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  • Created by: sagalets
  • Created on: 15-05-17 21:20
What are the functions of bones?
Skeleton support, protection, movement, storage of calcium, lipid and phosphate, haematopoiesis
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What is osteoporosis?
A metabolic bone disorder characterised with low bone mineral density and reduction of bone mass
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What is the primary concern in osteoporosis and why is treatment needed?
Fracture prevention
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What types of cells are responsible for bone maintenance and metabolism?
Osteoblasts and osteoclasts
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What minerals and elements of the diet are crucial for bone health?
Calcium and Vitamin D
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What diagnostic tests are available for osteoporosis and what do results represent?
DXA scan - shows bone mineral density (BMD) and represents the number of Standard Deviations away from the BMD of a 30-year old (T score) and average of the patient's age (z score)
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What is a pre-osteoportic state called and how is it chatacterized in terms of BMD?
Osteopenia; BMD between -1 and -2.5
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What is the first-line advice for osteoporosis?
Lifestyle modifications, increased exercise, strengthening muscles
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What is the first-line treatment/ osteoporosic fracture prevention?
Bisphosphonates (alendronic acid)
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What is adviced if alendronic acid is contraindicated or intolerated?
Risedronic acid or zoledronic acid (used second-line)
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What other treatments for osteoporosis are available?
Teriparatide (recombinant PTH), Raloxifen (SERM), Strontium Ralenate (DABA), Denosumab (monoclonal antibody)
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What additional treatment is recommended in osteoporosis?
Calcium supplements (daily norm 1000mg, 1200mg in osteoporosis) and Vitamin D to enhance calcium absorption
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What is the mechanism of action of Denosumab?
It is a ligand for osteoclasts; they are normally activated by RANK ligand released by osteoblasts, however, denosumab competitvely binds instead, blocking osteoclasts action
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How does exercise affect bone density?
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What types of osteoporosis are there?
Type 1 (due to loss of protective action of Oestrogen and decreased activity of osteoblasts); Type 2 (increased bone turnover due to mineral imbalance and Vit. D deficiency)
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What is the mechanism of action of Strontium Ranelate?
It encorporates into bone, decreases the action of osteocalsts and stimulates osteoblasts. Increases bone density, promotes osteoblast formation
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How do bisphosphonates work?
Increase calcium deposition in bone, inhibit bone resorption by osteoclasts (induce osteoclast apoptosis by preventing activation of Rho snall GTPases) and promote bone formation by osteoblasts
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How are bisphosphonates exctered?
Renally - important to check renal function before prescribing
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What are common side-effects of Alendronic acid?
Gastic and oesophageal ulcers, osteonecrosis of the jaw (rare) and atypical fractures
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How can Alendronic acid be taken and what additional counselling is required?
Once weekly; take 30 mins before food (as food slows absorption), do not lay down after taking and take with plenty of water
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What hormone is vitamin D a pro-drug for and where in the bosy is it synthesized?
Calcitriol, in the kidneys
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What are the functions of osteocytes?
Bone maintenance
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What bone disorders are characterized by severe vitamin D deficiency?
Osteomalacia and Ricket's disease (child onset)
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What disease is chatacterized by increased bone remodelling and patchy weakening of the bone?
Padget's disease. Treated with bisphosphonates
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What are SERMs are how do they benefit in osteoporosis?
Selective Estrogen Receptor Modulators (Raloxifen), bind to oestrogen receptors - agonists in some tissues (bone), antagonists in others.
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How can glucocorticoids induce osteoporosis?
Inhibit bone remodelling, insrease risk of fractures, induce disbalance of osteoblasts and osteoclasts, induce apoptosis of osteoblasts and osteocytes. stimulate bone resorption
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What is the advice for long-term glucocorticoid therapy?
Wait 3 months in between glucocorticoid exposure; prophylactic bisphosphonates and PTH hormone
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What endogenous hormones stimulate osteoblasts and bone matrix synthesis?
Thyroid hormone (thyroxine), growth hormone (from pituatory), calcitriol (kidneys), sex hormones (androgens - oestrogen)
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Where is calcitonin secreted from and what is its primary function?
From the C cells in thyroid glands, it inhibits osteoclasts, decreases calcium levels in the blood and can bring calcium to the bones; promotes calcium loss at kidneys
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How is parathyroid gland important in bone health?
PTH stimulates osteoclasts; increases calcium concentration in the blood, can take calcium away from the bones and increase reabsorption from the kidneys and the gut when blood calcium levels are low
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What drugs can induce osteoporosis?
Glucocorticods, antiepileptics, anticoagulants (heparin), Gonadotropin-releasing hormone agonists. (all long-term)
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How can antiepileptics induce osteoporosis?
They induce CYP450 enzyme that also metabolises Vitamin D, thus increasing its turnover and decreasing its effects upon Calcium absorption
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What are the possible side effects of taking calcium supplements?
Constipation, abdominal discomfort, nausea and vomitting, kidney stones
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How can calcitriol be administered?
IM or s/c injection; instranasally. Has to be administered together with Calcium supplements and vitamin D
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How is recombinant PTH beneficial in osteoporosis and how can it be administered?
s/c injection. Stimulates new bone growth
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What risks are associated with Oestrogen therapy?
DVT, blood clots, thrombosis, hot flushes, gallbladder disease, increased risk of endometrial cancer
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What are the possible side-effects of Strontium Ranelate?
Heart attack. Can also cause eosinophilitis, Stephen-Johnson syndrome, necrolysis
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What processes are involved in bone remodelling?
1. Microdamage - response of osteocytes 2. Recruitments of osteclasts 3. Bone resorption 4.Reversal (inhibition of osteoclasts) 5.Bone formation (collagenosteoid secretion by osteoblasts and mineralisation)
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What steps are involved in bone healing?
1.Haematoma formation (swelling and torn blood vessels) 2.Soft callus (granulation tissue formation, capillary growth) 3.Bony callus (new spongy bone) 4.Remodelling (reduction of bony callus, removal of excess material)
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What is osteoporosis?


A metabolic bone disorder characterised with low bone mineral density and reduction of bone mass

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What types of cells are responsible for bone maintenance and metabolism?


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