Osteoporosis

Definition | Aetiology | Pathophysiology | Risk Factors | Signs and Symptoms | Investigations | Management | References

Definition

Osteoporosis is a skeletal disorder characterised by decreased bone density and mass, leading to fragile bones that are more susceptible to fractures. It is often referred to as a "silent disease" because bone loss occurs without symptoms until a fracture occurs.

Aetiology

Osteoporosis results from an imbalance between bone resorption and bone formation. Factors contributing to this imbalance include:

• Ageing, which naturally decreases bone density
• Menopause, leading to reduced oestrogen levels in women, which accelerates bone loss
• Genetic predisposition, as a family history of osteoporosis increases risk
• Long-term use of corticosteroids or other medications that affect bone metabolism (e.g., anticonvulsants, aromatase inhibitors)
• Chronic conditions such as rheumatoid arthritis, hyperthyroidism, and chronic kidney disease
• Dietary factors, including inadequate intake of calcium and vitamin D
• Lifestyle factors, such as physical inactivity, smoking, and excessive alcohol consumption

Pathophysiology

The pathophysiology of osteoporosis involves:

• Increased osteoclast activity, leading to greater bone resorption
• Decreased osteoblast activity, resulting in reduced bone formation
• Net loss of bone mass, particularly affecting the trabecular (spongy) bone, which leads to reduced bone strength and increased fracture risk
• Disruption of bone microarchitecture, further compromising bone integrity

Risk Factors

• Advanced age, particularly in postmenopausal women
• Family history of osteoporosis or fractures
• Female gender, due to lower peak bone mass and the impact of menopause
• Low body weight or body mass index (BMI)
• Long-term use of corticosteroids or other medications that affect bone metabolism
• Smoking and excessive alcohol consumption
• Chronic conditions such as rheumatoid arthritis, hyperthyroidism, or chronic kidney disease
• Insufficient intake of calcium and vitamin D
• Physical inactivity or sedentary lifestyle

Signs and Symptoms

Osteoporosis is often asymptomatic until a fracture occurs. Signs and symptoms may include:

• Fractures, particularly of the hip, spine, and wrist, often occurring with minimal trauma
• Loss of height over time due to vertebral compression fractures
• Kyphosis, or a stooped posture, resulting from vertebral fractures
• Chronic back pain, often due to vertebral fractures
• Increased risk of falls due to reduced bone strength and muscle weakness

Investigations

Specific investigations to diagnose osteoporosis include:

• Dual-energy X-ray absorptiometry (DEXA) scan: The gold standard for measuring bone mineral density (BMD). Osteoporosis is diagnosed when the T-score is -2.5 or lower.
• Blood tests: To rule out secondary causes of osteoporosis, including serum calcium, phosphate, vitamin D levels, thyroid function tests, and renal function tests.
• X-rays: May show fractures or reduced bone density but are not typically used to diagnose osteoporosis.
• FRAX tool: A risk assessment tool that estimates the 10-year probability of a major osteoporotic fracture based on clinical risk factors and BMD.

Management

Primary Care Management

• Lifestyle modifications: Encouraging weight-bearing exercises, smoking cessation, and reducing alcohol intake.
• Dietary supplementation: Ensuring adequate intake of calcium (1,200 mg/day) and vitamin D (800-1,000 IU/day) through diet or supplements.
• Pain management: Analgesics such as paracetamol or NSAIDs for managing pain associated with fractures.
• Fall prevention: Assessing and addressing factors that increase the risk of falls, including vision correction, home safety measures, and physical therapy for balance training.

Specialist Management

• Bisphosphonates: First-line pharmacological treatment for osteoporosis, including alendronate, risedronate, or zoledronic acid, which work by inhibiting bone resorption.
• Denosumab: A monoclonal antibody that reduces bone resorption, used as an alternative to bisphosphonates, particularly in those who cannot tolerate bisphosphonates.
• Selective oestrogen receptor modulators (SERMs): Such as raloxifene, which mimic oestrogen's beneficial effects on bone without some of its risks.
• Hormone replacement therapy (HRT): May be considered in postmenopausal women for short-term management of menopausal symptoms and bone protection.
• Parathyroid hormone (PTH) analogues: Such as teriparatide, used in severe osteoporosis to stimulate bone formation.
• Regular monitoring: Follow-up DEXA scans every 1-2 years to monitor BMD and assess treatment efficacy.

References

1. NHS (2024) Osteoporosis. Available at: https://www.nhs.uk/conditions/osteoporosis/ (Accessed: 24 June 2024).
2. National Institute for Health and Care Excellence (2024) Osteoporosis: Assessing the Risk of Fragility Fracture. Available at: https://www.nice.org.uk/guidance/cg146 (Accessed: 24 June 2024).
3. British Medical Journal (2024) Osteoporosis: Clinical Features, Diagnosis, and Management. Available at: https://www.bmj.com/content/350/bmj.h2980 (Accessed: 24 June 2024).
4. National Osteoporosis Society (2024) Osteoporosis: Understanding the Disease. Available at: https://nos.org.uk/health-professionals/clinical-publications/ (Accessed: 24 June 2024).

Back to Top