Saw this on another list and thought some of you might be interested.
Nina
Preventing glucocorticoid-induced osteoporosis
Sep 15, 2002
Patient Care
Bone loss from glucocorticoid therapy is immediate and occurs at the
highest rate during the first 6 months. Judicious use of calcium, vitamin D,
hormone replacement therapy, and bisphosphonates at the onset of long-term
treatment can improve bone density.
Exogenous glucocorticoids are the treatment of choice for many medical
conditions, and their beneficial effects can be quite dramatic. Yet this
class of drugs is potentially one of the most toxic, with side effects
ranging from less serious medical conditions such as truncal obesity,
striae, and cataracts, to more serious ones such as hypertension, diabetes
mellitus, osteonecrosis, and osteoporosis. Glucocorticoids have been a known
risk factor for osteoporosis since the 1930s, when their association with
skeletal changes and endocrine tumors was first reported.1
By the 1950s, exogenous glucocorticoid therapy became widespread, and
the severity of glucocorticoid-induced osteoporosis (GIO) was more fully
appreciated. Recent data suggest that osteoporosis will develop in
approximately 50% of patients who undergo long-term glucocorticoid therapy,
thereby increasing their risk of sustaining spontaneous fractures.2
Long-term therapy with 7.5 mg/d of prednisone is associated with an average
of 3% bone loss annually. Despite its prevalence and significant morbidity,
this common iatrogenic disease is often underrecognized and inadequately
treated. This article will review the problem and suggest solutions.
HOW GLUCOCORTICOIDS CAUSE BONE LOSS
Bone is actively remodeled throughout adult life. Even in the absence
of glucocorticoid exposure, 25% of trabecular bone and 3% of cortical bone
are remodeled annually.
Osteoblasts and osteoclasts are the cell types largely responsible for
bone turnover. Osteoblasts are cuboidal cells found in clusters at the bone
surface. They produce a layer of osteoid, which matures over a period of 10
days by a process of calcification that, over the course of several months,
results in new bone. Osteoclasts are multinucleated giant cells responsible
for bone resorption. They attach to bone matrix via integrin receptors,
which help to create pockets of extracellular space bordered by folds of
ruffled osteoclast membrane. This process creates secondary lysosomes
characterized by a low pH and an enzyme-rich environment in which bone
matrix degradation occurs. When glucocorticoids cause bone resorption to
occur at a faster rate than bone formation, osteoporosis results.
Corticosteroid receptors are partitioned into two types:
mineralocorticoid (found in CNS and renal tissue) and glucocorticoid
(present in virtually all cells of the body). Glucocorticoid receptors
mediate both the anti-inflammatory and metabolic effects of corticosteroids.
When glucocorticoids bind to the cellular receptors, the resulting complex
migrates to the nucleus where gene expression is induced. Consequently, all
levels of the inflammatory cascade are inhibited. Glucocorticoids are most
effective at suppressing T lymphocytes and natural killer cells, but they
tend to be less effective at inhibiting mature B cells. Corticosteroids also
suppress proinflammatory cytokines such as tumor necrosis factor-alpha and
interleukin-1. They have inhibitory effects on inflammatory mediators such
as gamma interferon, prostaglandin E2, and leukotrienes. The overall result
appears to be preferential suppression of cellular immunity rather than
humoral immunity.
GIO occurs as a consequence of multiple direct and indirect effects of
glucocorticoids on bone formation and resorption, the metabolism of calcium
and vitamin D, and the modulation of sex hormones. Glucocorticoids directly
inhibit osteoblast proliferation and matrix synthesis and cause a decline in
circulating levels of osteocalcin. They have also been implicated in
osteoblast apoptosis. Since bone formation is linked to body mass and muscle
strength, the catabolic effects of corticosteroids on muscle may indirectly
reduce bone formation. Hence, glucocorticoids weaken bone formation by way
of a glucocorticoid-induced myopathy with its associated loss of the trophic
effect of muscle stress on bone.
Corticosteroids also reduce sex hormone levels. They specifically
suppress estrogen, luteinizing hormone, and follicle-stimulating hormone in
women, which normally act to inhibit bone resorption. Moreover, a loss of
estrogen is associated with a net increase in numbers of osteoclasts. The
resultant hypogonadism favors osteoclastic over osteoblastic activity.
In addition, glucocorticoids may indirectly accelerate bone resorption
by causing excessive calciuria. The reduced availability of substrate for
bone formation that results is worsened by impaired renal tubular
reabsorption of calcium caused by glucocorticoids as well as reduced serum
levels of 1,25-dihydroxyvitamin D. This net loss in calcium causes a
secondary hyperparathyroidism, leading to further resorption of bone.3
Furthermore, glucocorticoids also decrease trabecular bone mass by
interfering with bone-active cytokines such as insulinlike growth factors.
GIO becomes detectable by sensitive radiologic methods as early as 1
month into systemic glucocorticoid therapy. Dual-energy x-ray absorptiometry
(DXA) and quantitative CT are radiologic methods available for detecting low
bone mass. Of these techniques, DXA is less expensive and more widely
available. T-scores, which are used in clinical decision-making, represent
the number of standard deviations below or above the peak bone mass in a
young adult reference population of the same sex. According to the World
Health Organization, a T-score above -1 reflects normal bone density,
between -1 and -2.5 is osteopenia, and below -2.5 signifies osteoporosis.3 A
T-score below -2.5 in addition to a personal history of fractures indicates
severe osteoporosis.
Individuals at greatest risk for GIO are those experiencing high bone
turnover or those with a preexisting imbalance between resorption and
formation, including children aged 15 and younger, adults older than 50,
postmenopausal women, and immobilized patients. Bone loss occurs mostly in
areas of high turnover, such as trabecular bone of the vertebra, and
resulting spontaneous fractures commonly involve the vertebrae or ribs.4,5
In one study, current corticosteroid users were 2.7 times more likely to
sustain a hip fracture compared with nonusers.6
Significant metabolic bone disease due to glucocorticoid therapy
occurs in a short amount of time. Even low-dose, 6-week corticosteroid
treatment is associated with adverse effects on bone metabolism.7 In one
study, 10 mg/d of prednisone over a 2-month period adversely affected
calcium and bone metabolism by uncoupling bone formation and resorption.7
Another study found that 20 weeks of treatment with low-dose prednisone
induced a mean trabecular bone mineral density decline of 8.2% in patients
with rheumatoid arthritis.8 Susceptibility to fracture is dependent on
dosage, and the overall risk of fracture is increased during oral
corticosteroid therapy, becoming apparent within the first 3 months of
treatment.9 Therefore, preventive therapy for osteoporosis should commence
when glucocorticoids are first prescribed.2
PROPHYLAXIS AGAINST GIO
Early strategies for the prevention and treatment of GIO blunted the
adverse impact of steroids on bone but did not consistently improve bone
strength, as has been seen with the more recently released class of agents
known as bisphosphonates. Among those strategies were sodium restriction
with concurrent thiazide diuretic therapy and treatment with sodium fluoride
or calcitonin. In particular, the use of thiazide diuretics with salt
restriction remains of unproved benefit, while treatment with vitamin D
carries a risk of hypercalciuria and urinary stone formation. Sodium
fluoride stimulates bone formation but remains controversial because of the
resultant abnormal bone quality noted during such therapy.10
Over the past decade, however, some notable inroads toward the
reduction of corticosteroid-induced bone mineral loss were made.11-15 Most
notably, these include gonadal hormone supplementation and bisphosphonates,
both of which have antiresorptive properties and may maintain or increase
bone density in some persons taking corticosteroids. Calcitonin can be
effective in some cases and may be considered when bisphosphonates are not a
viable option.
In addition to using those therapies, the American College of
Rheumatology (ACR) recommends treating confounding comorbid conditions such
as hyperthyroidism.2 Lifestyle alterations that may improve bone health
include exercise, reduction of alcohol use, and avoidance of cigarettes.
Although the best preventive measure is to discontinue use of
glucocorticoids, in many situations this course of action is not feasible.
Glucocorticoids should be prescribed at the minimum effective dose. Topical
or inhaled agents are preferred over systemic corticosteroids, if practical.
Because bone loss is most rapid during the first 6 months of glucocorticoid
therapy, the ACR advises physicians to start all patients on calcium plus
vitamin D at the onset of treatment.
Calcitonin and vitamin D metabolites
Providing adequate substrate for bone formation includes
supplementation with calcium in addition to vitamin D. A daily intake of
1500 mg of elemental calcium, either through diet or supplements, reduces
bone turnover. In most patients, cholecalciferol, 400 to 800 IU/d, is
sufficient to maintain serum levels in a proper range. If high-dose
cholecalciferol is used, carefully check both serum and urine calcium levels
periodically.
Intranasal salmon calcitonin administered in dosages up to 400 IU/d
was shown in several studies to blunt the loss of bone mineral content.10
One study comparing prophylactic use of calcium, calcitriol, and calcitonin
found that only treatment with calcium and calcitriol (with or without
calcitonin) prevented or reduced bone loss from the lumbar spine.15 A
significant side effect of treatment was hypercalcemia. Variable dosing of
corticosteroid therapy and the lack of a placebo control group, however, may
limit interpretation of results of this particular study. Expert
consultation should be obtained before prescribing calcitriol.
Hormone replacement therapy
Corticosteroids reduce levels of sex hormones, thereby indirectly
facilitating osteoclastic bone resorption. Therefore, patients taking
glucocorticoids may benefit from hormone replacement therapy (HRT), a
strategy that is still being investigated. One study using gonadal hormone
replacement for patients receiving chronic glucocorticoid therapy
demonstrated either stability or improvement of bone mineral density in both
men and women.16
Bisphosphonates
Synthetic pyrophosphates that resist chemical
degradation-bisphosphonates-have recently become key players in treating and
preventing GIO. A study assessing the benefit of alendronate for patients on
long-term corticosteroid therapy found that those taking alendronate showed
increased bone mineral density in the lumbar spine, hips, and overall
compared to patients taking placebo.12 In addition, fewer new vertebral
fractures were observed in the alendronate group. The evidence suggests that
prophylaxis with alendronate, 5 mg/d, may be warranted in patients receiving
long-term glucocorticoids. More recently, a third-generation oral
bisphosphonate was shown to prevent bone loss in patients initiating
corticosteroid treatment. Risedronate, 5 mg/d, resulted in significant
positive treatment effects in both men and women after 12 months of
intervention.13 Other bisphosphonates that may help treat or prevent GIO
include IV pamidronate and the cyclical administration of etidronate.
Anabolic therapy
Recently, anabolic therapy, with parathyroid hormone in particular,
has shown promise in the treatment of GIO.17 Early studies, however, do not
reveal consistent improvement throughout the skeleton, and primary
prevention studies are yet to be completed.
EVIDENCE OF UNDERTREATMENT
Despite recent guidelines published by the ACR and numerous studies
establishing the efficacy of preventive therapy against GIO, growing
evidence suggests widespread underutilization of these measures. A telephone
survey of patients on long-term glucocorticoids reported that 29% were
taking calcium supplements and 45% were receiving vitamin D. Of the
postmenopausal women surveyed, 40% were receiving HRT, 14% were receiving
bisphosphonates, and 29% had undergone a DXA scan.18 In another study,
charts of 215 clinic patients on glucocorticoid therapy for more than 1
month were reviewed. Prophylaxis against GIO was prescribed for 58% of the
patients.10
The rheumatology staff at The George Washington University Medical
Center, Washington, DC, performed a similar retrospective chart review. In
this unpublished study, only 29% of the patients surveyed were given
preventive therapy, and only 16% were assessed via DXA scan. All of the
patients evaluated and given prophylaxis were women, most of whom were in
their 40s. Preventive therapy was typically initiated after the patient had
taken glucocorticoids for more than 2 years and at dosages equivalent to
more than 10 mg/d of prednisone. The results showed that even
university-based rheumatologists who commonly confront the adverse effects
of excess exogenous glucocorticoids infrequently evaluate for, or provide
prophylaxis against, GIO.
A history of a DXA scan correlated with a higher rate of preventive
therapy by increasing the likelihood of diagnosing GIO. Therefore,
increasing physician awareness concerning issues surrounding GIO may be of
significant importance in detecting and treating patients with metabolic
bone disease. These studies show the need to initiate a better approach to
educate patients and physicians regarding the importance of GIO prevention.
A checklist addressing issues pertinent to patients taking
glucocorticoids, such as adverse effects of corticosteroids, risk factors
for osteoporosis, previous DXA scan results, and preventive therapy
selected, may be a useful tool for physicians (see "Monitoring patients on
glucocorticoids"). This type of document can be placed in the charts of all
patients when initiating glucocorticoid therapy to serve as a reminder of
the increased risk of osteoporosis and the need for prophylaxis.
EDITED BY STACY DILORETO
REFERENCES
1. Cushing H. Basophile adenomas of the pituitary body. J Nerv Ment
Dis. 1932;76:50-56.
2. American College of Rheumatology Task Force on Osteoporosis
Guidelines. Recommendations for the prevention and treatment of
glucocorticoid-induced osteoporosis. Arthritis Rheum. 1996;39:1791-1801.
3. NOF Physician's Guide: Diagnosis. National Osteoporosis Foundation
Web site. Available at: http://www.nof.org/physguide/diagnosis.htm .
Accessed October 9, 2000.
4. Seeman E, Wahner HW, Offord KP, et al. Differential effects of
endocrine dysfunction on the axial and the appendicular skeleton. J Clin
Invest. 1982;69:1302-1309.
5. Lane NE, Mroczkowski PJ, Hochberg MC. Prevention and management of
glucocorticoid-induced osteoporosis. Bull Rheum Dis. 1995;44:1-4.
6. Cooper C, Coupland C, Mitchell M. Rheumatoid arthritis,
corticosteroid therapy and hip fracture. Ann Rheum Dis. 1995;54:49-52.
7. Lems WF, Jacobs JW, Van Rijn HJ, et al. Changes in calcium and bone
metabolism during treatment with low dose prednisone in young, healthy, male
volunteers. Clin Rheumatol. 1995;14:420-424.
8. Laan RF, van Riel PL, van de Putte LB, et al. Low-dose prednisone
induces rapid reversible axial bone loss in patients with rheumatoid
arthritis. Ann Intern Med. 1993;119:963-968.
9. Van Staa TP, Leufkens HG, Abenhaim L, et al. Use of oral
corticosteroids and risk of fractures. J Bone Miner Res. 2000;15:993-1000.
10. Eastell R, Reid DM, Compston J, et al. A UK Consensus Group on
management of glucocorticoid-induced osteoporosis: an update. J Intern Med.
1998;244:271-292.
11. Boutsen Y, Jamart J, Esselinckx W, et al. Primary prevention of
glucocorticoid-induced osteoporosis with intermittent intravenous
pamidronate: a randomized trial. Calcif Tissue Int. 1997;61:266-271.
12. Saag KG, Emkey R, Schnitzer TJ, et al. Alendronate for the
prevention and treatment of glucocorticoid-induced osteoporosis.
Glucocorticoid-Induced Osteoporosis Study Group. N Engl J Med.
1998;339:292-299.
13. Cohen S, Levy RM, Keller M, et al. Risedronate therapy prevents
corticosteroid-induced bone loss: a twelve-month, multicenter, randomized,
double-blind, placebo-controlled, parallel-group study. Arthritis Rheum.
1999;42:2309-2318.
14. Buckley LM, Leib ES, Cartularo KS, et al. Calcium and vitamin D3
supplementation prevents bone loss in the spine secondary to low-dose
corticosteroids in patients with rheumatoid arthritis: a randomized,
double-blind, placebo-controlled trial. Ann Intern Med. 1996;125:961-968.
15. Sambrook P, Birmingham J, Kelly P, et al. Prevention of
corticosteroid osteoporosis: a comparison of calcium, calcitrol, and
calcitonin. N Engl J Med. 1993;328:1747-1752.
16. Lukert BP, Johnson BE, Robinson RG. Estrogen and progesterone
replacement therapy reduces glucocorticoid-induced bone loss. J Bone Miner
Res. 1992;7:1063-1069.
17. Lane NE, Sanchez S, Genant HK, et al. Short-term increases in bone
turnover markers predict parathyroid hormone-induced spinal bone mineral
density gains in postmenopausal women with glucocorticoid-induced
osteoporosis. Osteoporos Int. 2000;11:434-442.
18. Aagaard EM, Lin P, Modin GW, et al. Prevention of
glucocorticoid-induced osteoporosis: provider practice at an urban county
hospital. Am J Med. 1999;107:456-460.
ARTICLE CONTRIBUTORS
DEBORAH T. ZAREK, MD, Internal Medicine Resident, Christiana Care
Health System-Christiana Hospital, Newark, Del.
JAMES D. KATZ, MD, Assistant Professor of Medicine, Division of
Rheumatology, The George Washington University Medical Center, Washington,
DC.
http://www.patientcareonline.com/patcare/article/articleDetail.jsp?id=117083