Makindo Medical Notes

Related Subjects: | Calcium Physiology | Bisphosphonates | Osteoporosis | Osteonecrosis of the Jaw

The World Health Organization (WHO) classification of osteoporosis is widely adopted and is based on the measurement of Bone Mineral Density (BMD), with reference to the number of standard deviations (SDs) from the BMD of an average 25-year-old woman (T-score).

About

• Osteoporosis is a bone disease characterized by decreased bone mass and deterioration of bony microarchitecture.
• In practice, it is diagnosed in individuals with a T-score < -2.5 SD or those with fragility fractures while at risk.
• Causes can include aging, other diseases, or the use of certain medications.

Classification

• Normal: T-score of -1 SD or higher.
• Osteopenia: T-score between -1 and -2.5 SD.
• Osteoporosis: T-score < -2.5 SD.
• Established Osteoporosis: T-score < -2.5 SD with associated fragility fracture(s).

Causes of Non-Age Related Osteoporosis

• Smoking
• Parental history of osteoporosis
• Alcohol consumption >4 units daily
• Rheumatoid arthritis
• Low BMI (<19)
• Prolonged immobility
• Untreated menopause
• Steroid use (>5mg/day of prednisolone)
• Hyperthyroidism, hyperparathyroidism, hypercalciuria
• Low testosterone (e.g., treatment of prostate cancer)
• Early menopause
• Renal or liver failure
• Erosive/inflammatory bone diseases (e.g., multiple myeloma, rheumatoid arthritis)
• Dietary calcium deficiency/malabsorption
• Type 1 Diabetes Mellitus

Clinical Presentation

• Often clinically and biochemically silent until a fracture occurs.
• Vertebral Fractures: Back pain, loss of height, kyphosis.
• Appearance of abdominal swelling due to the collapse of lumbar vertebrae.
• Other fractures: Neck of femur, Colles' fracture, humeral fractures.

Risk Factors for Osteoporosis

• Female sex
• Increasing age
• Caucasian or Asian ethnicity
• Smoking
• Low exposure to estrogen (late menarche, early menopause)
• Malabsorption syndromes (e.g., coeliac disease)
• Steroid usage (e.g., COPD, Cushing's syndrome)
• Hyperthyroidism, hyperparathyroidism
• Family history of osteoporosis
• Alcoholism
• Chronic heparin injection
• Methotrexate use
• Diabetes mellitus
• Immobilization
• Gaucher's disease
• Multiple myeloma
• Mastocytosis
• Note: Obesity is not considered a risk factor for osteoporosis.

Investigations

• Blood Tests: Full Blood Count (FBC), Urea & Electrolytes (U&E), Liver Function Tests (LFTs), C-reactive Protein (CRP).
• Imaging: DEXA Scan (Dual-Energy X-ray Absorptiometry): Preferred method for measuring Bone Mineral Density (BMD).
  • Focus on the hip rather than the spine.
  • Bone Mineral Density is compared with that of a young healthy adult.
  • T-score represents the number of standard deviations the BMD is from the young average.
  • Each decrease of 1 SD in BMD increases the risk of hip fracture by approximately 2.6-fold.
  • Not needed in older females with clear evidence of osteoporosis.
• Look for underlying causes in younger patients.

Management

• General Measures:
  • Smoking cessation.
  • Avoid excess alcohol consumption.
  • Engage in weight-bearing and balance exercises.
  • Maintain a calcium and vitamin D-rich diet.
  • Implement home fall risk prevention strategies.
• Bisphosphonates:
  • Alendronate: 10 mg daily or 70 mg weekly.
  • Risedronate Sodium: 5 mg daily or 35 mg once weekly.
  • These drugs increase BMD, reduce hip and vertebral fractures, and lower fracture risk by about 50% in postmenopausal osteoporosis.
  • Administration requires the patient to be able to sit up or stand and have no swallowing difficulties.
• Calcium and Vitamin D:
  • Calcium: 1g/day.
  • Vitamin D: 800 IU/day.
  • Target serum 25-hydroxyvitamin D level: ≥20 ng/mL (50 nmol/L).
• Denosumab: 60 mg subcutaneous injection every 6 months. It is a monoclonal antibody to RANK ligand, reducing bone resorption.
• Strontium Ranelate: Stimulates bone formation and reduces bone resorption. Dosage: 2g per sachet.
• Raloxifene: A selective estrogen receptor modulator that reduces bone resorption by osteoclasts.
  • Side effects: Hot flushes, venous thromboembolism (VTE), muscle cramps.
  • Benefits: Reduces breast cancer risk.
  • No effect on stroke or heart disease.
  • No evidence of benefit on non-vertebral fractures.
• Teriparatide: A recombinant form of parathyroid hormone used in the treatment of advanced osteoporosis.
  • Indicated in patients with a very high risk of fracture and T-score < -4 SD.
  • Dosage: 20 mcg daily by subcutaneous injection (maximum duration: 18 months, not to be repeated).
• Testosterone: May help in hypogonadal men by promoting trabecular connectivity.

Management of Steroid-Induced Osteoporosis

• At risk are those taking more than 7.5 mg/day of prednisolone for 3 or more months.
• Patients > 65 or those with a history of fragility fractures should be offered bone protection.
• Patients < 65 should undergo a bone density scan, with further management based on DEXA scan T-score.
  • Greater than 0: Reassure the patient.
  • Between 0 and -1.5: Repeat bone density scan in 1-3 years.
  • Less than -1.5: Offer bone protection.
• First-line treatment: Alendronate.
• Ensure patients are calcium and vitamin D replete.

Summary

SIGN Guidance

Primary Prevention

Secondary Prevention

Bisphosphonates

References

• FRAX® Fracture Risk Assessment Tool
• Scottish Intercollegiate Guideline Network. Management of Osteoporosis and the Prevention of Fragility Fractures. Edinburgh: SIGN; 2015. (SIGN Guideline No. 142)