Metabolic Bone Conditions Flashcards
Which bone disease has normal serum Ca, PO4, alkaline phosphatase, PTH, and 1,25 OH2 vitamin D
Osteoporosis
Which bone disease has low serum Ca, low PO4, high alkaline phosphatase, high PTH, and low 1,25 OH2 vitamin D
Osteomalacia
Which bone disease has normal serum Ca, PO4,, PTH, and 1,25 OH2 vitamin D, and very high alkaline phosphatase
Pagets
Which bone disease has low serum Ca, high PO4, normal or high alkaline phosphatase, high PTH, and low 1,25 OH2 vitamin D
Renal failure
Which bone disease has high serum Ca, low PO4, normal or high alkaline phosphatase, high PTH, and normal 1,25 OH2 vitamin D
Primary hyperparathyroidism
Why is 25 vit d often measured instead of 1,25 vit d
More long lived
Why does renal failure cause low serum 1,25 vit d but normal serum 25 vit d
1,25 synthesised in kidney
How does osteoporosis affect bone amount and mineralisation
Decr amount
Normal mineralisation
How does osteomalacia affect bone amount and mineralisation
Normal amount
Decr mineralisation
Why are women more affected by osteoporosis than men
Men start with more bone
Women have faster bone mass decline
Decline speeds up at menopause
How can bone mineral density be expressed
T score
Z score
T score
Number of standards deviations from the mean bone density for 30 year old of same gender and ethnicity
Z score
Number of standards deviations from the mean bone density for same age, gender and ethnicity
When is z score used
Young people w osteoporosis
What t score indicates osteoporosis
<2.5
What t score indicates osteopenia
-1- -2.4
What type of bone is more susceptible to osteoporotic bone loss
Trabecular
Why are vertebral bodies and femoral neck susceptible to osteoporotic bone loss
High proportion of trabecular bone
Osteoporosis
Relative incr in bone resorption not matched by formation
Osteoporosis treatments
Bisphosphonates
Calcium
Vitamin D
HRT - oestrogen
Raloxifene - Selective oestrogen receptor modulator
Teriparatide
Denosumab
BCD TROD
What is raloxifene
Selective oestrogen receptor modulator
What is teriparatide
Recombinant PTH
What is denosumab
Monoclonal antibody for RANKL that mimics OPG receptor
When is a selective oestrogen receptor modulator used instead of HRT
Women at risk of breast or uterine cancer
Primary osteoporosis treatment
Bisphosphonates
How do Bisphosphonates inhibit bone resorption
Deposited into hydroxyapatite making clasts less likely to degrade
Causes apoptosis in clasts that uptake bisphosphonate containing hydroxyapatite bone
Decr RANKL expression and decr OPG production by blasts -> mod blast to Clast signalling
Bisphosphonate complications
Less bone renewal leading to
Giant osteoclasts
Osteonecrosis of jaw
Atypical fractures
How are Bisphosphonate complications managed
Give pt Bisphosphonate holiday to allow bone renewal
What is osteopotegrin OPG
decoy receptor for RANKL
Why does teriparatide treatment give intermittent PTH exposure rather than continual OTH exposure
Intermittent exposure causes blasts proliferation
Chronic exposure causes clast differentiation
Romosozumab
Monoclonal antibody against sclerostin
Why does bone resorption decrease during lutealphase of menstrual cycle
High progesterone
Osteomalacia
Impaired mineralisation of bone matrix causing softening of bones
What causes osteomalacia
Insufficient calcium and phosphate to mineralise new bone osteoid
What is osteomalacia called in children
Rickets
Why does osteomalacia cause more deformity in children
Epiphyseal growth plate still open
More woven bone
How are serum calcium, phosphorus, and alkaline phosphatase levels in osteomalacia
calcium and phosphorus low
Alkaline phosphatase High
Pseudofractures/loosers lines
Areas of unmineralised bone that look like fractures of x ray
Common in osteomalacia
How much osteoid is unmineralised in normal bone
<20%
Why are Clast numbers increased in osteomalacia
Incr ca reabsorbtion
What subtpstance is used to label mineralising bone and asses bone mineralisation
Tetracycline
Osteomalacia treatment
Vitamin d supp
Calcium supp
Paget’s disease
Chronic Condition causing increased bone breakdown and growth
Dysfunction in What cell causes Paget’s
Osteoclasts - genetic + viral infection
3 phases of Paget’s
Incr rate of bone resorption
Compensatory/proliferative phase
Burnt out/sclerotic phase
What happens in the compensatory phase of Paget’s
Incr woven bone formation with disorganised deposition
Blast proliferation
Pagetic bone
Dense bone with little cellularity
Features of bone in Paget’s burnt out phase
Irregular thickened Trabeculae
Prominent cement line
Bone marrow replaced by fibrovascukar CT
Pagetic bone
Which bones are most commonly effected in Paget’s
Pelvis
Femur
Vertebrae
Skull
tibia
How can Paget’s cause CN palsies
Bone growth closes foramena and compresses nerves
What type of cancer is a rare complication of Paget’s
Osteosarcoma
Which bones do osteosarcomas most commonly affect
Long bones
Often near knee
Paget’s treatment
Bisphosphonates
Calcium
Vit d
Pain management
Surgery
Calcitonin (used less)
