Vertebral morphometry by X-ray absorptiometry: which reference data for vertebral heights?

INTRODUCTION

The recent improvement in the resolution of dual-energy X-ray absorptiometry (DXA) images enables most vertebral levels to be seen adequately and thus DXA may be a worthwhile alternative to radiologic morphometry for the identification of vertebral fractures (VF). In this multicenter study, we have derived reference data for vertebral heights and their ratios in Italian women using morphometric X-ray absorptiometry (MXA).

METHODS

DXA scans were acquired in 1254 consecutive pre- and postmenopausal women, (mean age 63.7 ± 11.3, range 26-88 yrs), referred to six osteoporosis centers. MXA analysis of these images was performed by the same operator measuring vertebral heights and height ratios from L4 to T4. We calculated measures of central tendency and dispersion of vertebral heights and vertebral ratios using different approaches (mean and standard deviation as well as median and interquartile range of raw data, mean and standard deviation of trimmed data using an iterative algorithm, and mean and standard deviation of not fractured vertebrae).

RESULTS

Independently of the approach that we used, all the measures of central tendency were similar, while significant differences were found when compared with reference ranges in other populations. The vertebral heights of our sample at every vertebral level were significantly smaller than both Rea population and the Lunar reference values, even after normalization. Splitting data according to age groups, there was a decrease in the vertebral heights and ratios between the younger and older women.

CONCLUSIONS

This study demonstrates that reference data for MXA should be population specific and age matched.

Carboxyl-terminal parathyroid hormone fragments: biologic effects

Carboxyl-terminal PTH fragments (C-PTH), are generated by both direct secretion from parathyroids in relation to serum calcium levels and catabolism of PTH operated by the Kupffer cells in the liver. These molecular fragments have been till recently regarded as inert byproducts of PTH metabolism, since they do not interact with the PTH/PTH-related peptide (rP) receptor, which mediates the classical hormone actions. Current findings instead indicate that C-PTH would interact with a putative C-PTH receptor. This way, C-PTH seem to exert specific effects on calcium homeostasis and bone metabolism, opposite to those of the synthetic agonist of PTH/PTHrP receptor (i.e. PTH 1-34). In vitro and in vivo data actually indicate that C-PTH, by interacting with specific receptors, could have an anti-calcemic action, as well as a pro-apoptotic effect on both osteocytes and osteoclasts. This in turn could result in a reduced activity of the latter cells, with a consequent inhibition of bone resorption.

Asymptomatic primary hyperparathyroidism: surgical and medical management

Primary hyperparathyroidism (PHPT) is a common endocrine disorder, frequently asymptomatic. Notwithstanding, mild PHPT may cause adverse skeletal effects that include high bone remodeling, reduced bone mineral density (BMD), and increased fracture risk. The definitive therapy for symptomatic and asymptomatic PHPT (aPHPT) is parathyroidectomy, which has been shown to increase BMD. In patients who choose not to be treated surgically or have contraindications for surgery, medical therapy should include drugs designed to protect the skeleton and/or to lower serum calcium, such as bisphosphonates, hormone replacement, and/or calcimimetic agents. However, there are currently no fracture data for any of these options. Obviously, there is the need for larger randomized controlled trials with fractures as end-points to evaluate the efficacy of medical treatment.

Calcium sensing receptor and renal mineral ion transport

Calcium sensing receptor (CaSR) is a component of the C family of the G protein-coupled receptors. It is ubiquitously expressed in human and mammal cells but is more expressed in parathyroid glands and kidney cells. It is located on the cell plasma membrane and senses the changes of extracellular calcium concentrations. Thus, it may modify cell functions according to serum calcium levels. CaSR has a key role in calcium homeostasis because it allows parathyroid glands and kidney to regulate PTH secretion and calcium reabsorption in order to keep serum calcium concentration within the normal range. CaSR appears as an important player in the regulation of renal calcium handling and body calcium metabolism. Thus, CaSR may protect human tissues against calcium excess. In kidneys, its protective effect includes the stimulation of diuresis and phosphate retention, along with the potential prevention of calcium precipitation and deposition in kidney tubules and interstitium.

Role of calcium-sensing receptor in bone biology

Extracellular calcium concentration changes are recognized by Ca++ sensing receptor (CaR), a member of the G-protein-coupled receptor family. Recently, progress has been made in the understanding of CaR functional role in bone cells, notwithstanding a lack of detailed knowledge about the identity of the cation receptors. It is generally agreed that a high extracellular calcium induces osteoblast proliferation and osteoclastogenesis inhibition. Potential implications that may be considered include a role for CaR in osteogenesis, in serum calcium homeostasis regulation, and as a factor coupling bone formation to resorption in bone remodeling. The localization of CaR in bone cells provides further knowledge of the mechanisms operating in the bone remodeling model; in fact, increased calcium gradient in the site of bone resorption favors osteoblast precursors chemotaxis and inhibits osteoclasts through the increase of [Ca++]e. In vitro data indicate that CaR is a physiological regulator of bone cells, regulating the recruitment, differentiation and survival of osteoblasts and osteoclasts. This leads to the concept that the CaR present in bone cells may be targeted by agonists or antagonists to control bone cell metabolism and bone remodeling.

The role of PPARγ for the osteoblastic differentiation

Peroxisome proliferator-activated receptor γ (PPARγ) is a ligand-activated transcription factor that belongs to the nuclear hormone receptor superfamily and functions as a heterodimer with a retinoid X receptor by binding to PPAR responsive elements. PPARγ plays an important role in adipocyte differentiation and is activated by long-chain fatty acid, peroxisome proliferators, and thiazolidinedione (TZD). TZD are agonists of PPARγ, act as insulin-sensitizing agents, and are widely prescribed in the management of different conditions characterized by insulin resistance. Osteoblasts and marrow adipocytes derive from common multipotential mesenchymal stem cell (MSC) progenitors. Lineage commitment of MSC is determined by expression and/or activation of specific transcription factors, such as Runx2 and Osterix in the case of osteoblasts, and PPARγ in the case of adipocytes. Many evidences indicate an important role of PPARγ in bone metabolism. Heterozygous PPARγ-deficient (PPARγ +/-) mice exhibit enhanced bone formation with increased osteoblastogenesis. Embryonic stem cells derived from PPARγ +/- mice spontaneously differentiate into osteoblasts. In mice and rats, the activation of PPARγ by TZD treatment, such as rosiglitazone (Rosi), causes bone loss, which results from an increase of marrow adipocytes and a decrease of osteoblasts, leading to a reduction of bone formation rate. Human studies have shown that pre- and post-menopausal women treated with Rosi have an increased risk of fracture compared to women treated with metformin and glyburide. Moreover, the modulation of the PPARγ expression is also implicated in the effects of mechanical loading on bone and in age-related bone loss.

Bone fragility in men: where are we?

Osteoporosis in men is an increasingly important clinical issue. About one in three osteoporotic fractures occur in men, and the consequences of these fractures are generally more severe than in women. Despite these evidences, osteoporosis remains under-recognized and undertreated in men. This review provides a summary of recent developments about the causes, pathogenesis, and treatment of osteoporosis in men.

Skeletal effect of natural early menopause

It is well-known that women with spontaneous or natural early menopause (NEM) (between ages of 40 and 45 yr) experience an increased risk of overall mortality, cardiovascular diseases, osteoporosis, neurological and/or psychiatric diseases, and other sequelae. On the contrary, the role of NEM is more contentious on the long-term bone consequences. The published data highlight that NEM has an ambiguous effect on bone mineral density, and is associated with an increased incidence of fractures, likely related to other risk factors rather than to osteoporosis. Therefore, an estrogen treatment should be considered for these women, especially if osteopenia is present at age of menopause.

Salt intake, hypertension, and osteoporosis

A high salt intake has been correlated with several pathological conditions such as hypertension, cardiovascular disease, renal calcium stones, and osteoporosis. Some of these diseases present a high prevalence in the elderly and common pathogenetic mechanisms are proposed for some of them. A high salt intake has been associated with hypertension as well as osteoporosis and one of the proposed pathogenetic mechanisms is an increased calcium excretion in urine. Urinary calcium loss induces a negative calcium balance that may predispose hypertensive subjects to developing greater bone loss. The gene which encodes for the thiazide- sensitive sodium-chloride cotransporter (NCCT) represents a possible link between hypertension and osteoporosis. Subjects heterozygous for an inactivating mutation of NCCT present a positive effect on bone density as shown by the significantly higher Z-scores at the lumbar spine and total femur. Recent clinical studies also support the benefit of ACE inhibitors in reducing fracture risk or improving bone metabolism. These data suggest that the renin-angiotensin system may be one of the several factors involved in bone metabolism. Hypertension, together with stroke, has been demonstrated to be a risk factor for osteoporosis. Although the risk associated with hypertension was limited in terms of relative risk, it may have a significant impact on the general population owing to the high prevalence of hypertension. The treatment of hypertension may thus be very useful in also giving protection against fractures.

Skeletal effects of oral anticoagulants

Vitamin K antagonists (VKA) are often used as oral anticoagulants (OA) in order to prevent thromboembolic diseases. In bone, vitamin K reduces bone resorption and functions as a co-factor in the post-translational carboxylation of several bone proteins. Osteocalcin (OC), the most abundant of these bone matrix proteins, is produced by osteoblasts and released in small amounts in blood as a specific marker of bone formation. Carboxylated proteins have a high affinity for calcium and are important in the incorporation of calcium into bone and bone formation. The increased levels of undercarboxylated osteocalcin can bring about an alteration of the bone mineral density and the risk of fracture, even if contradictory results have been observed in several epidemiologic studies. However, some, but not all reports, find that vitamin K deficiency, induced by hydroxycoumarins, may be associated with low bone mass. Additionally, epidemiologic studies have found that the use of OA may be associated with either increased or no change in fracture risk. Such divergent results may imply that human studies are compromised by the physical illnesses for which OA were prescribed. Additional epidemiological or cohort studies are warranted in order to determine whether potential pharmacological effects of VKA on bone metabolism may have clinical consequences.

Hyperhomocysteinemia: a biochemical link between bone and cardiovascular system diseases?

Homocysteine (HCY) is a sulfur-containing amino acid involved in two metabolic pathways, catalized by cystathionine-B-synthase and methionine synthase, depending on vitamin (vit) B6, B12, and folate levels and enzymatic activity of methylenetetrahydrofolate. High HCY levels (HHCY) are associated with cardiovascular (CV) and bone diseases, in particular osteoporosis (OP)/hip fracture. As regards the mechanisms involved in the link between HHCY, CV diseases (CVD), and OP, it has been proposed the role of lysyl-oxydase inhibition that might interfere with collagen crosslink formation. Some studies suggested the dysregulation of the osteoprotegerin/receptor activator of nuclear factor-kappaB (RANK) ligand/RANK axis, others the involvement of oxidative stress. These mechanisms may act both on bone and CV system, but whether the common denominator is HCY itself or HCY is merely a marker, remains to be clearly established. Folate, vit B6, and B12 supplementation is associated with HCY reduction, but is unable to certainly reduce the incidence of OP/fracture and CVD, probably because, in the majority of patients, HCY is only moderately increased.

Bisphosphonates and atherosclerosis

The relevance of association between osteoporosis and cardiovascular disease in clinical settings, and the evidence of a biological linkage between bone and vascular calcification, encourage the search of drugs that may act as dual-purpose therapies, concordantly enhancing bone density and reducing atherosclerosis. Bisphosphonates (BP) reduce bone resorption and fracture risk, and also seem to have the potential to reduce atherosclerotic process. This unexpected activity is the result of their interference with cholesterol synthesis, inflammatory progression, and oxidative stress. Although most animal studies show a clear anti-atherogenic activity of BP, data in humans are not consistent or conclusive, given the high affinity of BP for bone, which prevents them from accumulating in other tissues at the concentration required to exert a clear pharmacological effect.

Role of apoptosis in osteoporosis induced by glucocorticoids

Glucocorticoid (GC)-induced osteoporosis (GIO) is a common and serious complication of prolonged systemic GC use. Bone loss with risk of fractures resulting from GC therapy is a relatively common disorder, and is the most prevalent form of secondary osteoporosis. It is generally accepted that GC can cause a rapid bone loss, decreasing bone formation and increasing bone resorption in vitro as well as in vivo. The decrease in bone formation has been mainly attributed to GC effects on osteoblastogenesis and osteocyte apoptosis, while the increase in bone resorption has been referred to an extension of the life-span of pre-existing osteoclasts. This article focuses on newer molecular aspects regarding the apoptotic mechanisms involved in the pathogenesis of GIO and is based on a presentation that was held at the 3rd Congresso Nazionale in Osteoporosi Secondarie e Endocrinopatie, in Ancona, Italy, October 2007.

Adrenal incidentaloma: effects on bone metabolism

The effects of clinically inapparent adrenal masses or adrenal incidentalomas (AI) on bone metabolism are a controversial clinical problem related to their activity. Most of these lesions are non-functioning tumors and only a small percentage of patients exhibits a subclinical hypercortisolism (SH). The degree of clinical appearance of SH varies with the extent of hormone overproduction. However, it is controversial, up to now, if this disorder is associated with long-term morbidity and if the treatment to reverse subtle glucocorticoid excess is beneficial. Patients with AI represent an ideal field to evaluate if alterations of bone turnover may be considered a precocious sign of an abnormal pattern of endogenous steroid secretion. Several small trials have highlighted in AI with and without SH reduced levels of osteocalcin (OC), probably due to a reducted bone formation induced by a subtle excess of glucocorticoids. In patients with AI with and without SH low levels of OC might be considered a precocious sign of an abnormal pattern of slight cortisol hypersecretion and could become one of the pivotal criteria to decide whether these tumors deserve surgical excision.

Densitometry in glucocorticoid-induced osteoporosis

The technique of choice for the measurement of bone mineral density (BMD) in patients with glucocorticoid-induced osteoporosis (GIOP) is dual X-ray absorptiometry (DXA), which has been demonstrated to be reliable in diagnosing osteoporosis and monitoring bone mass variations over time in GIOP. However, in patients with both exogenous (i.e. due to glucocorticoid therapy) and endogenous cortisol excess, the BMD decrease does not fully explain the high risk of fractures. Therefore, the BMD thresholds in guidelines for the prevention of GC-related fractures are different and debated. Quantitative computed tomography (QCT), which is useful to separately study cortical and trabecular bone and to measure true "volumetric" BMD, has been suggested to be a better predictor of vertebral fractures than DXA. However, QCT has the limit of the possible underestimation of bone mass and QCT T-scores may be lower as compared to DXA T-score values for the same skeletal site. Quantitative ultrasound, which is considered to reflect both BMD and structural properties of bone such as connectivity and elasticity, is able to diagnose low BMD in GIOP, but its role in monitoring BMD changes and in predicting fracture's risk remains unknown. Low BMD and high rate of bone loss have been suggested to be possible complications even of subclinical hypercortisolism regardless for gender and gonadal status. On the other hand, low BMD and vertebral fractures may be the initial presentation of an otherwise asymptomatic cortisol excess.

Biochemical markers in glucocorticoid-induced osteoporosis

Following the introduction of corticosteroids as therapeutic agents in the 1950s, their use has been expanded so that today glucocorticoids are widely used. There are few studies in the literature directly aimed at describing the changes of bone markers following glucocorticoid administration. The interpretation of some of these investigations may be hampered by a number of confounding factors, whose influence is not always taken into consideration. In general, the effects of glucocorticoid administration are represented by a reduction in bone formation markers (particularly considering serum osteocalcin levels) and a trend to an increase or no change in bone resorption markers. The inconsistency of this last finding may be related to the time at which the observation is carried out and to the marker employed.

Effect of natural early menopause on bone mineral density

OBJECTIVES

Early menopause (EM) is included among the risk factors for osteoporosis. Several studies have shown that women with early menopause have lower bone mineral density (BMD) than those with normal expected age of menopause. The aim of our cross-sectional study was to investigate the effects of time of menopause on vertebral bone mass in healthy postmenopausal women and to evaluate if early menopause is a risk factor for lower vertebral BMD.

METHOD

We studied 782 who had never received drugs acting on bone mass. The study population was divided into three groups: women with early, normal (NM), and late (LM) menopause. Our study population was further categorized in 5-year age segments between 45 and >75.

RESULTS

The three groups examined did not differ for age, age at menarche, body mass index (BMI), and vertebral BMD, while there were significant differences in age at menopause and years since menopause. Our study showed that women with EM presented significantly lower vertebral BMD than NM and LM in 50-54 age segments. Beyond 55 years, EM, NM, and LM women had no differences in lumbar BMD values.

CONCLUSIONS

In conclusion, controversial data demonstrated that the absolute amount of bone loss is greater after early menopause than after normal or late menopause, even if a slight effect of early menopause on bone mass cannot be excluded.

Role of raloxifene on platelet metabolism and plasma lipids

BACKGROUND

This study was performed to understand the metabolic effects of raloxifene, a selective oestrogen receptor modulator, on platelets in healthy non-obese postmenopausal women. The data were compared to untreated subjects.

MATERIALS AND METHODS

Platelet nitric oxide activity (NO) and peroxynitrite level, platelet inducible and endothelial nitric oxide synthase expression and plasma lipids were evaluated at baseline and after 12 months of raloxifene or placebo treatment.

RESULTS

A significant increase of platelet NO and reduction of platelet peroxynitrite levels, as well as a decrease of inducible nitric oxide synthase expression, was observed 12 months after raloxifene therapy as compared to baseline or placebo treatment. Moreover, raloxifene treatment caused a significant increase in high-density lipoprotein cholesterol and a decrease of total cholesterol and low-density lipoprotein cholesterol were observed versus baseline values (P < 0.05). A significant positive correlation was observed between high-density lipoprotein cholesterol and platelet NO (r = 0.76, P < 0.005) in the raloxifene group.

CONCLUSION

Our results showed that raloxifene improves platelet metabolism in healthy postmenopausal women through an increase of the bioavailability of platelet NO by a reduction of iNOS and the beneficial effects on lipid metabolism. This mechanism of action of raloxifene on platelet activity may explain some cardiovascular protective effects of this selective oestrogen receptor modulator.

Morphometric dual-energy X-ray absorptiometry (MXA) for identification of vertebral fractures

Visual identification of vertebral fractures from spinal radiographs makes use of operator expertise in ruling out non-fracture deformities or normal variants. Morphometric X-ray absorptiometry (MXA) has recently been developed to assess vertebral deformity status quantitatively by dual energy X-ray absorptiometry (DXA). The reliability of MXA measurements depends on the precision of the technique, and this is influenced by system error, variability associated with morphometric analysis, and variability within study populations. This technique has proved to be useful in the identification and evaluation of osteoporotic vertebral deformities in both epidemiologic surveys and clinical trials. The major limitation of DXA vertebral assessment is the poor quality of images of thoracic vertebrae. We conclude that, used as a screening tool, this approach may help to identify vertebral fractures with a reduced radiation dose to the patient, and that technological improvements are necessary to improve image quality.

Hyperphosphatemia: effects on bone metabolism and cardiovascular risk

Hyperphosphatemia indicates a plasma inorganic phosphate (Pi) concentration greater than 5 mg/dl in the adult and 7 mg/dl in adolescent subjects. Pi homeostasis is maintained by several mechanisms (intestinal absorption, renal excretion, balance of Pi exchanges in and out of the cells, hormonal regulation). Most of the Pi, after intestinal absorption, undergoes urinary excretion suggesting that the kidney plays a major role in the maintenance of homeostasis and plasma concentration of the Pi, modifying its reabsorption in the proximal tubule where 3 types of sodium/ phosphate cotransporters have been identified (NPT). NPT2 is crucial for the Pi reabsorption and is modulated by several hormones (PTH and vitamin D3, phosphatonins) and non-hormonal factors. The hyperphospatemia is usually due to a decrease in renal function or a PTH absence (primary or secondary hypoparathyroidism) or phosphatonin deficiency. A correct serum Pi concentration is a critical condition for maintaining the calcium-phosphate (CaxPi) product within a safe range ensuring the physiological processes of bone mineralization; an increase of CaxPi product in extracellular fluids over a critical threshold, may promote processes of extraskeletal calcification. In the last few years several studies have shown that the pathogenetic mechanisms of vascular calcification do not imply a simple deposition of calcium phosphate crystals in the wall of the vessels affected by atherosclerotic lesions, but an active process making vascular smooth cells assume functional characteristics of osteoblasts. The consequences on bone are heterogeneous according to the pathogenetic mechanisms responsible for hyperphosphatemia.

Metabolic bone diseases during long-term total parenteral nutrition

Long-term total parenteral nutrition (TPN) is a procedure commonly applied to patients with advanced forms of intestinal malabsorption. Among TPN complications, bone metabolic diseases, such as osteoporosis and osteomalacia, are a common finding. Initially considered to be a manifestation of aluminium toxicity which followed massive contamination with the element of the solutions used in TPN, metabolic osteopathy during TPN is currently considered a multiform syndrome, with a multifactorial pathogenesis, which may manifest itself with vague or clear clinical pictures. In this review, we analyse clinical, pathogenetic, and therapeutic aspects of the most common bone metabolic diseases in patients undergoing long-term TPN.

Role of vitamin K on biochemical markers, bone mineral density, and fracture risk

Osteoporosis is a multifactorial chronic disease that may become even more prevalent and more of a public health problem in the decades to come. Recent research has indicated that a number of macro- and micronutrients are involved in the development of bone health. In the past decade it became evident that vitamin K played a significant role in human health beyond its well-established function in blood clotting. In fact, among the proteins known or suspected to be involved in bone and vascular biology there are several members of the vitamin K dependent or gamma-carboxyglutamic acid protein family. Based on the current evidence from epidemiologic and intervention studies, there are insufficient data to recommend a routine supplementation of vitamin K for optimal bone health. New experimental and placebo-controlled studies in humans should clarify our understanding of the role vitamin K plays in improving bone health.

Role of biochemical markers of bone remodeling in clinical practice

Bone tissue is subject to remodeling throughout the lifetime of an individual. Through a continuous remodeling cycle, actuated via the so-called 'bone remodeling units', old bone is resorbed by osteoclasts with the formation of cavities that are subsequently filled by osteoblasts. Bone loss observed in old age and in women after menopause is due to an imbalance between bone resorption and formation. Biochemical markers provide a dynamic view of the remodeling process, which covers rate of turnover and pathogenesis, and should improve fracture risk prediction. Furthermore, they can be used to monitor the short-term effects of therapy, and indicate if an excessive slowing of the remodeling process is occurring. When searching for markers of bone remodeling, biochemists have focused mainly on skeletal molecules that can be dosed in plasma and/or urine, as indicators of osteoblast function (i.e. bone alkaline phosphatase, osteocalcin, procollagene I C- and N-terminal propeptides) or osteoclast function (i.e. pyridinium crosslinks, collagen I C- and N-terminal telopeptides). The clinical significance of any marker for bone remodeling depends on two fundamental characteristics: specificity and variability. If the objective is to monitor therapeutic efficacy, it seems most rational to use a resorption marker for drugs that act principally on osteoclast, such as estrogens or bisphosphonates, while for drugs that act principally on osteoblast, such as PTH-peptides a marker for bone formation would be more appropriate.

Raloxifene and Cardiovascular Health: Its Relationship to Lipid and Glucose Metabolism, Hemostatic and Inflammation Factors and Cardiovascular Function in Postmenopausal Women

CHD is one of the most common serious chronic conditions in postmenopausal women and leads to extremely high risk for recurrent myocardial infarction and death. On the basis of the currently available randomized clinical-trial results the role of conventional HRT for treatment and prevention of CHD is rapidly evolving from presumed benefit to proven harm, at least in some categories of women yet to define. For this reason there has been a particular interest in potential clinical uses of selective estrogen receptor modulators (SERMs). SERMs are a class of compounds that can act as estrogen receptor (ER) agonists in some domains (bone and lipids) and acting as ER antagonists in others (breast and uterus). Raloxifene hydrochloride is an antiestrogen that is currently approved only to treat osteoporosis in postmenopausal women. Because of its effects on lipids and other biomarkers of cardiovascular risk, there is great interest in determining whether it may benefit the cardiovascular system. The great majority of data on cardiovascular effects of raloxifene concern effects on lipids and markers of thrombosis and inflammation. The purpose of this review is to summarize the best available evidence concerning raloxifene and cardiovascular disease focusing some areas known to be important risk factors for cardiovascular diseases: lipids and lipoproteins, glucose metabolism, hemostatic factors, markers of inflammation and cardiovascular function.

Effects of raloxifene on body fat distribution and lipid profile in healthy post-menopausal women

The aim of our prospective, randomised, controlled and open-label clinical study was to evaluate in healthy post-menopausal women the effects of raloxifene (RLX) on body fat distribution and lipids, and the correlations between these parameters. The fat distribution, by dual energy X-ray absorptiometry, and lipids were evaluated at baseline and after 1 yr in 50 post-menopausal women: 25 were treated with RLX 60 mg/die, while 25 served as control group (CG). After 1 yr, we observed in RLX-users a slight reduction of fat mass in trunk and central region and an increase in legs and, in relation to CG, significantly lower values of adiposity in trunk and abdominal region (p < 0.05). At the same time, HDL-cholesterol (HDL-C) and apolipoprotein A1 (ApoA1) were significantly increased in relation to baseline values and CG (p < 0.05) and apolipoprotein B (ApoB), total cholesterol/HDL-C, LDL cholesterol/ HDL-C, and ApoB/ApoA1 ratios significantly decreased compared to baseline values and CG (p < 0.05). No correlation was underlined among lipids and regional fat distribution. These results highlight the positive effect of RLX on lipids and suggest, for the first time, that RLX promotes the shift from android to gynoid fat distribution, and prevents the uptrend of abdominal adiposity and body weight compared with untreated women.

Markers of bone turnover: biochemical and clinical perspectives

Bone remodelling is a process by which bone grows and turns over. This process involves a series of highly regulated steps that depend on the interaction of two cell lineages, the osteoclasts and the osteoblasts. Information on metabolic activity of bone tissue are achieved with the determination, in blood and in urine, of biochemical products derived from the activity of this cells. The ability to determine bone turnover with biochemical markers has been enhanced considerably in recent years with the development of new assays for more sensitive and specific markers. These new markers can now replace the outdated and non-specific markers of bone remodeling such as serum total alkaline phosphatase (ALP) and urinary hydroxyproline (Hyp) determination. Biochemical markers of bone turnover can be classified according to the process that underlie in markers of bone formation, products of the osteoblast activity [bone ALP, osteocalcin (OC), procollagene I C- and N-terminal propeptides] and markers of bone resorption, products of the osteocalst activity [pyridinuim crosslinks, collagen I C- and N-terminal telopeptides (CTX-I and NTX-I), tartrate resistent acid phosphatase (TRACP) isoform 5b]. The interpretation of laboratory results should always include the consideration of potential sources of variability. Variation in the results of biochemical markers of bone metabolism can compromise their ability to characterize disorders of bone metabolism. Variation can be categorized into pre-analytical, analytical and biological sources. However, the determination of biochemical markers of bone turnover offers many advantages in clinical practice, since they are non-invasive, can be repeated often, and major changes occur in a short time.

Does bone mineral density predict fractures comparably in women and men?

Osteoporosis (OP) is a very common disease associated with increased morbidity, mortality and costs. For a 50-yr-old woman the lifetime risk of an osteoporotic fracture is 40%, while for a man of the same age the risk is 13%. Good evidence exists as to the correlation between bone mineral density (BMD) and fracture risk in post-menopausal women. The diagnosis of OP can be made when BMD is more >2.5 SD below the mean of normal young women (T-score < or = -2.5). In men it has not been possible, until now, to identify a definite T-score under which the diagnosis of OP can be made. Several studies produced conflicting results when they tried to answer the question as to whether males and females fracture at the same absolute BMD value. Men have a greater bone size than women even when this parameter is corrected for weight and body mass. As densitometric devices measure areal density, men appear to have a higher BMD than women. Some studies have shown that, for a given BMD, males and females have the same fracture risk, while other papers have demonstrated that fractured men have a higher BMD than fractured women. Another problem concerns the diagnosis of osteoporosis. In fact, when the T-score is calculated in men on the basis of a young female reference range the prevalence of osteoporosis can be underestimated. The official position of International Society for Clinical Densitometry (ISCD) may represent an "interim" answer in order to identify men at risk of fracture.

Cardiovascular disease and osteoporosis

Cardiovascular disease (CVD) and osteoporosis (OP) are public health problems with numerous epidemiological links and important economic consequences. Recent studies have demonstrated that CVD and cardiovascular mortality are associated with reduced bone mineral density (BMD) and bone fractures. These two conditions may be sustained by similar or common pathophysiological mechanisms and risk factors. There are several matrix proteins, such as type 1 collagen, proteoglycan, osteopontin, and osteonectin, which are found in bone and vascular matrix components. Matrix proteins play an important role both in bone formation and in the development of atherosclerosis. Estrogens also play a role in both CVD and OP through their effects on cytokines, such as IL-1, IL-6 and TNF-alpha and osteoprotegerin (OPG). The lack of estrogens induces an increase in these cytokines and a decrease in OPG, both implicated in the mechanisms of bone loss and atherogenesis. An additional link between CVD and OP seems to be related to the action of some drugs, such as bisphosphonates, statins and raloxifene. Several studies suggest that the mechanism of action of these drugs at cellular level may not be mutually exclusive, acting either in bone or in atherosclerotic plaque. However, further studies are necessary to define the relationship between CVD and OP more specifically and to understand the complex interaction of similar or common risk factors and genetic or molecular determinants.

Raloxifene: bone and cardiovascular effects

Raloxifene (RLX), a selective estrogen receptor modulator (SERM), is currently indicated for the prevention and treatment of post-menopausal osteoporosis. At present, RLX is evaluated in other areas of study that include the reduction of the risk of breast cancer and cardiovascular (CV) disease in post-menopausal women. This SERM acts as an estrogen agonist in the skeleton, on serum lipid metabolism and on a number of coagulation factors, while it is an estrogen antagonist in the breast and uterus. Although our current data are incomplete, RLX has a favourable risk-benefit safety profile and is one of the most promising medical agents not only for the prevention of osteoporosis, but also for a large number of other disorders in post-menopausal women.

Bone metabolism and mass in women with Cushing's syndrome and adrenal incidentaloma

OBJECTIVE

The aim of this study was to compare bone turnover and mass in women with either Cushing's syndrome (CS) or adrenal incidentaloma (AI), which is a possible model for minimal hypersecretion of cortisol.

DESIGN AND PATIENTS

We studied 15 patients with CS (seven premenopausal and eight postmenopausal women); 23 patients with AI (five premenopausal and 18 postmenopausal women) and 20 matched controls (seven premenopausal and 13 postmenopausal women). Alkaline phosphatase (ALP), bone alkaline phosphatase (bALP), osteocalcin (BGP), 24-h urinary pyridinoline (Pyr) and deoxypyridinoline (D-Pyr) and serum and 24-h urinary calcium and phosphorus were determined in all subjects. Bone mineral density (BMD) at lumbar spine and proximal femur was measured by dual energy X-ray absorptiometry (DEXA).

RESULTS

We found a significant reduction of BGP and serum phosphorus in CS and AI (P < 0.05) vs. controls and significantly lower levels of Pyr only in CS (P < 0.05) vs. AI and controls. Spinal and femoral BMD z-values were significantly lower (P < 0.05) in patients with CS (z-score: lumbar spine -1.44 +/- 1.5 and femoral neck -1.07 +/- 1; mean +/- SD) compared to AI and controls.

CONCLUSIONS

Our data show that hypercortisolism reduces osteoblastic function and bone resorption and that osteocalcin can contribute to the precocious diagnosis of silent glucocorticoid excess. Patients with active CS were found to have lower BMD, particularly at vertebral level.