Osteoporosis Flashcards
(40 cards)
What molecule reabsorbs bone cells?
Osteoclasts
What molecule forms bone cells?
Osteoblasts
What are the 3 compounds that control Ca lvls.
PTH, Calcitonin, Vitamin D.
What can Hypocalcaemia cause?
Increases muscle/nerve excitability, muscles spams of the respiratory muscles.
What can hypercalcaemia cause?
Decrease in muscle/nerve excitability, can cause cardiac arythmias.
What does RANKL do?
Increases osteoclast differentiation and decreases osteoclast apoptosis -> increasing their number and promoting bone resorption over long term.
What does Osteoprotegrin do?
Decoy receptor for RANKL. Decreases osteoclast number and promotes bone deposition over long term.
What effect does PTH have on fast exchange?
Rapid efflux of Ca2+ from small labile pool. Increase in cAMP -> movement of Ca2+ into cells from the bone fluid.
What effect does PTH have on slow exchange?
Activates osteoblasts to increase RANKL expression. Osteoclats increase bone resportion, which increases plasma [Ca]. Osteoblast building in inhibited.
What effect does PTH have on the kidneys?
Promote Ca retnetion (Ca2+ reabsorption occurs). Promotes PO43- excretion (decreases reabsorption). Causes an activation of vitamin D in the kindeys.
What does calcitonin do?
Antagonistic hormone to PTH. Secretion increased when there is an increase in [Ca2+]. Acts to decrease lvls of extracellular plasma by decreasing Ca2+ movement from the canaliculi fluid into the plasma. Inhibiting osteoclast activity.
What does vitamin D do?
Pre-hormone that increases Ca2+ absorption in the GIT.
Where in the body is Vitamin D activated in the body?
An OH group is added in the liver to form Calcifediol which is then stored until required.
Then another OH group is added in the kidney to form Calcitrol which is caused by PTH.
What does activated vitamin D do?
Acts as a nuclear receptor which causes transcription factor promoting gene expression. Which causes an increased absorption of Ca2+ in the GIT, increasing plasma Ca2+ and restoring Ca balance.
What is bone remodelling?
Where old bone is removed and replaced by new bone.
Osteoblast.
Fill in bony cavity with bone matrix & release cytokines to attract osteoclasts.
Osteoclast.
Release proteases which dissolve bone mineral matrix and collagen. releases chemical that attract osteoblasts.
What molecules control bone remodelling?
PTH, Activated vitamin D, IL-1, IL-6, TNF-alpha, GCSF.
What can cause bone loss?
Low Ca2+ intake, low exposure to sunlight, Alcohol, smoking, thin body type.
What is osteoporosis?
Common metabolic bone disease characterised by reduction in bone mass per unit volume that occur with increasing age.
What can you use to detect osteoporosis?
Dual energy X-ray absorptiometry (DEXA). Allows for acurate and reproducible mreasurement of BMD.
What is primary osteoporosis?
When patient has no other disorders known to cause osteoporosis.
Whar is secondary osteoporosis?
Osteoporosis due to another medical condition, Anorexia, IBD, Endocrine, RA.
Use of steroid therapy too.
What do corticosteroids do?
Decrease osteoblast activity.
Decrease Ca absorption from intestine and increase renal Ca loss.
