Bone Health - Lecture Flashcards
Two types of bone
Cortical (compact)
Trabecular (spongey, cancellous)
What is within bone structure?
Function of bone
Structure:
* Shape of body
* Protect organs
* Locomotion
* Respiration
Metabolic:
* Calcium reservoir
* Phosphorus
* Carbonate
* Buffer H+ changes
Haemopoesis
* RBC
* WBC
* Platelets
Deteminants of bone health
- Genetics
- Calcium
- Vitamin D
- Physical activity
- Healthy weight
Negative factors on bone health
- Smoking
- Alcohol
- Hypogonadism
- Malnutrition
- Drugs eg steroids, PPIs, statins, antiretrovirals, antifungals, anticonvulsants
Daily requirment of calcium
700mg per day for adults
What is calcium levels determined by?
- Dietary intae
- Intestinal absorption
- Bone resorption
- Urinary excretion
Foods high in calcium
- Milk/dairy products
- Tofu
- Nuts
- Fish
Vitamin D activation pathway
Main source of vitamin D
Sunlight
Then synthesised from 7-dehydroxycholesterol in body
What is Vitamin D2 and D3
D2 - ergocalciferol
D3 - cholecalciferol
Sources of dietary vitamin D
- Oily fish
- Red meat
- Liver
- Egg yolks
- Fortified cereals etc
Levels of 25 (OH) Vitamin D (Calcifediol) which are adequeate
- Less than 25nmol/L = deficient
- 25-50 = inadequate
- More than 50 = sufficient
RF for vitamin D deficiency
- 65 and older
- Low/no exposure to sun
- Malabsorption
- Severe liver or end stage CKD
- Medications eg laxatives, steroids
- Pregnancy and breastfeeding
- Obesity
Preventative measures for Vitamin D deficiency
- Safe sun exposure information
- Good diet sources of Vitamin D
- 400 IU of Vitamin D daily all year round for those with deficiency
- Others can have 400 IU just in autumn and winter
Complications of Vitamin D deficiency
- Rickets - children, Osteomalacia - adults
- Osteoporosis
- Fragility fractures
Exercise and bone health
- Need weight bearing exercise for bone health
- Over 65s need 150 mins per week of moderate exercise
- Can inc dancing, carrying groceries, up and down stairs, heavy gardening, yoga etc
What is peak bone mass?
- Max bone mass achieved during life
- Usually third decade
- Time to attain depends on genetics, hormones and environment
What is osteoporosis?
- Low bone mass
- Microarchitectural disruption
- Increased fragility
How is diagnosis of OP made?
- Fragility fracture - eg of spine, hip, wrist, humerus, pelvis, ribs
- OR T score -2.5 or less standard deviations at any site
How is T score calculated?
Do DEXA scan - dual energy x-ray absorbtiometry
This calculates bone mineral density
This is compared to bone density average of healthy young adult aged 30 of same sex
Standard deviation is calculated
T score value cut offs
-1 –> -2.4 is osteopenia
-2.5 or less = osteoporosis
When is DEXA scan not used?
- Pregnancy
- Implants, hardware devices in area of measurement - some reports are autogenerated, be careful with this as may be reading hip replacement density rather than bone etc
- Recently administered contrast
What is a fragility fracture?
Fracture that results from minor trauma or spontaneously eg falling from standing height
Who should be risk assessed for osteoporosis?
- Women over 65
- Men over 75
Or under these ages if:
* Previous fragility fracture
* Falls history
* Family history of hip fracture
* Rheumatoid arthirits
* Alcohol more than 3 units per day
FRAX score domains
- Age
- Height
- Weight
- Previous fragility fracture
- Parental hip fracture
- Current smoker?
- Glucocorticoid use
- RA
- Secondary OP
- Alcohol 3 or more units daily
- Femoral neck bone density - don’t have to use
What is then done following calculation of FRAX?
- Use FRAX to see what the 10yr risk of makor osteoporitic fracture is
- Then use NOGG (national OP guideline group) graph to see whether low, intermediate, high or very high risk (green, amber, red, dark red)
NOGG algorthim treatment
- Green Low risk - offer lifestyle advice
- Amber Intermediate risk - check BMD and recalculate
- Red High risk - treat and measure BMD
- Dark red very high risk - treat and consider specialist referral to rheum (paraenteral treatment maybe considered by them)
Treatment for OP
- Check calcium and vitamin D are adequate
- Bisphosphonates
- SERMs (selective oestrogen receptor modulators)
- Parathyroid hormone (teriparatide)
- Denosumab, Romosozumab - Biologics
Guidance for taking bisphosphonates
- Sit up for 45 minutes after taking - can cause oesophagitis
- Take on empty stomach - for absorption
- Do not eat and drink for 30mins-2hrs after taking
Examples of bisphosphonates
- Alendronic acid
- Ibandronic
- Risedronate
- Zoledronic acid (given once yearly IV infusion)
Come in tablet, liquid and injection
Takes 6-12 months to see effects
May need to take for 5+ yrs
Bisphosphonates side effects
- Oesophagitis
- Swallowing problems
- Stomach pain
- Osteonecrosis of jaw - esp occurs if existing dental problems
When is Denosumab given?
If bisphosphonates not seem to work/contraindicated
How is Denosumab taken?
- SC injections every 6 months
- Take for 5-10 yrs
Side effects of Denosumab
- Atypical fractures
- Hypocalcaemia
- Infection - immunosupression?
- Osteonecrosis of jaw
Z score Vs T score
Z score - compares to others same age and gender
T score - compares to that of 30yr old
