Rheum Flashcards
what is osteoporosis
loss of bone density without loss of bone mineralisation
results in increased susceptibility to bone fractures
what are the different types of osteoporosis
type 1 = post menopausal
type 2 = senile
secondary = disease process or medical tx
what are the risk factors for type 2 osteoporosis
fhx alcohol RA immobility untreated menopause
what are the risk factors for secondary osteoporosis
Steroid use Hyperthyroidism, hyperparathyroidism Alcohol Thin BMI <18 Testeosterone Early menopause Renal failure Erosive bone disease Diet - low vit D or Ca
how do steroids cause osteoporosis
cortisol inhibits osteoblasts and activares osteoclasts
bone breaks down, reduced bone density
how does hyperthyroidism cause osteoporosis
thyroxine inhibits osteoblasts
increased bone breakdown than formation
also hypercalcaemia
what is the clinical presentation for osteoporosis
usually asymptomatic
fragility or pathological fracture
- compression fracture - back pain, loss of height, loss of spine curve, hunched
- colles fracture - distal radius
- NOF fracture
3 cells within bone
osteoblasts - build bone secrete collagen and hydroxyapetite
osteoclasts - break down bone by secreting digestive enzymes and HCl breaks down bone -> releasing Ca and phosphate
osteocytes - osteoblasts stuck in bone matrix, act as mechanoreceptors
describe the effects of PTH
released from PTG in response to low serum Ca
1) leads to increased osteoclast activity - PTH stimulates RANK-l which stimulates osteoclasts to break down bone and release Ca
2) leads to increased Ca absorption - PTH acts on nephron, increases Ca reabsorption from DCT
3) increases synthesis of vit D - increases rate of vit D formation within kidney (higher vit D = increased Ca absorption from gut)
what does kidney disease lead to and why
renal osteodystrophy
kidneys produce less vit D
reduced Ca absorption from gut
leads to hypocalcaemia so PTH released
but PTH breaksdown bone -> weakening
why is there an increased risk of developing osteoporosis after menopause
menopause = low oestrogen
oestrogen inhibits osteoclasts - it stimulates OPG which inhibits RANK-l and thus prevents osteoclast activation
however, low oestrogen leads to less OPG and less inhibition of osteoclasts = greater bone breakdown = osteoporosis
which cells are activated more/less in osteoporosis
breakdown is faster than formation
so osteoclasts are activated more
osteoblasts are activated less
which bones are at greatest risk of fracture in osteoporosis
ribs
scapula
vertebrae
what is the FRAX tool
screening tool
assess person risk of fragility fracture over 10 years
performed in women 65+, men 75+
involves - age, BMI, comorbidities, smoking, alcohol, fhx, bone mineral density
what would blood tests shown in osteoporosis
all normal
what is the gold standard for osteoporosis investigation
DEXA scan
reading of the hip
generates 2 score - T and Z
T= value of bone density vs normal healthy population Z= value of bone density vs normal value for patient age
which score do we use to assess the severity of osteoporosis in DEXA
T-score
-1 = normal
management for osteoporosis
lifestyle advice - adequate ca and vit D intake
medical management
-bisphosphonates = aledronate or etidronate
how do bisphosphonates help osteoporosis
cause apoptosis of osteoclasts - stops bone degradation
side effects of bisphosphonaetes
oesophagtis
GORD
hypophosphataemia
osteonecrosis of jaw/external auditory canal
what is osteopenia
reduced bone density - not to the severity of osteoporosis