bone Flashcards
effect of corticosteroids on bone
direct
- reduction of osteoblast activity + lifespan
- suppression of replication of osteoblast precursors
- reduction in calcium absorption
indirect
- inhibition of gonadal + adrenal steroid production
which type of collagen is affected in osteogenesis imperfecta?
type 1
genetic mutation that affect maturation + organisation of type 1 collagen
osteogenesis imperfecta
brittle bones brone to fractures - due to mutations affecting matuaration + organisation of type 1 collagen
8 types depending on mutation - vary in severity, mild may present in adult
most autosomal dominant
osteogenesis imperfecta presentation
recurrent + inappropriate fractures
blue/grey sclera (whites of eyes)
dental problems deafness short stature triangle face hypermobility bone deformities - bowed legs, scoliosis
diagnosis of osteogenesis imperfecta
clinical
genetic testing can be done but not routine
xrays for fractures
management of osteogenesis imperfecta
no cure - fix + prevent further fractures
bisphosphonates - increase bone density
vit D supplementation
MDT - physio, occ, paeds, social workers
which bones are most affected in paget’s disease?
axial skeleton
pelxis
lumbar spine
skull
long bones
may be single site (monostotic) or multiple (polyostotic)
Paget’s disease
disorder of excessive bone turnover - overactivity of osteoblasts + osteoclats
uncoordinated, leads to patchy areas of sclerosis + lysis
increased risk of pathological fractures
Paget’s presentation
older patients
bone pain
bone deformity + fractures
hearing loss - bones of ear affected
Paget’s appearance on x-ray
bone enlargement + deformity - patchy
osteoporosis crcumscripta = well defined osteolytic lesions that appear less dense
cotton wool appearance of skull - patchy sclerosis + lysis
V-shaped defects in long bones
biochemistry in paget’s
raised alkaline phophatase - other LFTs normal
normal calcium
normal phosphate
Pagets investigations
X-ray - patchy, less dense bones
biochemistry - raised alkaline phosphatase
management of Paget’s
bisphosphonates
NSAIDs for pain
calcium + vit D - esp when on bisphosphonates
Paget’s complications
osteogenic sarcoma (osteosarcoma)
spinal stenosis + spinal cord compression
osteogenic sarcoma (osteosarcoma)
key complication of Paget’s
poor prognosis
increased focal pain, bone swelling, pathological fractures
what type of receptor is the calcium sensing receptor in the parathyroids?
G-protein couple receptor
plays an essential role in regulation of extracellular calcium homeostasis
osteoclasts
multinucleated cells responsible for bone resorption
derived from haematopoietic progenitors
osteoblasts
mononuclear cells derived from mesenchymal cells in the bone marrow stroma
–> responsible for bone formation
osteocytes
primary cell of mature bone + most common bone cell type
derived from osteoblasts
thought to sense mechanical strain on skeleton
common osteoporotic fracture sites
neck of femur
vetebral body
distal radius
humeral neck
osteoporosis investigations
DEXA scan
normal serum calcium + phosphate
indications for DEXA scan
> 50 yrs
< 50yrs with risk factors
FRAX / Qfracture >10%risk of fracture over 10yrs
osteoporosis treatment
lifestyle - diet, sun exposure
calcium + vit D supplements
what type of cells produce parathyroid hormone?
chief cells
produces parathyroid hormone in response to hypocalcaemia
how does parathyroid act to raise blood calcium?
increases osteoclast activity (reabsorbing calcium from bones0
increasing calcium absorption from the gut
increasing calcium absorption from kidneys
increasing vit D activity (increases calcium absorption from intestine)
symptoms of hyperparathyroidism
(hypercalcaemia)
renal stones
painful bones
abdominal groans - constipation, N+V
psychiatric moans - fatigue, depression, psychosis
primary hyperparathyroidism
uncontrolled parathyroid hormone produced directly by tumour of the parathyroid glands - leads to hypercalcaemia
treatment = surgically removing tumour
secondary hyperparathyroidism
where insufficient vit D or chronic renal failure leafs to low absorption of calcium from intestines, kidneys and bones
–> causes hypOcalcaemia
treatment = correcting vit D deficiency / renal transplant
tertiary hyperparathyroidism
when secondary continues for a long period of time causing hyperplasia of the glands
–> causes hypercalcaemia
treatment = surgically removing part of parathyroid tissue to return parathyroid hormone to appropriate level
