Osteoporosis

Overview

Snapshot

• A 68-year-old woman presents to her primary care physician with lower back pain of acute onset. She denies any trauma to the spine or any radiation of pain. Her last menstrual period was when she was 51-years-old. On physical exam, she has tenderness to palpation at the level of L4-L5, as well as a loss of lumbar lordosis. A dual-energy x-ray absorptiometry (DEXA) scan reveals a T-score of -2.7.

Introduction

• Clinical definition
  • decreased bone mass (osteopenia) that significantly increases the patient’s risk of fracture
• Epidemiology
  • incidence
    • most common types of osteoporosis are
      • post-menopausal
      • senile
  • risk factors 
    • post-menopausal women
    • being ≥ 65 years of age
    • people of Caucasian and Asian descent
    • lifestyle factors
      • poor physical activity 
      • vitamin D deficiency and poor calcium intake
      • smoking
      • alcohol use disorder
    • medications
      • warfarin
      • lithium
      • proton pump inhibitors
      • glucocorticoids 
    • hyperparathyroidism
    • hyperthyroidism
    • multiple myeloma
    • malabsorption syndromes
    • low body weight 
      • higher body weight associated with higher bone density
• Pathogenesis
  • in young adulthood, peak bone mass is achieved and this is determined by a number of factors (e.g., genetics)
    • after this peak bone mass is attained, there is a small decrease in bone formation with every cycle of bone remodeling
      • senile osteoporosis
        • osteoblasts have their biosynthetic and proliferative ability reduced with age
      • poor physical activity
        •  mechanical force on bone stimulates bone remodeling
          • athletes have increased bone density
        • decreased physical activity results in bone loss
        • weight-bearing physical activity results in increased bone mass and protects against osteoporosis 
      • decreased estrogen levels
        • such as in menopause, decreased estrogen levels increase bone resportion and formation
          • however, the rate of formation is less than resorption resulting in a net bone loss
          • increased osteoclast activity is significant in areas of bone with large surface area
            • such as the vertebral bodies, leading to vertebral compression fractures 
      • there is trabecular and cortical bone loss 
• Prognosis
• generally good if detected early and appropriately managed

Presentation

• Symptoms
  • fractures (e.g., vertberal and hip), otherwise, patients are typically asymptomatic
• Physical exam
• may see loss in height

Imaging

• DEXA
  • indication
    • all women ≥ 65 and all men ≥ 70 years of age 
  • notes
• T-score ≤ -2.5

Studies

• Labs
  • serum calcium, phosphorus, parathyroid hormone, and alkaline phosphatase are normal 
• Histology
• histologically normal; however, there is a decreased quantity of normal bone

Differential

Laboratory Abnormalities in Select Bone Disorders
Etiology	Serum Phosphate	Serum Calcium	Serum Alkaline Phosphatase	Parathyroid Hormone
Osteomalacia / rickets	Decreased	Decreased	Increased	Increased
Osteoporosis	Normal	Normal	Normal	Normal
Osteopetrosis	Normal	Normal or decreased	Normal	Normal
Paget disease of the bone	Normal	Normal	Increased	Normal
Osteitis fibrosa cystica	Primary hyperparathyroidismdecreasedSecondary hyperparathyroidismincreased	Primary hyperparathyroidismincreasedSecondary hyperparathyroidismdecreased	Primary and secondary hyperparathyroidismincreased	Primary and secondary hyperparathyroidismincreased
Hypervitaminosis D	Increased	Increased	Normal	Decreased

Treatment

• Conservative
  • calcium and vitamin D supplementation
  • strength training
  • smoking cessation
• Medical
  • bisphosphonates
    • indication
      • first-line for pharmacologic therapy in osteoporosis
  • teriparatide
    • indication
• considered first-line in patients with a very high risk of fracture

Complications

• Fragility fractures
  • hip
  • distal radius
  • vertebral body
  • proximal humerus