Osteoporosis Flashcards
What are the two main types of bone?
- Cortical bone
- Trabecular bone
What percentage of the body is made up of the cortical bone?
80%
What percentage of the body is made up of the trabecular bone?
20%
What is the cortical bone?
- Compact bone that forms the dense outer supporting structure
What is the trabecular bone?
- Spongy bone that forms the inner supporting structure
- Composed of a lattice or network branching bone spicules or trabecular and spaces filled with bone marrow
Bone is a static tissue. True or False
False
What is the bone renewal process called?
Remodelling - Old bone removed and replaced by new bone
What are bone resorbing cells called?
Osteoclasts
What are bone forming cells called?
Osteoblasts
What are osteoblasts?
- Fill in bony cavity with bone matrix
- Release cytokines to attract osteoclasts
What are osteoclasts?
- Release proteases which dissolve the bone mineral matrix and collagen and clear damaged bone
- Release chemicals that attract osteoblasts
Bone remodelling is under the control of what factors?
- Systemic hormones (parathyroid hormone and sex hormones (oestrogen and androgens))
- Activated vitamin D
- Cytokines (Interleukin-1 and Interleukin-6/ TNF-alpha/ GCSF)
- External factors
What is bone mass determined by:
- Peak bone mass that was attained at around age 30 years
- Rate of bone loss that commences in 4th decade
What is osteoporosis?
- Is a common metabolic bone disease characterised by reduction in bone mass per unit volume (thinning of the bones) that occurs with increasing age
- Micro-architectural deterioration of bone tissue with a consequent increase in bone fragility and susceptibility to fracture
Why is genetics involved in rate of bone loss?
Genetics factors (approx 75%)
- More likely to have osteoporosis if strong family history
- Possible involvement of several genes investigated: Vitamin D receptor gene / Oestrogen receptor / Interleukin (IL) -6 gene
What environmental factors affect rate of bone loss?
- Low calcium intake and/or absorption
- Low vitamin D intake or lack of exposure to sunlight
- Physical inactivity
- Alcohol
- Smoking
- Thin body type
How does WHO define osteoporosis?
WHO defines osteoporosis on the basis of bone mineral density (BMD) related to age
What does BMD stand for?
Bone mineral density
What is a T-score?
The number of standard deviations by which the individuals BMD (g/cm2) differs from the mean peak BMD for young adults of the same gender
When does fracture risk double?
Fracture risk doubles for every standard deviation below the mean
