Osteoporosis & metabolic bone disease Flashcards
What is bone and what are it’s functions
-Bone is a living tissue
Functions:
-Mechanical=supports muscle attachment
-Protective=to vital organs and bone marrow
-Metabolic-reserve for calcium& phosphate ions
State the different types of bone
- Flat
- Long
- Sesamoid
- Cortical
- Trabecular
What is remodelling/turnover
-A lifelong process where mature bone tissue is removed from the skeleton (a process called bone RESORPTION) and new bone tissue is formed (a process called OSSIFICATION or new bone formation)
What influences turnover
- Age
- peak bone mass
- Hormones
- Nutrition
State the characteristics of cortical bone
- 85% of skeleton mass
- Abundant in shaft of long bones
- Largely affected by hyperparathyroidism and post-menopausal period
- Controlled by systemic hormones and parathyroid hormones(PTH)
State the characteristics of trabecular bone
- 15% of skeleton mass
- Has a larger SA
- Bone remodelling occurs in environment of narrow cells & cytokines
Explain how bone turnover occurs
- OsteoCLASTS= large nucleated cells responsible for bone resorption
- Under the influence of signals the osteoclasts (receptor activator of nuclear factor kappa B-ligand ((RANKL)), interleukins, PTH,cytokines etc) initiate bone resorption)
- An acidified micro-environment is created between the osteoclasts and cell surface causing mobilization of mineralized content
- After osteoclastic resorption and apoptosis, proliferation of osteoblasts occur and finally mineralized bone is formed
How can we classify markers of bone turnover
- ) Bone resorption markers
2. )Bone formation markers
State the bone resorption markers
Urine: -Hydroxyproline -C telopeptide of type I collagen -N telopeptide of type I collagen Serum: -NTX -CTX
State the bone formation markers
Serum:
- Bone specific alkaline phosphatase
- Osteocalcin
- P1CP
- P1NP
Around what age bracket does the peak bone mass occur
25-40
When does bone mass start to decline
For females=menopause
For males & females= after 40
What is DEXA
- Dual energy X-ray absorptiometry
- A bone density scan using densitometry X-ray measures how much mineral is in the area being measured
- Results are given as ‘standard deviation’ (the number of units above or below average)
Define osteoporosis
- Systemic skeletal disorder
- Low bone mass
- Microarchitectural deterioration of bone tissue
- Increased risk of fracture
- A bone mineral densitry (BMD) Below 2.5 SD
Define osteopenia
- A bone density between lower end of normal range and osteoporosis
- A value of BMD between 1 and -2.5 SD
Define fragility fracture
A fracture following a fall from standing height or less, although vertebral fractures may occur spontaneously or as a result of routine activities
Why are woman at greater risk of osteoporosis?
-Due to the decrease in oestrogen production at the menopause, which accelerates bone loss
Outline the modifiable determinants of low bone structure and function
- Smoking
- Alcohol intake> 14units/week
- Low BMI<18.5 kg/m2
- Current or frequent use of glucocorticoid
- Vit D& calcium homeostasis
Outline the non-modifiable determinants of low bone structure and function
- Age: bone density decreases as you get older
- Gender: women accumulate less peak bone mass and lose more following menopause
- Ethnicity: caucasians & asians are at higher risk
- Previous fragility
- Family history of hip fracture
How is diabetes associated with low bone mass
- women with T1DM are 12x more likely to get hip fracture
- Women with T2DM have a 1.7 fold risk of hip fracture
- Low bone turnover, reduced anabolic effect of insulin and IGF1
- Poor vision,neuropathy increase potential of fracture
Which diseases are associated with low bone mass
- Diabetes
- Inflammatory rheumatic disease
- GI diseases
- Chronic liver disease
- Chronic kidney disease
- CF
- HIV
- Epilepsy
- MS
- Stroke
How can we quantify fracture risk?
- FRAX calculated 10year absolute risk of major osteoporotic fracture & hip fracture
- Hip BMD predicts fracture risk more than spine
- Bone markers in urine and serum are useful to monitor treatment and not for diagnosis
What investigations are useful for osteoporosis and metabolic bone disease?
- Bone profile: corrected calcium, phosphate, alkaline phosphatase, magnesium
- PTH
- 25 OH vitamin D
- Renal functions & LFTs
- Serum electrophoresis
- Coeliac screen
- TFTs
- Gonadotrophins
- DEXA
- x-rays
- MRI
How can we manage osteoporosis ?
- ) exercise interventions:
- static and dynamic weight bearing exercises slows down decline of hip and lumbar BMD - ) Diet:
- adequate calcium in diet to meet the recommendations of 700-1000 mg/day
- Because of inadequate sunshine hours and diet low in vit D at least 800 IU of vitamin D3 is recommended
