Learning Objectives

• Explain the pathophysiology of Osteoporosis, specifically the imbalance between osteoblasts and osteoclasts.
• Identify the diagnostic criteria (T-score) and screening guidelines for bone mineral density.
• List key risk factors, including hormonal, lifestyle, and pharmacological causes.
• Recognize the clinical presentation of vertebral compression fractures and other common fracture sites.

1. Pathophysiology and Bone Loss

Osteoporosis is characterized by a reduction in both trabecular (spongy) and cortical bone mass. Crucially, the bone that remains is normally mineralized—there is just less of it.

• Mechanism: Primarily due to increased bone resorption. This is often triggered by decreased estrogen levels (menopause), which normally limits osteoclast activity.
• Laboratory Values: A high-yield Step 1 fact is that Serum Calcium, Phosphate, and PTH are typically NORMAL in primary osteoporosis.
• Secondary Causes:
  • Drugs: Long-term Corticosteroids, Anticonvulsants, Heparin, and PPIs.
  • Conditions: Hyperparathyroidism, Multiple Myeloma, Malabsorption, and Hyperthyroidism.
  • Environment: Prolonged microgravity (space travel) or immobilization.

2. Diagnosis and Screening

Osteoporosis is often “silent” until a fracture occurs. Screening is essential for early detection.

• DEXA Scan: Dual-energy X-ray absorptiometry at the lumbar spine, total hip, and femoral neck.
• T-score -2.5: Diagnostic for Osteoporosis. (T-score between -1.0 and -2.5 is Osteopenia).
• Fragility Fracture: A diagnosis can be made regardless of T-score if a patient suffers a fracture from minimal trauma (e.g., falling from standing height).
• Screening: Recommended for all females 65 years old.

3. Clinical Consequences

Loss of bone density leads to characteristic skeletal changes and “fragility” fractures.

• Vertebral Compression Fracture: Presents with acute back pain, loss of height, and Kyphosis (Dowager’s hump).
• Colles Fracture: Fracture of the distal radius (common in FOOSH injuries).
• Hip Fractures: Specifically of the femoral neck; associated with high morbidity and mortality in the elderly.

Activity: Osteoporosis vs. Other Bone Diseases

Activity: