Osteoporosis
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Introduction
Osteoporosis is a decrease in bone density and quality, leading to problems with bone strength and leading to increased risk of fracture.
Osteoporosis affects 1:4 women and 1:8 men over 50. Over 1.4 million Canadians will be affected during their lifetime. After menopause, women have a 40% chance of an osteoporotic fracture.
Whites and Asians are more affected than blacks.
The Case of...
a simple case introducing clincial presentation and calling for a differential diagnosis to get students thinking.
Causes and Risk Factors
key risk factors include:
- low calcium intake
- low bone mineral density
- prior fragility fracture
- age
- family history
other major risk factors include:
- age over 65
- vertebral compression fracture
- kidney problems, leading to problems with vitamin D activation
- fragility fracture after age 40
- family history
- systemic glucocorticoid therapy over 3 mo
- Cushing's
- malabsorption syndrome
- persistent anovulation
- hyperparathyroidism
- propensity to fall
- x-ray appearance of osteopenia
- hypogonadism (testosterone is bone protective)
- early menopause (before age 45)
minor risk factors:
- Caucasian
- hyperthyroidism, past or present
- low BMI
- smoking
- rheumatoid arthritis
- chronic heparin therapy
- chronic anticonvulsant therapy
Pathophysiology
Can have primary osteoporosis, secondary, or other rarer forms.
main risk factor is loss of estrogen in women
Aggravated by general or regional inactivity; bone is very dynamic, and maintained bone loading is important.
Trabeculae orient along the lines of stress
osteoclasts have estrogen receptors and likely respond to a loss of the hormone.
women over 75 have accelerated loss of bone density
- glucocorticoids cause increased bone resorption; after 3 mo, vitamin D action is antagonized
- calcium excretion is also increased
- also acts on pituitary to suppress LH/FSH
- promotes apoptosis of osteoblasts
Signs and Symptoms
- history
- physical exam
History
Suspect osteoporosis in women with new onset back pain, a decrease in height (vertebral fractures), or thoracic kyphosis.
Physical Exam
Investigations
- screening
- lab investigations
- diagnostic imaging
Screening
Mass screening is not recommended.
Hip and spine are most commonly screened.
Women over 65, any post-menopausal women, or people with one major or two minor risk factors.
Lab Investigations
Bone biochemical markers can be used to identify people losing bone at an increased rate:
- nonspecific markers: alkaline phosphatase, urinary calcium/creatinine, hydroxyproline/creatinine
- specific markers: serum bone-specific AP
- osteocalcin
- procollagen I extension peptides
- plasma TRAP
- urine pyridinoline and deoxypyridinoline
Diagnostic Imaging
Bone density can be assessed in many ways:
- radiographs
- dual energy x-ray absorptiometry (DEXA)
- can be used to detect small changes over time
- quantitative CT
- ultrasound densitometry
- single or double photon absorptiometry
- bone biopsy
- other
falsely elevated values can occur in cases of sclerosis or compression fractures
status |
T-score |
normal |
+ 2.5 to -1.0 |
osteopenia |
- 1.0 to - 2.5 |
osteoporosis |
< -2.5 |
severe osteoporosis |
< -2.5 and fragility fracture |
Differential Diagnosis
Treatments
Regardless of risk factors and if no contraindications exist, all patients should be encouraged to take appropriate doses of calcium (1,500-2,000 mg per day) and vitamin D (800-1000 IU per day), and to engage in weight-bearing, and muscle-strengthening exercises.6,28 [References 6 and 28--Evidence level C, consensus/expert guidelines]
Other useful interventions to decrease the risk of osteoporosis and subsequent hip fracture include bisphosphonates or selective estrogen receptor modulators, smoking cessation, moderation of alcohol use, simplification of drug regimens, gait stabilization therapy, and the use of assistive devices to prevent falls.28,29,31 [References 29 and 31--Evidence level C, consensus/expert guidelines]
Medications
First line: Bisphosphonates, ie risedronate, alendronate.
Selective estrogen receptor modulators (SERMs), ie raloxifene
- increase BMD and lipid profile, as well as decreases breast cancer, though increases risk of DVT, PE, and hot flashes.
Hormone replacement therapy increases BMD, though the side effects (DVT, PE, CVD, cancer) outweigh benefits for most people. Use only in people with severe osteoporosis.
- calcitonin - only used for bone pain, not for increasing BMD
- PTH - short lived to increase osteoblast formation
Stimulators of bone formation include:
- PTH
Calcium supplementation (1,000 to 1,500 mg per day)
Vitamin D supplementation (400 to 800 IU per day)
Bisphosphonates (e.g., alendronate [Fosamax], risedronate [Actonel])
Selective estrogen receptor modulators (e.g., raloxifene [Evista])
Calcitonin
Regular physical activity (e.g., weight-bearing and muscle-strengthening exercises)
Reduction of modifiable risk factors (e.g., smoking cessation, alcohol abstinence)
Fall prevention (e.g., use of assistive devices, home safety practices, physical therapy for gait stabilization)
Anabolic steroids, pulsatile growth hormone, or parathyroid hormone therapy (experimental)
Consequences and Course
Twenty percent of women and 34% of men with hip fracture die within the first year, and 1/4 require long term care.
Resources and References
Society of Obstetricians and Gynecologists of Canada's 2006 Osteoporosis guidelines
Topic Development
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