Osteoporosis Diagnosis and Management in Postmenopausal Women Over 50
Screen all postmenopausal women ≥65 years with DXA of the hip and spine, and screen younger postmenopausal women (50-64 years) who have at least one additional risk factor beyond menopause using a two-step approach: first identify risk factors, then calculate FRAX score to determine screening necessity. 1
Screening Recommendations
Who to Screen
- All women ≥65 years: Universal DXA screening is recommended regardless of other risk factors 1
- Postmenopausal women 50-64 years: Screen with DXA if they have ≥1 additional risk factor beyond menopause (low body weight, parental hip fracture, current smoking, excess alcohol consumption) 1
- Any woman with a fragility fracture: Immediate DXA and treatment initiation, regardless of age 1, 2
Screening Method
- Dual-energy x-ray absorptiometry (DXA) at central sites (total hip, femoral neck, or lumbar spine) is the gold standard and only acceptable screening modality 1, 3
- DXA uses low radiation doses and correlates directly with bone strength and fracture outcomes 1
- Measure BMD at all three sites (lumbar spine, femoral neck, total hip) because fracture risk at a specific site is best predicted by measuring that site 1, 2
Diagnostic Criteria
T-Score Classification
- Normal: T-score ≥ -1.0 1, 2
- Osteopenia (low bone mass): T-score between -1.0 and -2.5 1, 2
- Osteoporosis: T-score ≤ -2.5 at the hip or spine 1, 2
Use the lowest T-score from any of the three measured sites (lumbar spine, femoral neck, or total hip) to classify bone density status. 2
Clinical Diagnosis Without DXA
A fragility fracture of the hip, vertebra, proximal humerus, pelvis, or distal forearm establishes an osteoporosis diagnosis irrespective of measured T-score 2
Critical Pitfall to Avoid
Do not use lumbar spine BMD measurements in patients with existing vertebral fractures, severe osteoarthritis, or aortic calcification—these conditions falsely elevate BMD values and will underestimate fracture risk 2
Fracture Risk Assessment
FRAX Calculation (Essential Step)
Calculate 10-year fracture probability using the WHO FRAX tool, which incorporates: 1, 2
- Age and sex
- Body mass index
- Femoral neck BMD (if available)
- Prior fragility fracture
- Parental hip fracture
- Current smoking
- Glucocorticoid use (≥3 months at ≥5 mg prednisone daily)
- Rheumatoid arthritis
- Secondary osteoporosis causes
- Alcohol intake (≥3 drinks/day)
Do not rely solely on T-scores without FRAX calculation for osteopenic patients, as many fractures occur within the osteopenic range. 2
Vertebral Fracture Assessment
Perform baseline vertebral fracture assessment (VFA) imaging using DXA because asymptomatic vertebral fractures are the strongest predictor of future fractures and mandate treatment regardless of FRAX score 2
Treatment Initiation Criteria
Initiate pharmacologic therapy when ANY of the following are present: 2
- T-score ≤ -2.5 at lumbar spine, femoral neck, or total hip
- History of fragility fracture (hip, vertebral, proximal humerus, pelvis, or distal forearm)
- Osteopenia (T-score -1.0 to -2.5) PLUS 10-year FRAX hip fracture risk ≥3% OR major osteoporotic fracture risk ≥20%
First-Line Pharmacologic Treatment
Oral Bisphosphonates (Mandatory First-Line)
Oral bisphosphonates are the required first-line agents based on high-certainty evidence showing 50% reduction in hip fractures and 47-56% reduction in vertebral fractures, with the most favorable balance of efficacy, safety, and cost. 2, 4, 5
- Alendronate 70 mg orally once weekly (preferred)
- Risedronate 35 mg orally once weekly OR 150 mg once monthly
Administration instructions (critical for efficacy): 2, 6
- Take on an empty stomach with 8 oz plain water
- Remain upright (sitting or standing) for 30-60 minutes after dose
- Wait at least 30 minutes before eating or taking other medications
- Separate from calcium supplements by several hours (calcium inactivates bisphosphonates)
Mechanism of Action
Alendronate binds to bone hydroxyapatite and specifically inhibits osteoclast activity, reducing bone resorption without directly affecting bone formation 6
Alternative Pharmacologic Options
Denosumab (Second-Line)
Denosumab 60 mg subcutaneously every 6 months is indicated when: 2, 4
- Bisphosphonates are contraindicated (severe renal impairment with eGFR <35 mL/min, esophageal disorders)
- Patient cannot tolerate oral bisphosphonates
CRITICAL WARNING: Upon discontinuation of denosumab, transition promptly to a bisphosphonate to avoid rebound vertebral fractures caused by rapid bone loss—abrupt discontinuation without transition is associated with multiple vertebral fractures 2, 4
Agents to Avoid
The following agents should NOT be used for osteoporosis treatment due to unfavorable benefit-to-harm ratios: 2, 4
- Menopausal estrogen therapy (increased stroke, venous thromboembolism, breast cancer risk)
- Estrogen plus progestogen therapy (higher invasive breast cancer and breast cancer mortality)
- Raloxifene (elevated thromboembolic events, pulmonary embolism, cerebrovascular death)
Universal Non-Pharmacologic Management
All patients require the following interventions regardless of whether they receive drug therapy: 2, 4
- Calcium 1,000-1,200 mg daily (dietary plus supplement) 2, 5
- Vitamin D 800-1,000 IU daily (target serum 25-hydroxyvitamin D ≥20 ng/mL) 2, 5
- Weight-bearing exercise ≥30 minutes on most days (walking, jogging) 2, 4
- Resistance and balance training to reduce fall risk 2, 4
- Mandatory smoking cessation counseling 2, 4
- Limit alcohol to <3 drinks per day 2, 4
- Fall-prevention strategies: home safety assessment, vision correction 2
Evaluation for Secondary Causes
Prior to treatment, obtain laboratory studies to identify reversible secondary osteoporosis: 2
- Serum 25-hydroxyvitamin D
- Calcium
- Phosphorus
- Parathyroid hormone
- Thyroid-stimulating hormone
- Complete blood count
- Comprehensive metabolic panel (creatinine, liver enzymes)
Secondary causes are identified in 44%-90% of postmenopausal women with osteoporosis, most commonly: 2, 4
- Vitamin D deficiency
- Primary hyperparathyroidism
- Hyperthyroidism (including iatrogenic excess levothyroxine)
- Chronic glucocorticoid use (≥5 mg prednisone daily for ≥3 months)
- Hypogonadism or premature menopause
- Malabsorption disorders
- Excessive alcohol consumption
Monitoring Strategy
During Treatment
Routine BMD testing is NOT recommended during the first 5 years of pharmacologic therapy because evidence does not show outcome benefit—bisphosphonates reduce fractures even when BMD does not increase or actually decreases 2, 4
When Monitoring Is Indicated
If BMD monitoring is clinically necessary (suspected non-adherence, secondary cause): 2
- Repeat DXA in 1-2 years using the same scanner and protocol
- Compare absolute BMD values (g/cm²), NOT T- or Z-scores
- Consider changes significant only if they exceed the facility's least significant change (typically 3%-5%)
After 5 Years
Reassess fracture risk using FRAX to determine if continued therapy is warranted 2, 4
Common Pitfalls to Avoid
Do not diagnose osteoporosis in premenopausal women or men <50 years using T-scores—use Z-scores instead, and a Z-score ≤-2.0 is considered abnormal 1, 2
Do not continue denosumab indefinitely without a planned transition to bisphosphonate—abrupt discontinuation leads to rapid bone loss and increased fracture risk 2
Do not use quantitative CT or peripheral DXA for diagnosis—only central DXA at hip and spine is acceptable for diagnosis and treatment decisions 1
Do not screen postmenopausal women <50 years unless they have a fragility fracture or specific high-risk conditions 1
Adverse Effects Monitoring
Common (Non-Serious)
- Mild upper GI symptoms with bisphosphonates 4
- Influenza-like symptoms, myalgias, arthralgias, headache (especially after zoledronic acid) 4
- Rash/eczema with denosumab 4
Rare but Serious
High-certainty evidence shows bisphosphonates cause no difference in serious adverse events compared to placebo at 2-3 years, but rare events include: 2, 4
- Osteonecrosis of the jaw
- Atypical subtrochanteric femoral fractures