, and over 60 pmol/mumol creatinine the correlation coefficient was respectively -0.094, 0.38, and 0.12. The two methods yielded variable profiles in the detection of circadian rhythms and these differences did not segregate with normal or pathological conditions. We conclude that the immunoassay proposed for the determination of urinary collagen cross-links is not immediately applicable to clinical use. The improvement of the antibody specificity will probably contribute to replace the HPLC method with the immunoassay.

Evaluation and comparison of urinary pyridinium crosslinks in two rat models of bone loss--ovariectomy and adjuvant polyarthritis--using a new automated HPLC method

A specific HPLC system was developed to assess urinary excretion of collagen crosslinks (pyridinoline (Pyr) and deoxypyridinoline (D.Pyr)) in two models of osteopenia in rats, ovariectomy and adjuvant polyarthritis. The sensitivity of this method was in the picomolar range. In ovariectomized rats, a specific model of bone resorption, Pyr and D.Pyr levels rose early, reaching a peak 2 weeks after surgery. Both levels remained raised during the whole observation period (6 weeks) with no change in the Pyr/D.Pyr ratio. So, in this high bone turnover model, hyperresorption is reflected by the parallel increase of both crosslinks resulting in a significant decrease of bone mineral density (BMD) at 6 weeks (-7.3% vs. control). In polyarthritic rats, in the 2 post-adjuvant weeks, Pyr levels increased in parallel with inflammatory parameters, whereas D.Pyr levels remained unchanged. This is in agreement with our previous report that at the end of the 2nd week after adjuvant there is no change in bone resorption. From the 3rd week, both Pyr and D.Pyr increased. The Pyr/D.Pyr ratio was always significantly higher in polyarthritic rats. These results suggest that the early increase of Pyr level reflects non-osseous collagen breakdown and that bone resorption occurs at a later stage when D.Pyr rises, leading to a dramatic decrease of BMD at 4 weeks (-17.7% vs. control). Taken together, our results suggest that in rat as in human, urinary Pyr is a marker of bone and cartilage breakdown, whereas D.Pyr is a specific marker of bone loss. This automated method described may constitute a very useful tool to evaluate bone and/or cartilage breakdown in rats and for the assessment of protective treatments.

Renal leak of calcium in post-menopausal osteoporosis

BACKGROUND

Urine calcium after an overnight fast is higher in osteoporotic than in normal post-menopausal women. The question is whether this is the cause or effect of the bone-losing state.

OBJECTIVE

To establish whether the elevated obligatory calcium loss in osteoporotic women is due to a raised filtered load of calcium or to reduced renal tubular reabsorption of calcium.

DESIGN

Covariance analysis using total plasma calcium and its fractions as the covariates.

PATIENTS

Eighty-two untreated post-menopausal women without vertebral compression and 137 untreated post-menopausal with vertebral compression all between the ages of 61 and 75 years.

MEASUREMENTS

After an overnight fast, calcium, albumin, globulins, anion gap and bicarbonate were measured in the plasma, and calcium, sodium and creatinine in the urine. The calcium fractions in plasma and the calcium/creatinine and sodium/creatinine ratios in urine were calculated. Bone density was measured in the distal forearm.

RESULTS

The ultrafiltrable and ionized calcium in the plasma and the calcium/creatinine ratio in the urine were significantly higher in the women with vertebral compression than in those without. On covariance analysis, neither total plasma calcium nor any of the plasma calcium fractions made a significant contribution to the difference in fasting urine calcium between normal and osteoporotic women, whether bone status was defined by vertebral compression or by bone density.

CONCLUSIONS

The increased obligatory calcium loss in osteoporotic women is not due to an increase in the filtered load of calcium and must therefore reflect reduced renal tubular reabsorption. This implies that the calcium loss in the urine is not the result of increased bone resorption but is more likely to be causal.

Urinary excretion of pyridinium cross-links in healthy women; the long-term effects of menopause and oestrogen/progesterone therapy

OBJECTIVES

We investigated the effect of the menopause when followed longitudinally for a decade to evaluate whether women with an increased bone loss continue to have elevated urinary excretion of pyridinium cross-links later in menopause. Furthermore, we investigated the effect of oestrogen/progesterone therapy on the urinary excretion of pyridinium cross-links.

PARTICIPANTS

In the cross-sectional study: 18 healthy premenopausal, 142 healthy post-menopausal women and 41 osteopenic post-menopausal women. In the longitudinal study: 45 healthy post-menopausal women followed up for 7-10 years after the menopause; these women were further divided into two equal groups, according to their loss of forearm bone mineral content over 2 years. In the oestradiol/progesterone double-blind, placebo-controlled 2-year trial: early post-menopausal women were given either hormone replacement therapy (n = 38) or placebo (n = 16).

MEASUREMENTS

The urinary excretion of pyridinoline/creatinine (Pyr/Cr) and urinary deoxypyridinoline/creatinine (D-Pyr/Cr), two new markers of bone resorption.

RESULTS

Pyr/Cr and D-Pyr/Cr increased significantly after the menopause (Pyr/Cr, 77%; D-Pyr/Cr, 98%, P < 0.001). Hormone replacement therapy reversed this increase towards premenopausal levels. Both pyridinium cross-links remained fairly constant during the first decade of the menopause, when measured in the longitudinal study. When the women were divided according to loss in forearm BMC, those with a loss greater than 3.5%/2 years had significantly higher levels of pyridinium cross-links (P < 0.05-0.01). Furthermore, both Pyr/Cr and D-Pyr/Cr were significantly higher in elderly osteopenic women (aged 68-72 years) than in age-matched non-osteopenic women (P < 0.01-0.001).

CONCLUSIONS

Both Pyr/Cr and D-Pyr/Cr, two new markers of bone resorption, increased significantly at the time of the menopause, thereafter remaining fairly constant during the first post-menopausal decade. Women with increased bone loss continue to have elevated urinary excretion of pyridinium cross-links during the first decade of the menopause. This post-menopausal change is reversed by hormone replacement therapy to the premenopausal level.

Monitoring bone resorption in early postmenopausal women by an immunoassay for cross-linked collagen peptides in urine

A new immunoassay using an ELISA approach for measuring urinary excretion of cross-linked N-telopeptides of type 1 collagen was evaluated as a specific measure of bone resorption. The assay was applied to 65 early postmenopausal women who participated in a placebo-controlled trial of the aminobisphosphonate, alendronate sodium. Eight blood and urine samples were collected over a 9 month interval. Baseline cross-linked peptide excretion varied from 26 to 216 pmol BCE (bone collagen/mumol Cr. Within-subject variability (CV) for cross-linked peptide excretion was 20.2% over the 9 months in placebo-treated subjects, substantially less than that observed for other biochemical markers of bone resorption: 45, 53, and 63% for fasting urinary calcium and hydroxyproline and 24 h urinary lysylpyridinoline (HPLC assay), respectively. Baseline cross-linked peptide excretion correlated significantly (p < 0.001) with baseline total urine lysylpyridinoline and serum osteocalcin, but not with the other biochemical markers. Initial peptide excretion also correlated inversely with lumbar spine bone mineral density at entry (r = -0.26, p < 0.05). Treatment for 6 weeks with alendronate produced a dose-dependent suppression of cross-linked peptide excretion (0 +/- 8, 29 +/- 6, 56 +/- 5, and 64 +/- 3% for 0, 5, 20, and 40 mg, respectively, p < 0.01 versus placebo for treatment effect), with a return toward pretreatment values during follow-up. Measurement of the urinary cross-linked N-telopeptides of type I collagen by this new ELISA approach appears promising as a simple and reliable method to assess overall bone resorption.(ABSTRACT TRUNCATED AT 250 WORDS)

Urinary bone resorption markers in patients with metabolic bone disorders

Recently, urinary pyridinoline and deoxypyridinoline have been commonly employed as bone resorption markers. We studied these markers in 17 patients with hyperthyroidism, 15 undergoing long-term anticonvulsant drug therapy, and 28 with postmenopausal osteoporosis. Both markers had significantly higher levels than those in age-matched control groups. Values of urinary pyridinoline and deoxypyridinoline correlated well with urinary hydroxyproline levels in patients with hyperthyroidism (r = 0.856, p < 0.001 for pyridinoline and hydroxyproline; r = 0.919, p < 0.001 for deoxypyridinoline and hydroxyproline); however, poor correlations were observed, especially between urinary deoxypyridinoline and urinary hydroxyproline (r = 0.357, NS) in patients with postmenopausal osteoporosis. To compare the discriminatory ability of urinary pyridinoline and deoxypyridinoline, receiver operating characteristic (ROC) curves were generated for each of these patient groups using data from age-matched healthy females as the control group. The areas under the curves for both markers were 100.0% in hyperthyroidism. The areas under the curves for pyridinoline in patients undergoing long-term anticonvulsant drug therapy (mean +/- SE; 98.1 +/- 2.8%) and postmenopausal osteoporosis (77.9 +/- 5.7%) were significantly higher than those for deoxypyridinoline in anticonvulsant drug therapy (92.4 +/- 3.3%) and in osteoporosis (64.9 +/- 4.3%). Using data from premenopausal healthy females as the control group, areas under ROC curves for urinary pyridinoline (100.0%) and deoxypyridinoline (94.8 +/- 5.9%) were significantly higher than those for urinary hydroxyproline (73.8 +/- 9.4%) in patients undergoing long-term anticonvulsant drug therapy. In patients with postmenopausal osteoporosis, those for urinary pyridinoline (97.0 +/- 2.8%) were also significantly higher than those for urinary hydroxyproline (74.0 +/- 6.4%).(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of norethisterone on bone related biochemical variables and forearm bone mineral in post-menopausal osteoporosis

OBJECTIVE

Progestogens may be a useful therapeutic alternative to oestrogen in the treatment of post-menopausal osteoporosis. The purpose of this study was to determine the effects of norethisterone on forearm bone mineral content and bone related biochemical variables in patients with post-menopausal osteoporosis.

DESIGN/PATIENTS

The effects of treatment with norethisterone (5 mg/day) on bone related biochemical variables was determined in 44 women with post-menopausal osteoporosis. The effects of norethisterone on forearm bone mineral content (FMC) were evaluated by serial measurements in 39 of these women.

MEASUREMENTS

We measured forearm mineral content, forearm mineral density, forearm fat content and fat-corrected forearm mineral density. Biochemical measurements included plasma calcium and plasma calcium fractions (ionized, protein bound, complexed and ultrafiltrable), alkaline phosphatase, bicarbonate, phosphate, albumin and globulins, serum parathyroid hormone, osteocalcin and 1,25-dihydroxyvitamin D, radiocalcium (45Ca) absorption and fasting urinary calcium/creatinine, sodium/creatinine, phosphate/creatinine and hydroxyproline/creatinine molar ratios.

RESULTS

After 4 months of treatment norethisterone produced a fall in plasma calcium (mean +/- SEM from 2.40 +/- 0.14 to 2.32 +/- 0.13 mmol/l, P < 0.001), primarily in the non-ionized calcium, due to a decrease in plasma bicarbonate (from 29 +/- 0.28 to 27 +/- 0.28 mmol/l, P < 0.001). There were decreases in urinary calcium/creatinine (from 0.41 +/- 0.03 to 0.19 +/- 0.02, P < 0.01) and sodium/creatinine (from 15 +/- 1.1 to 10 +/- 0.93, P < 0.001) molar ratios and a rise in the renal tubular maximum for calcium reabsorption (TmCa) (from 2.36 +/- 0.041 to 2.55 +/- 0.059 mmol/l of glomerular filtrate, P < 0.001). Plasma phosphate, urinary phosphate/creatinine and tubular maximum for phosphate reabsorption (TMP) all fell (P < 0.01). Both the urinary hydroxyproline/creatinine (P < 0.001) and plasma alkaline phosphatase (P < 0.001) fell. Serum parathyroid hormone rose from 4.1 +/- 0.36 to 5.5 +/- 0.51 pmol/l (P < 0.02) and radiocalcium absorption increased from 0.67 +/- 0.08 to 0.81 +/- 0.10 fx/h (P < 0.01). There was no change in serum 1,25-dihydroxy vitamin D. After treatment with norethisterone for 4 months there was an increase in forearm bone mineral content (P < 0.05) and a decrease in forearm fat content (P < 0.02). After two years treatment with norethisterone fat-corrected forearm bone mineral content rose (mean change 17.0 +/- 5.5 mg/cm, P < 0.01).

CONCLUSIONS

These results suggest that norethisterone prevents bone loss in post-menopausal osteoporosis by decreasing bone turnover, has a vitamin-D independent effect on intestinal calcium absorption, and increases serum parathyroid hormone levels.

[Assay of cross-linking molecules of collagen (pyridinolines) in the study of the degradation of bone tissue and articular cartilage]

Recent studies aimed at studying the degradation of the fibrillar collagens of bone and articular cartilage have lead to the discovery of naturally fluorescent crosslinking compounds derived from lysine and hydroxylysine. These small molecules characterized by an aromatic 3-hydroxypyridinium ring are present in significant amounts only in bone (pyridinoline and deoxy-pyridinoline) and cartilage (pyridinoline). Diseases characterized by an increased degradation of the fibrillar collagenous network are associated with an increased urinary excretion of both compounds: Pyridinoline and deoxypyridinoline are currently the most sensitive and specific markers of bone resorption. The purpose of this paper is to review current knowledge in the area of collagen crosslinking molecules with special emphasis on the pyridinium crosslinking amino acids and their potential clinical application as a marker of bone and cartilage degradation.

Evaluation of bone turnover in type I osteoporosis using biochemical markers specific for both bone formation and bone resorption

The aims of the study were to evaluate the use of bone-specific biochemical markers of turnover in type I osteoporosis, to test for evidence of heterogeneity of bone turnover in this condition, and to attempt to devise an 'uncoupling index' by using the relationship between bone-specific biochemical markers of bone formation and bone resorption. In women with type I osteoporosis (mean age 64 years, SD 5; n = 63) the mean level of serum osteocalcin, a specific biochemical marker of bone formation, was 9.9 ng/ml (SD 2.0), which was higher than the level in normal postmenopausal women (mean age 65 years, SD 6; n = 8.9 ng/ml (SD 2.0; p < 0.01). The variance of serum osteocalcin levels in the two groups was similar. Compared with this 11% increase in the biochemical marker for bone formation, the markers of bone resorption, total urinary deoxypyridinoline (bone-specific), pyridinoline and hydroxyproline were increased by 40% (p < 0.0001), 61% (p < 0.0001) and 25% (p < 0.01), respectively. Furthermore, these biochemical markers of bone resorption had greater variance in women in type I osteoporosis than in the normal postmenopausal women (p < 0.01). The urinary excretion of the free crosslinks deoxypyridinoline, pyridinoline and glycosylated pyridinoline were increased by 26% (p < 0.001), 17% (p < 0.01) and 13% (NS) respectively. An 'uncoupling index' was calculated for the difference between urinary deoxypyridinoline and serum osteocalcin using the results from the normal women and expressed as z-scores. We conclude that the pyridinium crosslinks of collagen enable better discrimination between normal and osteoporotic women than does hydroxyproline.(ABSTRACT TRUNCATED AT 250 WORDS)

Treatment of postmenopausal osteoporosis with salmon calcitonin nasal spray: evaluation by bone mineral content and biochemical patterns

We studied 21 women with postmenopausal osteoporosis, treated with salmon calcitonin nasal spray (100 IU/daily) and calcium (1 g/daily) for six months. Bone mineral content (BMC), measured before and at the end of therapy with lumbar dual photon absorptiometry, showed a significant increase (p < 0.01). At the end of the study, there was also a clear improvement of osteoporotic pain. Among biochemical markers of bone turnover, there was a significant (p < 0.01) reduction of urinary excretion of hydroxyproline. No side effect was registered and all patients had a good compliance to therapy.

[Zinc excretion in osteoporotic women]

Urinary zinc excretion was detected in 24 normal and 25 age matched osteoporotic women. The osteoporotic group was classified in two groups on the basis of bone mineral density (BMD) measurements. Urinary zinc excretion was 327 micrograms/g creat. in healthy subjects and 488 micrograms/g creat. in the "common porotic group". In the "trabecular porotic group" (decreased BMC with DEXA at the lumbar spine alone or together with the femoral neck, but with normal radius BMD) it was 455 micrograms/g creatinine while in the "cortical porotic group" (decreased BMD with SPA at the radius midshaft and/or all the sites measured) the zinc excretion was even higher, 588 micrograms/g creat. The difference between the normal and porotic groups was statistically significant, while within the porotic groups it was not, however the tendency was remarkable. A close significant correlation exists between BMC of radius and urinary zinc excretion. In the osteoporotic group the urinary calcium excretion was significantly higher, than in normal group (220.2 vs 145.2 mg/g creat, p < 0.01). The correlation between the urinary zinc and calcium excretion was not significantly statistically. Elevated urinary zinc excretion is characteristic in both types of involutional osteoporosis in women and therefore seems to be a potential new simple marker of bone resorption.

[Is it possible to identify women with rapid vertebral bone loss during menopause? Result of a longitudinal study of 92 women at the onset of menopause]

Low bone mass is the main risk factors for osteoporosis. The role of the rate of bone loss following cessation of menses is more difficult to evaluate. We prospectively studied vertebral bone loss in 92 women six months to three years after cessation of menses in order to determine the clinical and biological characteristics of the subgroup of subjects with accelerated bone loss. Clinical characteristics, hormone assay results, and values of the main biochemical markers of bone turnover were recorded at the initial evaluation and correlations between these parameters and the rate of bone loss were investigated. Serial measurements of vertebral bone density were performed using dual photon absorptiometry. Mean duration of the observation period was 31 +/- 13 months. Mean rate of bone loss was -1.66% per year (range 1.6% to 7.7%). In women with accelerated vertebral bone loss i.e., a greater than 2.5% decrease in bone density per year (25th centile), there were trends towards lower values for body mass index and weight (non-significant) and a significantly higher urinary calcium/urinary creatinine ratio (p < 0.05) as compared with the rest of the study group. Rate of bone loss was weakly correlated (p < 0.05) with body mass index (r = 0.22) and with the urinary calcium/urinary creatinine ratio (r = 0.23) but demonstrated no correlations with osteocalcin levels or serum alkaline phosphatase activity. In conclusion, none of the clinical features or laboratory parameters studied proved capable of reliably predicting the rate of vertebral bone loss in individual women shortly after cessation of menses.

Clinical pharmacology of alendronate sodium

Clinical studies have been performed to investigate the pharmacokinetics and pharmacodynamics of alendronate, an inhibitor of bone resorption for the treatment of osteoporosis. Alendronate is one of the most potent bisphosphonates currently undergoing clinical investigation (> 100-fold more potent than etidronate in vivo). The pharmacokinetics of alendronate are similar to those of other bisphosphonates. After a 2-h intravenous infusion, plasma concentrations of alendronate decline rapidly to approximately 5% of initial values within 6 h. About 50% of a systemic dose is excreted unchanged in the urine in the 72 h following administration. By analogy to its behavior in animals the remainder is assumed to be taken up by the skeleton. After sequestration into bone, the elimination of alendronate is very prolonged. The terminal half-life was estimated to be greater than 10 years. Despite prolonged skeletal residence, the biological effects of alendronate begin to diminish post-treatment, since the duration of effect reflects factors besides dose and cumulative drug exposure. When taken after an overnight fast, 2 h before breakfast, the oral bioavailability of alendronate averages approximately 0.75% of dose with substantial variability (coefficient of variation 55%-75%) both between and within subjects. Reducing the wait before food from 2 h to 1 h, or even 30 min, produces a mean reduction in absorption of 40%. Since the clinical efficacy of alendronate is indistinguishable whether it is given 30 min, 1h, or 3 h before a meal, the observed variability in bioavailability within this range is of little consequence. Dosing up to at least 2 h after a meal dramatically reduces absorption (80%-90%).

Preventive effects of transdermal 17 beta-estradiol on osteoporotic changes after surgical menopause: a two-year placebo-controlled trial

OBJECTIVE

The purpose of our study was to evaluate the effects of three dosages of transdermally administered 17 beta-estradiol on markers of bone loss in women who had recently undergone surgical menopause.

STUDY DESIGN

This was a 2-year, randomized, double-blind, placebo-controlled study that reviewed 127 women stratified by age. Biochemical indicators of bone metabolism in urine and serum were periodically assessed, as was bone mineral content of the lumbar spine and radius. Statistical analysis examined the percent changes from baseline in bone mineral density by using an analysis of covariance with treatment as a factor and the baseline value as a covariant, by performing all-pairwise comparisons among the three estradiol groups, and by testing for a linear dose-response relationship.

RESULTS

After 2 years of therapy, a significant dose-response relationship was detected.

CONCLUSION

This 2-year study demonstrates that transdermally administered 17 beta-estradiol is a safe and effective regimen for preventing bone loss in recently postmenopausal women.

Urinary excretion of glycosaminoglycans in patients with postmenopausal osteoporosis

The organic bone matrix contains glycosaminoglycans (GAG) of which the precise function and importance in bone mineralisation are still unclear. We examined 85 persons--35 healthy women (25 premenopausal [preMP] mean aged 40.7 years; 10 menopausal [MP] mean aged 59.3 years) and 50 patients with postmenopausal osteoporosis [PMOP] at a mean age 60.4 years. The dynamic of urinary excretion of GAG was measured in 24-hour collected urine by precipitation with cetylpyridinum chloride and spectrophotometry at 560 nm, corrected for the level of excretion of creatinine. There was a significant increase in GAG excretion in patients with PMOP compared with healthy persons (8.25 mg/g and 9.53 mg/g vs 24.11 mg/g; p < 0.0001). A significant positive correlation was established between GAG and calcium urinary excretion and a negative one between GAG and serum estradiol levels. During the treatment with calcitonin the excretion of GAG was decreased which can be used for monitoring the changes of bone metabolism.

Can urinary pyridinium crosslinks and urinary oestrogens predict bone mass and rate of bone loss after the menopause?

We measured urinary pyridinoline and deoxy-pyridinoline by high performance liquid chromatography, and urinary oestrogens by radioimmunoassay, in 68 healthy postmenopausal women to evaluate these assays for the prediction soon after the menopause of the risk of developing osteoporotic fractures in later life. Change in forearm bone mineral content was assessed by single photon absorptiometry over 4 years. Although there was no significant correlation between the pyridinium crosslinks and urinary oestrogens, we found that up to 58% of the variation in the rate of loss of bone mineral content in women soon after the menopause could be explained by pyridinoline and oestradiol glucuronide assays together with body mass index. Measurement of the urinary pyridinium crosslinks and oestradiol glucuronide may make a significant contribution to a biochemical screening procedure for future osteoporotic fracture.

Bone-resorption markers galactosyl hydroxylysine, pyridinium crosslinks, and hydroxyproline compared

We compared the clinical performances of four bone-resorption (BR) assays (hydroxyproline, HYP; galactosyl hydroxylysine, GHYL; deoxypyridinoline, DPD; and pyridinoline, PYD) in subjects with different BR rates: normal (adult men and premenopausal women), mildly increased (postmenopausal osteoporotic women), high (Paget disease patients), and very high (children). The discrimination power (Z score) and the accuracy (estimated by receiver-operating characteristic analysis) for GHYL, DPD, and PYD were compared with those for HYP. Discrimination power and accuracy were similar for high- and very-high-BR groups for all four assays. However in the mildly increased-BR group, DPD, GHYL, and PYD showed a higher discrimination power and accuracy than did HYP. The clinical performances of HYP, DPD, GHYL, and PYD are comparable for large changes in BR. For modest changes, DPD, GHYL, and PYD are more accurate and have a higher discrimination power than does HYP.

Potential value of urinary oestrogen assays in the identification of fast bone losers after the menopause

We determined the rate of change of bone mineral content (BMC) in the distal forearm of 89 healthy postmenopausal women by single-photon absorptiometry. The BMC measurements were taken at 6- or 12-monthly intervals for up to 4 years. Urinary oestrogen excretion and anthropometry were assessed at the time of the first BMC measurement. Urinary oestradiol glucuronide (E2G) excretion was related to the rate of change of 'proximal' BMC in women 1-7 years past the menopause (r = 0.52, p less than 0.01). Body mass index was less highly correlated with the rate of change of BMC in these women (r = 0.41, p less than 0.05). We conclude that urinary E2G excretion could contribute to a screening procedure for the assessment in women soon after the menopause of the risk of osteoporotic fracture in later life.

Urinary excretion of pyridinium crosslinks of collagen in patients with osteoporosis and the effects of bone fracture

Values for the urinary excretion of pyridinium crosslinks of collagen, pyridinoline and deoxypyridinoline, in a group of 30 elderly women with femoral fractures associated with osteoporosis and a group of 20 women without recent fracture but with overt or suspected osteoporosis were compared with 27 control subjects matched for age. Relative to the control group, the excretion of the crosslinks was significantly higher in the group with fractures and the group with osteoporosis. Fractures contributed markedly to the excretion of pyridinium crosslinks as the patients with fractures showed significantly higher excretion of pyridinoline and deoxypyridinoline than the group without recent fractures. This was confirmed by the fact that excretion of pyridinium crosslinks in patients with accidental bone fractures was significantly higher than for healthy control subjects matched for age and sex. The crosslinks appear to provide valid indices of bone resorption, but the effects of bone fracture must be considered in the clinical application of this technique.

Borderline-low serum thyrotropin level is correlated with increased fasting urinary hydroxyproline excretion

BACKGROUND

Recent studies suggest that even mildly supraphysiologic thyroid hormonal status accelerates bone loss. In hyperthyroidism, increased bone resorption is the predominant mechanism for bone loss. We postulated that the changes in thyroid hormone status as reflected by low-normal and minimally subnormal serum thyrotropin level would have an effect on bone turnover and could be detected by a simple, noninvasive marker of bone resorption, fasting urinary total hydroxyproline-creatinine excretion (THP/Cr).

METHODS

We retrospectively identified ambulatory patients with a restricted range of diagnoses who had had measurements of thyrotropin and THP/Cr performed within +/- 21 days.

RESULTS

Of the 86 patients, 47 had thyrotropin levels greater than 1.0 mU/L. In these patients, no correlation was evident for thyrotropin and THP/Cr. Of the other 39 patients, 11 had suppressed thyrotropin levels (less than 0.1 mU/L) and showed clearly elevated values for THP/Cr, as expected from previous studies of hyperthyroidism. For 28 patients with thyrotropin in the borderline and low-normal range of 0.1 to 1.0 mU/L, a significant negative correlation with THP/Cr was found. The THP/Cr was positively correlated with serum alkaline phosphatase level, as expected with increased bone turnover.

CONCLUSIONS

These results add further support to the hypothesis that even a minimal excess of thyroid hormones increases bone turnover and may contribute to accelerated bone loss.

Effects of three different calcium preparations on urinary calcium and hydroxyproline excretion in postmenopausal osteoporotic women

Some authors have claimed that 'solubilized' calcium preparations are better absorbed than calcium carbonate, while others have reported that all forms are equally well absorbed. We measured radiocalcium absorption in 35 postmenopausal osteoporotic women and then gave them on three successive evenings, in random order, three different proprietary calcium preparations (Sandocal containing 1 g of effervescent calcium, Calsup containing 1 g of calcium as the carbonate, and Caltrate containing 1.2 g of calcium as the carbonate). The daily urinary calcium excretion rose significantly and similarly on all three supplements and was greater in the high calcium absorbers than the low calcium absorbers. The fasting urinary hydroxyproline excretion was significantly decreased the morning after administration of each preparation, and one-way analysis of variance showed no significant difference between the days of administration or the type of supplement. The decrease was greater for high absorbers than for low absorbers on all three supplements but the differences did not reach statistical significance. By 36 hours after the last calcium supplement the urinary hydroxyproline had returned to baseline. The response of hydroxyproline excretion (and by implication bone resorption) appears to be rapid in onset and short lived. Strict compliance is therefore important in patients on calcium therapy.

Urinary excretion of pyridinoline crosslinks correlates with bone turnover measured on iliac crest biopsy in patients with vertebral osteoporosis

Vertebral osteoporosis, a common disorder in elderly women, is characterized by a wide spectrum of bone turnover abnormalities on iliac crest biopsy. The level of bone formation can be assessed noninvasively by measuring serum osteocalcin, whereas conventional biochemical markers of bone resorption lack specificity and do not reflect bone resorption assessed from histology. We measured the urinary excretion of pyridinoline crosslinks Pyr and D-Pyr, a specific marker of bone and cartilage collagen degradation, along with serum osteocalcin and urinary hydroxyproline, in 36 elderly women with vertebral osteoporosis who had a simultaneous iliac crest biopsy. Urinary pyridinoline crosslinks, but not hydroxyproline, correlated significantly with histologic resorption, assessed by the osteoclast surface (r = 0.35, p less than 0.05 for Pyr; r = 0.46, p less than 0.01 for D-Pyr). In addition, Pyr and D-Pyr were correlated with the bone formation rate as well as serum osteocalcin, with correlation coefficients ranging from 0.69 to 0.80, p less than 0.0001. These data indicate that Pyr and D-Pyr are sensitive markers of bone turnover in elderly women with vertebral osteoporosis. The poor correlation between the level of urinary collagen crosslinks and histological assessment of bone resorption indicates the low sensitivity of iliac crest histomorphometry in the measurement of resorption rate of the skeleton.

Effect of salt restriction on urine hydroxyproline excretion in postmenopausal women

Fasting calcium and hydroxyproline excretion are related to fasting sodium excretion in postmenopausal women. We postulate that calcium excretion is sodium dependent and that hydroxyproline excretion is calcium dependent. Therefore, we sought to lower urinary hydroxyproline, which is a marker of bone resorption, by lowering urinary sodium. Fasting urine samples were obtained from 59 postmenopausal women before and after 2 to 7 days of dietary salt restriction. The urinary sodium-to-creatinine ratio fell from 16 to 7; calcium to creatinine, 0.30 to 0.26; and hydroxyproline to creatinine, 18.2 to 16.8. In the 28 subjects with starting sodium-to-creatinine ratios greater than 15, the hydroxyproline-to-creatinine ratio fell from 19.6 to 16.3. Salt restriction may be one way of reducing bone resorption in postmenopausal women, particularly in those whose sodium intake is high.

Effect of menopause and hormone replacement therapy on the urinary excretion of pyridinium cross-links

Pyridinoline (Pyr) and deoxypyridinoline (D-Pyr) are two cross-links of collagen molecules that are present in the extracellular matrix and released during its degradation. In contrast to the wide distribution of collagen, Pyr is present in bone and cartilage, but not in significant amounts in other connective tissues, and D-Pyr appears to be specific for bone tissue. Therefore, the urinary excretion of Pyr and D-Pyr might be a sensitive marker of bone matrix degradation. Using a specific high pressure liquid chromatography assay we have measured Pyr and D-Pyr cross-links in a 24-h and a fasting urine sample in 60 early postmenopausal women and 19 premenopausal women matched for age. Menopause induced a 62% increase in Fu Pyr (49.8 +/- 18.7 vs. 30.8 +/- 8.0 pmol/mumol creatinine; P less than 0.001) and an 82% increase in Fu D-Pyr (8.2 +/- 3.4 vs. 4.5 +/- 1.4 pmol/mumol creatinine; P less than 0.001). In 20 postmenopausal women on hormone replacement therapy, urinary Pyr and D-Pyr returned to premenopausal levels within 6 months, contrasting with unchanged levels during placebo treatment. The 24-h excretion of Pyr and D-Pyr was significantly lower than the fasting excretion, but was similarly decreased after hormone replacement therapy. Pyr and D-Pyr excretion measured in the same urinary sample were highly correlated (r = 0.85 for fasting and 0.83 for 24-h sampling), but correlations between fasting and 24-h values were weak (D-Pyr, r = 0.30; Pyr, r = 0.29; P less than 0.05 for both). Correlations between urinary cross-links and other markers of bone turnover (Fu hydroxyproline/creatinine and plasma osteocalcin) were significant but low (Pyr vs. osteocalcin, r = 0.29, P less than 0.05; Pyr vs. hydroxyproline, r = 0/.34; P less than 0.01; D-Pyr vs. osteocalcin, r = 0.39; P less than 0.01), except for D-Pyr vs. hydroxyproline (r = 0.24; P = 0.07), suggesting that these markers reflect different events of bone metabolism. Finally, a single measurement of the fasting excretion, but not of the 24-h excretion, of cross-links was significantly correlated (Pyr, r = 0.34; P less than 0.05; D-Pyr, r = -0.46; P less than 0.01), with the subsequent spontaneous rate of bone loss assessed by repeated measurements of the radial bone mineral content in 37 postmenopausal women.(ABSTRACT TRUNCATED AT 400 WORDS)

Screening procedure for women at risk of developing postmenopausal osteoporosis

The present study includes 70 healthy, immediately postmenopausal women stratified according to future rate of bone loss. The stratification was performed by means of four parameters of bone turnover: serum alkaline phosphatase, fasting urinary calcium and hydroxyproline, and body weight, used in an equation developed in a previous study. After the stratification the women were followed without intervention for the next 24 months, with bone mass measurements every 3 months. The bone loss estimated at baseline by means of the equation correlated with the bone loss measured in the forearm (y = 0.72x - 1.52; r = 0.61; P less than 0.001). Plasma bone gla protein (BGP, osteocalcin), which is a new specific marker of bone formation, was now added to the model (replacing body weight). This increased the diagnostic validity (y = x; r = 0.76; P less than 0.001). From the present study we conclude that the postmenopausal bone loss can be predicted by means of four biochemical parameters determined in plasma and urine in women just after the menopause.

Discontinuous calcitonin treatment of established osteoporosis--effects of withdrawal of treatment

PURPOSE

The purpose of this study was to examine the effects of discontinuous treatments with intranasal salmon calcitonin on bone and calcium metabolism in postmenopausal women and to establish the effects of withdrawing treatment.

PATIENTS AND METHODS

This report presents data from 26 postmenopausal women with established osteoporosis (forearm fracture) 12 months after withdrawal of a 1-year double-blind, placebo-controlled therapy with intranasal calcitonin. The women then resumed treatment with calcitonin 200 IU plus calcium 500 mg daily in an open design for an additional 1-year period. A control group of 19 age-matched women (no forearm fracture) did not receive any treatment.

RESULTS

At the end of the 3 years, the control group had lost significantly more bone in the forearm (single photon absorptiometry) and spine (dual photon absorptiometry) than had the group treated with intranasal calcitonin for 2 years, whereas the group receiving calcitonin for 1 year had intermediate values. During the year of withdrawal, the rate of bone loss was similar in the women who had received calcitonin and those who had received placebo. Calcitonin was especially effective in women with initially high bone turnover and low bone mass. The bone response in the spine could, furthermore, be estimated by the changes in bone turnover.

CONCLUSION

Discontinuous treatment with intranasal calcitonin affects bone and calcium metabolism in established osteoporosis. In women with high-turnover osteoporosis, therapy results in a net gain of bone in both the peripheral and axial skeleton. Response to treatment may be monitored by changes in bone turnover.

Zinc excretion in osteoporotic women

The relation of zinc to the aging skeleton was investigated in 140 women aged 36-85 years, mostly postmenopausal, who attended the Jerusalem Osteoporosis Center. Osteoporosis was determined by lumbar spine radiograms (Smith index). Bone density (BD) of the distal radius was assessed by Compton spectroscopy and bone mineral content (BMC) at the same site by single-photon absorptiometry. Urine samples (24 h) were analyzed for zinc (UZn), hydroxyproline (UHP), calcium (UCa), magnesium (UMg), and phosphorus (UP) and expressed per gram creatinine. Patients with definite osteoporosis (n = 94) compared to subjects with borderline or no osteoporosis (n = 34) had a significantly higher mean age (67.4 versus 58.6 years), postmenopausal age (PMA, 19.9 versus 11.0), UZn (811 versus 581), UHP (23.5 versus 18.2), and UMg (90.4 versus 74.3). Urinary calcium UCa and phosphorus UP were similar in both groups. The bone mass measurements BD, BMC, and CI were lower in the osteoporotic group. Hyperzincuria (UZn above 800 micrograms/g creatinine) was found in 41 osteoporotic patients (45%) compared to 6 subjects in the control group (17%). In view of the positive correlation between UZn and age (r = 0.35, p = 0.001) and to eliminate the effect of age, a separate analysis was performed for 66 subjects under the age of 65 in whom the mean age was similar for the osteoporosis patients (n = 38) and control group (n = 28). Nevertheless, the osteoporosis patients still had a significantly higher mean UZn and UHP.(ABSTRACT TRUNCATED AT 250 WORDS)

Prevention of postmenopausal bone loss by tiludronate

76 healthy women, who had been menopausal for less than 96 months and who had never received any form of treatment to prevent bone loss, were entered into a randomised double-blind study. For the first 6 months, half the patients received tiludronate 100 mg daily, while the others received placebo. During the second 6 months, all patients received placebo. Bone mineral density of the lumbar spine decreased significantly by 2.1% (SE 0.8%) in the placebo group and did not significantly change in the tiludronate group (+1.33 [0.8]%). The difference in response between the groups was significant, as were the differences between values for corrected urinary hydroxyproline and calcium. Treatment with tiludronate was not followed by increased secretion of parathyroid hormone. A 6 month course of oral tiludronate may counteract postmenopausal bone loss for at least a year by decreasing bone resorption.