Osteoporosis Flashcards
what is bone remodelling?
where old bone is replaced by new bone
bone is an active tissue
what is bone remodelling controlled by?
osteoclasts and osteoblasts and osteocytes
what is bone resorption?
destruction of bone tissues leading to bone loss
-its where osteoclasts form cavities on bone surfaces
what is bone deposition?
-osteoblasts lay down new bone matrix
so formation of new bone
what is bone mineral density (BMD)?
-amount of minerals especially phosphorus and calcium in a bone volume
how does osteoporosis develop?
develops when bone resorption exceeds bone formation
-so when bone destruction is more than new bone formation
WHO definition for osteoporosis?
Bone mineral density above 2.5
AND
T-score of -2.5 or less
How is osteoporosis assessed?
Dual-energy X ray absorptiometry (DXA or DEXA)
-measures amount of bone at thoracolumbar spine, forearm, and hip
-measures bone mineral density
what is T-score?
compares patients bone mineral density to a healthy young adult
-osteoporosis = T-score = above 2.5
WHO CLASSIFICATION OF OSTEOPOROSIS
Normal = T-score = 1
Osteopaenia = T-score = -1 to -2.5
Osteoporosis = T-score = below -2.5
Severe osteopororsis = above -2.5
WHO CLASSIFICATION OF OSTEOPOROSIS
Normal = T-score = 1
Osteopaenia = T-score = -1 to -2.5
Osteoporosis = T-score = less than -2.5
Severe osteopororsis = above -2.5
the more negative score, the more severe osteoporosis
how is vitamin D converted to calcitriol?
Vitamin D3 is metabolised into (25-hydroxycholecalciferol) in liver.
then this is converted into CALCITRIOL known as (1,25-dihydroxycholecalciferol) in kidneys.
explain epidemiology of osteoporosis?
-High in white post-menopausal women
-white and asian women have equal risk
-Affects 1 in 3 women and 1 in 12 men in UK
-53% patients lose independence after hip fractures
-reduced quality of life and low self esteem from pain
what are the risk factors of osteoporosis?
Modifiable : smoking, excessive alcohol, low exercise, low calcium intake, low vit D
Non-modifiable : genetics, diabetes, rheumatoid arthritis, chronic liver disease
what are the primary causes of osteoporosis?
Primary causes:
-Female gender- reduced oestrogen levels so more bone loss. oestrogen plays important role in bone formation
-male gender - men have high bone mineral density so slower loss of BMD, fracture risk is less in men. men have shorter life expectancy.
-AGE - bone loss increases as age increases, low calcium and vit D intake from diet or sun. calcium and vit D important in bone health.
what are the secondary causes of osteoporosis?
-Premenopausal
-men younger than 70 years
- Drug induced - corticosteroids, thyroid hormone replacement drugs,
phenytoin increases vit D metabolism
what are the non-pharmacological treatment?
-quit smoking
-reduce alcohol intake
-take vit D and calcium
-weight bearing exercise e.g. running, walking, jogging
-fall prevention - use canes, assess living environment
-warn about drugs that alter blood pressure/balance
what are the pharmacological treatment for post-menopausal ostoporosis?
-Bisphosphonates -FIRST LINE!!! alendronate/risodranate
-HRT
-Calcitriol - if first line is unsuitable
-Raloxifene
-Parathyroid hormone- teriparatide
what is the treatment for corticosteroid induced osteoporosis?
- corticosteroids cause net bone loss and imbalance osteoblast and osteoclast activity
-if patient used 7.5mg or more daily for 3-6 months
-BISPHOPHONATE- FIRST LINE
-HRT IN WOMEN -SECOND LINE
Bisphosphonates for osteoporosis examples and MOA
-Alendronate
-Risedronate
-potent inhibitors of osteoclasts mediated bone resorption
-mimics effect of endogenous pyrophosphate
-reduces bone breakdown
-binds to hydroxyapatite crystals of bone so prevents bone growth and dissolution.
Bisphosphonates DOSING/pharmacology
dosing: daily or once weekly 35mg
- half time is very long (many years)
-poorly absorbed after oral
-absorption may be reduced if given with food, antacids, calcium, iron containing drugs, tea and coffee
- Avoid eGFR below 35ml/min
Key counselling points to give with bisphosphonate
- Take on empty stomach- 30mins before breakfast with full glass of water
-Do not take at bedtime
-Stand or sit upright for 30 mins after taking the tablet
-stop taking it if you develop dysphagia or new heartburn,
-report thigh, hip, groin pain, dental pain, swelling, ear pain, ear infection/discharge
HRT and their benefits on bone health
-HRT not recommended as first line -increases risk of breast cancer and blood clots
-there are oestrogen receptors on osteoclasts and osteoblasts
-oestrogen reduced osteoclast activity
-increases calcitriol concentration
-reduces renal calcium excretion
-reduces vertebral fracture risk
calcitriol in ostoporosis
-active form of Vit D
-1,25 dihydroxycholecalciferol (vitamin D3)
-maintains calcium homeostasis
-increases plasma calcium levels
-decreases renal calcium excretion
-reduces bone loss and fracture risk
-treats post-menopausal osteoporosis
Raloxifene pharmacology/dosing
-Selective oestrogen receptor modulator (SERM)
-treats post-menopausal osteoporosis
-has oestrogen agonist effect on bone
-increases bone mass
-well absorbed
-metabolised in liver
-undergoes first pass metabolism
-60mg DAILY
-Adverse effect: hot flush, VTE, leg cramps,
what does raloxifene interact with?
anticoagulants
colestryramine - can reduce absorption of raloxifene
Caution: history of VTE, unexplained uterine bleeding, hepatic impairment, stroke
what are the adverse effects of bisphosphonates
upper GI symptoms
abdominal pain
nausea
dyspepsia
Teriparatide dosing and MOA
-improved Bone mineral density
-stimulates new bone formation
-enhances bone growth
-licensed for:
-postmenopausal osteoporosis in women
-corticosteroid induced in men and women
-men at increased risk of fractures
denosumab in osteoporosis
human monoclonal antibody
-receptor activator of nuclear factor kappa-B ligand (RANKL)
-binds to RANKL inhibiting its action
-inhibits bone resorption
-adverse effects: skin infections, cellulitis, hypocalcaemia
- licensed use:
Treatment of postmenopausal osteoporosis in women and osteoporosis in men at an increased risk of fractures
calcium and vit D supplement
-offer to ALL patients
-at least 1000mg calcium daily
-calcium carbonate contains highest amount of calcium
-most common side effect is constipation
-calcium reduces rate of bone loss
-800iu vit D + 1g calcium daily
