Osteoporosis

Pathology

• Low bone mass, a change in the microarchitecture of bone tissue, with a consequent increase in bone fragility and susceptibility to fracture

Public Health Significance

• Increased incidence of fractures in people with osteoporosis causes significant health and social care burdens on the patient, their family and the healthcare system.
• There is evidence suggesting cost-effectiveness in screening and pharmacologic therapy for osteoporosis. However, differences in the healthcare settings between countries lead to differing strategies in osteoporosis screening.

Classification

• Generalized
  • Primary: Trabecular bone predominated; need to rule out secondary osteoporosis first
    • Post-menopausal
    • Advanced age
    • Idiopathic Juvenile Osteoporosis
  • Secondary: Cortical bone predominated
    • Disorder of collagen metabolism: Osteogenesis imperfecta
    • Endocrine/metabolic: thyrotoxicosis, hyperparathyroidism
    • Drugs: glucocorticoids, excessive thyroid medication
    • Nutritional: Malabsorption syndrome, Post gastric operation, Vitamin D deficiency
    • Others: rheumatoid arthritis
• Localised
  • Prolonged immobilization

Diagnosis (for generalised primary osteoporosis in adults)

• Clinical
• Bone densitometry
  • Dual-energy X-ray absorptiometry (DXA) = gold standard
    • Measurement site
      • Spine: sensitive, can be used for therapy follow up
      • Hip: most predictive of hip fracture risk
      • 1/3 Distal end radius
    • BMD reporting
      • T-score: used in post-menopausal/senile groups
        • Normal ≥ -1.0
        • -2.5 < Osteopaenia < -1.0
        • Osteoporosis ≤ -2.5
      • Z-score: used in premenopausal women or men < 50 years
        • Within the expected range for age: > -2.0
        • Below the expected range for age: ≤ -2.0
        • ^*Osteoporosis cannot be diagnosed with BMD alone in these groups

Indication for bone densitometry (According to Thai Osteoporosis Foundation: TOPF 2021)

Screening

• Age: Female ≥ 65 yrs, Male ≥ 70 yrs
• Women with a history of menopause/ Post bilateral Oophorectomy before age 45 yrs
• Premenopausal women with hypoestrogenism for more than 1 yr
• Postmenopausal women aged < 65 yrs or men aged < 70 years with any of the following risks
  • Use glucocorticoid equivalent of prednisolone 5 mg/day for at least 3 mo
  • Father or mother’s history of low-trauma hip fracture
  • BMI < 20 kg/mm²
  • Height loss ≥ 4 cm from maximal height or ≥ 2 cm from previous height
  • Women with aromatase inhibitor therapy
  • Men with androgen deprivation therapy
  • Radiological evidence of osteopenia, vertebral fracture
  • History of fragility fracture

Diagnosis and follow up

• Before starting osteoporosis treatment
• 1-2 years after treatment

Prevention

• Lifestyle modification
  • Adequate calcium and Vitamin D intake (including supplements)
  • Smoking cessation, avoiding heavy alcohol use
  • Weight-bearing exercise

Treatment

• 1^st line: Bisphosphonate
  • E.g.: alendronate(po), risedronate(po), ibandronate, zoledronic acid
  • Oral drug cause esophageal complications, e.g., GERD, esophagitis, esophageal ulcers
• 2^nd line
  • Teriparatide: PTH analogue
  • Denosumab: a monoclonal antibody to RANK-L (Osteoclast inhibitor)
  • SERM: raloxifene