Osteoporosis Flashcards
What is the function of osteoprogenitor cells?
Stem cell population that gives rise to osteobalsts
What is the function of osteoblasts?
Responsible for bone formation, cover the surface of the bone
What is the function of osteocytes?
Mature bone cells- embedded in the lacunae, they are relatively inactive. Maintain the bone matrix through cell-to-cell communication and influence bone remodelling. Mechanosensing
What is the function of osteoclasts?
Multinucleated, they are derived from haematopoietic cells, In response to mechanical stresses and physiological demands they resorb bone matrix by demineralisation
Describe the typical/generic changes in bone mass with increasing age
• 0-25 years: Bone gain, resorption35: Resorption>Formation, bone loss
What does osteoporosis look like macroscopically?
- Decreased size of osteons
- Thinning of trabeculae
- Enlargement of Haversian and marrow spaces
What are the risk factors for osteoporosis?
- Genetic/biological sex (because of menopause)
- Lifestyle/nutrition (less active increases risk)
- Medical conditions
- Drugs
- Previous fragility fracture
Describe the differences between bone mass in males and females
- Males have a larger bone mass overall with a higher peak
- Women’s bone mass decreases suddenly due to menopause (around 50) and then continues to decrease slightly
- Mens bone mass slowly decreases with age after peak bone mass achieved
What lifestyle and nutritional choices increase risk of fracture?
- Smoking
- Excess alcohol
- Sedentary
- Prolonged immobilisation
What medical conditions can increase the risk of fracture?
- anorexia nervosa
- Rheumatoid arthritis
- Early menopause <45 years
- Primary hypogonadism
- Secondary amenorrhea for more than one year
- Hyperthyroidism
- Primary hyperparathyroidism
- Multiple myeloma
- Transplantation
- Chronic renal, pulmonary or gastrointestinal disease
- Cushing’s disease / syndrome
Which drugs can increase the risk of fracture?
- Chronic corticosteroid therapy
- Excessive thyroid therapy
- Gonadotrophin releasing hormone agonist or antagonist
- Anticoagulants
- Anticonvulsants
- chemotherapy
By how many times does a previous wrist fracture increase the risk of:
a) Future hip fracture
b) Future vertebral fracture
a) Doubles the risk
b) Triples the risk
What are the non-modifiable risk factors for osteoporosis
- Biological sex
- Age
- Previous fracture
- Family history
- Long term steroid therapy
- Race
What are the modifiable risk factors for osteoporosis?
- Oestrogen delivery
- Smoking
- Alcohol
- Low calcium
- Low BMI
- Vitamin D deficiency
- Inactivity
What is Type 1 osteoporosis?
- Post menopausal
- Affects mainly cancellous bone
- Vertebral and distal radial fracture is common
- Related to the loss of oestrogen
- Female to male ratio 6:1
What is Type 2 osteoporosis?
- Age related in those over 75 years
- Affects cancellous and cortical bone
- Is related to poor calcium absorption
- Hip and pelvic fractures is common
- Female to male ratio 2:!
What are the clinical consequences of osteoporosis?
- Increase in bone fragility
* Susceptibility to fracture: micro- or fragility fracture
What is a fragility fracture?
- Low energy trauma
- Mechanical forces that would not ordinarily cause fracture
- WHO: “fall from a standing height or less”
Where are the common sites for an osteoporotic fracture?
- Proximal humerus
- Distal radius
- Spine
- Femoral neck
- Vertebral body
Describe the different outcomes of hip fractures and the likelihoods of them
- Fatal in 20-30% of cases
- Only 30% fully recover
- Permanently disables 50%
What investigations can be done
- Blood test
- Full blood count
- Serum biochemistry
- Bone profile
- thyroid function tests
- Testosterone and gonadotrophin levels in men
- X ray of lumbar and thoracic spine (>30% of bone loss is required to be visible)
- Bone density measurement
- DEXA
What is DEXA?
- Low dose x rays with two distinct energy peaks (one absorbed by soft tissue and the other by bone)
- Subtracting one from the other gives a patient’s bone mineral density (BMD)
What is a T score?
• DEXA
• Comparison with a young adult of the same gender with peak bone mass
• >-1 is normal
• -1 to -2.5 is Osteopenia (bone thinning)
•
What are the different treatments for osteoporosis?
- Bisphosphonates (halts loss of bone but doesn’t increase bone or improve bone quality- inhibits bone remodelling)
- Anabolic agents
- Ca 2+ supplements
- Hormone replacement therapy (carries an increased risk of breast cancer)
- Increase exercise
What is the mechanism of action of Bisphosphonates and give 2 examples
- Disrupts the activity of osteoporosisclasts
- Potential side effects - oesophagi’s, mandibular necrosis
- Halts bone loss by preventing bone remodelling which means the bone loss is halted but it doesn’t improve the quality of the bone or the BMD
- Alendronate
- Risedronate
What is the mechanism of action of anabolic agents and give 2 examples
- Stimulate bone production
- Treatments haven’t shown much promise
- Require injections on a regular basis
- Intermittent PTH
- Strontium ranelate
What is a risk of hormone replacement therapy?
It carries an increased risk of breast cancer
What is a Z score?
- DEXA
* Comparison of the patient’s BMD with data from the same age/sex/size
