What is the difference between the definitions of osteopenia and osteoporosis?
Osteopenia is a decrease in bone mass; osteoporosis is a markedly decreased bone mass such that fracture risk goes up
What part of the bone does osteoporosis affect the most?
Trabecular bone > cortical bone
In what parts of the skeleton is the high trabecular bone content? 3 listed
- Spine
- Head of femur
- Wrist (distal radius)
Why are elderly white females more likely to develop osteoporosis?
Men reach a higher peak bone mass than women. Bone mass decreases slowly after the age of 30 to 40, and loss is accelerated after menopause. Whites lose more mass than blacks.
What action does oestrogen normally have on bone?
Suppression of osteoclast activity
What are calcium, PTH, ALP levels in osteoporosis?
Normal - high yield
What produces RANK ligand? Where is its receptor? What is its function?
- Produced by osteoblasts
- RANK receptor is on osteoclasts
- Plays key role in osteoclast formation, function and survival
What inhibits RANK ligand? What is the function of this? What produces this inhibitor?
Osteoprotegerin (OPG): regulates bone resorption
Osteoblasts (also produce RANK ligand)
How do glucocorticoids cause osteoporosis on a molecular level?
- Suppress synthesis of OPG
- Increase production of RANK receptor on osteoclasts
END RESULT→ Increased bone resorption + reduced bone formation
What are the two main lifestyle factors that can increase osteoporosis risk?
Smoking, alcohol
Which antiepileptic drugs increase the risk of osteoporosis with long-term therapy? Explain why this happens
Phenobarbital, phenytoin, carbamazepine
- cytochrome P450 enzyme inducers
- increases breakdown of vitamin D → less calcium → increased PTH → bone loss
Explain how to avoid iatrogenic hyperthyroidism. How would fracture risk be altered if this was not prevented?
Measuring TSH levels: if low this indicates a lower dose of levothyroxine is needed. Hyperthyroidism accelerates bone loss and increases risk of osteoporosis and fractures
How can you diagnose osteoporosis? Two points
- Fragility fracture (fall from standing height or less causing fracture) or spontaneous compression fracture
- T score -2.5 or less
Explain how a DEXA scan measures the T score. What does the T score mean?
Dual energy x-ray absorptiometry
- Two x-rays of different energy levels aimed at bones (spine and hip)
- T score is patient’s bone mineral density vs density of a healthy 30-year-old
- >-1.0 is normal
Why are many elderly people short?
Shrinkage of spine over time from compression fractures, as well as kyphosis
