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65 Cards in this Set
- Front
- Back
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What are the types of bone |
Cortical bone (80%) Trabecular bone (20%) - large SA, more metabolically active |
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What is osteoid |
Organic matrix, collagen Type I , makes up 50% of bone |
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What are hydroxyapatite crystals |
99% of body calcium in bone, make up inorganic part of bone |
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How much of adult skeleton remodelled each year |
10% |
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What is the Haversion system |
Concentric rings of haversian system around central blood vessels what gives cortical bone strength |
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Major influences on bone turnover |
Mineral requirements hormones - pth vitD Diet Drugs Physical factors (eg exercise) Cytokines Age when young formation predominates, when old bone loss, menopause lead to acceleration of trabecular osteoclast activity |
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When is peak bone mass achieved |
30 years old |
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Bone and calcium metabolism |
Bone has 99% of body calcium as hydroxypatatie crystals Daily turnover 700mg Ca2+ |
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what physiological roles does calcium have |
cell signalling contraction mechansim |
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which has a higher conc of Ca cytoplasmic or extracellular |
Extracellular x 25 |
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Importance of PTH on Ca |
Increases Ca release from bone, decreases excretion at kidney |
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Importance of vit D on Ca |
increases bone mineralisation, decreases excretion at kidney Protects bone by increasing Ca and PO4 absorption from gut |
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Importance of calcitonin on Ca |
Increases calcium excretion at kidney and decreases release from bone |
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What drugs affect bone metabolism |
Bisphosphonates Oestrogens and analogues Calcium salts Vit D Corticosteroids is important for having adverse effects on bone |
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What is osteoporosis |
Reduction in bone density |
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Primary cause of osteoporosis |
Old age and post menopause |
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Secondary causes of osteoporosis |
Immobloisation Malnutrition or malabsorption Endocrine disease Drugs eg corticosteroids |
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How do we diagnose osteoporosis |
X rays can show loss of trabeculae and corticol thinning --> increasing transluence Photon absoprtiometry may confirm decrease in bone density Serum Calcium phosphate and alkaline phosphate are usually normal |
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DEXA screening |
T score is calculated |
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What are the major drugs for causing osteoporosis |
Corticosteroids! - prednisolone, hydrocortisone, dexamethasone |
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MOA of prednisolone |
bind to intracellular receptors to alter translation of DNA bone - they increase osteoclast activity, decrease Ca absorption and osteoblast differentiation |
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What drugs provide protection for long term corticosteroid use |
Bisphosphonates |
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Can heparin ever cause osteoporosis |
Yes if given long term |
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Administration of heparin |
Paraenteral as it is a large complex molecule that is broken down by gastric acid |
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Most common adverse effect of heparin |
Bleeding |
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Primary prevention of osteoporosis |
Bisphosphonates
exercise physical - hip protectors, safer flooring |
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Secondary prevention - Treatment |
Antiresorabative drugs eg bisphosphonates, oestrogens, raloxifene, calcitonin Bone forming drugs = parathyroid hormone, strontium ranelate |
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key therapeutic fractures of osteoporotic treamtne |
decrease vertebral fractures and non-vertebral factors |
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Common bisphosphonates |
Alendronic Acid Etidronate disodium ibandronic acid |
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How do biphosphonates work |
Reduce resorption by osteoclasts - hinder recruitement, stimulating osteoblasts to produce an inhibitor of osteoclast formation |
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Commonest bisphosphonate prescribed in UK |
Fosamax ie alendronic acid D |
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MOA of alendronic acid |
decreases osteoclast activity therefore bone loss |
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Indication |
Treatment of postmenopausal osteoporosis Prevention Page's disease of teh bone Malignant bone metastases |
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Adverse effects of alendronic acid |
GI upset Osteonecrosis of jaw Irritation of oesophagus |
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What's most important adverse effect of alendronic acid |
Irritation of oesophagus eg heart burn Patients must take pill with empty stomach only with water, then remain upright during 30 min of waiting As alendronic acid is large can remain lodged in lower parts of the oesophagus |
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What is HRT |
Oestrogen |
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MOA of oestrogen |
Interact with intracellular receptors --> inhibition of bone resorption by osteoclasts |
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Indication for using oestrogen |
Patients with menopausal symptoms Not for osteoporosis unless desparate |
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Adverse effects minor for oestrogen |
Vaginal bleeding Breast tenderness Mood distrubance |
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Major adverse effects of oestrogen |
Increase in endometrial cancer risk Increase in breast cancer risk Increase in VTE Increase in stroke |
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what is raloxifene
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Selective Estrogen Receptor Modulators |
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MOA of raloxifene |
Oestrogen receptor agonists at some tissues and antagonists at others eg breast |
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Indication of raloxifene |
Prevention and treatment of osteporosis Increase bone mass, decrease risk of vertbral fractures Decreases risk of breast cancer and decreases cardiovascular LDL cholesterol |
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Adverse effects of raloxifene |
Hot flushes Thromboembolism |
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Caltinonin what is it |
Naturally occurring hormone involved in calcium regulation and bone metabolism |
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When is calcitonin used |
used for pain relief after vertebral fractures when other analgesic measures are unsuccessful |
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Key adverse effects of calctinon |
Allergic reaction |
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Parathyroid hormone indication |
Treatment of osteoporosis - high fracture risk |
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What is teriparatide |
Modified form of PTH, stimulates new bone formaiton of osteoblasts and significantly increase bone mineral density |
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Prevention of Osteoporosis |
Balanced diet rich in calcium and VitD Weight bearing exercise Avoid smoking and excessive alcohol use Drugs eg aledronic acid when approiate eg women with risk factors or with confrimed osteoporosis or low bone mineral density |
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Indication of calcium supplements |
Prevention of osteoporosis Hypocalcaemia cardiac arrhythmias |
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Adverse effects of calcium supplements |
Hypercalcaemia --> anorexia, vomiting, polyuria, constipatio, weak |
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Indication for vitamin d |
Prevention of osteoporosis Hypoparathhyroidism, renal bone disease, rickets/osteomalacia |
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What form do we take vit d tablets in |
Oral ergocalciferol or alfacalcidol |
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Adverse effect of vitD |
Hypercalcaemia |
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Why do we need vit D |
To absorb calcium |
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What is renal osteodystrophy |
Bone dimineralisation that accompanies chronic kidney disease |
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Causes of renal bone disease |
Failure of 1-alpha hydroxylation required to activate vit D leads to low serum calcium and activation of parathyroid glands Phosphate retention tending to reduce free calcium ions |
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Diagnosis of renal bone disease |
Blood tests showing decreased calcium and Vit D and increased phosphate and parathyroid hormone |
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Treatment of renal bone disease |
Calcium and vit D supplementation restriction of dietary phosphate phosphate binders - eg calcium carbonate renal replacement - transplantation, haemodialysis |
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What is Paget's disease |
Osteitis deformans, disordered turnover of bone leads to loss of Haversian's system Bones become weakened and deformed Bone easily fractures |
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Clincal signs of Paget's disease |
characteristic large skull and long bone deformities |
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Possible causes of Paget's disease |
Genetic and environmental |
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Complications of Paget's Disease |
Pathological fractures Hypercalcaemia heart failuer Neurological Osteoarthritis Osteosarcomas |
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Treatment of osteomalacia and rickets |
Vit D replacement therapy Malabsorption is case then may require treatment by injection Phosphate supplements in familial hypophosphataemic rickets |
