Glucocorticoid-induced osteoporosis: how best to avoid fractures

Glucocorticoids are one of the most commonly prescribed medications and are used to treat a wide range of chronic inflammatory diseases. The main limitation of this therapy is the development of osteoporosis and bone fractures. Recent studies have given us insight into the epidemiology of glucocorticoid-induced fractures demonstrating both the magnitude of the problem and the types of patients who are likely to be most at risk. Additionally, several randomised trials have demonstrated beneficial effects of bone targeted medications in the setting of glucocorticoid-induced osteoporosis. This article will review these recent findings, will suggest when patients are likely to be at a significant risk of fracture and discuss how best to reduce this risk.

Association between bone mineral density and C-reactive protein in a large population-based sample

OBJECTIVE

Several studies suggest that bone mineral density (BMD) is reduced in chronic inflammatory diseases. Higher serum levels of C-reactive protein (CRP) have been associated with lower BMD in women and older adults. However, it is not clear whether this association holds in a representative sample of the general population. The purpose of this study was to examine the relationship between BMD and CRP level in a large representative US population-based sample from the National Health and Nutrition Examination Survey (NHANES).

METHODS

We included participants age ≥20 years with BMD (total and subregions) measured by dual x-ray absorptiometry scans and complete information on covariates from NHANES. The association between CRP level and BMD was evaluated using multivariate linear regression models, adjusting for potential confounders and further adjusting for comorbid diseases, medications, and serum vitamin D levels.

RESULTS

The study sample included 10,475 participants (53% Caucasian, 22% Mexican American, 18% African American, and 7% other races). Men had higher BMD and lower CRP concentrations than women. BMD (total body BMD as well as subtotal BMD and BMD of the extremities, ribs, and trunk subregions) was inversely associated with quintiles of CRP concentration both in men and in women in a dose-dependent manner (for total BMD, P for trend < 0.0001 for men, P for trend = 0.0005 for women). The associations were independent of medications, comorbidities, and other potential confounders. The results remained largely unchanged with further adjustment for serum vitamin D levels.

CONCLUSION

Among men and women in a large representative population-based sample, the CRP level was inversely and independently associated with total BMD in a dose-dependent manner.

Synovial DKK1 expression is regulated by local glucocorticoid metabolism in inflammatory arthritis

INTRODUCTION

Inflammatory arthritis is associated with increased bone resorption and suppressed bone formation. The Wnt antagonist dickkopf-1 (DKK1) is secreted by synovial fibroblasts in response to inflammation and this protein has been proposed to be a master regulator of bone remodelling in inflammatory arthritis. Local glucocorticoid production is also significantly increased during joint inflammation. Therefore, we investigated how locally derived glucocorticoids and inflammatory cytokines regulate DKK1 synthesis in synovial fibroblasts during inflammatory arthritis.

METHODS

We examined expression and regulation of DKK1 in primary cultures of human synovial fibroblasts isolated from patients with inflammatory arthritis. The effect of TNFα, IL-1β and glucocorticoids on DKK1 mRNA and protein expression was examined by real-time PCR and ELISA. The ability of inflammatory cytokine-induced expression of the glucocorticoid-activating enzyme 11beta-hydroxysteroid dehydrogenase type 1 (11β-HSD1) to sensitise fibroblasts to endogenous glucocorticoids was explored. Global expression of Wnt signalling and target genes in response to TNFα and glucocorticoids was assessed using a custom array.

RESULTS

DKK1 expression in human synovial fibroblasts was directly regulated by glucocorticoids but not proinflammatory cytokines. Glucocorticoids, but not TNFα, regulated expression of multiple Wnt agonists and antagonists in favour of inhibition of Wnt signalling. However, TNFα and IL-1β indirectly stimulated DKK1 production through increased expression of 11β-HSD1.

CONCLUSIONS

These results demonstrate that in rheumatoid arthritis synovial fibroblasts, DKK1 expression is directly regulated by glucocorticoids rather than TNFα. Consequently, the links between synovial inflammation, altered Wnt signalling and bone remodelling are not direct but are dependent on local activation of endogenous glucocorticoids.

Inflammatory regulation of glucocorticoid metabolism in mesenchymal stromal cells

Objective

Tissue glucocorticoid (GC) levels are regulated by the GC-activating enzyme 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1). This enzyme is expressed in cells and tissues arising from mesenchymal stromal cells. Proinflammatory cytokines dramatically increase expression of 11β-HSD1 in stromal cells, an effect that has been implicated in inflammatory arthritis, osteoporosis, obesity, and myopathy. Additionally, GCs act synergistically with proinflammatory cytokines to further increase enzyme expression. The present study was undertaken to investigate the mechanisms underlying this regulation.

Methods

Gene reporter analysis, rapid amplification of complementary DNA ends (RACE), chemical inhibition experiments, and genetic disruption of intracellular signaling pathways in mouse embryonic fibroblasts (MEFs) were used to define the molecular mechanisms underlying the regulation of 11β-HSD1 expression.

Results

Gene reporter, RACE, and chemical inhibitor studies demonstrated that the increase in 11β-HSD1 expression with tumor necrosis factor α (TNFα)/interleukin-1β (IL-1β) occurred via the proximal HSD11B1 gene promoter and depended on NF-κB signaling. These findings were confirmed using MEFs with targeted disruption of NF-κB signaling, in which RelA (p65) deletion prevented TNFα/IL-1β induction of 11β-HSD1. GC treatment did not prevent TNFα-induced NF-κB nuclear translocation. The synergistic enhancement of TNFα-induced 11β-HSD1 expression with GCs was reproduced by specific inhibitors of p38 MAPK. Inhibitor and gene deletion studies indicated that the effects of GCs on p38 MAPK activity occurred primarily through induction of dual-specificity phosphatase 1 expression.

Conclusion

The mechanism by which stromal cell expression of 11β-HSD1 is regulated is novel and distinct from that in other tissues. These findings open new opportunities for development of therapeutic interventions aimed at inhibiting or stimulating local GC levels in cells of mesenchymal stromal lineage during inflammation.

Endogenous glucocorticoids in inflammation: contributions of systemic and local responses

The anti-inflammatory actions of therapeutic glucocorticoids are well established and these drugs are widely used to treat a variety of inflammatory conditions. It is also clear that endogenously synthesised glucocorticoids have an important role in regulating inflammatory responses. Traditionally, our understanding of the effects of endogenous glucocorticoids has been based on the levels of glucocorticoids within the circulation. These levels are controlled by the hypothalamic-pituitary-adrenal axis. However, more recently it has been established that the local level of glucocorticoids is of potential importance. Situations where the local level of glucocorticoids may differ from the level in the circulation are illustrated in this review. In addition, the mechanisms regulating local glucocorticoid levels and actions are identified. Increasingly, it will be important to understand how the levels of glucocorticoids within the circulation and within the tissues are regulated in a coordinated manner.

Expression of 11β-hydroxysteroid dehydrogenase enzymes in human osteosarcoma: potential role in pathogenesis and as targets for treatments

Osteosarcoma (OS) is a primary malignant tumour of bone occurring predominantly in children and young adults. Despite chemotherapy, relapse is common and mortality remains high. Non-transformed osteoblasts are highly sensitive to glucocorticoids, which reduce proliferation and induce apoptosis. Previously, we observed that OS cells, but not normal osteoblasts, express 11β-hydroxysteroid dehydrogenase type 2 (11β-HSD2). This enzyme inactivates cortisol (active) to cortisone (inactive) and expression of 11β-HSD2 renders OS cells resistant to glucocorticoids. By contrast, the related enzyme 11β-HSD1 converts cortisone to cortisol and reduces OS cell proliferation in vitro. Some synthetic glucocorticoids (e.g. dehydrodexamethasone (DHD), inactive counterpart of dexamethasone (DEX)) have been reported to be activated by 11β-HSD2. We therefore investigated expression and enzymatic activity of 11β-HSD isozymes in human OS tissue, determined whether 11β-HSD expression has prognostic value in the response to therapy, and evaluated the potential use of synthetic glucocorticoids to selectively target OS cells. OS samples expressed both 11β-HSD1 and 11β-HSD2. 11β-HSD1 expression in pretreatment biopsy specimens positively correlated with primary tumour size. Expression and activity of 11β-HSD1 in post-treatment biopsies were unrelated to the degree of tumour necrosis following chemotherapy. However, high 11β-HSD2 expression in post-treatment biopsies correlated with a poor response to therapy. OS cells that expressed 11β-HSD2 inactivated endogenous glucocorticoids; but these cells were also able to generate DEX from DHD. These results suggest that OS treatment response is related to 11β-HSD2 enzyme expression. Furthermore, OS cells expressing this enzyme could be targeted by treatment with synthetic glucocorticoids that are selectively reactivated by the enzyme.

Glucocorticoids in bone and joint disease: the good, the bad and the uncertain

Therapeutic glucocorticoids are widely used to treat a variety of inflammatory conditions. However, the beneficial anti-inflammatory effects of glucocorticoids are limited by their detrimental effects on bone, including decreased bone density and increased fracture risk. Glucocorticoids adversely affect bone because they inhibit the amount of bone formed by osteoblasts. Surprisingly, through the expression of the 11beta-hydroxysteroid dehydrogenase type 1 (11beta-HSD1) enzyme, osteoblasts can generate active glucocorticoids (cortisol and/or prednisolone) from their inactive counterparts (cortisone and/or prednisone). 11beta-HSD1 activity in an individual predicts the impact of glucocorticoids on bone. 11beta-HSD1 expression within bone also increases with age and inflammation. This implicates locally produced glucocorticoids in age-related and inflammation-associated osteoporosis. Glucocorticoids are also generated by synovial tissue through the expression of 11beta-HSD1. Activity increases with joint inflammation and could represent a local anti-inflammatory system. The recognition that peripheral tissues generate glucocorticoids suggests that, for conditions associated with ageing or inflammation, one should consider glucocorticoid activity beyond the circulation.

Outcome of Cushing's disease following transsphenoidal surgery in a single center over 20 years

CONTEXT

Historically, Cushing's disease (CD) was associated with a 5-yr survival of just 50%. Although advances in CD management have seen mortality rates improve, outcome from transsphenoidal surgery (TSS), the current first-line treatment, varies significantly between centers.

OBJECTIVES

The aim of the study was to define outcome including mortality in a cohort of CD patients treated with TSS over 20 yr.

DESIGN

We conducted a retrospective cohort study of 80 patients who underwent TSS to treat CD between 1988 and 2009. In 72 cases, data on clinical features and outcomes were collected from medical records. In eight patients, records were unavailable, but in all cases mortality data were obtained from National Health Service (NHS) registries and recorded as standardized mortality ratio.

SETTING

The study was conducted in a United Kingdom tertiary referral center.

PATIENTS OR OTHER PARTICIPANTS

Adult patients confirmed to have CD participated in the study.

INTERVENTIONS

All patients underwent TSS.

MAIN OUTCOME MEASURE

Patients were subdivided into groups based on disease response after initial treatment. Mortality according to subgroup was also assessed.

RESULTS

Median follow-up for clinical data was 4.6 yr. Three outcome groups were identified: cure, 72% (52 of 72); persistent disease, 17% (12 of 72); and disease recurrence, 11% (eight of 72). Median time to recurrence after initial remission was 2.1 yr (interquartile range, 1.3-3.1 yr). Mean follow-up for mortality was 10.9 yr. Thirteen of 80 patients had died: five of 52 in the cure group, two of eight in the disease recurrence group, two of 12 with persistent disease, and four of eight of those followed up by NHS registry search only. Overall, the standardized mortality ratio was 3.17 [95% confidence interval (CI), 1.70-5.43], whereas in the cure group it was 2.47 (95% CI, 0.80-5.77), and it was 4.12 (95% CI, 1.12-10.54) for disease recurrence/persistent disease groups.

CONCLUSIONS

We report long-term cure rates in excess of 70%. Mortality is increased in CD and may be higher in patients with persistent/recurrent disease compared to patients cured after initial treatment.

Cost-effectiveness of the Concord Minimal Trauma Fracture Liaison service, a prospective, controlled fracture prevention study

We evaluated the cost-effectiveness of a fracture liaison service prospectively designed to have a parallel control group treated by standard care. The clinical effectiveness of this service was associated with an incremental cost-effectiveness ratio versus standard care of Australian dollars (AUD) 17,291 per quality-adjusted life year (QALY) gained.

INTRODUCTION

Osteoporotic fractures are a major burden for national health services. The risk of re-fracture following an osteoporotic fracture is particularly high. In a study unique in prospectively having a control group treated by standard care, we recently demonstrated that a Minimal Trauma Fracture Liaison (MTFL) service significantly reduces the risk of re-fracture by 80%. Since the service involves greater use of resources, we have now evaluated whether it is cost-effective.

METHODS

A Markov model was developed that incorporated fracture probabilities and resource utilization data (expressed in AUD) obtained directly from the 4-year MTFL service clinical study. Resource utilization, local cost and mortality data and fracture-related health utility data were used to calculate QALYs with the MTFL service and standard care. Main outcome measures were: additional costs of the MTFL service over standard care, the financial savings achieved through reduced fractures and changes in QALYs associated with reduced fractures calculated over a 10-year simulation period. Costs and QALYs were discounted at 5% annually. Sensitivity analyses quantified the effects of different assumptions of effectiveness and resource utilization associated with the MTFL service.

RESULTS

The MTFL service improved QALYs by 0.089 years and led to increased costs of AUD 1,486 per patient versus standard care over the 10-year simulation period. The incremental cost-effectiveness ratio versus standard care was AUD 17,291 per QALY gained. Results were robust under all plausible assumptions.

CONCLUSIONS

The MTFL service is a cost-effective intervention to reduce recurrent osteoporotic fractures.

Disorders of calcium metabolism and parathyroid disease

Pregnancy and lactation are associated with profound changes in calcium physiology. This can make interpretation of biochemical tests difficult during these times. Diseases of bone and calcium metabolism are uncommon during pregnancy but can be severe when they occur. These conditions are complicated by the need for dual consideration for the maternal and foetal health. These conditions are also much less well studied than related conditions that occur outside of pregnancy resulting in a reduction in evidence for and confidence in recommendations relating to management. This chapter will review the changes in calcium physiology that occur with pregnancy and lactation, describe the disorders of calcium and parathyroid physiology that can occur and outline the most appropriate way to manage these conditions.

Overview of the endocrine response to critical illness: how to measure it and when to treat

The assessment and manipulation of the endocrine system in patients with critical illness is one of the most complex and controversial areas in endocrinology. Severe acute illness causes dramatic changes in most endocrine systems. This can lead to considerable difficulty in recognising pre-existing endocrine disorders in severely ill patients. Critical care itself might also induce types of endocrine dysfunction not seen outside the critical care unit. It is important to clarify whether or not such endocrine dysfunction occurs. Where it does occur it is also important to determine whether endocrine intervention is useful in improving outcome. There is also the issue of whether endocrine manipulation in critically ill patients without endocrine dysfunction could benefit from endocrine intervention, e.g. to improve haemodynamics or reverse a catabolic state. This review will discuss some of these contentious issues. It will highlight how endocrine assessment of a patient with critical illness differs from that in other types of patient. It will emphasise the added need to place the biochemical assessment and its interpretation in the context of the patients underlying condition.

Can 11β-hydroxysteroid dehydrogenase activity predict the sensitivity of bone to therapeutic glucocorticoids in inflammatory bowel disease?

In healthy individuals measures of 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) enzyme activity predict the change in bone formation markers in response to therapeutic glucocorticoids. It is unclear whether these measures remain predictive in inflammatory disease. We therefore examined whether 11β-HSD1 activity predicts changes in bone markers and bone mineral density (BMD) in patients with inflammatory bowel disease (IBD) treated with therapeutic glucocorticoids. Prospective and cross-sectional studies were carried out in patients attending a gastroenterology clinic with active (n = 39) or clinically inactive (n = 34) IBD and healthy controls (n = 51). Urinary corticosteroid metabolite profiles were obtained on a spot urine sample and total corticosteroid metabolite excretion and 11β-HSD1 activity (measured as the ratio of tetrahydrocortisol to tetrahydrocortisone metabolites, [THF+alloTHF]/THE) determined. Patients with active disease were treated with an 8-week reducing course of oral prednisolone. The (THF+alloTHF)/THE ratio was significantly increased in patients with IBD, even those in clinical remission. The baseline (THF+alloTHF)/THE ratio failed to predict the decrease in bone formation markers or hip BMD. Measures of 11β-HSD activity do not predict bone loss during glucocorticoid treatment of active IBD, probably due to disease-related increases in 11β-HSD1 activity. Our observation of elevated 11β-HSD1 activity in clinically inactive IBD implicates gastrointestinal glucocorticoid activation in the maintenance of disease remission.

Glucocorticoid-induced osteoporosis - a disorder of mesenchymal stromal cells?

Glucocorticoids are a class of steroid hormones that are essential to life but cause serious harm in excess. The main clinical features of glucocorticoid excess are due to adverse effects on cells and tissues that arise from a common developmental precursor - the mesenchymal stromal cell (MSC; sometimes referred to as the mesenchymal stem cell). Interestingly glucocorticoids appear essential for the differentiation of cells and tissues that arise from MSCs. High levels of glucocorticoids are used in tissue engineering strategies to enhance the formation of tissues such as bone, cartilage, and muscle. This article discusses the paradox that glucocorticoids both enhance and impair MSC development and function. It will describe how endogenous glucocorticoids are likely to be important in these processes in vivo and will discuss the implications for therapies aimed at reducing the damage associated with the use of therapeutic glucocorticoids.

Impact of UK National Guidelines based on FRAX®--comparison with current clinical practice

OBJECTIVE

To assess whether clinician-determined treatment intervention thresholds are in line with the assessment of fracture risk provided by FRAX® and treatment recommendations provided by UK guidelines produced by the National Osteoporosis Guidelines Group (NOGG).

DESIGN, PATIENTS AND MEASUREMENTS

This was a retrospective cohort analysis of 288 patients consecutively referred for dual-energy X-ray absorptiometry (DXA) scanning from primary care immediately prior to the introduction of the FRAX® algorithm. In addition to DXA assessment, patients completed a clinical risk factor questionnaire which included risk factors used in the FRAX® algorithm. Initial risk assessment and treatment decisions were performed after DXA. FRAX® was used, retrospectively, with femoral neck T-score, to estimate fracture risk which was applied to NOGG to generate guidance on treatment intervention. Clinician- and NOGG-determined outcomes were audited for concordance.

RESULTS

There was concordance between clinician and NOGG treatment decisions in 215 (74.6%) subjects. Discordance was observed in 73 (25.3%) subjects. In the discordant group, seven subjects were given lifestyle advice when NOGG recommended treatment, 42 given treatment when NOGG recommended lifestyle advice only, and 24 were referred to a metabolic bone clinic for further evaluation. The reasons for treatment differences in subjects recommended treatment by clinician but not NOGG were largely (90.2%) attributed to the use of lumbar spine bone mineral density (BMD).

CONCLUSIONS

There is high concordance between clinician-determined and FRAX®-NOGG intervention. The absence of spine BMD from FRAX® is the primary source of discrepancy. This study provides some assurance of the validity of the treatment thresholds generated from FRAX®-NOGG in 'real-world' usage.

New perspectives in the management of primary hyperparathyroidism

Primary hyperparathyroidism (PHPT) is a biochemical syndrome caused by the inappropriate or unregulated overproduction of parathyroid hormone, Leading to hypercalcae-mia. It was previously considered a relatively rare disorder, with clinical manifestations dominated by renal and/or bone disease. However, in modern times the diagnosis is most frequently recognized coincidentally on biochemical testing in patients evaluated for unrelated complaints. Parathyroidectomy is the only curative treatment for PHPT, with improved outcomes in symptomatic patients following this procedure. However, surgical intervention in patients with no clear clinical features remains controversial. The National Institutes for Health (NIH) have developed consensus guidelines giving specific indications for when surgery is recommended in patients with asymptomatic PHPT. This article examines the impact of treatment on asymptomatic PHPT, focusing on bone disease, neurocognitive function, quality of Life, cardiovascular disease and mortality. Medical treatment options, including bisphospho-nates and cinacalcet, are also discussed.

The 11beta-hydroxysteroid dehydrogenase enzymes--arbiters of the effects of glucocorticoids in synovium and bone

Ever since the first use of cortisone, glucocorticoids have had a controversial role in the treatment of RA. There has been equally controversial research into the possible involvement of endogenous glucocorticoids, and their secretion via the hypothalamic-pituitary-adrenal (HPA) axis, in the development and persistence of inflammatory arthritis. Recently, our understanding of how glucocorticoids act has expanded substantially with the characterization of glucocorticoid-metabolizing enzymes that regulate glucocorticoid action at tissue level. These enzymes, the 11β-hydroxysteroid dehydrogenases, interconvert biologically inactive glucocorticoids such as cortisone and prednisone with their active counterparts, cortisol (hydrocortisone) and prednisolone. Without these enzymes, cortisone and prednisone would be therapeutically useless. Furthermore, in normal individuals, the activities of these enzymes influence the function of other components of the HPA axis. These enzymes are expressed in human synovial tissue and bone and have been implicated in the control of synovial inflammation, the development of periarticular bone loss and the sensitivity of bone to therapeutic glucocorticoids. This article reviews recent findings in this area that highlight the role of these enzymes in rheumatic diseases.

Primary hyperparathyroidism--is mild disease worth treating?

Most patients with primary hyperparathyroidism (PHPT) are asymptomatic at presentation. This presents the dilemma whether to treat surgically or manage by conservative follow-up. This article covers the risks of managing mild PHPT conservatively. Some of these risks are well established, for example worsening of bone disease and increased risk of nephrolithiasis. Others, such as effects on cardiovascular function or the risk of malignancy are more controversial. These factors are critical to decisions relating to surgical or conservative management of mild PHPT.

11Beta-hydroxysteroid dehydrogenase type 1 and its role in the hypothalamus-pituitary-adrenal axis, metabolic syndrome, and inflammation

CONTEXT

11Beta-hydroxysteroid dehydrogenase (11beta-HSD) enzymes are now appreciated to be important regulators of hormone action at a tissue level. 11Beta-HSD1 is widely expressed and increases glucocorticoid action through its unique ability to convert inactive glucocorticoids (cortisone in man, 11-dehydrocorticosterone in rodents) to their active forms (cortisol and corticosterone, respectively). The enzyme has roles in the normal hypothalamus-pituitary-adrenal (HPA) axis, has been implicated in metabolic syndrome, and may modulate various aspects of the immune response.

EVIDENCE ACQUISITION

A review of published, peer-reviewed medical literature (1990 to June 2009) on the physiology and pathophysiology of 11beta-HSD1 was performed with an emphasis on HPA axis consequences, the metabolic syndrome, and the inflammatory response.

EVIDENCE SYNTHESIS

Studies of patients with genetic defects in 11beta-HSD1 action show abnormal HPA axis responses with hyperandrogenism being a major consequence. The mechanisms underlying these abnormalities have been explored in mouse models with targeted deletion of components of the 11beta-HSD1 system. A range of experimental studies emphasize the role of 11beta-HSD1 in the metabolic syndrome and the potential for treatment with chemical inhibitors. An emerging area is the role of 11beta-HSD1 in the inflammatory response.

CONCLUSIONS

11Beta-HSD1 activity is an important component of the HPA axis and contributes to the metabolic syndrome and the normal immune response. Ongoing clinical observations and the development of selective inhibitors will further clarify the role of 11beta-HSD1 in these areas.