Osteoporosis Flashcards
Define osteoporosis
Imbalance of bone remodelling cause a decrease in bone mass and bone density, and a deterioration of bone microarchitecture. Clinically defined as 2.5 standard deviations or greater below average youth bone density.
- Most common bone disease and major public health concern
- Affects areas of high trabecular bone the most: spine, wrist, head of femur
List osteoporosis risk factors
- Age
- Female
- Menopause
- Family history
- Low physical activity
- Smoking
- Alcohol
- Low vitamin D levels
- Low dietary calcium
- Drugs (e.g. corticosteroids)
- Diseases (e.g. hyperthyroidism)
Describe the concept and mechanism of osteo porosis
Osteoporosis occurs when the coupling of bone resorption and bone formation is disrupted. Factors include:
- Genetic
- Age
- Mechanical loading
- Mineral balance: vitamin D, PTH, sex steroids
Best way to prevent osteoporosis?
Maximize peak bone mass as youth and minimize bone loss with age. Peak bone mass affected by: - Genetics - Amount of physical activity - Dietary calcium intake - Smoking
Outline roles of vitamin D
- Ensures that enough blood calcium and phosphate is available
- Low vitamin D leads to increased PTH
Outline roles of PTH
- Increases bone resorption
- Reduces bone density
- Increased by both low vitamin D or low calcium
Outline roles of sex hormones:
- Maintains coupling between osteoblasts and osteoclasts
- Keeps bone cells alive
- Reduce bone turnover
- Mechanically strengthen bone
Explain mechanical loading’s interaction with maintenance of bone mass
- Needed to promote formation of bone
- Causes bone to remodel in areas that experience stresses
Explain interaction of low sex hormones in maintenance of bone mass
Low estrogen and testosterone: Results in impaired coupling resorption and formation -> net effect is bone loss. Deficiency from: - anorexia - Congenital deficiency - Alcoholism - Menopause - Age
List fracture risks from low sex hormones
- Low bone mass
- More dead bone cells
- Loss of connectivity
- High bone turnover
- Poor bone geometry
Explain interaction of testosterone and maintaining bone mass
Testosterone (androgens)
- Causes bone remodelling to resorb inner bone and form bone on outer surface
- Greater strengthens the bone (per mass)
Explain interaction of oestrogen and maintenance of bone mass
Estrogen
- Maintains balance between bone formation and resorption
- Keeps bone cells alive (e.g. osteoblasts and osteocytes)
- Reduces rates of bone turnover
Outline the mechanisms of bone loss due to glucocorticoid excess or sex steroid deficiency
- E.g. cortisone
- Effects -> cause decrease in bone mass:
1) Gut: decreases calcium absorption
2) Kidney: Increases calcium loss
3) Bone: decreases osteoblasts (i.e. lowers bone formation)
Explain the mechanisms of drugs used to treat osteoporosis
Pharmacological treatment for OP:
- Bone resorption inhibitors:
1) Bisphosphonates -> kill osteoclasts on bone surface; inhibit bone remodelling: e.g. risedronate, alendronate and zoledronic acid.
2) RANKL-inhibitor - Bone formation stimulators: calcium and vitamin D
Discuss issues associated with hip fractures, including risk factors for falls, disability and death after hip fracture and prevention of falls.
Hip fracture:
- 20000 per year
- Most serious fracture for elderly
- 20% die within a year
- Most survivors don’t regain full function.
Risk factors for hip fracture:
- Osteoporosis
- Impaired balance
- Muscle weakness
- Low body weight
- Tallness
- Smoking
- Low calcium intake
