Assessing drug effect from distributional data: A population approach with application to Duchenne Muscular Dystrophy treatment.

BACKGROUND AND OBJECTIVE: In Duchenne Muscular Dystrophy (DMD) treatment, muscle fiber size can be considered as an indicator of muscle health and function. In particular, the statistical distribution of fibers cross-sectional areas (CSAs) has been used as quantitative efficacy endpoint. For each patient, assessment of treatment effect relies on the comparison of pre- and post-treatment biopsies. Since biopsies provide "distributional data", i.e. empirical distributions of fibers CSA, the comparison must be carried out between the empirical pre- and post-treatment distributions. METHODS: Here, distributional fiber CSA data are analyzed by means of a hierarchical statistical model based on the population approach, considering both the single patient and the population level. RESULTS: The proposed method was used to assess the histological clinical effects of Givinostat, a compound under study for DMD treatment. At the single patient level, a two-component Gaussian mixture adequately represents pre- and post-treatment distributions of log-transformed CSAs; drug effect is described via a dose-dependent multiplicative increase of muscle fiber size. The single patient model was also validated via muscle composition data. At the patient population level, typical model parameters and inter-patient variabilities were obtained. CONCLUSIONS: The proposed methodological approach completely characterizes fiber CSA distributions and quantifies drug effect on muscle fiber size, both at the single patient and at the patient population level. This approach might be applied also in other contexts, where outcomes measured in terms of distributional data are to be assessed.

Association between amygdala reactivity and a dopamine transporter gene polymorphism.

Essential for detection of relevant external stimuli and for fear processing, the amygdala is under modulatory influence of dopamine (DA). The DA transporter (DAT) is of fundamental importance for the regulation of DA transmission by mediating reuptake inactivation of extracellular DA. This study examined if a common functional variable number tandem repeat polymorphism in the 3' untranslated region of the DAT gene (SLC6A3) influences amygdala function during the processing of aversive emotional stimuli. Amygdala reactivity was examined by comparing regional cerebral blood flow, measured with positron emission tomography and [(15)O]water, during exposure to angry and neutral faces, respectively, in a Swedish sample comprising 32 patients with social anxiety disorder and 17 healthy volunteers. In a separate US sample, comprising 85 healthy volunteers studied with blood oxygen level-dependent functional magnetic resonance imaging, amygdala reactivity was assessed by comparing the activity during exposure to threatening faces and neutral geometric shapes, respectively. In both the Swedish and the US sample, 9-repeat carriers displayed higher amygdala reactivity than 10-repeat homozygotes. The results suggest that this polymorphism contributes to individual variability in amygdala reactivity.

From trial and error to trial simulation III: a framework for interim analysis in efficacy trials with antidepressant drugs.

Clinical trials with antidepressant drugs often fail to detect drug effect, even with drugs that are known to be efficacious. In a previous publication, we showed that a model-based approach is required to address some of the existing challenges in the design of clinical trial protocols. Here, we illustrate how the implementation of an interim analysis (IA) may help to identify studies that are headed for failure, early in the trial before completion of treatment. In contrast to traditional IA procedures, an adaptive Bayesian approach is proposed to optimize the timing of analysis and decision criteria for futility and efficacy, taking into account enrollment rate and treatment response at intermediate visits in the trial. Validation procedures involving re-enrollment of patients confirmed the performance of the method. Our findings reveal that optimization of the timing and decision criteria at the interim stage is critical for the accuracy of the conclusions about treatment efficacy or futility.

Evidence of altered bone turnover, vitamin D and calcium regulation with knee osteoarthritis in female twins.

BACKGROUND: Osteoarthritis (OA) is a disorder of the whole synovial joint organ. There is growing evidence of the importance of bone turnover in OA, and human studies have demonstrated that the subchondral bone is metabolically active in OA. The aim of this study was to assess the relationships of radiographic knee OA with altered bone turnover and calcium regulation. METHODS: We performed a matched and unmatched case-control study using twins assessed for OA. The subjects were 1644 female Caucasian twin pairs (266 monozygotic and 556 dizygotic) aged 24-79 yr from the St Thomas' UK Adult Twin Registry. Assays for measures of bone turnover [bone-specific alkaline phosphatase, osteocalcin and urinary deoxypyridinoline (DPD)] and calcium regulation [serum parathyroid hormone (PTH), 25-hydroxyvitamin D, serum calcium, serum magnesium and serum phosphate] were performed. The radiological features of knee OA were graded on a four-point scale (0-3) for osteophytes and a five-point scale (0-4) for Kellgren and Lawrence classification. Adjustment for age, body mass index (BMI) and relatedness was made. Conditional logistic regression analysis was also used to estimate the odds ratio (OR) and 95% confidence intervals (CI) for having radiological features of knee OA per standardized unit difference of serum variable between twins. RESULTS: Of the 1644 women studied, 474 (28.8%) had radiological evidence of knee osteophytes. There was evidence of increased bone turnover, increased PTH levels and decreased vitamin D levels in this group compared with those without osteophytes. No association was seen with joint space loss. After adjusting for age, BMI and relatedness, all of the differences disappeared except for a significant increase 10% in urinary DPD (P = 0.04). Discordant twin pair analysis (performed on a subgroup of 229 pairs) confirmed modest increases in bone resorption indicated by urinary DPD (OR 1.67, 95% CI 0.88-3.16) and a significant decrease in serum magnesium (OR 0.65, 95% CI 0.46-0.92) in the co-twins with OA. CONCLUSION: Bone resorption is increased in women with knee OA, consistent with metabolically active subchondral bone. However, bone formation, vitamin D and calcium regulation were not different after adjusting for age and BMI. The results suggest that bone resorption is increased in the presence of OA. Although we cannot clearly differentiate a cause or effect relationship, these results suggest that this is related to disease mechanisms and point to potential diagnostic or therapeutic avenues for bone resorption in OA.

Intravenous clodronate in the treatment of reflex sympathetic dystrophy syndrome. A randomized, double blind, placebo controlled study.

OBJECTIVE: To evaluate the efficacy of intravenous (i.v.) clodronate in patients with reflex sympathetic dystrophy syndrome (RSDS) and to assess the urinary excretion of type I collagen crosslinked N-telopeptide (NTx) before and after the treatment. METHODS: Thirty-two patients with RSDS were randomized to receive either i.v. clodronate 300 mg daily for 10 consecutive days or placebo. Forty days later, the placebo treated patients received the clodronate treatment. Outcome measures included as a primary endpoint the visual analog scale of pain (VAS, range 0-100); secondary endpoints were a clinical global assessment (CGA, range 0-3) and an efficacy verbal score (EVS, range 0-3). Clinical and biochemical assessments were performed before the treatment, 40 (T40), 90 (T90), and 180 (T180) days later. RESULTS: At T40 the 15 patients randomized to clodronate treatment showed significant decreases of VAS and CGA (p = 0.002, p = 0.001, respectively). Compared with the placebo group (17 patients), significant differences were found in all clinical variables (VAS: p = 0.001; CGA: p = 0.001; EVS: p<0.0001). A further clinical improvement was observed throughout the study. Pooling the results of all 32 patients after clodronate treatment, at T180 the overall percentage decrease of VAS was 93.2+/-15.6%, with 30 patients significantly improved or asymptomatic. Significant inverse correlations between baseline NTx values and decreases of VAS were found at T90 (p = 0.03) and T180 (p = 0.01). No adverse events related to treatment occurred. CONCLUSION: A 10 day i.v. clodronate course is better than placebo and effective in the treatment of RSDS. NTx seems to be a predictive factor for clodronate efficacy.

Altered bone metabolism in inflammatory bowel disease: there is a difference between Crohn's disease and ulcerative colitis.

OBJECTIVES: The aims of this study were to assess bone metabolism in inflammatory bowel disease (IBD) patients and to evaluate potential differences between Crohn's disease (CD) and ulcerative colitis (UC) with respect to the mechanisms underlying bone loss in this group of diseases. DESIGN AND SETTING: This was a cross-sectional study which started in 1992. Patients were randomly selected for invitation to participate and were examined during the years 1992-95 in one research clinic in Milan. SUBJECTS AND METHODS: Fifty-one patients suffering from CD (30 women and 21 men, mean age 38.7 +/- 13.2 years) and 40 with UC (15 women and 25 men, mean age 34.4. +/- 12.5 years) entered the study. Thirty healthy subjects were selected as sex- and age-matched controls (C). Spine and femoral neck bone mineral density (expressed as T score), calciotropic hormones (parathyroid hormone, PTH; 25-hydroxycholecalciferol, 25(OH)D3; 1,25-hydroxycholecalciferol, 1, 25(OH)D3) and biochemical markers of bone turnover (ostecalcin, OC; total alkaline phosphatase, ALP; type I collagen C-terminal telopeptide, ICTP) were evaluated. RESULTS: Spine and femur T scores were similar in the two groups (spine: CD = -1.49 +/- 1.46; UC = -1. 67 +/- 1.13; femur: CD = -1.80 +/- 1.36; UC = -1.60 +/- 1.03). Based upon the WHO guidelines, only 8% of CD patients and 15% of UC patients had a normal bone mineral density (BMD), 55% (CD) and 67% (UC) were osteopenic, and 37% (CD) and 18% (UC) were osteoporotic. The distribution amongst the three different diagnostic groups was not significantly different between CD and UC groups (P = 0.11). PTH and 25(OH)D3 concentrations were not significantly different between CD and UC patients and controls, whilst 1,25(OH)D3 concentrations were significantly lower in both CD and UC patients compared with controls (P < 0.05). Bone turnover was increased in UC but not in CD patients, as shown by significantly increased concentrations in UC patients of both OC (CD = 7.77 +/- 5.06, UC = 10.03 +/- 6.24, C = 6. 58 +/- 2.87, P < 0.05 vs. C) and ICTP (CD = 5.74 +/- 3.94, UC = 10.2 +/- 8.47, C = 3.48 +/- 0.95, P < 0.05 vs. CD and C). In a stepwise regression that included age, sex, disease duration and cumulative prednisolone dose as independent variables, the femur T score was significantly inversely related to disease duration (r2 = 0.125, F = 6.06) in CD patients. In UC patients, the spine T score was inversely related to age (r2 = 0.107, F = 5.49) and significantly related to sex (more negative in males: r2 = 0.3, F = 16.1); the femur T score was significantly related to sex (more negative in males) and inversely related to the cumulative prednisolone dose (r2 = 0.283, F = 7.3). CONCLUSIONS: These data show that IBD patients have a diffuse osteopenia, the degree of which is not different in CD and UC; however, bone turnover is significantly higher in UC. Finally, osteopenia is related to disease duration in CD, whilst it is related to the male sex and glucocorticoid treatment in UC.

High prevalence of hypovitaminosis D among free-living postmenopausal women referred to an osteoporosis outpatient clinic in northern Italy for initial screening.

To establish the prevalence of hypovitaminosis D among free-living postmenopausal women referred to an osteoporosis outpatient clinic in Northern Italy, we evaluated 25-hydroxyvitamin D (25(OH)D) levels in 570 postmenopausal women who had been consecutively referred to our clinic in the 12 months beginning October 1995. Parathyroid hormone (PTH), serum calcium (Ca), creatinine (Cr) and osteocalcin (OC), urinary calcium (Ca24h) and creatinine (Cr24h), and the bone mineral density of the lumbar spine (LBMD) and femur (FBMD) were also measured. 1,25-Dihydroxyvitamin D (1,25(OH)2D) concentrations were measured in 23 women. All women had normal electrolyte serum concentrations and kidney function. Mean +/- SD 25(OH)D concentration was 18.3 +/- 8.3 ng/ml. A significant (p < 0.001) seasonal variation was seen for both 25(OH)D and PTH. Women were divided into two groups based on their vitamin D status: low vitamin D status (25(OH)D < 12 ng/ml, n = 161, 28%) and normal vitamin D status (25(OH)D > or = 12 ng/ml, n = 409, 72%). Hypovitaminosis D was found in 38.5% of all the women in the time period December-May and in 12.5% in the other half-year; among women > 70 years old 51% had hypovitaminosis D in the time period December-May and 17% in the other half-year. PTH was significantly (p < 0.05) increased, and Ca24h, OC and FBMD significantly (p < 0.05) decreased in women with hypovitaminosis D. 1,25(OH)2D positively correlated with 25(OH)D (p < 0.0001), but did not correlate with PTH, age or creatinine clearance. In conclusion, hypovitaminosis D is an important, underestimated problem in Italian free-living postmenopausal women referred to an outpatient osteoporosis clinic.

Short-term variations in bone remodeling biochemical markers: cyclical etidronate and alendronate effects compared.

Bone-remodeling markers have been proposed to monitor antiosteoporotic therapy, as substantial changes in these markers usually occur in a relatively short time interval. In this study we have evaluated the short term effects of two bisphosphonates on bone-remodeling markers with the aim of 1) defining the shortest reliable time interval after which markers should be measured, and 2) comparing the effects of different bisphophonates. To do so, 74 postmenopausal women with a lumbar spine t score of at least -1 were randomly allocated to 4 different treatments: calcium carbonate (500 mg/day; n = 18), 5 mg/day alendronate (A5; n = 18), 10 mg/day alendronate (A10; n = 20), and cyclical etidronate (CE; n = 18). Serum and 24-h urine samples were collected at baseline and 14, 28, 56, and 84 days after the beginning of therapy. Type I collagen N-terminal (NTx) and C-terminal (CTx) telopeptides and total deoxypyridinoline (tDPD) were measured in urine and normalized for urinary creatinine excretion. Osteocalcin and bone alkaline phosphatase in serum were measured. Alendronate (at both doses) and CE significantly decreased bone-remodeling markers, whereas calcium carbonate did not. Bone resorption markers reduction reached a plateau 14 (A10) or 28 (A5 and CE) days after the beginning of treatment, whereas osteocalcin and bone alkaline phosphatase were significantly reduced at 56 (A10) and 84 (CE) days. The global effects of alendronate and CE on NTx and CTx (calculated as the area under the curve) were significantly different from those of calcium (P < 0.05), but were not significantly different from each other. The percent change from baseline obtained with tDPD, NTx, or CTx during bisphosphonate treatment were significantly different (P < 0.05), but this difference disappeared when the variability in the calcium carbonate group was taken into account. In conclusion, this study shows that 1) etidronate and alendronate induce a significant and rapid reduction in bone-remodeling markers; 2) the changes in NTx, CTx, and tDPD urinary excretions reach a plateau after 2-4 wk of treatment; and 3) short term treatments with CE or alendronate induce similar changes in the urinary excretion of NTx and CTx.

17 beta-Estradiol and tamoxifen prevent the over-glycosylation of rat trabecular bone collagen induced by ovariectomy.

We have recently demonstrated that ovariectomy in the rat causes over-glycosylation of collagen which is restricted to trabecular bone. In order to obtain further evidence, we studied whether estrogen or tamoxifen treatment prevented over-glycosylation of trabecular bone collagen. Forty one-hundred-day-old female rats were subjected to ovariectomy (n = 30) or sham-operation (n = 10). Starting the day of the operation, sham-operated rats were treated with vehicle, while ovariectomized rats were divided into three groups and treated with vehicle (n = 10), estrogen (n = 10) or tamoxifen (n = 10). Five rats from each group were sacrificed at 115 and 145 days of age. Femurs and tibiae were separated into cortical and trabecular bone, demineralized, hydrolyzed and analyzed by HPLC for hydroxylysine glycoside and hydroxyproline content. Hydroxylysine glycoside content was expressed as a molar ratio with hydroxyproline. The results can be summarized as follows: 1) cortical bone collagen glycosylation did not vary among the different groups; 2) over-glycosylation of trabecular bone collagen observed in the ovariectomized rats was prevented by the administration of either 17 beta-estradiol or tamoxifen. These data demonstrated that estrogens affect glycosylation of trabecular bone collagen.

Comparison of the clinical performance of the immunoenzymometric assays for N-terminal and C-terminal type I collagen telopeptides and the HPLC assay for pyridinium cross-links.

We evaluated the clinical performances of the immunoenzymometric assays for type I collagen N-terminal and C-terminal telopeptides and the HPLC assay for total deoxypyridinoline, in distinguishing between subjects with a moderately increased bone resorption rate (women in postmenopause) and subjects with normal bone resorption rate (women in premenopause). The postmenopausal group consisted of 61 women who had been in menopause for no more than 10 years, while the premenopausal group consisted of 52 healthy women with normal menstrual cycles. The biochemical markers were measured in a 24 hour urine sample and the results expressed as the molar ratio with urinary creatinine. The clinical performances were estimated by calculating the accuracy (as the area under a Receiver Operated Characteristic (ROC) curve: mean +/- SEM) and the discriminating power (as score) of each assay in distinguishing postmenopausal subjects from premenopausal subjects. Type I collagen C-terminal telopeptide, type I collagen N-terminal telopeptide and total deoxypyridinoline were significantly higher in the postmenopausal than in the premenopausal group (p < 0.01). Accuracies of these three markers ranged from 66.8 +/- 5.1% to 76.8 +/- 4.3%, while Z scores ranged from 3.54 to 5.67. Type I collagen C-terminal telopeptide, type I collagen N-terminal telopeptide and total deoxypyridinoline were not significantly different in their accuracy or discriminating power. All markers were highly correlated with coefficients of correlation ranging from 0.61 to 0.77. In summary, this study shows that 1) the immunoenzymometric assays for type I collagen N-terminal telopeptide and type I collagen C-terminal telopeptide show a high accuracy and discriminating power in distinguishing subjects with different bone resorption rate; 2) the results obtained with these immunoenzymometric assays are comparable to those obtained with the HPLC assay for total deoxypyridinoline. In conclusion our data support the use of the immunoenzymometric assays for type I collagen N-terminal telopeptide and type I collagen C-terminal telopeptide for estimating bone resorption.

Effect of fluvastatin on lipids and fibrinolysis in coronary artery disease.

This randomized, double-blind, placebo-controlled study shows that 20-week fluvastatin treatment induces beneficial changes in the lipid panel and a shift in the fibrinolytic pathway toward activation through a decrease in tissue plasminogen activator antigen. Fluvastatin treatment causes no variation in lipoprotein(a) circulating levels.

Effects of pyridoxine neurotoxicity on a distribution of calcitonin gene-related peptide binding sites.

The possibility of changes in binding sites for calcitonin gene-related peptide (CGRP) in response to sensorial denervation was studied in rats after pyridoxine-induced neurotoxicity. Changes in CGRP binding sites were evaluated by an in vitro autoradiographic technique using [125I]-Tyr-rat-CGRP as a ligand. A bidirectional binding response was obtained: an increased binding, in comparison with the respective control, was observed in spinal cord and cerebellar regions whereas a decreased binding was noted in cerebrum. CGRP binding in selective areas comparising the pathways that are responsible for transmitting sensory impulses have shown significant changes. These results suggest that CGRP plays a modulatory role in the central nervous system. This study has also proposed and evaluated pyridoxine toxicity as a model for studying sensory denervation.

Truncation of the amino terminus of PTH alters its anabolic activity on bone in vivo.

In vitro studies of parathyroid hormone (PTH) structure and function have suggested that the anabolic effect of PTH on bone requires the presence of amino acid residues 28-34 (domains for protein kinase C activation and mitogenic activity), but not amino acid residues 1-7 (adenylate cyclase activation domain). We have tested this hypothesis with in vivo studies of human PTH (hPTH) analogs. Serum biomarkers and selected histomorphometric parameters of bone formation and resorption were assessed in adult, female, Sprague-Dawley rats following 19 daily injections of vehicle, 10 micrograms/kg body weight (bw) of hPTH(1-38), or a dose range of 10, 40, and 100 micrograms/100 g bw of hPTH(2-38) or hPTH(3-38). Treatment with hPTH(1-38) increased serum osteocalcin, the percentage of osteoblast surface, percentage of osteoid surface, percentage of bone volume, trabecular thickness, and bone formation rate, while it decreased the percentage of osteoclast surface. The hPTH(2-38) fragment exhibited 10%-25% of the in vivo anabolic activity of hPTH(1-38), while it had no effect on the percentage of osteoclast surface. The hPTH(3-38) fragment exhibited no biological activity on bone. In contrast, serum INS-PTH (intact-N-terminal specific PTH) levels were similarly and significantly increased above control in rats treated with hPTH(1-38), hPTH(2-38), or hPTH(3-38) at the same dose. This preliminary finding suggests that the differential activity of these peptides on bone is not due to differences in the circulating level of immunoreactive PTH (intact and amino-terminal fragments of PTH from endogenous and exogenous sources) several hours after PTH injection. However, we can draw no conclusion regarding the relative clearance rates of these peptides. Last, because hPTH(3-38) was without any detectable biological activity on rat bone in vivo, its mitogenic activity was confirmed in two osteoblast-like cell lines. In summary, the anabolic effect of hPTH(1-38) on bone in vivo was (1) diminished by removal of amino acid residue 1, and (2) abolished by the removal of amino acid residues 1 and 2. Although these findings suggest that the therapeutic benefits of exogenous PTH administration may depend upon activation of not only protein kinase C, but also adenylate cyclase, they do not rule out a differential PTH response due to other causes, e.g., metabolic inactivation.

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.

Collagen type I of rat cortical and trabecular bone differs in the extent of posttranslational modifications.

This study sought to evaluate whether the architecture of the matrix of cortical and trabecular bone is exactly the same. For this purpose we analyzed the extent of some posttranslational modifications of type I collagen, which is the major component of bone matrix. Ten female and 10 male 100-day-old rats were sacrificed and the content of hydroxylysine, glycosylated hydroxylysine, and pyridinium cross-links of collagen from cortical and trabecular bone was determined. The amount of each compound was expressed as a molar ratio with hydroxyproline. The collagen posttranslational modification pattern appears to be the same in both sexes but with a higher extent of differences in females compared with males. Comparing cortical and trabecular bone, the former contains a higher amount of hydroxylysine residues whereas in the latter, glycosylation of hydroxylysine is higher and pyridinium cross-link concentration is lower. Moreover, an inverse linear relationship between glycosylated hydroxylysine and pyridinium cross-links concentration was established, both for female (r = -0.455, P = 0.04) and male rats (r = -0.426; P = 0.06). This paper discusses what these findings may mean in functional terms.

Detection of pyridinium cross-links in human bile.

This study evaluated whether pyridinium cross-links, which are positively charged, besides renal clearance are also cleared by the liver into bile. In 13 human bile samples tested, we were able to detect both pyridinoline (PYD) and deoxypyridinoline (DPD) in small amounts which were estimated to be about 1-2% of the amount usually found in urine. To further evaluate the amount of pyridinium cross-links excreted through bile, we studied the stability of these compounds at the alkaline pH of bile. No effect on their stability was detected over a 6-hour incubation. The origin of these molecules in bile and the significance of this finding in the use of PYD and DPD as bone resorption markers are discussed.

Biochemical markers of bone metabolism in the assessment of osteoporosis.

Several biochemical markers are available for the study of bone metabolism. The characteristics of these markers are reviewed and their potential application in osteoporosis is examined. It is concluded that biochemical markers are potentially useful in identifying those at risk of developing osteoporosis, selecting appropriate treatment, monitoring therapy, and studying the pathogenesis of osteoporosis.

Effect of bisphosphonate therapy and parathyroidectomy on the urinary excretion of galactosylhydroxylysine in primary hyperparathyroidism.

BACKGROUND: In patients with mild or asymptomatic primary hyperparathyroidism a reliable index of bone resorption might be useful for appropriate management. Hydroxyproline is the most commonly used marker of bone resorption but its low specificity and sensitivity are known. Galactosylhydroxylysine, an amino acid mainly represented in bone collagen, has been proposed as a more suitable index of bone resorption. In this study we evaluated the sensitivity of galactosylhydroxylysine and hydroxyproline assays in following the changes of their urinary levels in 12 patients with mild primary hyperparathyroidism before and after treatment with bisphosphonate and surgery. METHODS: Serum and fasting urine specimens were obtained from 12 women with mild primary hyperparathyroidism before and after bisphosphonate treatment (2.5 mg daily for 5 days, intravenously) and after a further 25 days; in 7 patients biochemical tests were also performed 1 and 6 days after parathyroidectomy. Galactosylhydroxylysine was assayed by an HPLC method and hydroxyproline by a RIA commercial kit. RESULTS: Baseline galactosylhydroxylysine urinary levels were far above the normal range in all the patients whilst in 8 of them baseline hydroxyproline levels were normal. Bisphosphonate treatment significantly decreased bone turnover as shown by a significant fall in serum calcium (from 2.9 to 2.6 mmol/l; P < 0.001) and in galactosylhydroxylysine and hydroxyproline (-55 and -31% respectively). Twenty-five days after the end of treatment, resorption increased again and serum calcium and galactosylhydroxylysine, but not hydroxyproline, rose significantly towards basal levels. One day after parathyroidectomy serum calcium, galactosylhydroxylysine and PTH showed reduction below normal ranges. PTH and galactosylhydroxylysine returned to normal values at day 6 after parathyroidectomy. No changes in hydroxyproline levels were seen. Galactosylhydroxylysine, but not hydroxyproline, correlated significantly with serum calcium and PTH. CONCLUSION: Galactosylhydroxylysine appears to be a sensitive index of bone resorption, useful in the clinical assessment of bone involvement and in the management of patients with mild primary hyperparathyroidism.

Age-related decreases in insulin-like growth factor-I and transforming growth factor-beta in femoral cortical bone from both men and women: implications for bone loss with aging.

We determined the skeletal content of insulin-like growth factor-I (IGF-I) and transforming growth factor-beta (TGF beta) in human bone as a function of age, using 66 samples of femoral cortical bone obtained from 46 men and 20 women between the ages of 20-64 yr. We found a linear decline in the skeletal content of IGF-I (nanograms per mg protein) with donor age (r = -0.43; P < 0.001) in the total population. The skeletal content of TGF beta also decreased with age (i.e. 1/TGF beta vs. age; r = 0.28; P < 0.02) for the total population. We did not observe any difference in the skeletal growth factor content between male and female donors. IGF-I content, when analyzed by decade divisions of age, showed a reduction between the 20- to 29-yr-old and the 50- to 59-yr-old subjects (P < 0.02). The loss rate of IGF-I was 1.56 ng/mg protein.yr, corresponding to a net loss of 60% of skeletal IGF-I between the ages of 20-60 yr. The loss rate of TGF beta was 0.03 ng/mg protein.yr, corresponding to a net loss of 25% of the skeletal TGF beta between the ages of 20-60 yr.