Kinetics of 99mtechnetium-tin-methylene-diphosphonate in normal subjects and pathological conditions: a simple index of bone metabolism

Bone metabolism of the jaw in response to bisphosphonate: a quantitative analysis of bone scintigraphy images

We examined the changes in the bone metabolism of the jaw in response to BP treatment, and we used bone SPECT-CT to analyze the site-specific bone metabolism between the jaw and other sites of bone. We compared the changes in the bone metabolism of each part of bone in response to BP treatment by performing a quantitative analysis of bone scintigraphy images between patients treated with low-dose BP for osteoporosis (LBP group; n = 17), those treated with high-dose BP for metastatic bone tumor (HBP group; n = 11), and patients with other oral disease who required bone scintigraphy, with no history of BP treatment (control group; n = 40). The study endpoint was the mean standardized uptake value (SUV) of the uptake of Tc-99 m methylene diphosphonate (MDP) in each group. The mean SUVs of the HBP group were significantly lower at the axial bone of the cervical vertebra, thoracic vertebra, sternum, and rib compared to those of the LBP and control groups. The LBP group's mean SUV was significantly higher at the temporal bone, the anodontia part of the alveolar bone in maxilla, the vital teeth part of alveolar bone in the mandible, and the temporomandibular joint. There was no significant difference among the three groups at the mandibular angle and mandibular ramus. Our analyses revealed that the bone metabolism of the jaw and temporal bone in the BP-treated patients was enhanced, and no suppression of bone remodeling in the jaw by BP was observed.

Comparison between CEA, TPA, CA 15/3 and Hydroxyproline, Alkaline Phosphatase, Whole Body Retention of 99mTc MDP in the follow-up of Bone Metastases in Breast Cancer

The development of bone metastases in cancer can be monitored easily using three markers: 24 h urinary hydroxyproline excretion (HOP) (an index of osteoclastic activity), serum alkaline phosphatase (Alk.Ph.) (an index of osteoblastic activity) and 24 h whole body retention of 99mTc-methylene diphosphonate (WBR%) (an index of bone turnover). To evaluate the effectiveness of this group of bone tumor markers in breast cancer we compared it with the following group of three markers which are commonly used in the monitoring of breast cancer and in the follow-up of advanced disease with or without bone metastases: carcinoembryonic antigen (CEA), tissue polypeptide antigen (TPA) and breast carcinoma antigen (CA 15/3).

In 48 patients with bone metastases CEA, TPA and CA 15/3 were shown to be sensitive (79%, 85%, 90% respectively), while HOP, Alk.Ph. and WBR%, which are commonly accepted as reliable markers of bone activity, showed a lower sensitivity (67%, 46%, 75% respectively).

These results may be explained by the lack of osteoclastic or osteoblastic (or both) activity at the time of diagnosis. This explanation is supported by the fact that the bone markers HOP, Alk.Ph. and WBR% were found to be more sensitive than the others in the subsequent follow-up study.

We conclude that in our study, CEA, TPA and CA 15/3 are at first more sensitive than Alk. Ph., HOP and WBR% but during the follow-up Alk.Ph., HOP and WBR% are possibly both more specific and more sensitive

Biokinetics of 90Sr in Male Nonhuman Primates

The current study tests the hypothesis that the biokinetics of Sr can be represented by simplification of the ICRP publication 78 Sr model. Default and proposed models were evaluated by their ability to predict injected activity and more thoroughly define the activity residing in the skeleton of rhesus monkeys. The data obtained from studies done by Patricia Durbin and her colleagues at the Lawrence Berkley National Laboratory were used to create a profile of the activity residing in the skeleton at the time of sacrifice. Post mortem data along with periodic whole body count data were used to optimize the biokinetic parameters using the Integrated Modules for Bioassay Analysis (IMBA), Weighted Likelihood Monte-Carlo Sampling (WeLMoS) program to better predict the intake and fit of the bioassay data. Analysis of the default ICRP 78 parameters resulted in an overprediction of activity in the skeleton for a male cohort by as much as 180%. Using Monte Carlo sampling methods, three models were developed and optimized for a composite cohort of male monkeys. Of the three developed models, one model proved to have the best predictive capabilities. The optimized model C obtained for the male cohort was then tested on a validation cohort to test predictive capabilities. Using the optimized model C parameters, the ability to predict activity in the skeleton was improved in comparison to ICRP 78. Prediction of the intake from bioassay data was also improved by a factor of 2 in comparison to ICRP 78. The results suggest that the modified transfer rates of model C could be used as default parameters for biokinetic nonhuman primate modeling and potentially extrapolated to humans.

Dissociation between global markers of bone formation and direct measurement of spinal bone formation in osteoporosis

Regional bone metabolism measured using 18F-fluoride PET was assessed in 72 postmenopausal women classified as normal, osteopenic, or osteoporotic. Lower values of regional bone formation activity at the lumbar spine were seen in osteoporotic women, whereas global markers of bone formation were significantly increased.

INTRODUCTION

Evaluations of global bone remodeling have revealed that increased bone turnover is a feature of patients with osteoporosis. The noninvasive functional imaging technique of 18F-fluoride positron emission tomography (PET) allows the direct quantitative assessment of bone metabolism at specific sites in the skeleton, including the clinically important site of the lumbar spine.

MATERIALS AND METHODS

The aim of this study was to compare regional skeletal kinetics in 72 postmenopausal women (mean age, 61 years) classified as normal, osteopenic, or osteoporotic according to their BMD T score at the lumbar spine. Each woman had a dynamic PET scan of the lumbar spine after injection of 90 MBq 18F-fluoride ion and measurements of biochemical markers of bone formation and resorption. The arterial plasma input function was derived using aorta arterial activity from the PET image. Time-activity curves were obtained by placing regions of interest over the lumbar vertebrae. A three-compartmental model was used to calculate bone blood flow (K1) and the net plasma clearance of tracer to bone mineral (Ki), reflecting regional osteoblastic activity (ml/minutes/ml). Rate constants k2, k3, and k4, which describe transport between plasma, the extracellular fluid (ECF) compartment, and the bone mineral compartment, were also measured.

RESULTS

The net uptake of fluoride to the bone mineral compartment (Ki) was significantly lower in the osteoporotic group compared with both the osteopenic and normal groups, with a mean difference of 0.005 ml/minutes/ml (16.7%). The fraction of the tracer in the extravascular tissue space that underwent specific binding to bone mineral (k3/k2 + k3) was also significantly reduced in the women classified as osteoporotic. In contrast, levels of bone-specific alkaline phosphatase (BSALP) were significantly higher in the osteoporotic group compared with the normal and osteopenic groups by 35% and 27%, respectively. A significant negative correlation (r = -0.41) was observed between levels of BSALP and the fraction of the tracer that underwent specific binding to bone mineral.

CONCLUSION

Lower values of Ki, a measurement of regional bone formation activity, were seen in women classified as osteoporotic, whereas levels of BSALP, a measure of global bone formation, were significantly increased. These findings are suggestive of increased global skeletal bone turnover in women with postmenopausal osteoporosis but with relatively reduced regional bone formation at the predominantly trabecular site of the lumbar spine.

Bone as an effect compartment : models for uptake and release of drugs

"Bone-seeking agents" are drugs characterised by high affinity for bone, and are disposed in bone for prolonged periods of time while maintaining remarkably low systemic concentrations. As a consequence, the bone becomes a reservoir for bone-seeking agents, and a site of both desirable and adverse effects, depending on the pharmacological activities of the specific agent. For some agents, significant systemic effects may also be produced following their prolonged release from bone, a process that is governed mostly by the rate of bone remodelling. This review covers the pharmacokinetic and pharmacodynamic features of bone-seeking agents with different pharmacological properties, including drugs (bisphosphonates, drug-bisphosphonate conjugates, radiopharmaceuticals and fluoride), bone markers (tetracycline, bone imaging agents) and toxins (lead, chromium, aluminium). In addition, drugs that do not possess bone-seeking properties but are used for therapy of bone diseases (such as antibacterials for treatment of osteomyelitis) are discussed, along with targeting of these drugs to the bone by conjugation to bone-seeking agents, local delivery systems, and other approaches. The pharmacokinetic and pharmacodynamic behaviour of bone-seeking agents is extremely complex due to heterogeneity in bone morphology and physiology. This complexity, accompanied by difficulties in human bone research caused by ethical and other limitations, gave rise to modelling approaches to study bone drug disposition. This review describes the pharmacokinetic models that have been proposed to describe the pharmacokinetic behaviour of bone-seeking agents and predict bone concentrations of these agents for different doses and patient populations. Models of different types (compartmental and physiologically based) and of different complexity have been applied, but their relevance to drug effects in the bone tissue is limited since they describe the behaviour of the "average" drug molecule. Understanding of the cellular and molecular processes responsible for the heterogeneity of bone tissue will provide better comprehension of the influence of microenvironment on drug bone disposition and the resulting pharmacological response.

Quantitative studies of bone with the use of 18F-fluoride and 99mTc-methylene diphosphonate

This article discusses methods for quantifying bone turnover based on tracer kinetic studies of the short-lived radiopharmaceuticals 99mTc-MDP and 18F-fluoride. Measurements of skeletal clearance obtained by using these tracers reflect the combined effects of skeletal blood flow and osteoblastic activity. The pharmacokinetics of each tracer is described, together with some of the quantitative tests of skeletal function that have been described in the literature. The physiologic interpretation of quantitative measurements of bone obtained with the use of short half-life radionuclides is discussed, and the advantages and limitations of 99mTc-MDP and 18F-fluoride are compared and contrasted. Currently, 18F-fluoride dynamic positron emission tomography (PET) is the technique of choice for physiologically precise quantitative studies of bone. However, comparable data could probably be obtained by using 99mTc-MDP if methods for single photon emission computed tomography (SPECT) quantitation were improved.

Radiation hazards from horses undergoing scintigraphy using technetium-99m

This paper quantifies the extent of the radiation hazard to personnel from horses undergoing scintigraphy using technetium99m methylene diphosphonate (99Tcm-MDP). From the data produced it is possible to derive safe working protocols which are comfortably within the legislated limits for whole body doses as set out in the Ionising Radiations Regulations 1985. Measurements were made of the surface and environmental activities which result from individuals undergoing scintigraphic evaluation and also from urine contaminated bedding. The use of both high and low activities in the assessment of the radiation hazard to personnel and owners is considered.

Age-related changes in the global skeletal uptake of technetium-99m methylene diphosphonate in healthy women

A short-term evaluation of global skeletal uptake (GSU) of technetium-99m methylene diphosphonate (MDP) was performed in 40 healthy female subjects with a wide age range in order to investigate the clinical performance of the technique and to detect the age-related changes in bone turnover. The results obtained were compared with measurements of the main biochemical markers of skeletal metabolism. We found that GSU increases progressively with age, independently of concomitant changes in renal function; significant correlations with biochemical markers of bone formation were also found. Therefore, the method appears to provide useful information concerning the bone turnover rate, and is also applicable to elderly people owing to its simplicity.

Effects of continuous percutaneous estradiol administration on skeletal turnover in postmenopausal women: a 1-year prospective controlled study

The aim of this study was to investigate the short and long term effects of continuous percutaneous administration of estradiol (E2) cream on skeletal turnover in women in surgical postmenopause. Forty women were randomly divided into two groups, one treated with a single daily application of 3 mg/day E2 cream continuously for 12 months, the other receiving placebo cream. Forearm densitometry was performed before and at the end of treatment. Serum E2, osteocalcin (BGP), alkaline posphatase (AP) and urinary N-telopeptide of type I collagen (NTX) were also measured at baseline, month 4 and 12 of the protocol. At month 4, bone turnover was also assessed by evaluating 99mtechnetium-methylene diphosphonate (99mTc-MDP) skeletal uptake. Changes in E2, BGP, AP and NTX as well as 99mTc-MDP skeletal uptake in hormone group vs. placebo were significant after 4 months of treatment. At month 12, proximal site densitometry showed no variation in either group whereas the percentage of variation in distal site measurements resulted significantly different with an increase in the hormone group and a reduction in the placebo group. In conclusion continuous percutaneous administration of E2 cream was effective in rapidly reducing bone turnover in postmenopausal women and in counteracting the accelerated postmenopausal bone loss.

Inhibition of calculi fragment growth by metal-bisphosphonate complexes demonstrated with a new assay measuring the surface activity of urolithiasis inhibitors

To evaluate compounds for the long-term inhibition of urinary calculi growth, we applied a newly developed in vitro assay to various metal-ligand complexes. The new experimental model--the preadsorbed calculi growth assay--was based upon the initiation of crystal growth in a metastable solution of calcium and oxalate with uniform granules derived from human renal calculi. Potential inhibitors were first absorbed onto the surface of the calculi granules, following which the loss of calcium from the seeded metastable solution was monitored as the indicator of calcium oxalate deposition. This assay allowed participation in the reaction by any matrix components present in the human calculi granules and limited the effect of the inhibitors to the calculi surface. Some complexes of metal ions with bisphosphonates had strong inhibitory effects, as opposed to citrate complexes which had minimal effect in this assay. Tin was the most potent metal ion, and pamidronate was the most potent bisphosphonate; together they slowed the growth of calculi granules to 9% of control. The inhibition by Tin-bisphosphonate complexes persisted despite a week of continual rinsing with a solution of sodium chloride and calcium. If the metal-bisphosphonate complexes are active in vivo as well, they might be considered for prophylaxis of calcium oxalate calculi or the prevention of regrowth of residual fragments following lithotripsy.

Hypercalcemia in breast cancer

Hypercalcemia is relatively frequent in malignancy with or without osteolytic bone metastases. It is thought that neoplastic cells may secrete substances which not only stimulate osteoclastic activity but are also capable of modifying the absorption, excretion, and resorption of calcium and phosphate ions. Since 1987, we have studied 24 breast cancer patients with hypercalcemia (22 with bone metastases and two without). The group of 22 patients with bone metastases were divided into two subgroups. The first consisted of 10 patients with high serum levels of humoral factors, such as parathyroid hormone-related protein (PTHrP), and/or prostaglandin E2 (PGE2) and/or interleukin 1 (IL-1), and high levels of bone markers, such as alkaline phosphatase, bone Gla protein and urinary hydroxyproline. The second subgroup consisted of 12 patients with high levels of bone markers alone. Bone histologic analysis showed an osteoclastic activation surrounding metastatic tumor tissue in six out of 10 patients of the first subgroup, while an evident osteolysis caused by the tumor cells was noted in seven out of 12 patients of the second subgroup. The two patients without bone metastases showed normal biochemistry and bone histologic examination. The authors, having tried to explain the pathogenesis of hypercalcemia, emphasize the importance of humoral factors secreted by tumor cells as a direct or indirect cause of hypercalcemia. The origin of hypercalcemia remains unclear in two patients without bone metastases.

Weekly chemotherapy in advanced prostatic cancer

This randomised phase II study was performed in order to evaluate the effectiveness of a weekly chemotherapy regimen in advanced prostatic carcinoma patients (stage D2) refractory to hormonal therapy. Seventy-two cases were studied: they were randomised in a 2:1 ratio to receive either epirubicin (30 mg m-2 weekly) or doxorubicin (25 mg m-2 weekly); 48 patients received epirubicin and 24 received doxorubicin. After 12 courses of chemotherapy, the 45 evaluable patients in the epirubicin arm showed a response rate of 37.7% and the 21 evaluable patients in the doxorubicin arm showed a response rate of 33.3% (P = 0.51). Pain intensity, bone and prostatic tumour markers rapidly and significantly decreased in responders. An improvement in physical symptoms, functional conditions and in emotional well-being was observed in the majority of the treated patients. The histological analysis of bone metastases, performed before and after 12 courses of chemotherapy showed a significant reduction in neoplastic invasion and in new bone formation in responders. Cardiac performance worsened in five out of 45 patients and in ten out of 21 during the first 12 courses of epirubicin or doxorubicin respectively (P = 0.014). The median survival was 12.5 months in the epirubicin arm and 8.0 months in the doxorubicin arm (P = 0.042). Our data indicate that in advanced prostatic carcinoma, a weekly epirubicin regimen may give rapid palliative results, similar to that of doxorubicin, but with less side-effects.

99mTc-medronate uptake in the temporomandibular joints of young rats treated with a mandibular hyperpropulsor

To correct maxillomandibular sagittal discrepancies in growing children, most functional appliances position the mandible more anteriorly than its habitual relation with the maxilla. The aim of this study was to evaluate the effects of such a procedure on the mineralization of the temporomandibular joints in young growing rats. Temporomandibular joint uptake of a radioactive bone marker, technetium 99m methylene diphosphonate (99mTc-MDP), was measured over time as a hyperpropulsor appliance was being worn intermittently 12 hours/day. As the uptake of 99mTc-MDP decreased in control animals, it increased significantly in the joints of treated rats before returning to the baseline level after 5 weeks of treatment. These results suggest that intermittent anterior positioning of the mandible induces a high rate of bone and cartilage remodeling in the joints of growing rats and that bone-seeking radiopharmaceutical uptake, with 99mTc-MDP, may be a useful technique to monitor joint adaptation to an experimental functional change.

Isotope retention for assessment of bone turnover in involutional osteoporosis

A continuous bone remodelling takes place throughout life at different turnover speed according to age, physiological and pathological conditions. The evaluation of bone turnover may be of value for a prognostic and therapeutical assessment. Calcium bone exchange may be considered a suitable marker of bone turnover; for this reason 47Ca or 45Ca kinetics may be used; these methods have been employed in the past. Labelled diphosphonates, and in particular 99Technetium-methylene-diphosphonate (99TcmDP) are simpler and safer, because these substances are strongly and almost completely stored in bone and not absorbed by the soft tissue; for this reason they are used at the present time. The evaluation of blood levels and 24 hrs urinary elimination of 99TcmDP is used to measure whole bone diphosphonate retention (WBR). This parameter is positively correlated with other markers of bone turnover such as alkaline phosphatase (AP), osteocalcin (OC), urinary hydroxyproline (HOP). A bicompartmental analysis schedule of 99TcmDP distribution has been proposed some years ago and therefore applied by our group, based on the mathematical evaluation of serum concentration at different times and urinary elimination of the label given intravenously. This method provides the possibility to calculate not only WBR but also total body retention (TBR) and a constant (Kbh) which reflects the influx speed of the tracer in the bone. Kbh probably represents a more sensitive index of bone turnover than WBR. It presents a better correlation with AP and OC values and also shows some (statistically less significant correlations with some indices of bone remodelling obtained by histomorphometry on bone biopsies.(ABSTRACT TRUNCATED AT 250 WORDS)

Hypocalcemia in patients with prostate cancer

We report a case of severe hypocalcemia in a patient with prostate cancer and extensive metastatic bone disease. The hypocalcemia in this patient was most likely on the basis of extensive accretion of calcium into the bones. We further studied 112 patients with prostate cancer, 15 of whom were discovered to be hypocalcemic on the basis of serum total calcium measurement. Fourteen of these 15 patients had bone metastases. Serum total calcium, total protein, and albumin levels were significantly lower in patients with bone metastases (n = 61) than those without (n = 51). Hypocalcemia could be explained on the basis of hypoalbuminemia or renal failure in these patients. Plasma ionized Ca measurements were made in 47 of the total 112 patients. Only one patient with extensive bone metastases was found to be hypocalcemic on the basis of ionized calcium measurement. Therefore, apparent hypocalcemia based on total calcium measurement is common in patients with prostate cancer (14% of all and 23% of those with bone metastases), whereas true hypocalcemia based on ionized calcium determinations is unusual.

Bone turnover in postmenopausal osteoporosis. Effect of calcitonin treatment

To investigate the effectiveness of calcitonin treatment of postmenopausal osteoporosis in relation to bone turnover, we examined 53 postmenopausal osteoporotic women before and after one year of therapy with salmon calcitonin (sCT), at the dose of 50 IU every other day. Baseline evaluation revealed that 17 (32%) patients had high turnover (HTOP), and 36 (68%) normal turnover osteoporosis (NTOP) as assessed by measurement of whole body retention (WBR) of 99mTc-methylene diphosphonate. The two groups did not differ in terms of bone mineral content (BMC) measured by dual photon absorptiometry at both lumbar spine and femoral diaphysis. However, HTOP patients had higher levels of serum osteocalcin (OC) and urinary hydroxyproline excretion (HOP/Cr). Multivariate regression analysis showed no correlation between parameters of bone turnover (WBR, OC, HOP/Cr) and both femoral and vertebral bone density; the latter being negatively correlated only with the years elapsed since menopause (R2 = 0.406). Treatment with sCT resulted in a significant increase of vertebral BMC in the 53 patients taken as a whole group (+/- 7%, P less than 0.001). When the results obtained in HTOP and NTOP were analyzed separately, only those with HTOP showed a marked increment of spinal BMC (+22%, P less than 0.001), NTOP subjects neither gained nor lost bone mineral during the study. Femoral BMC decreased in the whole group after sCT therapy (-3%, P less than 0.003). However, HTOP patients maintained initial BMC values, whereas those with NTOP lost a significant amount of bone during the study period (-5%, P less than 0.001). The increase of vertebral bone mass was associated with a marked depression of bone turnover detectable in both subsets of patients and in the whole group.

IN CONCLUSION

(a) assessment of bone turnover cannot help predict the severity of bone loss in postmenopausal osteoporosis; (b) calcitonin therapy appears to be particularly indicated for patients with high-turnover osteoporosis, resulting in a net gain of bone mineral in the axial skeleton and a slowing of bone loss in the appendicular bones.

GFR-corrected 24-hour whole body retention of diphosphonate: an improved index of bone metabolism

The 24-hour whole body retention of diphosphonate (WBR) depends on bone uptake and renal clearance of diphosphonate. To evaluate the influence of glomerular filtration we measured WBR, creatinine clearance (CrCl) and s-alkaline phosphatase (s-AP) in 91 normals and 79 patients with different calcium metabolic disorders. As presumed, a negative correlation between CrCl and WBR exists (r = -0.67, p less than 0.001). By defining CrCl = 100 ml/min as standard, we have introduced a new mathematical model which allows recalculation of the measured WBR to WBR at CrCl = 100 ml/min (WBR100): WBR100 = [(1-WBR) x 100/WBR x CrCl +1]-1 Whole body retention at a clearance of 100 ml/min is demonstrated to be independent of CrCl (r = 0.14, NS). Using this approach we estimate that deviations of CrCl below 70 ml/min and above 150 ml/min lead to more than 25% increase/decrease in WBR. Using s-alkaline phosphatase as a standard, it is shown that WBR overestimates bone formation when CrCl is low. This new model permits the interpretation of WBR measurements in terms of bone turnover in patients with low glomerular filtration rates.

Bisphosphonate whole body retention test: relations to bone mineralization rate, renal function and bone mineral content in osteoporosis and metabolic bone disorders

The bisphosphonate whole body retention test (WBR) has been used to estimate bone mineralization rate (bone turnover). Bisphosphonates given i.v. are taken up by bone or excreted in urine. The aim of the present investigation was to test the efficacy of WBR in estimating bone mineralization rate (m) and to evaluate the influence of renal function (Clcr) and bone mass (forearm bone mineral content; BMC) on WBR. The 24-h retention of 3.7 MBq 99mTc-HMBP (1-hydroxymethylene-1,1-bisphosphonate) (Osteoscan) given i.v. was measured by a medium sensitive whole body counter in thirty-one patients with hyperparathyroidism (n = 14), hyperthyroidism (n = 8) or hypothyroidism (n = 9) (group 1) and in seventy-six females with postmenopausal spinal crush fracture osteoporosis (group 2). In the same individuals m was calculated from a 7-day 47Ca-kinetic study using the expanding calcium pool model. Multiple regression analysis of WBR vs. m and Clcr in group 1 disclosed that WBR correlated positively to m [rp = 0.49, P less than 0.01 (rp = partial correlation coefficient)] and inversely to Clcr (rp = -0.44, P less than 0.02). Inclusion of BMC in the analysis did not reveal any significant partial correlation between WBR and BMC (rp = -0.33, 0.05 less than P less than 0.10). In group 2 WBR correlated inversely to Clcr (rp = -0.48, P less than 0.001) but showed no significant relation to m (rp = 0.10, NS).(ABSTRACT TRUNCATED AT 250 WORDS)

Studies on diphosphonate kinetics. Part II: Whole body bone uptake rate during constant infusion--a refined index of bone metabolism

To elaborate the understanding of diphosphonate kinetics, a non compartmental analysis is introduced. Using continuous infusion of 99mTc-methylene diphosphonate (Tc-MDP) and 51Cr-EDTA, as a cotracer, the diphosphonate clearance to bone (BDC) can be calculated. BDC is found to correlate well with the 24 h whole body retention of diphosphonate (WBR) (r = 0.89, P less than 0.01) when renal function is normal, but not in cases of reduced 51Cr-EDTA clearance. These findings indicate that BDC measurements are superior to the WBR technique in the estimation of bone turnover, especially when renal function is reduced. The BDC measurements may also constitute a useful tool for studies of diphosphonate uptake in bone, the foundation of bone scintigraphy.

Determination of bone turnover by urinary excretion of 99mTc-MDP

Two methods of estimating bone turnover were investigated. The 24 h whole body retention (WBR) of intravenously injected 99mTc methylene disphosphonate (99mTc-MDP), a precise, accurate, and generally accepted method, was compared with a new, simple, measurement involving assessment of the 24 h urinary excretion (UE) of 99mTc-MDP. The WBR and UE were measured in 50 normal subjects, 10 patients with thyrotoxicosis, and 10 patients with chronic renal failure. The precision was 4.8% and 2.7%, respectively, and the two methods were highly significantly correlated (r = 0.99, SEE = 2.9%, p less than 0.001). In addition, urinary 99mTc-MDP excretions at 0 h-4 h (UE4) and 0 h-8 h (UE8) after injection were calculated in 49 subjects. The estimation of WBR from UE4 or UE8 was considerably poorer than from UE (for UE4: r = -0.83, SEE = 8.7%, and for UE8: r = -0.90, SEE = 6.8%) and the precision of UE4 and UE8 was 7.2% and 7.8%, respectively, and greater than those of both UE and WBR. It is concluded that the UE bone turnover measurement may become a simple, radiation dose-saving method to diagnose and monitor the treatment of metabolic bone diseases.

Bone turnover in healthy adults measured by whole body retention and urinary excretion of 99mTc-MDP. Normalization by bone mass

Whole body retention (WBR) and urinary excretion (UE) of 99mTc-diphosphonate, two complementary methods of measuring the total bone turnover, were performed in 161 normal subjects, 82 women and 79 men, aged 20-70 years. Both WBR and UE were a function of age in the women, whereas there were no age-dependent differences in the men. Between the women and men in identical age groups, the differences did not reach significance. Total body bone mineral (TBBM) was measured by dual photon absorptiometry (DPA) in all subjects. This was done in order to obtain expressions for bone turnover per bone mass as a function of age and sex. This correction emphasized the general picture seen in the raw WBR and UE data: bone turnover was constant in the men throughout life and in the women before the menopause, and only moderate differences were found between the sexes before the age of 50. After this age the mean female values increased sharply. It is noteworthy that none of the postmenopausal subjects showed low turnover values. Our data clearly demonstrate that an increase in bone turnover is part of the pathophysiology of the well-known bone loss in postmenopausal women.

Assessment of metabolic bone disease: review of new nuclear medicine procedures

In the management of patients with metabolic bone disease, nuclear medicine laboratories offer two nontraumatic procedures of potential clinical importance: bone mineral measurements and bone scintigraphy. Bone mineral measurements from the radius, lumbar spine, and hip obtained with use of absorptiometry or computed tomography can be used to predict the risk of fracture at these skeletal sites, can determine the severity of bone loss for the assessment of a benefit-versus-risk ratio on which appropriate therapy can be based, and can substantiate the effectiveness of therapy over time. Bone scintigraphy with use of labeled diphosphonate allows assessment of focal and, in defined circumstances, of total skeletal bone turnover in patients with normal kidney function. Both of these techniques have been used successfully in studies of population groups for the evaluation of trends. Their application to the management of individual patients is currently being evaluated.

Measurements of whole body retention of diphosphonate and other indices of bone metabolism in 125 normals: dependency on age, sex and glomerular filtration

Measurements of 24-h whole body retention of 99m-Tc-MDP (WBR) has been performed in 125 normal volunteers, together with determinations of serum alkaline phosphatase, urinary hydroxyproline excretion and creatinine clearance. WBR decreased slightly from the 3rd to the 4th decade, after which it increased gradually in the older age-groups. Serum alkaline phosphatase followed an identical pattern, while the urinary hydroxyproline excretion demonstrated a marked but temporary rise in the post-menopausal age-groups. Finally, the creatinine clearance decreased gradually in the older age groups. Analysis of variance demonstrated that WBR varied independently with serum alkaline phosphatase and creatinine clearance, while no relationship between WBR and the hydroxyproline excretion was found. It seems likely that the increasing retention of diphosphonate in elderly persons reflects rising osteoblastic activity as well as decreasing glomerular filtration.

25-Hydroxycholecalciferol as an antagonist of adverse corticosteroid effects on phosphate and calcium metabolism in man

The present study was performed in 30 patients who needed steroid therapy: courses of triamcinolone or DTM 8-15 given orally lasted 30 days. In 15 of these patients glucoactive corticosteroids were administered in combination with 5 micrograms/day of 25OH-vitamin D3 (25OHD3). 47Calcium oral test and 99mTc-MDP kinetics, as an index of bone turnover, were performed at the beginning of the therapy and after 30 days. At the end of treatment a significant improvement of intestinal radiocalcium transport together with a decrease in bone turnover in the group of patients treated with 25OHD3 was observed. As it concerns plasma calcium level, inorganic phosphate, the urinary excretion of calcium, phosphate and hydroxyproline no significant difference between the two groups examined were noticed. These results indicate that the adverse effects of glucoactive corticosteroids on intestinal calcium transport and bone turnover may be counteracted by the combined administration of physiological doses of 25OHD3.

Urinary 99m-Tc-diphosphonate excretion as a simple method to quantify bone metabolism

Twenty-four-hour whole-body retention (WBR) of 99m-Tc-methylene-diphosphonate (an index of bone turnover) was determined by whole-body counting (WBRs) and complementarily by urine counting (WBRu) in nineteen subjects with normal to highly increased bone turnover. WBRs and WBRu correlated well (r = 0.94, P less than 0.001), and gave almost the same results. Both WBRs correlated equally well with serum alkaline phosphatase and urine hydroxyproline/creatinine (r = 0.82-0.93). Coefficient of variation in WBRu was 7.0%, determined by duplicate measurements in sixteen normals. The injected dose of diphosphonate did not influence WBRu. However, since almost 50% of the diphosphonate excreted in urine appeared during the first few hours after the i.v. injection, the method of WBRu requires careful urine collection. Thus, the simple WBRu determination provides the same information on bone metabolism as does the more cumbersome and expensive WBRs technique.

Whole body and regional retention of 99mTc-labeled pyrophosphate at 24 hours: physiological basis of the method for assessing the metabolism of bone in disease

The retention of 99mTc-labeled pyrophosphate (PPi) at 24 h was measured in 235 patients, 119 of whom had a normal bone metabolism. The mean retention in the group of normal subjects is 52% of the injected dose. Reproducibility of the measurement in a given person is 5.5% coefficient of variation (CV). The value depends strongly on sex (higher in males) and age (higher with increasing age, especially in cortical bone). Retention increases slowly with the decrease in glomerular filtration rate (GFR) between 50 and 120 ml/min; it rises very rapidly with values below 50 ml/min. The slowing down of the GFR with age does not account for the increase in PPi retention with age. When expressed as a percentage of the expected value for sex and age, retention is frequently low in osteoporosis (P less than .001), more so when urinary hydroxyproline is low; it is normal or high in osteomalacia, and in some cases rises after vitamin D treatment is started; it is high in hyperparathyroidism (P less than .01). The PPi retention is correlated with bone calcium accretion rate, alkaline phosphatase level, and above all, the urinary hydroxyproline level. The lower the bone mineralization (Ca/hydroxyproline ratio in biopsy), the higher the retention value. We conclude that the PPi retention is an index of bone metabolism when GFR is higher than 50 ml/min. It allows for classification of metabolic bone diseases according to the bone turnover rate. It has the advantage over the usual biologic examinations in that it affords better observation of highly localized bone disorders and can be used in combination with a morphologic record, the bone scintigraphy.