Osteoporosis

Intro & Risks - Bone Basics & Breakers

• Definition: Low bone mass, microarchitectural decay, ↑ fracture risk.

  ⭐ WHO: Osteoporosis = BMD T-score ≤ -2.5 (spine, hip, femoral neck).

• Epidemiology: Common in postmenopausal women, elderly. India: High; ~1/3 women, ~1/8 men >50 yrs.
• Risk Factors:
  • Non-Modifiable: Age, female, genetics, early menopause (<45 yrs), prior fracture.
  • Modifiable: 📌 ACCESS
    • Alcohol
    • Corticosteroids (≥5mg pred/day, ≥3 mo)
    • Calcium low
    • Estrogen low
    • Smoking
    • Sedentary
  • Others: Vit D deficiency, low BMI, some meds (anticonvulsants, PPIs).

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Pathophys & Types - How Bones Weaken

• Pathophysiology: Bone remodeling imbalance: ↑osteoclast activity (resorption), ↓osteoblast activity (formation).

  • RANKL/OPG Pathway:
    • ↑RANKL (Receptor Activator of Nuclear factor Kappa-B Ligand) → ↑osteoclast differentiation & activity.
    • OPG (Osteoprotegerin - decoy receptor for RANKL) → ↓osteoclast activity.
    • Estrogen ↓ (e.g., postmenopause) → ↑RANKL & ↓OPG → ↑bone resorption.

  ⭐ In postmenopausal osteoporosis, estrogen deficiency leads to increased expression of RANKL and decreased OPG, tipping the balance towards bone resorption.

• Types of Osteoporosis:

  • Primary Osteoporosis:
    • Type 1 (Postmenopausal): Estrogen ↓. Affects mainly trabecular bone.
    • Type 2 (Senile): Age-related (typically > 70 years). Affects trabecular & cortical bone.
  • Secondary Osteoporosis: Result of other conditions or medications.
    • Key Causes: Corticosteroids (most common drug-induced), hyperparathyroidism, anticonvulsants, malabsorption syndromes, Chronic Kidney Disease (CKD).

Diagnosis & Workup - Spotting Brittle Bones

• Clinical Features: Often silent until fragility fracture.
  • Common sites: Hip, vertebra, wrist.
  • Signs: Height loss, kyphosis.
• Diagnosis:
  • DEXA Scan: Gold standard.
    • T-score: Osteopenia (-1.0 to -2.4), Osteoporosis (≤ -2.5).
    • Z-score: For premenopausal women, men <50 yrs, children.
  • FRAX Tool: Calculates 10-year fracture probability.
• Key Investigations (to exclude secondary causes):
  • Serum Calcium, Phosphate, ALP.
  • Vitamin D (25-OHD).
  • PTH.

⭐ A DEXA T-score of -2.5 or lower at the lumbar spine, total hip, or femoral neck is diagnostic of osteoporosis. A history of fragility fracture also diagnoses clinical osteoporosis irrespective of T-score.

Treatment & Prevention - Building Bone Armor

• Non-Pharmacological & Prevention Strategies:
  • Calcium & Vitamin D supplementation (e.g., Calcium 1000-1200mg/day, Vitamin D 800-1000 IU/day)
  • Regular weight-bearing & muscle-strengthening exercise
  • Smoking cessation & alcohol moderation (≤1-2 drinks/day)
  • Fall prevention measures (home safety, balance training)
• Pharmacological Therapy:
  • Antiresorptives: Target osteoclast activity
    • Bisphosphonates: Alendronate (70mg/week orally), Risedronate (35mg/week orally or 150mg/month orally), Zoledronic acid (5mg IV annually)
    • Denosumab (RANKL inhibitor): 60mg SC every 6 months
    • SERMs (e.g., Raloxifene 60mg/day orally - esp. for younger postmenopausal women with spinal osteoporosis)
  • Anabolics: Stimulate osteoblast activity
    • Teriparatide (PTH analogue): 20mcg SC daily (max 2 years)

⭐ Oral bisphosphonates (e.g., Alendronate) are generally first-line pharmacological therapy. Must be taken on an empty stomach with a full glass of water, remaining upright for at least 30-60 minutes to prevent esophagitis. 📌 Alendronate: All Alone (empty stomach), Ample wAter, Afterwards Avoid recumbency.

High‑Yield Points - ⚡ Biggest Takeaways

• Osteoporosis is defined by low bone mass and microarchitectural deterioration, leading to ↑ fracture risk.
• Most common fractures: Vertebral compression fractures (most frequent), hip, and distal radius (Colles').
• Gold standard diagnosis: DEXA scan with a T-score ≤ -2.5.
• Serum calcium, phosphate, and ALP are typically normal in uncomplicated osteoporosis.
• Key risk factors include postmenopausal state, prolonged corticosteroid use, and vitamin D deficiency.
• Bisphosphonates (e.g., alendronate) are first-line treatment; teriparatide for severe cases.
• The FRAX score is a tool used to estimate the 10-year probability of major osteoporotic fracture.