At what bone mineral density T-score should medication be started for osteoporosis?

When to Start Medication for Osteoporosis

Pharmacologic treatment for osteoporosis should be initiated in patients with a T-score ≤ -2.5 at the lumbar spine, femoral neck, or total hip, or in those with a history of fragility fracture regardless of BMD. 1, 2

Diagnostic Thresholds for Treatment

T-Score Based Recommendations

• Treatment is strongly recommended for all postmenopausal women and men over 50 years with a T-score ≤ -2.5 (WHO definition of osteoporosis) 1
• Diagnosis is based on the lowest T-score at any of the recommended DXA measurement sites (lumbar spine, femoral neck, or total hip) 2
• A history of fragility fracture (hip, spine, shoulder, forearm) warrants treatment regardless of BMD, as this is a strong predictor of future fractures 2

FRAX-Based Recommendations for Osteopenia

• For patients with T-scores between -1.0 and -2.5 (osteopenia), use the FRAX tool to guide treatment decisions 1, 2
• Treatment is recommended when the 10-year probability of:
  • Hip fracture is ≥ 3% OR
  • Major osteoporotic fracture is ≥ 20% 1

Special Populations with Modified Thresholds

Glucocorticoid-Induced Osteoporosis

• For patients on long-term glucocorticoids, the treatment threshold is lower (T-score ≤ -1.5) 3
• This lower threshold is justified because fractures occur at higher BMD levels in glucocorticoid-induced osteoporosis compared to postmenopausal osteoporosis 3
• In patients over 65 years on glucocorticoids, treatment may be initiated without prior DXA as most will have T-scores below -1.5 3

Patients with Inflammatory Conditions

• High-risk threshold for intervention in patients with inflammatory bowel disease on long-term steroids is T-score ≤ -1.5 1
• Consider a FRAX 10-year risk of 20% for major osteoporotic fracture as an alternative threshold 1

Cancer Patients on Aromatase Inhibitors

• For patients on aromatase inhibitors, initiate treatment if T-score is < -2.0 or if the patient has prior fracture 2

Efficacy Considerations

• Anti-osteoporotic medications reduce fracture risk regardless of baseline BMD, though effects tend to be larger in those with T-scores ≤ -2.5 4
• Significant fracture risk reduction is seen even in patients with T-scores above -2.5, supporting treatment in high-risk individuals even without severe osteoporosis 4
• The number needed to treat (NNT) is much higher in osteopenic patients (NNT>100) compared to patients with fractures and T-scores below -2.5 (NNT 10-20) 5

Common Pitfalls to Avoid

• Relying solely on BMD without considering clinical risk factors can miss approximately half of the people who will develop osteoporotic fractures 2
• Failing to recognize that vertebral fractures are diagnostic of osteoporosis and warrant treatment, even if BMD is not in the osteoporotic range 2, 3
• Overlooking the need for treatment in patients with fragility fractures regardless of BMD 2
• Not considering lower treatment thresholds for special populations (e.g., those on glucocorticoids) 1, 3

Supportive Measures

• All patients should receive adequate calcium (1000-1200 mg/day) and vitamin D (600-800 IU/day based on age) 1
• Recommend weight-bearing exercise, smoking cessation, and limiting alcohol consumption 1, 2
• Address potentially modifiable risk factors: vitamin D deficiency, low calcium intake, sedentary lifestyle 6

By following these evidence-based guidelines for initiating osteoporosis treatment, clinicians can effectively reduce fracture risk and improve outcomes in at-risk patients.