Bone health Flashcards
What is bone mineral content and bone mineral density?
- BMC: bone mineral content- mass expressed as absolute value (g)
- BMD: bone mineral density- mass expressed as mass per unit area or volume
What age does bone mass peak?
30
When is the maximum bone mineral density attained?
Adolescence
What do osteoblasts and osteoclasts do?
-B- building (osteoblasts)
-C- catabolising (osteocytes)
What is bone remodelling?
continuous cycle of replacement of old bone tissue with new bone tissue
What is the role of vitamin D in bone remodelling?
Vitamin D maintains calcium and phosphate homeostasis by a negative feedback loop with PTH, aids calcium and phosphate absorption and triggers calcium mobilisation from bone when blood calcium is low
What are signs of a vitamin D deficiency?
Often see higher PTH level (secondary hyperparathyroidism)
Under-mineralized or under calcified bone matrix
Hypocalcaemia- muscle cramps and twitching
What are the consequences of vitamin D deficiency?
Rickets and osteomalacia
What is osteomalacia?
Impaired bone remodelling- not enough minerals coming in to repair rigidity of the bone in final process of modelling due to lack of vitamin D
Pseudofractures
‘‘Softening of the bones’’
What is rickets?
Disorder of the growth plates
Impaired bone mineralization and long bone growth
Treated with vitamin D and calcium intake or supplements combined
Can be hereditary or non hereditary
What are the most common causes of rickets?
Vitamin D or calcium deficiency
What is osteoporosis?
Often referred to as a silent disease
Multifactorial skeletal disease
Low bone mass and microartchitectural deterioration
How is osteoporosis diagnosed?
Low bone mineral density or fragility fracture
What is the appearance of osteoporosis?
gaps within bone tissue- honeycomb pattern with big holes
What are the modifiable, non modifiable and other risk factors for osteoporosis?
-Non-modifiable: being female, age, family history, white or asian, early menopause
-Modifiable: diet, excess alcohol, cigarette smoking, sedentary lifestyle
-Other: anorexia, oophorectomy, steroids, low testosterone
What is osteopenia?
At risk of osteoporosis but not progressed enough
What is a DEXA scan?
The new gold standard of bone mineral measuring, X-ray beams at different energies, bone and soft tissue calculated by attenuation of x-ray beams passing through the body
What are the negatives of DEXA scan?
Some radiation exposure and difficult to make comparisons in growing children or children with linear growth faltering.
Children may be moving too much
What did the BONUSkids study look at?
-Bone and muscle mass in kids
-have compared children in the UK and Bangladesh
-Looking at how different levels of vitamin D supplementation affects childs bone and muscle development
What is the FRAX tool?
Simiilar to QRISK tool, assesses risk of fracture in the next 10 years
What are the treatment options of osteoporosis?
Anti-catabolic agents, anabolic agents
What is the dominant mineral in hydroxyapatite?
Calcium
What is the VITamin D and omegA-3 trial? (VITAL)
RCT in US- supplemented high dose vit D vs placebo, found no effect on fracture prevention. Findings not generalisable to populations at risk of calcium/vit D deficiency as there was already a high baseline vit D status. Controversy around the trial
When does dietary protein have a protective effect on bone mass?
If calcium and vitamin D is adequate
