Metabolic bone conditions Flashcards
Describe the blood serum results in osteoporosis
All normal
Describe the blood serum results in osteomalacia
Calcium low
Potassium low
Alkaline phosphatase high
PTH and vit D normal
Describe the blood serum results in Pagets
All normal except alkaline phosphatase
Describe the blood serum results in renal failure
Calcium low Potassium high Alkaline phosphatase either normal or high PTH high Vit D low
Describe the blood serum results in primary hyperparathyroidism
Calcium high Phosphate low Alkaline phosphatase either normal or high PTH high normal vit D
What is alkaline phosphatase produced from
Osteoblasts (bone) and the liver
At what rate is bone lost at the age of 40 onwards
0.7% a year
What speed is bone mass lost after menopause
2-9% a year
What 2 scores can bone mineral density expressed as
T or Z score
What is a T score
Number of standard deviations from the mean young (30y) same gender and ethnicity
What is a Z score
Number of standard deviations from mean aged, same gender and ethnicity
In terms of T score, when and how is a diagnosis of osteoporosis made
t score below 2.5
What does DEXA stand for
Dual energy X-ray absorptiometry
What is the prevalence of osteoporosis at
a) 50 and
b) 80
a) 2%
b) >25%
In terms of T score, when is a diagnosis of osteopenia made
between 1 and 2.4
What kind of bones are more susceptable to osteoporotic bone loss
High proportion of trabecular bone
Give 2 examples of bone susceptible to osteoporosis
Vertebral bodies
Femoral neck
Briefly describe/ define osteoporosis
Relative increase in resorption is not matched by formation. Bone is normally mineralised so there is less bone
Is loss evenly distributed in osteoporosis
No- trabeculae bone is more at risk
Why is trabeculae bone more at risk of osteoporosis
Because it has a greater surface area, and is in areas that respond to new stresses
How does osteoporotic bone differ to normal bone
Cortices and trabeculae are thinned
How would you treat an osteoporosis patient who is over 75 and has low trauma fracture
Bisphosphonate calcium and vit D
How would you treat an osteoporosis patient aged 50-75 and low trauma fracture
DEXA scan
Why are calcium supplements given to people with osteoporosis
Reduce negative calcium balance
Why are vitamin D supplements given to people with osteoporosis
Significant numbers of elderly are deficient
Name 5 non supplemental treatments for osteoporosis
HRT Selective oestrogen receptor modulator Bisphosphonates Teriparatide Denosumab
How does denosumab work
Monoclonal antibody that binds to RANKL
Inhibits osteoclast formation
Name a selective oestrogen receptor modulator
Raloxifene
Why are bisphosphonates given to treat osteoporosis
Potent inhibitors of bone resoprtion
Reduce fracture risk by 50%
Name 3 complications of bisphosphonates
Giant osteoclasts
Osteonecrosis of the jaw
Atypical fractures
Why is teriparatide used to treat osteoporosis
Intermittent exposure to PTH will activate osteoblasts more than osteoclasts
How is denosumab administered
Subcutaneous injection every 6 months
What is the colloquial name for ostemalacia
Rickets
Briefly describe the underlying pathophysiology of osteomalacia
- Insufficient calcium and phosphate to mineralise new bone osteoid
- Bones softer and more liable to bend/ fracture
What does osteomalacia usually result from
Vit D deficiency
Is osteomalacia more or less deforming in adults than children and why
Less deforming because the epiphyseal growth plates are closed
What can looser lines on an x-ray suggest
Pseudofractures
What are pseudofractures
Areas of unmineralised bone which can progress to insufficiency fractures.
Where do pseudofractures most commonly form
At areas of higher bone turnover
What % of osteroid is unmineralised in normal bone
<20%
Describe the bone biopsy of an osteomalcia patient
Wide seams of unmineralised osteroid
Mineralised bone green in severe cases
Up to 100% covered by unmineralised osteoid
What must osteoid thickness be greater than
14um
3 treatments for osteomalacia
Vit D supplements
Dietary- calcium
Sun or UV
What foods may be recommended to increase calcium
Milk, bread, beans, pulses, dried fruit, green + leafy veg
What % of the population have Pagets disease when aged
a) >50
b) >80
a) 3%
b) 10%
State the 3 phases of Pagets disease
1) Initially increased rate of bone resorption
2) Compensatory phase/ proliferative
3) Burnt out phase/ sclerotic
What happens in the first phase of Pagets
Large number of giant osteoclasts
What happens in the second phase of Pagets
Increased bone formation
Accelerated deposition in disorganised manner
What happens in the sclerotic phase of Pagets
Hypercellularity may diminish
Bone is dense
Hyper-vascular bone marrow
How does the bone appear in the final stage of Pagets
Prominent cement lines
Bone marrow replaced by fibrovascular CT
Name 5 bones commonly affected by pagets
Pelvis Femur Vertebrae Skull Tibia
Name a rare, late complication of Pagets disease
Osteosarcoma
In what % of paget cases does osteosarcoma occur
1|%
What is osteosarcoma
Among the most malignant of cancers
Usually in a long bone, near the knee
Can spread rapidly usually to lungs
5 treatment options for Pagets disease
Bisphosphonates Calcium and vit D supplements Pain management Surgery Calcitonin
How do bisphosphonates work to treat Pagets
Work directly on osteoclasts to slow bone resorption
What is the duration of bisphosphonates for pagets
- oral 2-6 months
- IV single infusion to 3 infusions
What is the other name for sclerostosis
Van Buchem Syndrome
Genetic inheritence of sclerostosis
Autosomal recessive
Clinical signs of sclerostosis
Endosteal hyperotosis
Resistant to fracture
Excessive heigh
What is sclerostin secreted by and what does it do
Osteocytes
Inhibits osteoblasts and thus bone formation
How is sclerostosis treated
By an antibody to sclerostini (romosozumab)
