Intact parathyroid hormone levels are not elevated in glucocorticoid-treated subjects

New insights into the vitamin D/PTH axis in endocrine-driven metabolic bone diseases

BACKGROUND

Endocrine regulation of bone metabolisms is the focus of the "Skeletal Endocrinology" series of meetings.

AIMS

To report on the outcome of the discussion on the role of vitamin D/PTH axis in endocrine osteopathies held during the 10th Skeletal Endocrinology Meeting which took place in Stresa (Italy) in March 2023.

OUTCOMES

Vitamin D/PTH axis has relevant influence on several outcomes in the general population and in patients affected by endocrinopathies such as hypoparathyroidism and secreting pituitary adenomas.

CONCLUSIONS

Assessing the status of the vitamin D/PTH axis and using vitamin D and PTH as therapeutic agents is mandatory in several endocrine-related bone metabolic conditions.

Endocrine sequelae of hematopoietic stem cell transplantation: Effects on mineral homeostasis and bone metabolism

Hematopoietic stem cell transplantation (HSCT) is an established therapeutic strategy for the treatment of malignant (leukemia and lymphoma) and non-malignant (thalassemia, anemia, and immunodeficiency) hematopoietic diseases. Thanks to the improvement in patient care and the development of more tolerable conditioning treatments, which has extended the applicability of therapy to the elderly, a growing number of patients have successfully benefited from HSCT therapy and, more importantly, HSCT transplant-related mortality has consistently reduced in recent years. However, concomitantly to long term patient survival, a growing incidence of late HSCT-related sequelae has been reported, being variably associated with negative effects on quality of life of patients and having a non-negligible impact on healthcare systems. The most predominantly observed HSCT-caused complications are chronic alterations of the endocrine system and metabolism, which endanger post-operative quality of life and increase morbidity and mortality of transplanted patients. Here, we specifically review the current knowledge on HSCT-derived side-effects on the perturbation of mineral metabolism; in particular, the homeostasis of calcium, focusing on current reports regarding osteoporosis and recurrent renal dysfunctions that have been observed in a percentage of HSC-transplanted patients. Possible secondary implications of conditioning treatments for HSCT on the physiology of the parathyroid glands and calcium homeostasis, alone or in association with HSCT-caused renal and bone defects, are critically discussed as well.

Comparable efficacy of denosumab and romosozumab in patients with rheumatoid arthritis receiving glucocorticoid administration

OBJECTIVES

Romosozumab is a newly released and widely known molecular-targeted drug for severe osteoporosis treatment with comparable effectiveness to denosumab. However, there have been no reports discussing the efficacy of those treatments for rheumatoid arthritis (RA) patients, especially those receiving glucocorticoids. This retrospective observational registry study compared the efficacy of 12-month treatment of denosumab and romosozumab in RA patients under the influence of glucocorticoid intake.

METHODS

Following propensity score matching, 36 patients each in the denosumab and romosozumab groups were analysed in this study. Drug effectiveness was evaluated by measuring bone mineral density (BMD) at the lumbar spine, total hip, and femoral neck at baseline, 6 and 12 months as well as alterations in P1NP, TRACP-5b, and simplified disease activity index (SDAI). The occurrence of adverse events and new fractures was also assessed.

RESULTS

At 12 months of treatment, BMD at the lumbar spine was increased by 7.5% in the denosumab group and 8.7% in the romosozumab group, which were both significantly and comparably elevated over baseline. At the total hip and femoral neck, romosozumab tended to exhibit favourable efficacy to increase BMD versus denosumab. Both P1NP and TRACP-5b were significantly lower in the denosumab group as compared with the baseline. Conversely in the romosozumab group, P1NP was increased over baseline, while TRACP-5b was decreased. Regarding SDAI alterations, both the romosozumab and denosumab groups exhibited comparable improvements in RA disease activity over time during treatment. Recorded adverse events and new fractures during treatment were few and minor in both groups.

CONCLUSIONS

Romosozumab exhibited comparable efficacy to denosumab for increasing BMD even under the influence of glucocorticoids for treating RA. Both drugs may be therefore suitable for managing osteoporosis in patients with RA and glucocorticoid intake.

Risk for osteoporosis and fracture with glucocorticoids

Glucocorticoid use is ubiquitous and is associated with multiple adverse reactions. Among them, osteoporosis and bone fractures are of our concern. In this review, we present current evidence on the effect of glucocorticoids on bone mineral density and the risk of fractures, the mechanisms underlying those effects, and the recommendations for monitoring and treating patients who take them. The bone mineral density of the lumbar spine and total hip is lower, and the risk of fractures is higher in glucocorticoid users than non-users. These effects have a rapid onset, are dose-dependent, and improve soon after discontinuation of glucocorticoids. They also appear to occur even with non-systemic routes of administration and with low doses. Glucocorticoids reduce bone mineral density by increasing osteoclast activity and decreasing osteoblast and osteocyte activity. Calcium metabolism and parathyroid hormone activity are less important than was initially thought. Treatment decisions are on risk stratification using clinical, radiographic, and prediction tools. Our armamentarium for the treatment and prevention of glucocorticoid-induced osteoporosis includes calcium and vitamin D, bisphosphonates, recombinant parathyroid hormone, monoclonal antibodies against receptor activator of nuclear factor kappa-B ligand, and hormone treatments.

Stimulation of osteoclast formation and bone resorption by glucocorticoids: Synergistic interactions with the calcium regulating hormones parathyroid hormone and 1,25(OH)2-vitamin D3

Osteoporosis is a significant health problem, with skeletal fractures increasing morbidity and mortality. Excess glucocorticoids (GC) represents the leading cause of secondary osteoporosis. The first phase of glucocorticoid-induced osteoporosis is increased bone resorption. In this Chapter, in vitro studies of the direct glucocorticoid receptor (GR) mediated cellular effects of GC on osteoclasts to affect bone resorption and indirect effects on osteoblast lineage cells to increase the RANKL/OPG ratio and stimulate osteoclastogenesis and bone resorption are reviewed in detail, together with detailed descriptions of in vivo effects of GC in different portions of the skeleton in research animals and humans. Brief sections are devoted to contrasting functions of GC in osteonecrosis, vitamin D formation, in vitro and in vivo bone resorptive actions dependent on vitamin D receptor and vitamin D toxicity, as well as the molecular basis of GR action. Included are also more detailed assessments of the interactions of GC with the major calcium regulating hormones, 1,25(OH)₂-vitamin D3 and parathyroid hormone, describing the in vitro increases in RANKL/OPG ratios, osteoclastogenesis and synergistic bone resorption that occurs when GC is combined with either 1,25(OH)₂-vitamin D3 or parathyroid hormone. Additionally, a molecular basic for the synergistic interaction of GC with 1,25(OH)₂-vitamin D3 is provided along with a suggested molecular basic for the interaction between GC and parathyroid hormone.

Expression of Renal Vitamin D and Phosphatonin-Related Genes in a Sheep Model of Osteoporosis

Simple Summary

Osteoporosis is a significant public health issue around the world, with post-menopausal osteoporosis due to estrogen deficiency resulting in approximately ¾ of cases. Treatment with glucocorticoids is another common cause of osteoporosis in humans. Sheep are a well-established model for osteoporosis in humans. In this study, aged sheep had their ovaries removed (ovariectomy) to simulate estrogen deficiency, and some sheep were also treated with glucocorticoids. The results showed that expression of the gene klotho in the kidney had the most marked difference in ovariectomized sheep treated with glucocorticoids for 2 months followed by a recovery period of 3 months. Klotho is known as the “anti-aging” hormone and is an important regulator of calcium and phosphorus metabolism. It may therefore be involved in the recovery of bone mineral density seen in ovariectomized sheep treated with glucocorticoids for 2 months followed by euthanasia at 5 months. As such, it could be an important treatment target for osteoporosis in humans.

Abstract

Osteoporosis is a significant public health issue around the world, with post-menopausal osteoporosis due to estrogen deficiency resulting in approximately ¾ of cases. In this study, 18 aged Merino ewes were ovariectomized, and 10 were controls. Three of the ovariectomized ewes were treated weekly with 400 mg of methylprednisolone for 5 months and three were treated weekly for 2 months, followed by a 3-month recovery period. At 2 months, five control animals and six ovariectomized animals were euthanized. At 5 months, all the remaining ewes were euthanized. Kidney samples were collected postmortem for qPCR analysis of NPT1, PTH1R, NPT2a, NPT2c, Klotho, FGFR1IIIc, VDR, CYP24A1, CYP27B1, TRPV5, TRPV6, CalD9k, CalD28k, PMCA and NCX1. Ovariectomized sheep had significantly greater VDR expression compared with other groups. Ovariectomized sheep treated with glucocorticoids for 2 months followed by euthanasia at 5 months showed significant differences in TRPV5, CYP24A1 and klotho gene expression compared to other groups. Differences in klotho expression were most marked after adjustment for repeated measures (p = 0.1). Klotho is known as the “anti-aging” hormone and is involved in calcium and phosphorus metabolism. Klotho may be involved in the recovery of bone mineral density in ovariectomized sheep treated with glucocorticoids for 2 months followed by euthanasia at 5 months. Further research on the role of klotho is recommended.

Glucocorticoid-induced osteoporosis: pathophysiological role of GH/IGF-I and PTH/VITAMIN D axes, treatment options and guidelines

Glucocorticoid-induced osteoporosis is the most frequent form of secondary osteoporosis caused by chronic exposure to glucocorticoid excess. Pathogenesis of glucocorticoid-induced osteoporosis is multifactorial including direct effects of glucocorticoids on bone cells and indirect effects of glucocorticoids on several neuroendocrine and metabolic pathways. Fragility fractures occur early in glucocorticoid-induced osteoporosis and anti-osteoporotic drugs along with calcium and vitamin D should be started soon after exposure to glucocorticoid excess. This paper summarizes some of the main topics discussed during the 9th Glucocorticoid-Induced Osteoporosis Meeting (Rome, April 2016) with a specific focus on the role of growth hormone/insulin-like growth factor-1 and parathyroid hormone/vitamin D axes in the pathogenesis of glucocorticoid-induced osteoporosis and the controversial aspects concerning therapeutic approach to skeletal fragility in this clinical setting.

Glucocorticoid-Induced Osteoporosis

Glucocorticoids are widely used to treat several diseases; however, one of their major consequences is a deleterious effect on bone that may lead to glucocorticoid-induced osteoporosis. Fractures may begin to occur within 3 months of commencing oral glucocorticoid therapy, and may even occur in patients receiving low doses. The good news is that with effective management, bone loss and fractures can be prevented or greatly reduced in patients receiving glucocorticoids. Despite clear practice guidelines, glucocorticoid-induced osteoporosis often goes undiagnosed and untreated in many patients. In this article, a current overview of glucocorticoid-induced osteoporosis is provided, including how to recognize, prevent and treat osteoporosis in pre- and postmenopausal women receiving glucocorticoid therapy.

[Mechanisms and therapeutics of glucocorticoid-induced osteoporosis]

Mechanisms of glucocorticoid-induced osteoporosis (GIOP) are categorized into local and systemic effects. In the local mechanisms, direct inhibitory effect of glucocorticoid on bone formation is thought to be one of the important mechanisms of GIOP. In contrast, secondary hyperparathyroidism induced by negative balance of calcium due to inhibition of absorption and increase of excretion is an important systemic mechanism of GIOP. Other mechanisms of GIOP are also shown in this review. From clinical points of view, serum markers for evaluation of GIOP have been discussed. Osteocalcin, procollagen type I N-terminal peptide, and bone-specific alkaline phosphatase as markers of bone formation are decreased in GIOP. Collagen I N-terminal telopeptide and tartrate resistent acid phosphatase isoform 5b as markers of bone resorption are increased in GIOP. Clinical guidelines have recommended that bisphosphonate is the first choice for the treatment of GIOP. Teriparatide is recombinant human parathyroid hormone 1-34, which should be considered as a therapeutic option for those at high risk of bone fracture. Denosumab, an anti receptor activator of nuclear factor-β ligand approved as a drug for postmenopausal osteoporosis was also effective for GIOP in clinical trials.

Autoimmune hypocalciuric hypercalcemia unresponsive to glucocorticoid therapy in a patient with blocking autoantibodies against the calcium-sensing receptor

CONTEXT

Autoantibodies directed against the calcium-sensing receptor (CaSR) have been reported in several individuals with various autoimmune disorders and PTH-mediated hypercalcemia. Previously, glucocorticoid treatment has been shown to decrease the CaSR autoantibody titers and normalize the hypercalcemia in a patient with autoimmune hypocalciuric hypercalcemia (AHH).

OBJECTIVE

The objective of the study was to evaluate a patient with AHH for the presence of blocking autoantibodies against the CaSR and to monitor her biochemical and serological responses to a trial of glucocorticoid therapy.

RESULTS

Glucocorticoid treatment had no effect on serum total or ionized calcium concentration or serum PTH levels, all of which remained at higher than normal levels. In contrast, on prednisone, urinary calcium excretion increased from overtly hypocalciuric levels to normal values. Anti-CaSR autoantibodies were detected at similar levels in the patient's serum before, during, and after glucocorticoid treatment. Functional testing of these antibodies showed that they inhibited the stimulatory effect of extracellular Ca(2+) on ERK1/2 but did not suppress the calcium-induced accumulation of inositol-1-phosphate.

CONCLUSIONS

We report a patient with AHH with frankly elevated PTH levels who was found to have autoantibodies against the CaSR. The hypercalcemia and CaSR autoantibody titers failed to respond to glucocorticoid therapy, unlike a previously reported patient with similar clinical and biochemical features. The anti-CaSR antibody-mediated inhibition of CaSR-stimulated ERK1/2 activity, but not of inositol-1-phosphate accumulation, suggests that ERK1/2 may mediate, at least in part, the regulation of PTH secretion and urinary calcium excretion by the CaSR.

New understanding of glucocorticoid action in bone cells

Glucocorticoids (GCs) are useful drugs for the treatment of various diseases, but their use for prolonged periods can cause severe side effects such as osteoporosis. GCs have a direct effect on bone cells, where they can arrest bone formation, in part through the inhibition of osteoblast. On the other hand, GCs potently suppress osteoclast resorptive activity by disrupting its cytoskeleton based on the inhibition of RhoA, Rac and Vav3 in response to macrophage colony-stimulating factor. GCs also interfere with microtubule distribution and stability, which are critical for cytoskeletal organization in osteoclasts. Thus, GCs inhibit microtubule-dependent cytoskeletal organization in osteoclasts, which, in the context of bone remodeling, further dampens bone formation.

Bone involvement in exogenous hypercortisolism

Corticosteroids remain a key component in the management of many disorders. Bone loss resulting from long-term administration of these drugs is common and osteoporosis induced by corticosteroids is the most frequent cause of secondary osteoporosis in nearly 50% of individuals on chronic corticosteroid therapy suffering from an osteoporotic fracture at some point. This article reviews the epidemiology and pathogenesis of glucocorticoid-induced osteoporosis.

Short-term effects of glucocorticoid therapy on biochemical markers of bone metabolism in Japanese patients: a prospective study

Glucocorticoid (GC) therapy induces rapid bone loss, but the early changes in calcium and bone metabolism in patients treated with GC have not been clarified. To investigate the changes in calcium and bone metabolism during the early stage of GC therapy, we analyzed various biochemical markers of bone metabolism. The serum levels of calcium (Ca), phosphorus, parathyroid hormone (PTH), osteocalcin (OC), bone alkaline phosphatase (BAP), and type I collagen cross-linked N-telopeptide (NTx), as well as the urinary levels of Ca, creatinine, and NTx, were measured on days 0, 3, 7, and 28 of GC therapy. The subjects were divided into the following four groups: 9 patients receiving pulse therapy (P), 18 patients receiving prednisolone (PSL) at doses > or =40 mg/day (H), 9 patients receiving PSL at doses > or =20 mg/day (M), and 11 patients receiving PSL at doses < or =10 mg/day (S). The serum OC level showed a marked decrease on day 3 of GC therapy (-41.2% +/- 6.6%, P < 0.01), while the BAP level decreased gradually. Both serum and urinary NTx levels significantly increased on day 7 of GC therapy (9.9% +/- 4.5%, P < 0.05, and 42.2% +/- 10.6%, P < 0.01, respectively). Urinary Ca excretion was increased on day 3 of GC therapy and continued to increase until 4 weeks, while intact PTH showed an increase on day 3 and then remained constant until 4 weeks. In groups P and H, there were significant early changes in OC, BAP, NTx, and intact PTH levels, as well as urinary Ca excretion. Even a PSL dose of <10 mg/day caused a decrease in the serum OC level. In conclusion, the biochemical markers of Ca and bone metabolism showed different kinetics depending on the dose of GC, and it is important for patients on high-dose GC therapy to receive prophylaxis for bone loss from the start of GC treatment.

Bone microarchitecture in males with corticosteroid-induced osteoporosis

SUMMARY

Microarchitectural changes in trabecular bone were analyzed by microcomputed tomography (microCT) and histomorphometry in 24 patients with corticosteroid-induced osteoporosis. The microCT images revealed a reduction in trabecular thickness only on frequency distribution curves, with no increase in trabecular separation. Trabecular plate thinning and perforations were easily identified.

INTRODUCTION

Corticosteroid-induced osteoporosis (CSIOP) is mediated by direct actions of the drug on bone cells. The result is a decrease in trabecular bone mass and a reduction in trabecular thickness, but connectivity is believed to remain rather well preserved.

METHODS

Twenty-four transiliac bone biopsies from patients with CSIOP were studied conjointly by histomorphometry [with two-dimensional (2D) architectural descriptors] and microCT (with 3D analysis of trabecular characteristics, including trabecular thickness and separation). The frequency distribution of thickness and separation were compared with data obtained in nine control subjects.

RESULTS

2D histomorphometry revealed a decrease in bone volume and trabecular thickness in the bone biopsies of the CSIOP patients when compared to those of the controls. MicroCT appeared to be able to identify the reduction in thickness only when the frequency distribution of trabecular thickness was computed. No difference for the curves of the frequency distribution of trabecular separation was evidenced between patients and controls. MicroCT and 2D histomorphometric results were correlated, but 2D analysis appeared to be more sensitive. However, microCT identified a very specific thinning of the trabecular plates in their center that corresponds to the earlier stages of perforations.

CONCLUSION

Trabecular plate thinning can be observed and perforations occur on very thin plates in CSIOP patients.

Duodenal calcium absorption in dexamethasone-treated mice: functional and molecular aspects

Reduced intestinal calcium absorption may be part of the pathogenesis of glucocorticoid-induced osteoporosis. 1,25(OH)2D3 is the major regulator of the expression of the active duodenal calcium absorption genes: TRPV6 (influx), calbindin-D9K (intracellular transfer) and PMCA1b (extrusion). We investigated the influence of dexamethasone (5 days: 2 mg/kg bw) on calcium absorption in vivo and on the expression of intestinal and renal calcium transporters in calcium-deprived mice. Total and free 1,25(OH)2D3-concentrations were halved, in line with decreased 25(OH)D3-1-alpha-hydroxylase and increased 24-hydroxylase expression. Nevertheless, no difference in duodenal or renal calcium transporter expression pattern could be detected between vehicle and dexamethasone-treated mice. Accordingly, dexamethasone did not affect in vivo calcium absorption. By contrast, increased calcemia and collagen C-terminal telopeptide levels reflected increased bone resorption. Decreased osteocalcin levels suggested impaired bone formation. Hence, short-term glucocorticoid excess in young animals affected bone metabolism without detectable changes in intestinal or renal calcium handling.

Glucocorticoid-Induced Osteoporosis: Mechanisms and Therapeutic Approach

GCs constitute a therapeutic class largely used in clinical medicine for the curative or supportive treatment of various conditions involving the intervention of numerous medical specialties. Beyond their favorable therapeutic effects, GCs almost invariably provoke bone loss and a rapid increase in bone fragility, with its host of fractures. Men and postmenopausal women constitute a preferential target for the bone complications of GCs. The premenopausal status is not, however, a shelter; bone loss also happens in young women who are on GCs. Exposure to GCs yields a fracture risk exceeding the risk conferred by a low BMD per se. Therefore, some reason exists to settle the BMD threshold for therapeutic intervention not at -2.5 T-scores but at -1.0 or -1.5 T-scores, even if no prospective randomized trial so far endorses that opinion. Nowadays, bisphosphonate therapy should be proposed to every patient at risk for fragility fracture, along with calcium and vitamin D supplementation. Studies of other therapeutic modalities (eg, promoters of bone formation) are in progress.

The pathogenesis, epidemiology and management of glucocorticoid-induced osteoporosis

Oral glucocorticoids (GCs) are frequently used in the treatment of inflammatory conditions, such as rheumatoid arthritis or asthma. They have adverse skeletal effects, primarily through reductions in bone formation and osteocyte apoptosis. Several findings indicate that changes in the quality of bone may significantly contribute to the increased risk of fracture and that loss of BMD only partially explains the increased risk of fracture in oral GC users. Epidemiological studies have found that the increases in the risk of fracture in oral GC users are dose dependent and occur within three months of starting GC therapy. Daily doses of >2.5 mg prednisone equivalent have been associated with increases in the risk of fractures and randomised studies reported adverse skeletal effects with daily doses as low as 5 mg. After discontinuation of GC treatment, the risk of fracture may reduce towards baseline levels unless patients previously used high cumulative doses of oral GCs. Users of inhaled GCs have also an increased risk of fracture, especially at higher doses. But it is likely that this excess risk is related to the severity of the underlying respiratory disease, rather than to the inhaled GC therapy. It has been recommended that patients who start on oral GC therapy should receive calcium and vitamin D supplementation. Patients with a higher risk of fracture should also receive a bisphosphonate.

Glucocorticoid-induced osteoporosis

Glucocorticoid-induced osteoporosis is the most frequent cause of secondary osteoporosis. Glucocorticoids cause a rapid bone loss in the first few months of use, but the most important effect of the drug is suppression of bone formation. The administration of oral glucocorticoid is associated with an increased risk of fractures at the spine and hip. The risk is related to the dose, but even small doses can increase the risk. Patients on glucocorticoid therapy lose more trabecular than cortical bone and the fractures are more frequent at the spine than at the hip. Calcium, vitamin D and activated forms of vitamin D can prevent bone loss and antiresorptive agents are effective for prevention and treatment of bone loss and to decrease fracture risk. Despite the known effects of glucocorticoids on bone, only a few patients are advised to take preventive measures and treat glucocorticoid-induced osteoporosis.

Mechanisms of glucocorticoid action in bone

Glucocorticoids induce rapid bone loss and increase the risk for osteoporotic fractures. The mechanisms include a phase of increased bone resorption, probably a result of the increased expression of receptor activator of nuclear factor-k-B ligand and colony stimulating factor-1, followed-up by a decrease in bone formation. This effect is central to the actions of glucocorticoids in bone and it is secondary to the loss of bone forming cells, caused by an inhibition of cell differentiation and an increase in the apoptosis of mature osteoblasts and osteocytes. Glucocorticoids also inhibit the function of mature osteoblasts and suppress the synthesis of insulin-like growth factor-I, an agent that enhances bone formation. Glucocorticoids alter the growth hormone/insulin-like growth factor axis in cartilage and, as a consequence, suppress linear growth.

Influence of glucocorticoids on human osteoclast generation and activity

Using human peripheral blood mononuclear cells as osteoclast precursors, we showed that dexamethasone stimulated osteoclast generation at a pharmacological concentration but did not affect the life span of human osteoclasts. Dexamethasone also dose-dependently increased signals for osteoclastogenesis.

INTRODUCTION

Glucocorticoid-induced osteoporosis is a common and serious disease. Glucocorticoids predominantly affect osteoblast proliferation and life span. Much of the bone loss is caused by reduced bone formation, but there is also an element of increased bone resorption.

MATERIALS AND METHODS

Human peripheral blood mononuclear cells were cultured on whale dentine and induced to differentiate to osteoclasts by RANKL and human macrophage-colony stimulating factor (M-CSF). Osteoclast activity was quantified by pit area. RANKL and osteoprotegerin (OPG) expression in osteoblasts were measured by real-time RT-PCR.

RESULTS

In the early phase of osteoclast generation (0-16 days), cultures from two different donors showed that dexamethasone at 10(-8) M increased pit area by 2.5-fold, whereas lower concentrations had no effect. At the highest dexamethasone concentration (10(-7) M), pit area was reduced. In 21-day cultures from three other donors, a similar increase was seen with dexamethasone at 10(-8) M. There was, however, no evidence of increased life span of osteoclasts with dexamethasone. In human primary osteoblasts, dexamethasone dose-dependently reduced OPG and increased RANKL expression as measured by quantitative real time RT-PCR.

CONCLUSION

These data provide some explanation at a cellular and molecular level for the observed increase in bone resorption seen in patients treated with glucocorticoids and indicate that there are clear direct effects of glucocorticoids on bone resorption in human cell systems that may differ from other species.

Glucocorticoid-induced osteoporosis

Glucocorticoids are important drugs in the treatment of variety diseases, but long-term period use can lead to various adverse effects, including osteoporosis. Glucocorticoid-induced osteoporosis is mainly caused by inhibition of osteoblastic bone formation, which results not only in decreased bone mineral density, but reduction of bone strength by trabecular thinning in bone microstructures. The evidence suggests that daily oral glucocorticoid doses higher than 5 mg prednisolone or equivalent increase the risk of fracture within 3-6 months after the start of therapy. High-dose inhaled glucocorticoids may also increase fracture risk. The diagnostic procedures are similar to those for primary osteoporosis, but the diagnostic threshold for bone mineral density needs to be higher than that for primary osteoporosis. Treatment with vitamin D, calcitonin, sex hormone replacement, and bisphosphonates has been shown to be effective, and bisphosphonates have been demonstrated to be the most valuable drugs for glucocorticoid-induced osteoporosis. There are several lines of evidence indicating that they are effective in preventing and treating low bone mineral density and in reducing fracture risk.

Chronic glucocorticoid treatment alters spontaneous pulsatile parathyroid hormone secretory dynamics in human subjects

OBJECTIVE

Spontaneous parathyroid hormone (PTH) secretory dynamics include tonic and pulsatile components. It is not known how glucocorticoids might alter these secretory dynamics.

DESIGN

The aim of our study was to evaluate spontaneous fluctuations in serum PTH levels in six adult male patients (aged 31-64 years) receiving chronic (>6 months) therapy with glucocorticoids (daily dosage >7.5 mg of prednisone or dose equivalent of other corticosteroid) as compared with a control group of 10 age- and sex-matched normal subjects.

METHODS

Peripheral venous blood sampling was performed every 3 min for 6 h from 0900 to 1500 h. Plasma PTH release profiles were subjected to deconvolution analysis, a method that resolves measured hormone concentrations into secretion and clearance components, and to an approximate entropy (ApEn) estimate, that in turn provides an integrated measure of the serial regularity or orderliness of the release process.

RESULTS

In the glucocorticoid-treated group, the PTH tonic secretory rate was reduced (4.3+/-0.74 vs 8.8+/-1.4 pg/ml per min in controls, P = 0.017). There was, however, an increase in the fractional pulsatile PTH secretion (42+/-8.2 vs 18.3+/-3.9 pg/ml per min, P = 0.006) in glucocorticoid-treated vs normal subjects. Mean overall PTH concentration, as well as mean integrated area, was similar among normal and glucocorticoid-treated subjects.

CONCLUSIONS

These results demonstrate, for the first time, that chronic glucocorticoid treatment induces a redistribution of spontaneous PTH secretory dynamics by reducing the amount released in tonic fashion and increasing the amount released as pulses.

Modulation of bone turnover by alfacalcidol and/or alendronate does not prevent glucocorticoid-induced osteoporosis in growing minipigs

The study was performed to clarify the effects of active vitamin D (alfacalcidol) and/or alendronate (ALN) on bone tissue turnover in glucocorticoid (GC)-treated growing minipigs. Göttingen minipigs aged 8 months were divided into six groups (n = 5 each): group BC, killed for baseline control; group GC, injected subcutaneously with prednisolone (0.5 mg/kg body weight [BW] per day, 5 days/week for 24 weeks); group VC, treated with vehicle alone; group alf, treated with oral alfacalcidol at 0.1 microm/kg BW per day, 5 days/week; group ALN, treated with alendronate 1 mg/kg BW per day; and group alf* ALN, treated with both alf and ALN as above. Biochemical examinations dual-energy X-ray absorptiometry, micro-computed tomography, peripheral quantitative computed tomography, and histomorphometry were performed. In group GC, all bone chemical markers were lower than in group VC. GC treatment reduced the age-dependent augmentation of bone mass and structure by reducing the bone formation rate (BFR) and activation frequency (Ac.f) relative to VC in lumbar bone and femoral cortex. Trabecular and osteonal wall thickness values did not change by GC. Treatments with alf, ALN, and alf* ALN did not have substantial effects on bone mass or structure. Alf treatment maintained lumbar BFR and Ac.f, while ALN reduced osteoclasts. Femoral cortical Ac.f values were not affected by these treatments. GC caused reduced bone formation, leading to low tissue turnover and imbalance of bone formation and resorption. Modulation of bone tissue turnover by alfacalcidol and/or alendronate failed to maintain the growth-dependent increases in mass and structure in GC-treated young minipigs.

Insulin-induced hypoglycemia suppresses plasma parathyroid hormone levels in patients with adrenal insufficiency

Hypoglycemia has been reported to cause suppression of parathyroid hormone (PTH) levels in serum in normal subjects. It is possible that increasing cortisol levels in response to hypoglycemia was responsible. To examine this possibility the acute PTH response to insulin administration and resulting hypoglycemia was examined in patients with adrenal insufficiency. The possible acute impact of insulin-induced hypoglycemia on bone formation and bone resorption in the absence of an endogenous cortisol response was also examined. A prospective open study was undertaken to examine the acute effects of insulin and resulting hypoglycemia on PTH levels, on bone formation as indicated by serum levels of aminoterminal propeptide of type 1 procollagen (PINP), and on bone resorption as indicated by serum levels of beta carboxy terminal telopeptide of type 1 collagen (beta-CTx). Seven patients with adrenal insufficiency participated. These patients were studied on 3 occasions under different conditions: (1) when insulin was administered to induce hypoglycemia while the patients received their routine glucocorticoid replacement; (2) when the patients received their routine glucocorticoid replacement, but were not rendered hypoglycemic; and (3) when they did not receive glucocorticoid replacement and were not rendered hypoglycemic, ie, untreated. This facilitated isolation of the PTH response to insulin and hypoglycemia from the effects of the normal increase in endogenous cortisol levels in response to hypoglycemia. Blood samples were taken at baseline and after 3 hours while the subjects continued fasting for measurement of plasma glucose, serum ionized calcium (Cai), magnesium, phosphate, PINP, PTH, and beta-CTx. Insulin 0.075 IU/kg body weight was given intravenously after the first blood sample. The usual morning glucocorticoid replacement dose was given 20 minutes after the baseline blood sample was obtained. After the administration of insulin, plasma glucose decreased from 4.8 +/- 0.5 to 2.7 +/- 0.5 mmol/L, mean +/- SD (P < .0001). PTH was not influenced by time or glucocorticoid treatment, but decreased in response to insulin-induced hypoglycemia (P < .05). Serum levels of PINP and beta-CTx decreased when untreated between 9 AM and 12 PM (P < .05), but were not independently influenced by insulin-induced hypoglycemia or glucocorticoid treatment. Serum levels of Cai increased and serum phosphate levels decreased in response to insulin-induced hypoglycemia, while serum phosphate levels were also independently influenced by time decreasing between 9 AM and 12 PM (P < .05). There was no effect of time, insulin-induced hypoglycemia, or glucocorticoid treatment on serum levels of magnesium. Possible mechanisms involved in the acute decrease in serum PTH observed include a direct effect of insulin or hypoglycemia or an indirect effect, eg, increased sympathomimetic activity on PTH secretion or on calcium or phosphate intercompartmental shifts.

Protective effect of vitamins K2 and D3 on prednisolone-induced loss of bone mineral density in the lumbar spine

BACKGROUND

Although vitamin K2 has been shown to prevent prednisolone-induced loss of bone mineral density of the lumbar spine in patients with chronic glomerulonephritis, the magnitude of this effect remains to be clarified. The aim of this prospective study is to compare the protective effect of vitamin K2 with that of vitamin D3 on prednisolone-induced loss of bone mineral density in patients with chronic glomerulonephritis.

METHODS

Sixty patients (28 men, 32 women) were randomly divided into 4 groups (n = 15 each group): control (group C), vitamin D3 alone (alfacalcidol, 0.5 microg/d; group D), vitamin K2 alone (menatetrenone, 45 mg/d; group K), and vitamins D3 plus K2 (group D + K). Alfacalcidol and menatetrenone therapy were started at the same time as prednisolone. Bone mineral density of the lumbar spine (L2 to L4) was determined by means of dual-energy X-ray absorptiometry, and various biochemical parameters of calcium and bone homeostasis were assessed before and at the end of week 8 of treatment.

RESULTS

Treatment with prednisolone alone caused loss of bone mineral density, which could be fully prevented in groups D, K, and D + K. However, marked reductions in levels of several biochemical markers of both bone formation and resorption also were observed in all groups. The preventive effect in groups K and D + K on loss of bone mineral density induced by prednisolone was similar to that in group D. The elevation in serum calcium levels observed in group D was attenuated in group D + K.

CONCLUSION

Protective effects of vitamin K2 or vitamins D3 and K2 on prednisolone-induced loss of bone mineral density are similar to that of vitamin D3.

Dexamethasone enhances osteoclast formation synergistically with transforming growth factor-beta by stimulating the priming of osteoclast progenitors for differentiation into osteoclasts

Long-term administration of glucocorticoids (GCs) causes osteoporosis with a rapid and severe bone loss and with a slow and prolonged bone disruption. Although the involvement of GCs in osteoblastic proliferation and differentiation has been studied extensively, their direct action on osteoclasts is still controversial and not conclusive. In this study, we investigated the direct participation of GCs in osteoclastogenesis. Dexamethasone (Dex) at <10(-8) M stimulated, but at >10(-7) M depressed, receptor activator of NF-kappaB ligand (RANKL)-induced osteoclast formation synergistically with transforming growth factor-beta. The stimulatory action of Dex was restricted to the early phase of osteoclast differentiation and enhanced the priming of osteoclast progenitors (bone marrow-derived monocytes/macrophages) toward differentiation into cells of the osteoclast lineage. The osteoclast differentiation depending on RANKL requires the activation of NF-kappaB and AP-1, and the DNA binding of these transcription factors to their respective consensus cis-elements was enhanced by Dex, consistent with the stimulation of osteoclastogenesis. However, Dex did not affect the RANKL-induced signaling pathways such as the activation of IkappaB kinase followed by NF-kappaB nuclear translocation or the activation of JNK. On the other hand, Dex significantly decreased the endogenous production of interferon-beta, and this cytokine depressed the RANKL-elicited DNA binding of NF-kappaB and AP-1, as well as osteoclast formation. Thus, the down-regulation of inhibitory cytokines such as interferon-beta by Dex may allow the osteoclast progenitors to be freed from the suppression of osteoclastogenesis, resulting in an increased number of osteoclasts, as is observed in the early phase of GC-induced osteoporosis.

Effect of glucocorticoids on bone density

Glucocorticoid therapy is the most common cause of secondary iatrogenic osteoporosis. The bone loss occurs predominantly due to a decrease in bone formation, although increased bone resorption also occurs. Glucocorticoids induce osteoblast apoptosis and increase osteoclast survival and activity. Most of these effects are mediated through the RANKL-OPG system but perturbations in gonadal hormone activity and calcium balance may also contribute significantly to bone loss. Future therapies in the treatment and prevention of glucocorticoid-induced osteoporosis may be targeted at restoring the hormonal and cytokine balance to nullify the apoptotic effect of glucocorticoids on bone forming cells.

Glucocorticoid-induced osteoporosis: pathophysiological data and recent treatments

Long-term glucocorticoid therapy promptly induces osteoporosis, whose severity depends on the dose and duration of the treatment. Recent data suggest that there is no safety threshold for adverse effects on bone. Glucocorticoid therapy impairs calcium intestinal absorption, dramatically suppresses osteoblastic formation, and stimulates osteocyte apoptosis. In contrast, the contribution of secondary hyperparathyroidism and increased bone resorption, although frequently mentioned, is now a focus of controversy. Beneficial effects on bone have been obtained with calcium and vitamin D supplementation, as well as with hormone replacement therapy (HRT) in postmenopausal women. Bisphosphonates are clearly effective in preventing and treating glucocorticoid-induced osteoporosis, although their mechanism of action in this condition remains poorly understood. Parathyroid hormone (PTH) is being evaluated as a potential therapeutic agent for glucocorticoid-induced osteoporosis.

[Prevalence of vitamin D deficiency in populations at risk for osteoporosis: impact on bone integrity]

BACKGROUND

Nowadays, severe deficiency of vitamin D is not a common finding in most developed countries. However, the prevalence of vitamin D insufficiency is relatively high and it can contribute to the descent of bone mass in osteoporosis risk populations. The objective of our study was to evaluate the prevalence of vitamin D insufficiency in postmenopausal women (PMW), patients with inflammatory bowel disease (IBD) and corticosteroid-dependent asthmatic patients (CAP) and to analyze its relationship with bone mineral density (BMD) and calciotropic hormones.

PATIENTS AND METHOD

We studied 299 patients (PMW: 161; IBD: 61; CAP: 77). In all cases, serum levels of PTH and 25OHD were determined and the BMD (DXA, Hologic QDR1000) in lumbar spine (LS) and femoral neck (FN) was measured.

RESULTS

Vitamin D insufficiency (25OHD < 15 ng/ml) was observed in 39.1% patients with PMW, 70.7% patients with IBD and 44.2% patients with CAP. 25OHD concentrations were lower in EII patients (p = 0.003) and PTH concentrations were higher in MPM (p < 0.001). We found a negative correlation between PTH and 25OHD in the overall group and this correlation persisted after considering each group separately. After adjusting for remaining variables, 25OHD was found to be significantly associated with BMD at lumbar spine and/or femoral neck in the three groups.

CONCLUSIONS

In populations at risk of osteoporosis, there is a high prevalence of vitamin D insufficiency. This insufficiency has a significant effect on bone integrity.

Molecular mechanisms of glucocorticoid-induced osteoporosis

Bone loss resulting from long-term glucocorticoid therapy is common and clinically relevant. A number of different glucocorticoid-mediated effects are responsible for the reduction in bone density: (i) glucocorticoid-induced direct impairment of osteoblast, osteocyte, and osteoclast function leads to reduced bone remodeling and diminished repair of microdamage in bone; (ii) the effects of parathyroid hormone (PTH) might be more pronounced in the presence of glucocorticoids, whereas vitamin D plays a lesser role in the pathogenesis of steroid-induced osteoporosis; (iii) glucocorticoids antagonize gonadal function and inhibit the osteoanabolic action of sex steroids; and (iv) increased renal elimination and reduced intestinal absorption of calcium lead to a negative calcium balance that has been suggested to promote secondary hyperparathyroidism. From a mechanistic point of view, all of the aforementioned effects have long been considered to be mediated at the molecular level exclusively by genomic actions. However, there is now increasing evidence for the existence of rapid glucocorticoid effects that are incompatible with this classical mode of action. These rapid effects, termed nongenomic effects, are mediated by glucocorticoid interactions with biological membranes, either through binding to membrane receptors or by physicochemical interactions. It is possible, but has yet to be shown, that these effects play a role in the pathogenesis of glucocorticoid-induced osteoporosis.

An update on glucocorticoid-induced osteoporosis

In general, bone loss from glucocorticoid treatment occurs rapidly within the first 6 months of therapy. Glucocorticoids alter bone metabolism by multiple pathways; however, the bone loss is greatest in areas rich in trabecular bone. Preventive measures should be initiated early. It is the author's opinion that all subjects initiating treatment with prednisone at 7.5 mg or greater require calcium supplementation (diet plus supplement) at a dose of 1500 mg and vitamin D at a dose of 400 to 800 IU/d. If the patient is going to remain on this dose of glucocorticoid for more than 4 weeks, an antiresorptive agent should be started (e.g., estrogen, bisphosphonate, raloxifene). If a patient has established osteoporosis and is either initiating glucocorticoid therapy or is chronically treated with prednisone at 5 mg d or greater in addition to calcium and vitamin D supplementation, a potent antiresorptive agent (bisphosphonate) should be started. A bone mineral density measurement of either the lumbar spine or the hip may be helpful is assessing an individual's risk of osteoporosis, may improve compliance with treatment, and can be used to monitor the efficacy of the prescribed therapy. There is no reason to withhold treatment for glucocorticoid-induced bone loss until a bone mass measurement is taken, however. In motivated patients, a weight-bearing and resistance exercise program should be prescribed to help retain muscle strength and prevent depression. If hypercalciuria develops with glucocorticoid use, either thiazide diuretics or sodium restriction may be helpful. In patients who continue to lose bone or experience fracture's despite antiresorptive therapy while on glucocorticoids, bone-building anabolic agents (e.g., hPTH 1-34 or PTH 1-84) may be available someday soon.

Glucocorticoid-induced osteoporosis

During normal bone remodeling, the supply of new osteoblasts and osteoclasts and the timing of the death of osteoclasts, osteoblasts and osteocytes by apoptosis are critical determinants of the initiation of new BMUs and the extension or reduction of the lifetime of existing ones. Many of the effects of chronic glucocorticoid administration on bone can be explained by decreased birth of osteoblast and osteoclast precursors and increased apoptosis of mature osteoblasts and osteocytes, disrupting the fine balance among these processes. Therapeutic agents that alter the prevalence of apoptosis of osteoblasts and osteoclasts can correct the imbalance in cell numbers that is the basis of the diminished bone mass and increased risk of fractures, found in glucocorticoid-induced osteoporosis.

Steroid-induced osteoporosis in systemic lupus erythematosus

The patient with SLE is at considerable risk of osteoporosis, because of the inflammatory disease itself, its consequences, and its treatments. Because of their extensive use, glucocorticoids are thought to be the most frequent cause of drug-related osteoporosis and may be responsible for much of the bone loss in lupus. This article focuses on the mechanisms of steroid-induced osteoporosis in SLE and outlines strategies for prevention and treatment.

Evaluation of bone metabolism after the use of an inhaled glucocorticoid (flunisolide) in patients with moderate asthma

OBJECTIVE

We have investigated the effects of the inhaled corticosteroid flunisolide on bone metabolism and adrenal function in patients with moderate asthma.

SUBJECTS AND DESIGN

Twenty ambulatory patients (13 females, 7 males, mean age +/- SD of 36.4 +/- 12.4 years) with moderate asthma were recruited. None had taken corticosteroids for at least 1 month. Flunisolide 500 microg was given twice a day for 10 weeks, without any other medication. Blood and urine were collected before and at the end of treatment course. Cortisol (basal and 1 h after ACTH 250 microg i.v.) was measured to evaluate adrenal function. A peak cortisol response of 496 nmol/l was considered an adequate response. Serum ionized calcium, intact PTH, plasma osteocalcin (OC) and urinary pyridinoline (Pyr) and deoxy-pyridinoline (D-Pyr) were measured to evaluate bone metabolism. Wilcoxon paired test was performed for statistical analysis. Results are expressed as mean +/- SD.

RESULTS

In most patients (85%), there was no difference after treatment with flunisolide on basal and stimulated cortisol levels. We found a significant decrease of OC (3.55 +/- 1.42 to 2.97 +/- 1.05 nmol/l) and Pyr (66.4 +/- 20.0 to 59.5 +/- 24.9 pmol/micromol creatinine) levels after treatment (P < 0.05). We also observed a positive correlation between the variations seen in pre and post treatment values of OC and Pyr/D-Pyr.

CONCLUSIONS

The use of inhaled flunisolide 1000 microg/day for 10 weeks had no suppressive effect on adrenal function in the majority of asthmatic patients studied. However, the effects seen on bone and mineral metabolism, evidenced by the significant fall in osteocalcin and pyridinoline levels, may indicate a possible systemic effect of this drug. Clinical consequences of long-term treatment with flunisolide need to be further evaluated.

[Prevention of glucocorticoid induced osteoporosis]

INTRODUCTION

It is generally accepted that moderate to high dose glucocorticoid therapy is associated with bone loss and increased fracture risk. The degree of bone loss is closely related to the cumulative corticosteroid dose and the highest rate of bone loss is observed in the first 3 to 6 months of therapy.

CURRENT KNOWLEDGE AND KEY POINTS

Optimal management strategies to prevent bone loss should include the use of the lowest efficacious dose of glucocorticoid. Alternate day dosing and bolus do not provide effective protection. Prevention should basically include adequate calcium intakes and additional vitamin D. All patients should be encouraged to modify their lifestyles, including smoking cessation and limitation of alcohol consumption; physical exercise for 30 minutes to 1 hour every day should also be recommended. Sodium restriction and thiazide diuretics have been shown to improve hypercalciuria that sometimes accompanies glucocorticoid therapy. Hormone replacement therapy should be recommended in postmenopausal women, while estrogen-containing oral contraceptives should be advocated in young women with menstrual irregularities, except for patients with systemic lupus erythematosus.

FUTURE PROSPECTS AND PROJECTS

Dual-energy X-ray absorptiometry may be useful in patient with high risk of glucocorticoid-induced osteoporosis, as it allows accurate measurements of bone mineral density. Etidronate recently proved to be efficacious in preventing bone loss and decreasing the number of vertebral fractures in menopausal women.

The science and therapy of glucocorticoid-induced bone loss

Glucocorticoids are critical in the management of chronic, noninfectious, inflammatory diseases. Bone loss is a most devastating side effect of these powerful medications. Glucocorticoids produce bone loss by altering calcium metabolism, suppressing gonadal hormone production, and inhibiting bone formation. Now that the mechanism of glucocorticoid-induced bone loss is understood and effective medications are available, this disease can be prevented and reversed.

Osteoporosis after organ transplantation

Within the past 2 decades, organ transplantation has become established as effective therapy for endstage renal, hepatic, cardiac, and pulmonary disease. Regimens to prevent rejection after transplantation commonly include high-dose glucocorticoids and calcineurin-calmodulin phosphatase inhibitors (the cyclosporines and tacrolimus), which are detrimental to bone and mineral homeostasis, and are associated with rapid bone loss that is often superimposed upon an already compromised skeleton. The incidence of fracture ranges from 8% to 65% during the first year after transplantation. In general, fracture rates are lowest in renal transplant recipients and highest in patients who receive a liver transplant for primary biliary cirrhosis. Rates of bone loss and fracture are greatest during the first 6 to 12 months after transplantation. Postmenopausal women and hypogonadal men appear to be at increased risk. Although no pretransplant densitometric or biochemical parameter has yet been identified that adequately predicts fracture risk in the individual patient, low pretransplant bone mineral density does tend to increase the risk of fracture, particularly in women. However, patients may sustain fractures despite normal pretransplant bone mineral density. Although the pathogenesis of the rapid bone loss is multifactorial, prospective biochemical data suggest that uncoupling of bone formation from resorption may be in part responsible, at least during the first 3 to 6 months. Prevention of transplantation osteoporosis should begin well before transplantation. Patients awaiting transplantation should be evaluated with spine radiographs, bone densitometry, thyroid function tests, serum calcium, vitamin D, parathyroid hormone, and testosterone (in men). Therapy for osteoporosis, low bone mass, and potentially reversible biochemical causes of bone loss should be instituted during the waiting period before transplantation. In patients with normal pretransplant bone density, therapy to prevent early posttransplant bone loss should be instituted immediately following transplantation. Most pharmacologic agents available for therapy of osteoporosis have not been subject to prospective controlled studies in organ transplant recipients. However, antiresorptive drugs, such as biphosphonates, appear to hold therapeutic promise.

Corticosteroid-induced bone loss in men

Lack of consistent information concerning the pathophysiology of corticosteroid-related bone loss may be due to coexisting independent factors that influence bone mineral density (BMD). For example, the disease being treated may increase bone turnover and cause bone loss, and its severity may influence the dose of corticosteroids chosen. Similarly, disease remission due to the treatment or disease progression despite treatment may influence bone turnover and the rate of bone loss. The hormonal changes purportedly responsible for reduced bone formation or increased bone resorption may be the result of the disease, not the corticosteroids. To determine the pathophysiology of corticosteroid-related bone loss, we conducted a controlled, prospective study in men with no systemic illness treated with corticosteroids to reduce antisperm antibodies. We measured BMD using dual x-ray absorptiometry and circulating biochemical and hormonal determinants of bone turnover in 9 men before and during prednisolone treatment and in 10 age-matched controls. The results were expressed as the mean +/- SEM. There were no differences in BMD between the two groups at baseline. The patients received 50 mg prednisolone daily for 3.7 +/- 0.6 months (range, 1-6). BMD decreased by 4.6 +/- 0.8% at the lumbar spine (P = 0.0007), by 2.6 +/- 0.6% at the trochanter (P = 0.004), and by 4.8 +/- 1.9% at the Ward's triangle (P < 0.04). The decrease in lumbar spine BMD correlated with the cumulative dose of corticosteroids (r = -0.49; P = 0.03). Serum osteocalcin and skeletal alkaline phosphatase decreased by 28.5 +/- 15.5% (P = 0.08) and 24.2 +/- 8.6% (P < 0.03), respectively. The decrease in lumbar spine BMD correlated with the decrease in osteocalcin (r = -0.48; P < 0.02). Serum testosterone and sex hormone-binding globulin decreased by 28.6 +/- 4.4% (P < 0.003) and 28.5 +/- 8.3% (P < 0.007), respectively. The testosterone/sex hormone-binding globulin ratio did not change. The decrease in total testosterone correlated with the decrease in osteocalcin (r = -0.40; P = 0.05). There were no detectable changes in urinary C-telopeptide, serum PTH, or serum calcium. Estradiol decreased by 23.5 +/- 11.4% (P < 0.003). Corticosteroid therapy results in rapid bone loss, probably due to reduced bone formation. Neither increased bone resorption nor secondary hyperparathyroidism appears to contribute to the rapid bone loss. Whether the reduction in bone formation may be partly mediated by changes in sex steroids remains unclear.